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Op amp advice

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Anonymous
November 13, 2004 12:21:58 PM

Archived from groups: rec.audio.pro (More info?)

For you op-amp experts I need some advice...

Just got a new (old) mixing console, Peavey/AMR 2400, and there is a
noticeable level of noise in the master module when I pull up the faders,
even though there is no signal from any of the channels. I called Peavey's
tech dept and they suggested replacing the op-amps in the master module, as
they age they lose their tolerances and can cause noise (it sounds like
white noise). The manual shows that it contains a bunch of 5532's, a few TL
074's, a few TL 072's, and a 741. I did a search at Digikey's website, and
found that there seems to be many "versions" of each chip, each with a
difference suffix to the chip number. I can physically replace the chips,
but determining the right version is beyond my expertise.

What would the difference be for each version, and which do you think would
be best for my application Or would it really matter? Tried Google for the
answer but not finding anything concrete.

Thanks in advace,

Matt

--
---
Matt Macchiarolo
mlmacchiarolo at comcast dot net
AIM screen name RTI1182

"We must not confuse dissent with disloyalty." -Edward R. Murrow

More about : amp advice

Anonymous
November 13, 2004 1:44:48 PM

Archived from groups: rec.audio.pro (More info?)

Have a look at www.ti.com , they may be different package styles or
temperature ranges. Op amps getting noisy with age seems unlikely....
although there might be lower noise units that are pin compatible. You may
wish to check the power supply noise level.... With your meter on AC
millivolts measure the ripple on your DC power supply.... less than 10 MV
should be expected... good supply run about 2 MV for a 24VDC or lower
supply.

Rgds:
Eric

"Matt Macchiarolo" <matt@nospamplease.com> wrote in message
news:tPCdnQ1GnOAzhQvcRVn-sQ@comcast.com...
> For you op-amp experts I need some advice...
>
> Just got a new (old) mixing console, Peavey/AMR 2400, and there is a
> noticeable level of noise in the master module when I pull up the faders,
> even though there is no signal from any of the channels. I called Peavey's
> tech dept and they suggested replacing the op-amps in the master module,
as
> they age they lose their tolerances and can cause noise (it sounds like
> white noise). The manual shows that it contains a bunch of 5532's, a few
TL
> 074's, a few TL 072's, and a 741. I did a search at Digikey's website, and
> found that there seems to be many "versions" of each chip, each with a
> difference suffix to the chip number. I can physically replace the chips,
> but determining the right version is beyond my expertise.
>
> What would the difference be for each version, and which do you think
would
> be best for my application Or would it really matter? Tried Google for the
> answer but not finding anything concrete.
>
> Thanks in advace,
>
> Matt
>
> --
> ---
> Matt Macchiarolo
> mlmacchiarolo at comcast dot net
> AIM screen name RTI1182
>
> "We must not confuse dissent with disloyalty." -Edward R. Murrow
>
>
>
Anonymous
November 13, 2004 1:44:49 PM

Archived from groups: rec.audio.pro (More info?)

> Just got a new (old) mixing console, Peavey/AMR 2400,
> and there is a noticeable level of noise in the master
> module when I pull up the faders, even though there is
> no signal from any of the channels.

Where are the channel faders? Are they all the way up/down, or at "normal"
operating positions?

Almost any electronics will produce audible noise under the "wrong" conditions.
Is everything (including your monitor amps) set up as it would be when making a
recording?
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Anonymous
November 13, 2004 3:53:13 PM

Archived from groups: rec.audio.pro (More info?)

Thanks for all the advice, folks.

Channel faders are all down. I am still in the process of connecting the
console to the rest of the studio, but I did get a mix through it, and
that's when I noticed the noise.

The noise seems to be only coming from the master module, the input channels
are actually pretty quiet. According to the previous owner, the master
module was affected with a power surge at one time that blew out the fuse
resistors in the power input circuit to the module...could this have
affected the op amps as well?

"William Sommerwerck" <williams@nwlink.com> wrote in message
news:10pchf7dlorcgdc@corp.supernews.com...
> > Just got a new (old) mixing console, Peavey/AMR 2400,
> > and there is a noticeable level of noise in the master
> > module when I pull up the faders, even though there is
> > no signal from any of the channels.
>
> Where are the channel faders? Are they all the way up/down, or at "normal"
> operating positions?
>
> Almost any electronics will produce audible noise under the "wrong"
conditions.
> Is everything (including your monitor amps) set up as it would be when
making a
> recording?
>
Anonymous
November 13, 2004 3:53:14 PM

Archived from groups: rec.audio.pro (More info?)

> According to the previous owner, the master module was affected
> with a power surge at one time that blew out the fuse resistors in
> the power input circuit to the module... could this have affected
> the op amps as well?

I don't know, but such a failure calls for some careful troubleshooting (such as
using an AC voltmeter to see if one stage is particularly noisy).

Assuming the master module uses inexpensive tab-case regulators, it wouldn't
hurt to replace them. Whether a wholesale replacement of other components is
justified, I don't know.
Anonymous
November 13, 2004 4:04:14 PM

Archived from groups: rec.audio.pro (More info?)

Eric K. Weber <eric-nospam@webermusic.com> wrote:
>Have a look at www.ti.com , they may be different package styles or
>temperature ranges. Op amps getting noisy with age seems unlikely....
>although there might be lower noise units that are pin compatible. You may
>wish to check the power supply noise level.... With your meter on AC
>millivolts measure the ripple on your DC power supply.... less than 10 MV
>should be expected... good supply run about 2 MV for a 24VDC or lower
>supply.

TI never could make decent op-amps. While it does seem very unlikely,
I could see op-amps getting noisy as they age if they have package
contamination problems... and if anyone has package contamination issues,
it would be TI. They had to buy out Burr-Brown because they couldn't make
decent linear stuff in-house.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
November 13, 2004 6:28:34 PM

Archived from groups: rec.audio.pro (More info?)

In article <tPCdnQ1GnOAzhQvcRVn-sQ@comcast.com> matt@nospamplease.com writes:

> Just got a new (old) mixing console, Peavey/AMR 2400, and there is a
> noticeable level of noise in the master module when I pull up the faders,
> even though there is no signal from any of the channels. I called Peavey's
> tech dept and they suggested replacing the op-amps in the master module, as
> they age they lose their tolerances and can cause noise (it sounds like
> white noise).

Yeah, Peavey's advice sounds like white noise, or just plain horse
manure. I've never heard of op amps that "age" and "lose their
tolerance." More likely it's a bad resistor, a bad capacitor, a bad
switch, or a bad solder joint. Could even be a dirty connector
contact. While there may be better sounding op amps available today,
take care of the real source of the noise first or you'll still have
it after you replace the chips.


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
November 13, 2004 6:33:35 PM

Archived from groups: rec.audio.pro (More info?)

So I am learning.

"Mike Rivers" <mrivers@d-and-d.com> wrote in message
news:znr1100362543k@trad...
>
> In article <tPCdnQ1GnOAzhQvcRVn-sQ@comcast.com> matt@nospamplease.com
writes:
>
> > Just got a new (old) mixing console, Peavey/AMR 2400, and there is a
> > noticeable level of noise in the master module when I pull up the
faders,
> > even though there is no signal from any of the channels. I called
Peavey's
> > tech dept and they suggested replacing the op-amps in the master module,
as
> > they age they lose their tolerances and can cause noise (it sounds like
> > white noise).
>
> Yeah, Peavey's advice sounds like white noise, or just plain horse
> manure. I've never heard of op amps that "age" and "lose their
> tolerance." More likely it's a bad resistor, a bad capacitor, a bad
> switch, or a bad solder joint. Could even be a dirty connector
> contact. While there may be better sounding op amps available today,
> take care of the real source of the noise first or you'll still have
> it after you replace the chips.
>
>
> --
> I'm really Mike Rivers (mrivers@d-and-d.com)
> However, until the spam goes away or Hell freezes over,
> lots of IP addresses are blocked from this system. If
> you e-mail me and it bounces, use your secret decoder ring
> and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
November 13, 2004 6:45:26 PM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> For you op-amp experts I need some advice...
>
> Just got a new (old) mixing console, Peavey/AMR 2400, and there is a
> noticeable level of noise in the master module when I pull up the faders,
> even though there is no signal from any of the channels. I called Peavey's
> tech dept and they suggested replacing the op-amps in the master module, as
> they age they lose their tolerances and can cause noise (it sounds like
> white noise).

That's total rubbish.

I'd only expect on op-amp to go noisy if there was a manufacturing or
encapsualation defect.

> The manual shows that it contains a bunch of 5532's, a few TL
> 074's, a few TL 072's, and a 741. I did a search at Digikey's website, and
> found that there seems to be many "versions" of each chip, each with a
> difference suffix to the chip number. I can physically replace the chips,
> but determining the right version is beyond my expertise.

The suffixes relate to commercial / industrial / military temperature range and
the package ( dual in line / SMT etc ).

TL072s in this product are likely to be TL072CP in TI ( Texas Instruments who
originated them ) speak - commercial plastic 8 pin dil - but the suffixes vary
from manufacturer to manufacturer.


> What would the difference be for each version, and which do you think would
> be best for my application Or would it really matter? Tried Google for the
> answer but not finding anything concrete.

Well you need the commercial type in the same package as you want to replace.

I don't expect you're going to go anywhere with this though. Old products
didn't have today's noise specs and it isn't just the op-amps. 'Thermal noise'
from resistors can't be 'replaced out' for example. Older designs paid less
attention to thermal noise issues.

Peavey also weren't exactly known as great mixing console makers, so don't
expect too much anyway.

The 5532 is actually quite quiet and is still in very regular use. TL072s are
somewhat noisier by todays's standards but still have their applications.

Random replacement really isn't going to buy you much. You'd have to find the
noisiest areas and substitute better parts to be honest ( assuming that it
would make a difference over the thermal noise ).


Graham
Anonymous
November 13, 2004 7:30:35 PM

Archived from groups: rec.audio.pro (More info?)

On Sat, 13 Nov 2004 15:45:26 +0000, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

>Matt Macchiarolo wrote:
>
>> For you op-amp experts I need some advice...
>>
>> Just got a new (old) mixing console, Peavey/AMR 2400, and there is a
>> noticeable level of noise in the master module when I pull up the faders,
>> even though there is no signal from any of the channels. I called Peavey's
>> tech dept and they suggested replacing the op-amps in the master module, as
>> they age they lose their tolerances and can cause noise (it sounds like
>> white noise).
>
>That's total rubbish.
>
>I'd only expect on op-amp to go noisy if there was a manufacturing or
>encapsualation defect.
>
>> The manual shows that it contains a bunch of 5532's, a few TL
>> 074's, a few TL 072's, and a 741. I did a search at Digikey's website, and
>> found that there seems to be many "versions" of each chip, each with a
>> difference suffix to the chip number. I can physically replace the chips,
>> but determining the right version is beyond my expertise.
>
>The suffixes relate to commercial / industrial / military temperature range and
>the package ( dual in line / SMT etc ).
>
>TL072s in this product are likely to be TL072CP in TI ( Texas Instruments who
>originated them ) speak - commercial plastic 8 pin dil - but the suffixes vary
>from manufacturer to manufacturer.
>
>
>> What would the difference be for each version, and which do you think would
>> be best for my application Or would it really matter? Tried Google for the
>> answer but not finding anything concrete.
>
>Well you need the commercial type in the same package as you want to replace.
>
>I don't expect you're going to go anywhere with this though. Old products
>didn't have today's noise specs and it isn't just the op-amps. 'Thermal noise'
>from resistors can't be 'replaced out' for example. Older designs paid less
>attention to thermal noise issues.
>
>Peavey also weren't exactly known as great mixing console makers, so don't
>expect too much anyway.
>
>The 5532 is actually quite quiet and is still in very regular use. TL072s are
>somewhat noisier by todays's standards but still have their applications.
>
>Random replacement really isn't going to buy you much. You'd have to find the
>noisiest areas and substitute better parts to be honest ( assuming that it
>would make a difference over the thermal noise ).
>
>
>Graham
>
Further to Grahams's excellent advice, I will make some slightly
educated guesses:

The noise was always there. Our expectations have gotten higher.

The first op-amp in the channel, with the smallest (mic level) input
signal, is the biggest contributor to the noise. If it's a TL072,
consider replacing it with a newer, quieter design.

Do any of our experts have a suggestion for a TL072 replacement in
this application? I'm not familiar with the schematic of this mixer,
so I won't even venture a guess.

Mike T.
Anonymous
November 13, 2004 8:00:26 PM

Archived from groups: rec.audio.pro (More info?)

"Mike T." wrote:

> On Sat, 13 Nov 2004 15:45:26 +0000, Pooh Bear
> <rabbitsfriendsandrelations@hotmail.com> wrote:
>
> >Matt Macchiarolo wrote:
> >
> >> For you op-amp experts I need some advice...
> >>
> >> Just got a new (old) mixing console, Peavey/AMR 2400, and there is a
> >> noticeable level of noise in the master module when I pull up the faders,
> >> even though there is no signal from any of the channels. I called Peavey's
> >> tech dept and they suggested replacing the op-amps in the master module, as
> >> they age they lose their tolerances and can cause noise (it sounds like
> >> white noise).
> >
> >That's total rubbish.
> >
> >I'd only expect on op-amp to go noisy if there was a manufacturing or
> >encapsualation defect.
> >
> >> The manual shows that it contains a bunch of 5532's, a few TL
> >> 074's, a few TL 072's, and a 741. I did a search at Digikey's website, and
> >> found that there seems to be many "versions" of each chip, each with a
> >> difference suffix to the chip number. I can physically replace the chips,
> >> but determining the right version is beyond my expertise.
> >
> >The suffixes relate to commercial / industrial / military temperature range and
> >the package ( dual in line / SMT etc ).
> >
> >TL072s in this product are likely to be TL072CP in TI ( Texas Instruments who
> >originated them ) speak - commercial plastic 8 pin dil - but the suffixes vary
> >from manufacturer to manufacturer.
> >
> >
> >> What would the difference be for each version, and which do you think would
> >> be best for my application Or would it really matter? Tried Google for the
> >> answer but not finding anything concrete.
> >
> >Well you need the commercial type in the same package as you want to replace.
> >
> >I don't expect you're going to go anywhere with this though. Old products
> >didn't have today's noise specs and it isn't just the op-amps. 'Thermal noise'
> >from resistors can't be 'replaced out' for example. Older designs paid less
> >attention to thermal noise issues.
> >
> >Peavey also weren't exactly known as great mixing console makers, so don't
> >expect too much anyway.
> >
> >The 5532 is actually quite quiet and is still in very regular use. TL072s are
> >somewhat noisier by todays's standards but still have their applications.
> >
> >Random replacement really isn't going to buy you much. You'd have to find the
> >noisiest areas and substitute better parts to be honest ( assuming that it
> >would make a difference over the thermal noise ).
> >
> >
> >Graham
>
> Further to Grahams's excellent advice, I will make some slightly
> educated guesses:
>
> The noise was always there. Our expectations have gotten higher.

Pretty likely !


> The first op-amp in the channel, with the smallest (mic level) input
> signal, is the biggest contributor to the noise. If it's a TL072,
> consider replacing it with a newer, quieter design.

EEEK !!! I hope no mic stage goes straight into a TL07x. You *should* find some
transistors there. I'm pretty certain it won't be a transformer input mic stage btw
( cost reasons ).


> Do any of our experts have a suggestion for a TL072 replacement in
> this application? I'm not familiar with the schematic of this mixer,
> so I won't even venture a guess.

I was trying to think of one. There's nothing in the 'commodity' ( i.e. affordable !
) IC market that I can think of immediately that is also bi-fet but I have a
nagging feeling somewhere there's something with a *slightly* lower noise figure.
Don't use bi-fets much these days,!

The more esoteric devices from Burr-Brown ( now TI ) and Analog Devices will have
lower noise figures for sure.

Thing is - there's no guarantee that there'll be a useful improvement until you
diagnose the root cause of the noise sources. You could end up spending more bucks
than a new Behringer costs.


Graham
Anonymous
November 13, 2004 9:27:07 PM

Archived from groups: rec.audio.pro (More info?)

"Mike T." <miket@invalid.net> wrote in message
news:nadcp01i2kmtvc6gcciitt0nndqi61toik@4ax.com...

>> Further to Grahams's excellent advice, I will make some slightly
> educated guesses:
>
> The noise was always there. Our expectations have gotten higher.
>
> The first op-amp in the channel, with the smallest (mic level) input
> signal, is the biggest contributor to the noise. If it's a TL072,
> consider replacing it with a newer, quieter design.
>
> Do any of our experts have a suggestion for a TL072 replacement in
> this application? I'm not familiar with the schematic of this mixer,
> so I won't even venture a guess.

I don't know the schematic of this mixer either, but I'd guess that the
TL072 isn't the first opamp in the chain; that's probably a 5532.

But I'm not clear on one thing: you heard the noise just pushing up the
master faders, or pushing up the master *and* the channel faders? If the
latter, what was plugged into the inputs?

If the answer is, "Nothing", then try this experiment. Push up the master
and one channel fader. Listen to and/or measure the noise. Now pull down the
channel fader and plug a dummy XLR plug into the microphone input, with a
150-ohm metal film resistor soldered between pins 2 and 3. Push the fader
back up. If the noise is a lot less, stop worrying. You were hearing the
sound of an open-circuit input, which will almost always be worse than one
with something plugged in. And since you won't be opening a fader on a
channel with nothing plugged into it, you can relax.

Peace,
Paul
Anonymous
November 13, 2004 10:04:37 PM

Archived from groups: rec.audio.pro (More info?)

Paul Stamler wrote:

> "Mike T." <miket@invalid.net> wrote in message
> news:nadcp01i2kmtvc6gcciitt0nndqi61toik@4ax.com...
>
> >> Further to Grahams's excellent advice, I will make some slightly
> > educated guesses:
> >
> > The noise was always there. Our expectations have gotten higher.
> >
> > The first op-amp in the channel, with the smallest (mic level) input
> > signal, is the biggest contributor to the noise. If it's a TL072,
> > consider replacing it with a newer, quieter design.
> >
> > Do any of our experts have a suggestion for a TL072 replacement in
> > this application? I'm not familiar with the schematic of this mixer,
> > so I won't even venture a guess.
>
> I don't know the schematic of this mixer either, but I'd guess that the
> TL072 isn't the first opamp in the chain; that's probably a 5532.
>
> But I'm not clear on one thing: you heard the noise just pushing up the
> master faders, or pushing up the master *and* the channel faders? If the
> latter, what was plugged into the inputs?
>
> If the answer is, "Nothing", then try this experiment. Push up the master
> and one channel fader. Listen to and/or measure the noise. Now pull down the
> channel fader and plug a dummy XLR plug into the microphone input, with a
> 150-ohm metal film resistor soldered between pins 2 and 3. Push the fader
> back up. If the noise is a lot less, stop worrying. You were hearing the
> sound of an open-circuit input, which will almost always be worse than one
> with something plugged in. And since you won't be opening a fader on a
> channel with nothing plugged into it, you can relax.

Good point.

I'm aware that many 'music / guitar shops' make exactly this kind of mistake
when demoing mixers.

They say " you're mixer's noisy ". Actually of course - it's the absence of the
150-200 ohm source resistance that makes the circuit noisy as we know. But
*they* don't get it.

Graham
Anonymous
November 13, 2004 10:04:38 PM

Archived from groups: rec.audio.pro (More info?)

It's just the master faders. No channel faders are up.

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:41965AC5.10E3F8CA@hotmail.com...
> Paul Stamler wrote:
>
> > "Mike T." <miket@invalid.net> wrote in message
> > news:nadcp01i2kmtvc6gcciitt0nndqi61toik@4ax.com...
> >
> > >> Further to Grahams's excellent advice, I will make some slightly
> > > educated guesses:
> > >
> > > The noise was always there. Our expectations have gotten higher.
> > >
> > > The first op-amp in the channel, with the smallest (mic level) input
> > > signal, is the biggest contributor to the noise. If it's a TL072,
> > > consider replacing it with a newer, quieter design.
> > >
> > > Do any of our experts have a suggestion for a TL072 replacement in
> > > this application? I'm not familiar with the schematic of this mixer,
> > > so I won't even venture a guess.
> >
> > I don't know the schematic of this mixer either, but I'd guess that the
> > TL072 isn't the first opamp in the chain; that's probably a 5532.
> >
> > But I'm not clear on one thing: you heard the noise just pushing up the
> > master faders, or pushing up the master *and* the channel faders? If the
> > latter, what was plugged into the inputs?
> >
> > If the answer is, "Nothing", then try this experiment. Push up the
master
> > and one channel fader. Listen to and/or measure the noise. Now pull down
the
> > channel fader and plug a dummy XLR plug into the microphone input, with
a
> > 150-ohm metal film resistor soldered between pins 2 and 3. Push the
fader
> > back up. If the noise is a lot less, stop worrying. You were hearing the
> > sound of an open-circuit input, which will almost always be worse than
one
> > with something plugged in. And since you won't be opening a fader on a
> > channel with nothing plugged into it, you can relax.
>
> Good point.
>
> I'm aware that many 'music / guitar shops' make exactly this kind of
mistake
> when demoing mixers.
>
> They say " you're mixer's noisy ". Actually of course - it's the absence
of the
> 150-200 ohm source resistance that makes the circuit noisy as we know. But
> *they* don't get it.
>
> Graham
>
Anonymous
November 13, 2004 10:06:18 PM

Archived from groups: rec.audio.pro (More info?)

"Eric K. Weber" wrote:

> Have a look at www.ti.com , they may be different package styles or
> temperature ranges. Op amps getting noisy with age seems unlikely....
> although there might be lower noise units that are pin compatible. You may
> wish to check the power supply noise level.... With your meter on AC
> millivolts measure the ripple on your DC power supply.... less than 10 MV
> should be expected... good supply run about 2 MV for a 24VDC or lower
> supply.

I target around 300uV on +/-17V. ;-)

It doesn't need to be that good though. Op-amps have excellent power supply
rejection normally.


Graham
Anonymous
November 13, 2004 10:08:10 PM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> Eric K. Weber <eric-nospam@webermusic.com> wrote:
> >Have a look at www.ti.com , they may be different package styles or
> >temperature ranges. Op amps getting noisy with age seems unlikely....
> >although there might be lower noise units that are pin compatible. You may
> >wish to check the power supply noise level.... With your meter on AC
> >millivolts measure the ripple on your DC power supply.... less than 10 MV
> >should be expected... good supply run about 2 MV for a 24VDC or lower
> >supply.
>
> TI never could make decent op-amps. While it does seem very unlikely,
> I could see op-amps getting noisy as they age if they have package
> contamination problems... and if anyone has package contamination issues,
> it would be TI. They had to buy out Burr-Brown because they couldn't make
> decent linear stuff in-house.

A certain person I know reputedly bought a batch of 'cheap' TL071/2s that
allegedly may have been immersed in salt water ( salvaged cargo ).

They went noisy it seems !


Graham
Anonymous
November 13, 2004 10:16:10 PM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> Thanks for all the advice, folks.
>
> Channel faders are all down. I am still in the process of connecting the
> console to the rest of the studio, but I did get a mix through it, and
> that's when I noticed the noise.
>
> The noise seems to be only coming from the master module, the input channels
> are actually pretty quiet. According to the previous owner, the master
> module was affected with a power surge at one time that blew out the fuse
> resistors in the power input circuit to the module...could this have
> affected the op amps as well?

That's an unusual claim. The master module will share the power supply with all
the other channels.

A 'power surge' is also an unusual claim. Mixers normally use IC voltage
regulators that prevent any such problem from troubling the circuitry.

What 'fuse resistors' does he refer to ? There's often an RC 'decoupling'
network on the power input to a channel / module - does he mean them ? If the
resistors on just that module blew - then it's unlikely a 'power surge' was
involved. Maybe a *fault* !!! To be honest it sounds a bit like he's talking
out of his arse. He may however be misinterpreting something.

It *did* sound a little like your bus mix amps might be noisy from your general
description. You could selectively replace the probable 5532s on that part of
the circuitry, just to see, at low cost.

Noisy bus amp = noisy mixer even when channel faders are down.

What's the 741 doing btw ?


Graham
Anonymous
November 13, 2004 10:16:11 PM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:41965D7A.9B3592BC@hotmail.com...

>
> What's the 741 doing btw ?
>

Don't have the slightest idea, reading schematics is like Greek to me.
Though it's there and there is only one. Perhaps something to do with the
mono switch?
Anonymous
November 13, 2004 10:34:59 PM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> It's just the master faders. No channel faders are up.

Ok - sounds like noisy bus amps.

Most likely a / some 5532s. There's going to be some circuitry following them
though that could also be influencing things.

If you can identify the op-amp that's the bus mix section - then selective
replacement as a test would make sense.

I guess it's possible a chip's gone noisy - but it's rare. Maybe the Peavey guys
know something they're not letting on about ?


Graham
Anonymous
November 13, 2004 10:35:00 PM

Archived from groups: rec.audio.pro (More info?)

Thanks Pooh,

Tracing it down through signal path diagram, the path for either L or R
goes Bus, Summing Amp, Master Trim, another op amp, Bus Send/Return, fader,
master output...breaking the normalled connection in the insert kills the
noise, so I'm guessing it's either the summing amp or the other one in that
chain, both of which are around 5532's. Am I making any sense?

Got a fax number? I can fax you the schematics...

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:419661E3.49193E00@hotmail.com...
>
> Matt Macchiarolo wrote:
>
> > It's just the master faders. No channel faders are up.
>
> Ok - sounds like noisy bus amps.
>
> Most likely a / some 5532s. There's going to be some circuitry following
them
> though that could also be influencing things.
>
> If you can identify the op-amp that's the bus mix section - then selective
> replacement as a test would make sense.
>
> I guess it's possible a chip's gone noisy - but it's rare. Maybe the
Peavey guys
> know something they're not letting on about ?
>
>
> Graham
>
Anonymous
November 13, 2004 10:35:00 PM

Archived from groups: rec.audio.pro (More info?)

Is this noise the same on both channels.... if so it's more likely either a
power supply issue or a design issue.

Rgds:
Eric

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:419661E3.49193E00@hotmail.com...
>
> Matt Macchiarolo wrote:
>
> > It's just the master faders. No channel faders are up.
>
> Ok - sounds like noisy bus amps.
>
> Most likely a / some 5532s. There's going to be some circuitry following
them
> though that could also be influencing things.
>
> If you can identify the op-amp that's the bus mix section - then selective
> replacement as a test would make sense.
>
> I guess it's possible a chip's gone noisy - but it's rare. Maybe the
Peavey guys
> know something they're not letting on about ?
>
>
> Graham
>
>
Anonymous
November 13, 2004 10:35:01 PM

Archived from groups: rec.audio.pro (More info?)

Oops, there should be another amp between the return and the fader, and then
two parallel amps (to balance the output, I imagine) between the fader and
the output

"Matt Macchiarolo" <matt@nospamplease.com> wrote in message
news:1qadnXG29fH39QvcRVn-pg@comcast.com...
> Thanks Pooh,
>
> Tracing it down through signal path diagram, the path for either L or R
> goes Bus, Summing Amp, Master Trim, another op amp, Bus Send/Return,
fader,
> master output...breaking the normalled connection in the insert kills the
> noise, so I'm guessing it's either the summing amp or the other one in
that
> chain, both of which are around 5532's. Am I making any sense?
>
> Got a fax number? I can fax you the schematics...
>
> "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
> news:419661E3.49193E00@hotmail.com...
> >
> > Matt Macchiarolo wrote:
> >
> > > It's just the master faders. No channel faders are up.
> >
> > Ok - sounds like noisy bus amps.
> >
> > Most likely a / some 5532s. There's going to be some circuitry following
> them
> > though that could also be influencing things.
> >
> > If you can identify the op-amp that's the bus mix section - then
selective
> > replacement as a test would make sense.
> >
> > I guess it's possible a chip's gone noisy - but it's rare. Maybe the
> Peavey guys
> > know something they're not letting on about ?
> >
> >
> > Graham
> >
>
>
Anonymous
November 13, 2004 10:35:01 PM

Archived from groups: rec.audio.pro (More info?)

I'll swap out those 5532's poohbear indicated, and see if it helps...I'll
try the power supply if that doesn't help. Though if it was a power supply
issue it would probably be evident on all channels, and it doesn't seem to
be.

"Eric K. Weber" <eric-nospam@webermusic.com> wrote in message
news:T8vld.26$a91.4552@news.uswest.net...
> Is this noise the same on both channels.... if so it's more likely either
a
> power supply issue or a design issue.
>
> Rgds:
> Eric
>
> "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
> news:419661E3.49193E00@hotmail.com...
> >
> > Matt Macchiarolo wrote:
> >
> > > It's just the master faders. No channel faders are up.
> >
> > Ok - sounds like noisy bus amps.
> >
> > Most likely a / some 5532s. There's going to be some circuitry following
> them
> > though that could also be influencing things.
> >
> > If you can identify the op-amp that's the bus mix section - then
selective
> > replacement as a test would make sense.
> >
> > I guess it's possible a chip's gone noisy - but it's rare. Maybe the
> Peavey guys
> > know something they're not letting on about ?
> >
> >
> > Graham
> >
> >
>
>
Anonymous
November 13, 2004 11:09:19 PM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
> news:41965D7A.9B3592BC@hotmail.com...
>
> >
> > What's the 741 doing btw ?
> >
>
> Don't have the slightest idea, reading schematics is like Greek to me.
> Though it's there and there is only one. Perhaps something to do with the
> mono switch?

If you have the schematics - can you scan them ( master section a tleast )
and post in alt.binaries.schematics.electronics ?

I'll take a look. Would be able to advise better.


Graham
Anonymous
November 13, 2004 11:09:20 PM

Archived from groups: rec.audio.pro (More info?)

I don't have a scanner, got a fax machine?

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:419669EF.54C938CF@hotmail.com...
>
> Matt Macchiarolo wrote:
>
> > "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
> > news:41965D7A.9B3592BC@hotmail.com...
> >
> > >
> > > What's the 741 doing btw ?
> > >
> >
> > Don't have the slightest idea, reading schematics is like Greek to me.
> > Though it's there and there is only one. Perhaps something to do with
the
> > mono switch?
>
> If you have the schematics - can you scan them ( master section a tleast )
> and post in alt.binaries.schematics.electronics ?
>
> I'll take a look. Would be able to advise better.
>
>
> Graham
>
>
Anonymous
November 13, 2004 11:20:36 PM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> I don't have a scanner, got a fax machine?

Yup.

My bad to post it here but here goes ( dial international access ) ( then UK
code - 44 ) followed by 1727 then 765452.

Plain paper fax btw. Only understands A4 ( international ) paper size - not some
of the funny US sizes. Try one page first to see how it goes.


Graham
Anonymous
November 13, 2004 11:20:37 PM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:41966C94.8848FA35@hotmail.com...
>
> Matt Macchiarolo wrote:
>
> > I don't have a scanner, got a fax machine?
>
> Yup.
>

Fax is transmitting. I won't give out your fax number. :-)

741 is in section A-4 of the lower schematic (Left Bus).
Anonymous
November 13, 2004 11:20:37 PM

Archived from groups: rec.audio.pro (More info?)

It should scale to A4 with no problem.... and if he is calling from the
USA.. it's

011 44 1727 765452

011 international prefix...
44 UK country code....

Rgds:
Eric

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:41966C94.8848FA35@hotmail.com...
>
> Matt Macchiarolo wrote:
>
> > I don't have a scanner, got a fax machine?
>
> Yup.
>
> My bad to post it here but here goes ( dial international access ) ( then
UK
> code - 44 ) followed by 1727 then 765452.
>
> Plain paper fax btw. Only understands A4 ( international ) paper size -
not some
> of the funny US sizes. Try one page first to see how it goes.
>
>
> Graham
>
>
Anonymous
November 13, 2004 11:58:59 PM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
> news:41966C94.8848FA35@hotmail.com...
> >
> > Matt Macchiarolo wrote:
> >
> > > I don't have a scanner, got a fax machine?
> >
> > Yup.
>
> Fax is transmitting. I won't give out your fax number. :-)
>
> 741 is in section A-4 of the lower schematic (Left Bus).

Ok - got it.

Is that the size you got it ? A bit on the tiny side. Having trouble
reading it.

The good news is that the 741 clearly isn't in the audio path ( as I
suspected ).

I'm having trouble reading the U numbers but the ICs for the bus amps are
the ones ( one on each page ) that are on the top left hand corner - note
the connections to BUS GND and a 10UH inductor. Looks like one half of
the dual op-amp is the bus amp - the other half is the fader buffer -
pretty classic.

If *anything* is going to make a difference - it's them !

The resistor values around the bus amps aren't *too* bad regarding
thermal noise but I would use lower. But that's a re-design.


Graham
Anonymous
November 13, 2004 11:59:00 PM

Archived from groups: rec.audio.pro (More info?)

Thanks Pooh! Next time I'm in the UK I will buy you a pint of Greene King!
Until then I will raise a glass of Old Speckled Hen to you!

Both schematics are on one page, 8.5x11...fairly tiny.

Those op amps are U1A and U1B, a=left b=right. . Those are the summing amps,
correct? You don't think the U5's (section D-4) could be a factor? All those
are 5532's. The manual includes a PCB diagram so I can find those pretty
easily.

If you were to replace those resistors, what would you recommend?

And what does that 741 do?
"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:41967593.7EBCA191@hotmail.com...
>
> Matt Macchiarolo wrote:
>
> > "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
> > news:41966C94.8848FA35@hotmail.com...
> > >
> > > Matt Macchiarolo wrote:
> > >
> > > > I don't have a scanner, got a fax machine?
> > >
> > > Yup.
> >
> > Fax is transmitting. I won't give out your fax number. :-)
> >
> > 741 is in section A-4 of the lower schematic (Left Bus).
>
> Ok - got it.
>
> Is that the size you got it ? A bit on the tiny side. Having trouble
> reading it.
>
> The good news is that the 741 clearly isn't in the audio path ( as I
> suspected ).
>
> I'm having trouble reading the U numbers but the ICs for the bus amps are
> the ones ( one on each page ) that are on the top left hand corner - note
> the connections to BUS GND and a 10UH inductor. Looks like one half of
> the dual op-amp is the bus amp - the other half is the fader buffer -
> pretty classic.
>
> If *anything* is going to make a difference - it's them !
>
> The resistor values around the bus amps aren't *too* bad regarding
> thermal noise but I would use lower. But that's a re-design.
>
>
> Graham
>
>
>
>
>
Anonymous
November 13, 2004 11:59:01 PM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
>
> The resistor values around the bus amps aren't *too* bad regarding
> thermal noise but I would use lower. But that's a re-design.

Might be a good idea to measure them and see that they are still the values
that the schematic says they should be. That's a possible noise source...
not so common with modern film resistors but it happens.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
November 14, 2004 12:58:48 AM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> Thanks Pooh! Next time I'm in the UK I will buy you a pint of Greene King!
> Until then I will raise a glass of Old Speckled Hen to you!

Cheers then !


> Both schematics are on one page, 8.5x11...fairly tiny.
>
> Those op amps are U1A and U1B, a=left b=right. . Those are the summing amps,
> correct?

Ok - wondered if that might be so.

> You don't think the U5's (section D-4) could be a factor? All those
> are 5532's. The manual includes a PCB diagram so I can find those pretty
> easily.

The other op-amps operate at high signal levels so the noise contribution there
won't be an issue.

No need to replace.

> If you were to replace those resistors, what would you recommend?

Well, I'd most likely use something like 4k7 feedback Rs in place of 22k. You
can't do that without altering the channel values though or the gain structure
gets screwed.


> And what does that 741 do?

Given the quality of the fax it's tricky to say. Is there a peak led there
though. Maybe that's it ?

TI's part number for the DIL 5532 is NE5532AP btw.

http://focus.ti.com/docs/prod/folders/print/ne5532a.htm... - log in as a tech and
request samples !

Philips / Signetics have stopped making it. NJR / JRC ( New Japan Radio
Corporation ) also source it.


Graham
Anonymous
November 14, 2004 12:58:49 AM

Archived from groups: rec.audio.pro (More info?)

> > Those op amps are U1A and U1B, a=left b=right. . Those are the summing
amps,
> > correct?
>
> Ok - wondered if that might be so.

According to the signal path diagram, they correspond to the summing amps.
>
> > You don't think the U5's (section D-4) could be a factor? All those
> > are 5532's. The manual includes a PCB diagram so I can find those pretty
> > easily.
>
> The other op-amps operate at high signal levels so the noise contribution
there
> won't be an issue.
>
> No need to replace.
>
> > If you were to replace those resistors, what would you recommend?
>
> Well, I'd most likely use something like 4k7 feedback Rs in place of 22k.
You
> can't do that without altering the channel values though or the gain
structure
> gets screwed.

Gotcha.
>
>
> > And what does that 741 do?
>
> Given the quality of the fax it's tricky to say. Is there a peak led there
> though. Maybe that's it ?
>
Ah yes, that makes sense to be the signal/peak LED circuit, it uses a
bicolor LED that is green with signal and red when within 3dB of clipping,
according to the manual...

When I get a chance I'll swap out those 5532's and we'll see what
happens...thanks for all your help!!
Anonymous
November 14, 2004 12:58:50 AM

Archived from groups: rec.audio.pro (More info?)

Well I just pulled the master module and it looks like it has been modded..
the 5532 in question seems to have been replaced with an LT1358, and some of
the others were replaced with TLE2082's, along with some other components
that were added. This console had 5 input channels modified by Audio
Upgrades, it looks as if the master module has been modified as well...looks
like I'll be calling Jim again.

Thanks for everyone's help!

Matt

"Matt Macchiarolo" <matt@nospamplease.com> wrote in message
news:T9ydnTbcLIFoGQvcRVn-gA@comcast.com...
> > > Those op amps are U1A and U1B, a=left b=right. . Those are the summing
> amps,
> > > correct?
> >
> > Ok - wondered if that might be so.
>
> According to the signal path diagram, they correspond to the summing amps.
> >
> > > You don't think the U5's (section D-4) could be a factor? All those
> > > are 5532's. The manual includes a PCB diagram so I can find those
pretty
> > > easily.
> >
> > The other op-amps operate at high signal levels so the noise
contribution
> there
> > won't be an issue.
> >
> > No need to replace.
> >
> > > If you were to replace those resistors, what would you recommend?
> >
> > Well, I'd most likely use something like 4k7 feedback Rs in place of
22k.
> You
> > can't do that without altering the channel values though or the gain
> structure
> > gets screwed.
>
> Gotcha.
> >
> >
> > > And what does that 741 do?
> >
> > Given the quality of the fax it's tricky to say. Is there a peak led
there
> > though. Maybe that's it ?
> >
> Ah yes, that makes sense to be the signal/peak LED circuit, it uses a
> bicolor LED that is green with signal and red when within 3dB of clipping,
> according to the manual...
>
> When I get a chance I'll swap out those 5532's and we'll see what
> happens...thanks for all your help!!
>
>
>
Anonymous
November 14, 2004 1:44:29 AM

Archived from groups: rec.audio.pro (More info?)

"Eric K. Weber" wrote:

> It should scale to A4 with no problem.... and if he is calling from the
> USA.. it's

Ssssh ! It's a secret !

Yeah, it came through OK.

Had some past trouble with the 'legal' size paper though.

Pretty much all paper sizes here ( and rest of world ) are now international
standards. Just the USA goes its own way with the stuff you enherited from us
Brits mainly I think - lol.


Graham
Anonymous
November 14, 2004 2:52:12 AM

Archived from groups: rec.audio.pro (More info?)

I would not send a lot of time changing parts, the problem is most likely in
the design. If the design is the problem, look to zener diodes or high
value resistors in the input section.

John


"Eric K. Weber" <eric-nospam@webermusic.com> wrote in message
news:T8vld.26$a91.4552@news.uswest.net...
> Is this noise the same on both channels.... if so it's more likely either
a
> power supply issue or a design issue.
>
> Rgds:
> Eric
>
> "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
> news:419661E3.49193E00@hotmail.com...
> >
> > Matt Macchiarolo wrote:
> >
> > > It's just the master faders. No channel faders are up.
> >
> > Ok - sounds like noisy bus amps.
> >
> > Most likely a / some 5532s. There's going to be some circuitry following
> them
> > though that could also be influencing things.
> >
> > If you can identify the op-amp that's the bus mix section - then
selective
> > replacement as a test would make sense.
> >
> > I guess it's possible a chip's gone noisy - but it's rare. Maybe the
> Peavey guys
> > know something they're not letting on about ?
> >
> >
> > Graham
> >
> >
>
>
Anonymous
November 14, 2004 3:57:10 AM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> Well I just pulled the master module and it looks like it has been modded..
> the 5532 in question seems to have been replaced with an LT1358, and some of
> the others were replaced with TLE2082's, along with some other components
> that were added. This console had 5 input channels modified by Audio
> Upgrades, it looks as if the master module has been modified as well...looks
> like I'll be calling Jim again.

Ok - I pulled up the spec sheet for the LT1358.

It's a kind of 'esoteric' device.

http://www.linear.com.cn/prod/datasheet.html?datasheet=...

I wouldn't put it in an audio path without careful evaluation.

Suggest you replace parts with originals ! They probably worked fine !

Then it might sound better.

Idiots who do unsubstantiated 'upgrades' should be shot. I believe you have
access to guns in the USA ? Just joking !


Graahm
Anonymous
November 14, 2004 3:57:11 AM

Archived from groups: rec.audio.pro (More info?)

I'll try that, but seeing as there are some cap and resistor replacements
and additions, non-stock jumpers, and other modifications, it seems the
opamp replacements are only part of the picture. I'll still would like to
contact the fellow who did the mod on Monday. (He's got 4 of the input
channels now, anyway, for a different reason).

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:4196AD66.D89669AA@hotmail.com...
>
>
> Matt Macchiarolo wrote:
>
> > Well I just pulled the master module and it looks like it has been
modded..
> > the 5532 in question seems to have been replaced with an LT1358, and
some of
> > the others were replaced with TLE2082's, along with some other
components
> > that were added. This console had 5 input channels modified by Audio
> > Upgrades, it looks as if the master module has been modified as
well...looks
> > like I'll be calling Jim again.
>
> Ok - I pulled up the spec sheet for the LT1358.
>
> It's a kind of 'esoteric' device.
>
> http://www.linear.com.cn/prod/datasheet.html?datasheet=...
>
> I wouldn't put it in an audio path without careful evaluation.
>
> Suggest you replace parts with originals ! They probably worked fine !
>
> Then it might sound better.
>
> Idiots who do unsubstantiated 'upgrades' should be shot. I believe you
have
> access to guns in the USA ? Just joking !
>
>
> Graahm
>
Anonymous
November 14, 2004 4:33:54 AM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> I'll try that,

Shooting him ? Yeah - might work.

> but seeing as there are some cap and resistor replacements
> and additions, non-stock jumpers, and other modifications, it seems the
> opamp replacements are only part of the picture. I'll still would like to
> contact the fellow who did the mod on Monday. (He's got 4 of the input
> channels now, anyway, for a different reason).

Hmmmmm !

I recommend restoring to original spec.

Looks like ppl have been fiddling without knowing their stuff.


Graham
Anonymous
November 14, 2004 2:33:07 PM

Archived from groups: rec.audio.pro (More info?)

"Matt Macchiarolo"
> For you op-amp experts I need some advice...
>
> Just got a new (old) mixing console, Peavey/AMR 2400, and there is a
> noticeable level of noise in the master module when I pull up the faders,
> even though there is no signal from any of the channels.


** Bet you have selected every mic channel simultaneously - right ?

Bet you have the monitor speakers next to your ears in a quiet room -
right ?

Bet you have a monitor amp with less than 1 volt input sensitivity -
right ?


Do I sound just a bit cynical ?????

Yep - cos I just spent hours, at the owners insistence, removing a faint
buzzing noise from a studio monitor amp that ONLY EXISTED when the input was
open circuit !!!!!





................. Phil
Anonymous
November 14, 2004 2:33:08 PM

Archived from groups: rec.audio.pro (More info?)

No, no and no. See the rest of this thread.

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2vnne3F2ntt8eU1@uni-berlin.de...
>
> "Matt Macchiarolo"
> > For you op-amp experts I need some advice...
> >
> > Just got a new (old) mixing console, Peavey/AMR 2400, and there is a
> > noticeable level of noise in the master module when I pull up the
faders,
> > even though there is no signal from any of the channels.
>
>
> ** Bet you have selected every mic channel simultaneously - right ?
>
> Bet you have the monitor speakers next to your ears in a quiet
om -
> right ?
>
> Bet you have a monitor amp with less than 1 volt input
nsitivity -
> right ?
>
>
> Do I sound just a bit cynical ?????
>
> Yep - cos I just spent hours, at the owners insistence, removing a
faint
> buzzing noise from a studio monitor amp that ONLY EXISTED when the input
was
> open circuit !!!!!
>
>
>
>
>
> ................ Phil
>
>
>
>
>
>
>
Anonymous
November 14, 2004 2:33:09 PM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> No, no and no. See the rest of this thread.

Don't bother abour Phil, he's our resident rodent / troll.

He loves to jump to conclusions based on everyone else being stupider than him
!

Some actually *are* but not many.


Regds, Graham
Anonymous
November 14, 2004 2:33:10 PM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:4196ABE2.FD8239CA@hotmail.com...
>
> Matt Macchiarolo wrote:
>
> > No, no and no. See the rest of this thread.
>
> Don't bother abour Phil, he's our resident rodent / troll.

Every group seems to have one.
Anonymous
November 14, 2004 2:33:11 PM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
> news:4196ABE2.FD8239CA@hotmail.com...
> >
> > Matt Macchiarolo wrote:
> >
> > > No, no and no. See the rest of this thread.
> >
> > Don't bother abour Phil, he's our resident rodent / troll.
>
> Every group seems to have one.

He's a classic !

Shame really since he's quite knowledgeable. Thing is - he has no
personal ...... errrrrr .. anything

No redeeming features. He just likes to pop shots at others.

Gets boring.

Anyway - I suggest you replace your ICs with the original parts
specified. It may sound better then.

You might also care to kick the arse of the bloke who sold it to you !

The schematics suggest it's one of Peavey's better consoles btw.



Graham
Anonymous
November 14, 2004 2:33:12 PM

Archived from groups: rec.audio.pro (More info?)

>
> You might also care to kick the arse of the bloke who sold it to you !
>
> The schematics suggest it's one of Peavey's better consoles btw.

No worries, I knew I would have to do some work on it. It was a great deal
so I really don't mind. Even with the noise, it sounds much better than the
Mackie 8-bus it replaced (flame suit on).
Anonymous
November 14, 2004 2:33:13 PM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> > You might also care to kick the arse of the bloke who sold it to you !
> >
> > The schematics suggest it's one of Peavey's better consoles btw.
>
> No worries, I knew I would have to do some work on it. It was a great deal
> so I really don't mind. Even with the noise, it sounds much better than the
> Mackie 8-bus it replaced (flame suit on).

LOL !

You won't find many Mackie fans here.

Except maybe for SRM 450s - I have to admit they don't sound bad ( oh, except
for the so-called mic pre ) . I guess RCF had something to do with that ?


Graham
Anonymous
November 14, 2004 2:33:14 PM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear wrote:

> Matt Macchiarolo wrote:
>
> > > You might also care to kick the arse of the bloke who sold it to you !
> > >
> > > The schematics suggest it's one of Peavey's better consoles btw.
> >
> > No worries, I knew I would have to do some work on it. It was a great deal
> > so I really don't mind. Even with the noise, it sounds much better than the
> > Mackie 8-bus it replaced (flame suit on).
>
> LOL !
>
> You won't find many Mackie fans here.
>
> Except maybe for SRM 450s - I have to admit they don't sound bad ( oh, except
> for the so-called mic pre ) . I guess RCF had something to do with that ?

Ooops !

I mean RCF made the SRM 450 sound good - didn't mean to infer anytrhing about the
mic pre-amp !

The SRM mic pre is abominable. Don't know why they ( Mackie ) bothered frankly !


Graham
Anonymous
November 14, 2004 2:33:15 PM

Archived from groups: rec.audio.pro (More info?)

Graham, I replaced U1 with a 5532 and there was no appreciable difference,
granted my test was just my ears. It's useable for now, I just need to get
it looked at before my next mix session.

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:4196B847.6B1773CE@hotmail.com...
>
>
> Pooh Bear wrote:
>
> > Matt Macchiarolo wrote:
> >
> > > > You might also care to kick the arse of the bloke who sold it to you
!
> > > >
> > > > The schematics suggest it's one of Peavey's better consoles btw.
> > >
> > > No worries, I knew I would have to do some work on it. It was a great
deal
> > > so I really don't mind. Even with the noise, it sounds much better
than the
> > > Mackie 8-bus it replaced (flame suit on).
> >
> > LOL !
> >
> > You won't find many Mackie fans here.
> >
> > Except maybe for SRM 450s - I have to admit they don't sound bad ( oh,
except
> > for the so-called mic pre ) . I guess RCF had something to do with that
?
>
> Ooops !
>
> I mean RCF made the SRM 450 sound good - didn't mean to infer anytrhing
about the
> mic pre-amp !
>
> The SRM mic pre is abominable. Don't know why they ( Mackie ) bothered
frankly !
>
>
> Graham
>
Anonymous
November 14, 2004 2:33:16 PM

Archived from groups: rec.audio.pro (More info?)

Matt Macchiarolo wrote:

> Graham, I replaced U1 with a 5532 and there was no appreciable difference,
> granted my test was just my ears. It's useable for now, I just need to get
> it looked at before my next mix session.

Kind of expected that ( as per previous posts ) .

Your bus noise is either thermally dominated ( resistor values that you can't
easily change throughout ) or op-amp input noise dominated. Would have to take a
few minutes to do the the calculations.

Are you sure that the result is unacceptable ?


Graham
Anonymous
November 14, 2004 2:33:16 PM

Archived from groups: rec.audio.pro (More info?)

In article <ruqdndJUNODXIQvcRVn-qg@comcast.com>,
Matt Macchiarolo <matt@nospamplease.com> wrote:
>Graham, I replaced U1 with a 5532 and there was no appreciable difference,
>granted my test was just my ears. It's useable for now, I just need to get
>it looked at before my next mix session.

Put the board on an extender and put an AM radio next to it. Is it causing
radio interference? If you got a scope, poke around on supply lines and
signal pins and look for something fuzzy.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
!