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Noisy Behringer ADA8000 preamps

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Anonymous
July 14, 2005 7:39:54 PM

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

I just bought one of the Behringer ADA8000 converters. I hooked it up
to my Digi 002 via ADAT lightpipe. It worked and sounded good
until.... I turn the gain knob all the way up. I noticed that the
amount of noise was different on each channel, ie. channel 1 is really
noisy, channel 2 a little less, channel 6 is dead quiet, etc. If I use
external preamps the noise is inaudible, but if I'm hooking up a Shure
SM7b that needs a lot of gain, the noisier channels are a problem.

I started trying to diagnose the problem. I noticed that the amount of
noise changed when I moved the AC power cable from the ADA8000 around.
I am on the fourth floor in a warehouse in Chicago so RFI and noisy AC
lines are an issue. I use a furman power conditioner, but not one of
the expensive ones. Also, I noticed if I moved the ADA8000 away from
the Digi 002 the noise got quieter on Channel 1 which is the noisiest
channel. I noticed that the amount of noise increased on channel 1 if
I plugged in more mic cables to the ADA8000 inputs. So when I had 8
cables plugged in, the noise on Channel 1 was louder.

Is this problem typical of cheap gear and my circumstance, or do I have
a dud? Is it worth sending back or should I just use external pres?

Thanks for your help.
July 15, 2005 10:05:49 AM

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

I wonder if that could be noise from a switching power supply up in the
100's kHz range that gets aliased back down to the audio range.

Does it sound like hum or noise?

Can you post a recording of the noise?

Mark
Anonymous
July 15, 2005 10:58:05 AM

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

In article <1121380794.518936.285080@f14g2000cwb.googlegroups.com> jpanall@artic.edu writes:

> I just bought one of the Behringer ADA8000 converters. I hooked it up
> to my Digi 002 via ADAT lightpipe. It worked and sounded good
> until.... I turn the gain knob all the way up.

So, don't turn the gain knob all the way up. Sing louder. What do you
want for twenty five bucks a channel? A Neve and Lavry?


--
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
Related resources
Anonymous
July 15, 2005 12:32:33 PM

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

I would describe the noise as a hum, but not a straight 60 Hz hum. It
has way more harmonics and also some hiss. I did my test with the
inputs open, I did not short them. The rack is next to my computer.
There is a furman power conditioner, Digi 002, Presonus MP20 in the
rack. Also, I do have some unshielded speakers and a pioneer receiver
in the vicinity.

I have experienced problems in this space with an acoustic guitar
pickup also. Depending on where you stand and which way you face it
picks up noise. I'm guessing there is a lot of stuff to compete with.
There are power transformers just outside of the building. There is a
nearby cellphone relay tower and we used to pickup some radio station
on our practice PA.

I think the ADA8000 sounds great for the money when used at line level.
I was just baffled by the fact that the channels varied in noise level
with the gain cranked.

> So can we assume that by "noise" you mean specifically "power-
> line hum"?
>
> Otherwise, I think of white noise ("hiss") when people say "noise",
> whereas hum specifically is called "hum" (to avoid this kind of
> confusion).
>
> Were you performing your "test" with the inputs open? I'd be
> interested in finding what it sounds like with the inputs shorted
> (which is the usual method for this kind of test).
>
> Do you have it in a rack adjacent to any other equipment, or
> was it out in the free-air?
Anonymous
July 15, 2005 12:45:01 PM

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

<jpanall@artic.edu> wrote:
>
>Is this problem typical of cheap gear and my circumstance, or do I have
>a dud? Is it worth sending back or should I just use external pres?

No, it's just like that. It's mostly the result of poor circuit board
layout, I suspect. The ADA8000 appears to be very sensitive to stray
magnetic fields for one thing.

Whether you decide to take it back or use external preamps is your decision.
I had one for review for a bit, and I sent it back.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
July 15, 2005 3:28:36 PM

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

<jpanall@artic.edu> wrote in message
news:1121380794.518936.285080@f14g2000cwb.googlegroups.com...
>I just bought one of the Behringer ADA8000 converters. I hooked it up
> to my Digi 002 via ADAT lightpipe. It worked and sounded good
> until.... I turn the gain knob all the way up. I noticed that the
> amount of noise was different on each channel, ie. channel 1 is really
> noisy, channel 2 a little less, channel 6 is dead quiet, etc. If I use
> external preamps the noise is inaudible, but if I'm hooking up a Shure
> SM7b that needs a lot of gain, the noisier channels are a problem.
>
> I started trying to diagnose the problem. I noticed that the amount of
> noise changed when I moved the AC power cable from the ADA8000 around.
> I am on the fourth floor in a warehouse in Chicago so RFI and noisy AC
> lines are an issue. I use a furman power conditioner, but not one of
> the expensive ones. Also, I noticed if I moved the ADA8000 away from
> the Digi 002 the noise got quieter on Channel 1 which is the noisiest
> channel. I noticed that the amount of noise increased on channel 1 if
> I plugged in more mic cables to the ADA8000 inputs. So when I had 8
> cables plugged in, the noise on Channel 1 was louder.
>
> Is this problem typical of cheap gear and my circumstance, or do I have
> a dud? Is it worth sending back or should I just use external pres?
>
> Thanks for your help.
>

I have 2 of these, and only use the line ins. The amount of noise on the mic
pres varies from Channel to Channel here too, so it's probably not a fault -
more likely cheap power supply / grounding? Not sure.

The Mic pres aren't as "Invisible" as they'd have us believe. Still, a
pretty cheap way of adding I/O via ADAT.

Good luck!

Geoff
Anonymous
July 15, 2005 3:28:37 PM

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

jpanall wrote ...
>I just bought one of the Behringer ADA8000 converters. I hooked it up
> to my Digi 002 via ADAT lightpipe. It worked and sounded good
> until.... I turn the gain knob all the way up. I noticed that the
> amount of noise was different on each channel, ie. channel 1 is really
> noisy, channel 2 a little less, channel 6 is dead quiet, etc. If I use
> external preamps the noise is inaudible, but if I'm hooking up a Shure
> SM7b that needs a lot of gain, the noisier channels are a problem.
>
> I started trying to diagnose the problem. I noticed that the amount of
> noise changed when I moved the AC power cable ....

So can we assume that by "noise" you mean specifically "power-
line hum"?

Otherwise, I think of white noise ("hiss") when people say "noise",
whereas hum specifically is called "hum" (to avoid this kind of
confusion).

Were you performing your "test" with the inputs open? I'd be
interested in finding what it sounds like with the inputs shorted
(which is the usual method for this kind of test).

Do you have it in a rack adjacent to any other equipment, or
was it out in the free-air?
Anonymous
July 15, 2005 3:28:38 PM

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

"Richard Crowley" <richard.7.crowley@intel.com> wrote in
message
news:D b738o$biu$1@news01.intel.com
> jpanall wrote ...

>> I just bought one of the Behringer ADA8000 converters. I
>> hooked it up to my Digi 002 via ADAT lightpipe. It
worked
>> and sounded good until.... I turn the gain knob all the
way
>> up. I noticed that the amount of noise was different on
each
>> channel, ie. channel 1 is really noisy, channel 2 a
little
>> less, channel 6 is dead quiet, etc. If I use external
>> preamps the noise is inaudible, but if I'm hooking up a
Shure
>> SM7b that needs a lot of gain, the noisier channels are a
>> problem.

>> I started trying to diagnose the problem. I noticed that
the
>> amount of noise changed when I moved the AC power cable
.....

> So can we assume that by "noise" you mean specifically
"power-
> line hum"?

> Otherwise, I think of white noise ("hiss") when people say
> "noise", whereas hum specifically is called "hum" (to
avoid
> this kind of confusion).

> Were you performing your "test" with the inputs open? I'd
be
> interested in finding what it sounds like with the inputs
> shorted (which is the usual method for this kind of test).

> Do you have it in a rack adjacent to any other equipment,
or
> was it out in the free-air?

This story mystifies me. I'm front-ending my 02R96 with a
pair of ADA8000s, and they just work. I have a friend who
also has a pair of ADA8000s that he uses with his DDX3216
and they work just fine for him.

Then, there's the published experiences and tests of the
AudioRail boys who are happy with theirs, and recommend them
to their customers -
http://audiorail.home.comcast.net/ADA8000.htm This includes
an analysis comparing the distortion and noise performance
of various channel pairs
http://audiorail.home.comcast.net/ADA8000_RMAA_noise.gi... .
In short, the channels match within 2 dB or better for noise
performance.

How do ADA8000's most obviously reveal their humble origins?

(1) Their mic inputs only have a 50 dB gain range.

(2) Their mic inputs can only handle +6 dBu without
clipping.

Millenia and Great River are not shaking in their boots, but
the ADA8000 are pro grade and respectible performers,
particularly for the price. In terms of actual measured
performance, we know a lot more about the ADA8000 than the
high end mic preamps I just jokingly compared them to.
Anonymous
July 15, 2005 3:28:39 PM

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

Arny Krueger wrote:

> How do ADA8000's most obviously reveal their humble origins?
> ....................
>
> (2) Their mic inputs can only handle +6 dBu without
> clipping.

That's awful. My totally standard Studiomaster designs handle more than
that and we don't even call the mic pre by any fancy name !

Graham
Anonymous
July 15, 2005 3:28:40 PM

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

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote
in
message news:42D78B15.BB12E9DB@hotmail.com
> Arny Krueger wrote:
>
>> How do ADA8000's most obviously reveal their humble
origins?
>> ....................
>>
>> (2) Their mic inputs can only handle +6 dBu without
>> clipping.

> That's awful. My totally standard Studiomaster designs
handle
> more than that and we don't even call the mic pre by any
fancy
> name !

Its the sort of thing that one can handle easily if they
have a few mic attenuators about. I do - from my Mackie
days.

Well, they get credit for admiting it right up front in the
product specs.

I wonder what this number is specified to be for other mic
preamps.
Anonymous
July 15, 2005 3:28:41 PM

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

"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:if2dnSyzgdMRE0rfRVn-2Q@comcast.com
> "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote
> in
> message news:42D78B15.BB12E9DB@hotmail.com
>> Arny Krueger wrote:

>>> How do ADA8000's most obviously reveal their humble
origins?
>>> ....................

>>> (2) Their mic inputs can only handle +6 dBu (at 10 dB
gain) without
>>> clipping.

What is not specified is clipping point at unity gain which
could be as much as +16 dBu.

>> That's awful. My totally standard Studiomaster designs
handle
>> more than that and we don't even call the mic pre by any
fancy
>> name !

> Its the sort of thing that one can handle easily if they
> have a few mic attenuators about. I do - from my Mackie
> days.

> Well, they get credit for admiting it right up front in
the
> product specs.

> I wonder what this number is specified to be for other mic
> preamps.

Answering my own question -

http://www.mil-media.com/docs/products/hv3c.shtml

MAXIMUM INPUT LEVEL 20 Hz - 40 kHz+23 dBu*

and the asterisk says:

* Approximately equivalent to the output of a B&K 4012
microphone in a 145 dB SPL soundfield.


http://www.mackie.com/pdf/onyx1220_om.pdf

MAXIMUM INPUT LEVEL

Mic input +21dB at unity gain

http://www.gracedesign.com/products/801/model801.htm

-not specified-

http://www.greatriverelectronics.com/mp2nvlrg.html

-not specified-
Anonymous
July 15, 2005 3:46:34 PM

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

<jpanall@artic.edu> wrote in message
news:1121441553.628785.57980@g43g2000cwa.googlegroups.com

> I would describe the noise as a hum, but not a straight 60
Hz
> hum. It has way more harmonics and also some hiss. I did
my
> test with the inputs open, I did not short them.

That is frankly an open-circuit test which is an irrelevant
test, see below. The *real* test involves plugging in an XLR
connector with a say a 150 ohm resistor soldered from pins
2 to 3.

A mic will source the preamps mic input with a similar
impedance in actual use. However the mic may come with a lot
of baggage you don't want to include in a test of just the
preamp.

>The rack is next to my computer. There is a furman power
conditioner, Digi
> 002, Presonus MP20 in the rack. Also, I do have some
> unshielded speakers and a pioneer receiver in the
vicinity.

You might want to rearrange the order of the contents of the
rack.

> I have experienced problems in this space with an acoustic
> guitar pickup also.

OK, so you have a lot of stray magnetic fields. Not good.

> I think the ADA8000 sounds great for the money when used
at
> line level. I was just baffled by the fact that the
channels
> varied in noise level with the gain cranked.

On this unit, the line level inputs go through the same
electronics as the mic inputs. Farily typical for low and
medium priced mic preamps with line inputs. The difference
is that there is an attenuator complete with built-in source
impedance is hooked up when you use the line input. It might
be that simply plugging a unwired TRS connector into each
line input would give you a more real-world test, if its too
much to wire up a few mic simulators-terminators.
Anonymous
July 15, 2005 7:27:02 PM

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

jpanall wrote ...
> I have experienced problems in this space with an acoustic guitar
> pickup also. Depending on where you stand and which way you face it
> picks up noise. I'm guessing there is a lot of stuff to compete with.
> There are power transformers just outside of the building. There is
> a
> nearby cellphone relay tower and we used to pickup some radio station
> on our practice PA.

So you are "testing" it open-circuit (a mostly meaningless
exercise) in a known bad location. That is one equation and
two unknowns, good luck solving THAT problem.
Anonymous
July 15, 2005 7:59:20 PM

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

<jpanall@artic.edu> wrote in message
news:1121441553.628785.57980@g43g2000cwa.googlegroups.com...
> I would describe the noise as a hum, but not a straight 60 Hz hum. It
> has way more harmonics and also some hiss. I did my test with the
> inputs open, I did not short them. The rack is next to my computer.
> There is a furman power conditioner, Digi 002, Presonus MP20 in the
> rack. Also, I do have some unshielded speakers and a pioneer receiver
> in the vicinity.

Well, that's a different story. How the thing performs with nothing in the
input is really not relevant...try this: make up a dummy plug by soldering a
150-ohm resistor, preferably metal film, between pins 2 & 3, then test the
noise performance of the various channels with that plugged into each one
successively. I think you'll find it's a lot quieter.

> I think the ADA8000 sounds great for the money when used at line level.
> I was just baffled by the fact that the channels varied in noise level
> with the gain cranked.

If they're picking up radio-frequency interference (RFI) from that cell
tower or a nearby UHF station, the level of RFI will vary from place to
place, and two inputs an inch or two apart will pick up different amounts of
crud. No joke -- in a bad RFI situation, I've found moving a wire an inch
can change the level from acceptable to atrocious. Plus they're different
distances from the power supply.

Still, none of that means anything unless something's plugged in.

Peace,
Paul
Anonymous
July 15, 2005 10:42:07 PM

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

In article <1121441553.628785.57980@g43g2000cwa.googlegroups.com> jpanall@artic.edu writes:

> I would describe the noise as a hum, but not a straight 60 Hz hum. It
> has way more harmonics and also some hiss. I did my test with the
> inputs open, I did not short them.

That's really pretty meaningless. Make yourself a "dummy microphone"
by putting a jumper between pins 2 and 3 of an XLR plug and check the
noise and hum level with that plugged into the input. I suspect that
much of the hiss will go away. The hum with harmonics may not.

> I have experienced problems in this space with an acoustic guitar
> pickup also. Depending on where you stand and which way you face it
> picks up noise.

Par for the course. Turn off your computer, or at least turn off your
monitor.


--
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
July 16, 2005 12:00:17 PM

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

jpanall@artic.edu wrote:

> I would describe the noise as a hum, but not a straight 60 Hz hum. It
> has way more harmonics and also some hiss.

If that product uses an SMPS ( is it 'universal voltage' ? ) it might be
pickup from that. The UB series mixers use an SMPS contoller the modulates
the switching frequency and can cause audible 'hum'. Maybe the same here ?


> I did my test with the
> inputs open, I did not short them.

Big mistake.

Your test method is invalid since it is not how the product is meant to be
used.

Now repeat with a 150 or 200 ohm resistor between pins 2 and 3 of the XLR
inputs.

Graham
Anonymous
July 16, 2005 5:33:09 PM

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

"Paul Stamler"
>
> Well, that's a different story. How the thing performs with nothing in the
> input is really not relevant...try this: make up a dummy plug by soldering
> a
> 150-ohm resistor, preferably metal film, between pins 2 & 3, then test the
> noise performance .....


** Why prefer a metal film resistor - Paul ??????

Do you expect thermal noise to vary from one type of resistor to another
????

That would contradict the laws of physics.

Maybe Paul Stamler thinks the earth is flat too - to keep in character.

He obviously thinks he can get away with publishing a pack of ridiculous
lies about capacitor ESR and self inductance.

What an arrogant cretin.



............ Phil
Anonymous
July 16, 2005 5:33:10 PM

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

Somebody put Phil back on his meds.
Please...



On 7/15/05 11:33 PM, in article 3jrdfmFm88hnU1@individual.net, "Phil
Allison" <philallison@tpg.com.au> wrote:

> Maybe Paul Stamler thinks the earth is flat too - to keep in character.
>
> He obviously thinks he can get away with publishing a pack of ridiculous
> lies about capacitor ESR and self inductance.
>
> What an arrogant cretin.
>
>
>
> ........... Phil
>
>
Anonymous
July 16, 2005 7:07:10 PM

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

"Phil Allison" <philallison@tpg.com.au> wrote in
news:3jrdfmFm88hnU1@individual.net:

>
> "Paul Stamler"
>>
>> Well, that's a different story. How the thing performs with
>> nothing in the input is really not relevant...try this: make
>> up a dummy plug by soldering a
>> 150-ohm resistor, preferably metal film, between pins 2 & 3,
>> then test the noise performance .....
>
>
> ** Why prefer a metal film resistor - Paul ??????
>
> Do you expect thermal noise to vary from one type of resistor
> to another ????
>
> That would contradict the laws of physics.

Thermal noise is not the only contributing factor in resistors.
It usually is the **dominant** factor, but some resistor
constructions, e.g. thick film on certain substrates, show
higher noise than the theory would suggest.


--
Bob Quintal

PA is y I've altered my email address.
Anonymous
July 16, 2005 7:07:11 PM

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

Bob Quintal <rquintal@sPAmpatico.ca> wrote:
>"Phil Allison" <philallison@tpg.com.au> wrote in
>>
>> ** Why prefer a metal film resistor - Paul ??????
>>
>> Do you expect thermal noise to vary from one type of resistor
>> to another ????
>>
>> That would contradict the laws of physics.
>
>Thermal noise is not the only contributing factor in resistors.
>It usually is the **dominant** factor, but some resistor
>constructions, e.g. thick film on certain substrates, show
>higher noise than the theory would suggest.

Shot noise on carbon comp resistors is high enough that it's often
much greater than the thermal noise.

There is a discussion of this in Molchenbacher's classic _Low Noise
Electronic Design_ text. He goes into the various mechanisms of
shot noise in resistors in great detail.

The disadvantage of metal films is that you can't visually tell when
they fail. Carbon comps will often go up in a big cloud of smoke,
easily indicating where the overcurrent condition is. Metal films just
go quietly open.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
July 16, 2005 7:49:39 PM

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

"SSJVCmag"


** Can't use a toilet or a tree like most folk - this cretin has to
publicly piss in people's pockets instead.


How gross.



.............. Phil
Anonymous
July 17, 2005 5:06:37 PM

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

"Bob Quintal"
> "Phil Allison"
> "Paul Stamler"
>>>
>>> Well, that's a different story. How the thing performs with
>>> nothing in the input is really not relevant...try this: make
>>> up a dummy plug by soldering a
>>> 150-ohm resistor, preferably metal film, between pins 2 & 3,
>>> then test the noise performance .....
>>
>>
>> ** Why prefer a metal film resistor - Paul ??????
>>
>> Do you expect thermal noise to vary from one type of resistor
>> to another ????
>>
>> That would contradict the laws of physics.
>
> Thermal noise is not the only contributing factor in resistors.
> It usually is the **dominant** factor, but some resistor
> constructions, e.g. thick film on certain substrates, show
> higher noise than the theory would suggest.


** Not without a voltage to excite that noise.

The ONLY noise possible with NO voltage applied is thermal.



........... Phil
Anonymous
July 17, 2005 5:09:25 PM

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

"Scott Dorsey"

> Shot noise on carbon comp resistors is high enough that it's often
> much greater than the thermal noise.


** Not when used as a dummy load on a mic input.

Or any situation where there is no significant voltage across the resistor.

Pay attention to the context - dickhead.


.......... Phil
Anonymous
July 27, 2005 12:55:23 PM

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

On Tue, 26 Jul 2005 11:05:21 -0400, jpanall@artic.edu wrote
(in article <1122390321.532555.214320@o13g2000cwo.googlegroups.com>):

> Anyone have any idea what is causing this. If you listen close you can hear
> it slowly flanging.



Sounds like there's a light on a residential grade dimmer. Oh, you said
elevator shaft, how close ARE you to it?

Plug all of your gear into one outlet and see if the noise goes away.

Ty Ford



-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com
!