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schematic and prints for akg 451 pad?

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Anonymous
November 26, 2004 11:44:00 PM

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

there seems to be a big shortage of -20db pads for 451's out there.
especially now that everyone is jumping on the lollipop bandwagon.
i'm suprised the BLUE hasn't started offering pads. i've been
searching for a couple of -20db pads for a couple of years now with no
luck, so i'm thinking of building a bunch myself. my dad is a
machinist who can take care of the metal work. i just need to figure
out what's going on inside. i think it's just a couple of resistors.
does anyone have a schematic, blue print, words of advice, one i could
borrow and reverse engineer, etc?
thanks
kurt
Anonymous
November 27, 2004 11:07:29 AM

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

Kurt Ballou <godcity@aol.com> wrote:
>there seems to be a big shortage of -20db pads for 451's out there.
>especially now that everyone is jumping on the lollipop bandwagon.
>i'm suprised the BLUE hasn't started offering pads. i've been
>searching for a couple of -20db pads for a couple of years now with no
>luck, so i'm thinking of building a bunch myself. my dad is a
>machinist who can take care of the metal work. i just need to figure
>out what's going on inside. i think it's just a couple of resistors.
>does anyone have a schematic, blue print, words of advice, one i could
>borrow and reverse engineer, etc?

It's a capacitive shunt. This is why it affects the sound so substantially.
I really recommend avoiding the things as much as possible, but you can
build one with a single NPO cap shunted across the capsule.

Note that a -20 dB pad on the CK1 is going to have much less than a -20 dB
drop on the BLUE capsules, since they have a larger area and therefore more
capacitance.

If there is any way you can pad down on the output instead of the input
of the electronics, THERE you can use a resistive pad which will have
much less of a sonic effect. But if the mike electronics are clipping,
you're stuck.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
November 27, 2004 2:28:57 PM

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

In article <d9baa238.0411262044.471b1b44@posting.google.com> godcity@aol.com writes:

> there seems to be a big shortage of -20db pads for 451's out there.
> especially now that everyone is jumping on the lollipop bandwagon.
> i'm suprised the BLUE hasn't started offering pads. i've been
> searching for a couple of -20db pads for a couple of years now with no
> luck, so i'm thinking of building a bunch myself. my dad is a
> machinist who can take care of the metal work.

Maybe you should offer your dad's services to BLUE. They said that the
reason why they didn't make pads (and swivels, too) was because the
machining was too expensive and a new one would cost too much. But if
you can get the machining for free, the rest is easy.

I think it's just a capacitor. If you were to send the mechanical
parts to BLUE, I'm sure they'd put the guts in there for a very
reasonable price and verify that it worked correctly.


--
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
November 27, 2004 2:28:58 PM

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

"Mike Rivers" <mrivers@d-and-d.com> wrote in message
news:znr1101562460k@trad...
>
> In article <d9baa238.0411262044.471b1b44@posting.google.com>
> godcity@aol.com writes:
>
>> there seems to be a big shortage of -20db pads for 451's out there.
>> especially now that everyone is jumping on the lollipop bandwagon.
>> i'm suprised the BLUE hasn't started offering pads. i've been
>> searching for a couple of -20db pads for a couple of years now with no
>> luck, so i'm thinking of building a bunch myself. my dad is a
>> machinist who can take care of the metal work.
>
> Maybe you should offer your dad's services to BLUE. They said that the
> reason why they didn't make pads (and swivels, too) was because the
> machining was too expensive and a new one would cost too much. But if
> you can get the machining for free, the rest is easy.
>
> I think it's just a capacitor. ...

The pads I have inspected (not an exhaustive survey, but a few)
look like they are simply small-value capacitors. Can't cost more
than a buck or two worth of components. All of the cost seems
to be in the low-volume mechanical components. Machining the
relatevly large-diameter, small-pitch threads would appear be the
tricky part
Anonymous
November 27, 2004 2:28:59 PM

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

On Sat, 27 Nov 2004 09:34:44 -0800, "Richard Crowley"
<rcrowley7@xprt.net> wrote:

>All of the cost seems
>to be in the low-volume mechanical components. Machining the
>relatevly large-diameter, small-pitch threads would appear be the
>tricky part
>

Those treads are a pisser. I have one mic that the capsule screws
smoothly into a pad and the pad smoothly into the body but to screw
the capsule directly into the body is next to impossible. I've tried a
few machine shops to see if someone could clean up the threads but no
one had any tap/die that size.


Frank /~ http://newmex.com/f10
@/
Anonymous
November 27, 2004 3:16:08 PM

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

"Kurt Ballou" <godcity@aol.com> wrote in message
news:D 9baa238.0411262044.471b1b44@posting.google.com...
> there seems to be a big shortage of -20db pads for 451's out there.
> especially now that everyone is jumping on the lollipop bandwagon.
> i'm suprised the BLUE hasn't started offering pads. i've been
> searching for a couple of -20db pads for a couple of years now with no
> luck, so i'm thinking of building a bunch myself. my dad is a
> machinist who can take care of the metal work. i just need to figure
> out what's going on inside. i think it's just a couple of resistors.
> does anyone have a schematic, blue print, words of advice, one i could
> borrow and reverse engineer, etc?
> thanks
> kurt


If the electronic part of it is that simple, building a couple of resistors
and a tiny switch into the body might be less complex a task. Squeezing a
few parts onto the pcb should be far easier than any metalwork.

Predrag
Anonymous
November 27, 2004 6:11:50 PM

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

Frank Vuotto <deepthrob@hotmail.com> wrote:
>On Sat, 27 Nov 2004 09:34:44 -0800, "Richard Crowley"
><rcrowley7@xprt.net> wrote:
>
>>All of the cost seems
>>to be in the low-volume mechanical components. Machining the
>>relatevly large-diameter, small-pitch threads would appear be the
>>tricky part
>
>Those treads are a pisser. I have one mic that the capsule screws
>smoothly into a pad and the pad smoothly into the body but to screw
>the capsule directly into the body is next to impossible. I've tried a
>few machine shops to see if someone could clean up the threads but no
>one had any tap/die that size.

I don't think you can make taps and dies like that, not if you want them
to last long at all. A good shop should be able to chase the threads
on a lathe but they're going to need a small precision lathe because a
typical engine lathe won't do threads that fine.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
November 27, 2004 9:48:26 PM

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

In article <10qhelmgaepjad1@corp.supernews.com> rcrowley7@xprt.net writes:

> Machining the
> relatevly large-diameter, small-pitch threads would appear be the
> tricky part

That's correct. If they had used pipe threads, they'd be cheap. <g>



--
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 28, 2004 12:54:32 AM

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

the threads can be cut on a lathe or a milling machine with a 4th
axis. i'm sure dad would whip me up a few for free, but any sort of
volume production couldn't be done cheaply.
any idea how much attenuation different capacitor values would have?
and how are they wired?
Anonymous
November 28, 2004 1:51:52 AM

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

Frank Vuotto wrote:
> On Sat, 27 Nov 2004 09:34:44 -0800, "Richard Crowley"
> <rcrowley7@xprt.net> wrote:
>
>
>> All of the cost seems
>> to be in the low-volume mechanical components. Machining the
>> relatevly large-diameter, small-pitch threads would appear be the
>> tricky part
>
>
>
> Those treads are a pisser. I have one mic that the capsule screws
> smoothly into a pad and the pad smoothly into the body but to screw
> the capsule directly into the body is next to impossible. I've tried a
> few machine shops to see if someone could clean up the threads but no
> one had any tap/die that size.

That's why they changed the design for the C460/C480 series.

Skipper or Martens (if you're listening) why no lollipops for the newer bodies?
Anonymous
November 28, 2004 11:53:54 AM

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

Kurt Ballou <godcity@aol.com> wrote:
>the threads can be cut on a lathe or a milling machine with a 4th
>axis. i'm sure dad would whip me up a few for free, but any sort of
>volume production couldn't be done cheaply.

Show him the threads. If he's got an old West Bend, you're going to
be out of luck cutting them, I bet. But on a precision lathe it should
be not too big a deal.

>any idea how much attenuation different capacitor values would have?
>and how are they wired?

They are wired parallel to the capsule, and the degree of attenuation
depends on the capacitance of the capsule. If the capsule has 22 pF
between diaphragm and stator, then a 22 pF shunt will halve the output.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
November 28, 2004 7:36:21 PM

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

Kurt Albershardt <kurt@nv.net> wrote:

> Skipper or Martens (if you're listening) why no lollipops for the newer
> bodies?

Bet the monsoon of cheapie import LDC's compared to the number of 480
users out there makes it a risky financial undertaking (so to speak...).

Hell, why not offer one that rides on a CMC6?

--
ha
Anonymous
November 29, 2004 11:12:48 PM

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

Kurt Ballou <godcity@aol.com> wrote:
> there seems to be a big shortage of -20db pads for 451's out there.
> especially now that everyone is jumping on the lollipop bandwagon.
> i'm suprised the BLUE hasn't started offering pads. i've been
> searching for a couple of -20db pads for a couple of years now with no
> luck, so i'm thinking of building a bunch myself. my dad is a
> machinist who can take care of the metal work. i just need to figure
> out what's going on inside. i think it's just a couple of resistors.
> does anyone have a schematic, blue print, words of advice, one i could
> borrow and reverse engineer, etc?
> thanks

It's a good point about getting BLUE to do it since they have already
got some of the machining in place.

But I would be hesitant about using the pads since the connection of
the capsule to the body is a big weak point in the 451. This is a great
source of noise, and you may be adding more. (Though presumably if you
need to pad it down, noise won't be a problem?).

I would also think that it is difficult to create these things since
the body is what conducts the ground and it limits the type of pads
that can be designed. And no matter what, you will have trouble with
how the shunt resistor connects to the body in the pad.

I am not an EE, so, please feel free to shoot me down!

Rob R.
Anonymous
November 29, 2004 11:12:49 PM

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

Rob Reedijk wrote:
>
> It's a good point about getting BLUE to do it since they have already
> got some of the machining in place.
>
> But I would be hesitant about using the pads since the connection of
> the capsule to the body is a big weak point in the 451. This is a great
> source of noise, and you may be adding more.

Which reminds me: I'd like to leave the A60M thread adapters on my B6's semi-permanently so they threads don't get mangled. I'd much prefer that they unscrew from the C460B amplifiers since those threads are much less subject to damage.

Is there a conductive equivalent to locktite?
Anonymous
November 30, 2004 12:40:01 AM

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

"Rob Reedijk" wrote ...
> I would also think that it is difficult to create these things since
> the body is what conducts the ground and it limits the type of pads
> that can be designed. And no matter what, you will have trouble with
> how the shunt resistor connects to the body in the pad.

All the pads I've seen are simply a single capacitor in
series with the signal path. No connection to the shell.
Anonymous
November 30, 2004 2:33:06 AM

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

On Mon, 29 Nov 2004 21:40:01 -0800, "Richard Crowley"
<rcrowley7@xprt.net> wrote:
>
>All the pads I've seen are simply a single capacitor in
>series with the signal path. No connection to the shell.
>

As I recently mentioned, I have a 451 with problem threads. Works
with a pad and not without one. Today I disassembled a -10 db pad and
disconnect the cap, I took pictures and posted them, linked on the
bottom of my floobydust page.

http://www7.taosnet.com/f10/floobydust.htm


The 75pf clearly goes from the center post to the case.


Frank /~ http://newmex.com/f10
@/
Anonymous
November 30, 2004 5:46:36 PM

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

The fine threads on the 451's are a continuing problem, we have
several what have damaged threads and are being heldn together with
tape.

Frank, I noticed in your annotation to the photos you marked the
centre piller has bein a switch of some sort. I thought it was jut
spring loaded to make a good contact.

Also in the recordings I make (classical music) it more a problem of
getting enought gain, and not too much noise, I've never used even a
-10dB pad.

Peter.


Frank Vuotto <deepthrob@hotmail.com> wrote in message news:<0d4oq0h7a8apv123dk9p37ak6lqjlar6ak@4ax.com>...

>
> As I recently mentioned, I have a 451 with problem threads. Works
> with a pad and not without one. Today I disassembled a -10 db pad and
> disconnect the cap, I took pictures and posted them, linked on the
> bottom of my floobydust page.
>
> http://www7.taosnet.com/f10/floobydust.htm
>
>
> The 75pf clearly goes from the center post to the case.
>
>
> Frank /~ http://newmex.com/f10
> @/
Anonymous
November 30, 2004 7:30:06 PM

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

On 30 Nov 2004 14:46:36 -0800, peter.bell@cisra.canon.com.au (Peter
Bell) wrote:

>The fine threads on the 451's are a continuing problem, we have
>several what have damaged threads and are being heldn together with
>tape.
>
>Frank, I noticed in your annotation to the photos you marked the
>centre piller has bein a switch of some sort. I thought it was jut
>spring loaded to make a good contact.
>
>Also in the recordings I make (classical music) it more a problem of
>getting enought gain, and not too much noise, I've never used even a
>-10dB pad.
>
>Peter.
>
>
>Frank Vuotto <deepthrob@hotmail.com> wrote in message news:<0d4oq0h7a8apv123dk9p37ak6lqjlar6ak@4ax.com>...
>
>>
>> As I recently mentioned, I have a 451 with problem threads. Works
>> with a pad and not without one. Today I disassembled a -10 db pad and
>> disconnect the cap, I took pictures and posted them, linked on the
>> bottom of my floobydust page.
>>
>> http://www7.taosnet.com/f10/floobydust.htm
>>
>>
>> The 75pf clearly goes from the center post to the case.
>>
>>
>> Frank /~ http://newmex.com/f10
>> @/
Anonymous
November 30, 2004 9:01:30 PM

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

Ooops, sorry about that blank post.

On 30 Nov 2004 14:46:36 -0800, peter.bell@cisra.canon.com.au (Peter
Bell) wrote:

>The fine threads on the 451's are a continuing problem, we have
>several what have damaged threads and are being heldn together with
>tape.
>

Tape never worked for me, the mics made that awful noise they make
when there is a bad contact ( ok Scott, that's your cue). The threads
inside the body were completely gone (flat) on one side. The
non-pad-pad is working great.

>Frank, I noticed in your annotation to the photos you marked the
>centre piller has bein a switch of some sort. I thought it was jut
>spring loaded to make a good contact.

No, it's not really a switch. The spring in the capsule pushes the
pillar into contact withe the 2 wires putting the cap across
(parallel) the capsule


>
>Also in the recordings I make (classical music) it more a problem of
>getting enought gain, and not too much noise, I've never used even a
>-10dB pad.
>

I may have to rig a switch for the pad cap because I sometimes use
these mics for drum overheads and they absolutly need to be padded
there.
Anonymous
November 30, 2004 10:22:17 PM

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

Richard Crowley <rcrowley7@xprt.net> wrote:
> "Rob Reedijk" wrote ...
>> I would also think that it is difficult to create these things since
>> the body is what conducts the ground and it limits the type of pads
>> that can be designed. And no matter what, you will have trouble with
>> how the shunt resistor connects to the body in the pad.

> All the pads I've seen are simply a single capacitor in
> series with the signal path. No connection to the shell.

Like I said, I am not an EE! I have seen Frank Vuotto's web photos of
the pad which confirms what you said.

But you still have an extra coupling on the ground path. And this ground
path is a weakness in the design.

Rob R.
Anonymous
November 30, 2004 10:22:18 PM

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

In article <coih99$564$1@news1.chem.utoronto.ca>,
Rob Reedijk <reedijk@hera.med.utoronto.ca> wrote:
>Richard Crowley <rcrowley7@xprt.net> wrote:
>> "Rob Reedijk" wrote ...
>>> I would also think that it is difficult to create these things since
>>> the body is what conducts the ground and it limits the type of pads
>>> that can be designed. And no matter what, you will have trouble with
>>> how the shunt resistor connects to the body in the pad.
>
>> All the pads I've seen are simply a single capacitor in
>> series with the signal path. No connection to the shell.
>
>Like I said, I am not an EE! I have seen Frank Vuotto's web photos of
>the pad which confirms what you said.
>
>But you still have an extra coupling on the ground path. And this ground
>path is a weakness in the design.

Sure, but there are so many other things wrong with it that the issue is
fairly academic.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
December 1, 2004 1:06:53 AM

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

frank,
thanks so much for the pics. very helpful. any idea what cap value
for approx -20 or -30 db?
also, can you describe the switch? it is spring loaded? is that
really a switch, or is it just something that assures good contact?
thanks
kurt


Frank Vuotto <deepthrob@hotmail.com> wrote in message news:<0d4oq0h7a8apv123dk9p37ak6lqjlar6ak@4ax.com>...
> On Mon, 29 Nov 2004 21:40:01 -0800, "Richard Crowley"
> <rcrowley7@xprt.net> wrote:
> >
> >All the pads I've seen are simply a single capacitor in
> >series with the signal path. No connection to the shell.
> >
>
> As I recently mentioned, I have a 451 with problem threads. Works
> with a pad and not without one. Today I disassembled a -10 db pad and
> disconnect the cap, I took pictures and posted them, linked on the
> bottom of my floobydust page.
>
> http://www7.taosnet.com/f10/floobydust.htm
>
>
> The 75pf clearly goes from the center post to the case.
>
>
> Frank /~ http://newmex.com/f10
> @/
Anonymous
December 1, 2004 10:18:58 AM

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

"Scott Dorsey"
>
> Sure, but there are so many other things wrong with it that the issue is
> fairly academic.


** If Dorsey recommends something - then do the exact opposite.




.............. Phil
Anonymous
December 2, 2004 8:18:27 PM

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

ok. plans are moving along to fabricate some pads. anyone know how
to dismantle a 451?
Anonymous
December 3, 2004 4:58:23 PM

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

"Kurt Ballou"
>
> ok. plans are moving along to fabricate some pads. anyone know how
> to dismantle a 451?


** No need to dismantle it for what you are doing.

Anyhow, IIRC there is a internal clip ring holding the XLR base in place.

Remove it and the whole guts slides out.





................ Phil
!