schematic and prints for akg 451 pad?

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
24 answers Last reply
More about schematic prints
  1. 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."
  2. 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
  3. 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
  4. 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
    @/
  5. Archived from groups: rec.audio.pro (More info?)

    "Kurt Ballou" <godcity@aol.com> wrote in message
    news:d9baa238.0411262044.471b1b44@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
  6. 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."
  7. 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
  8. 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?
  9. 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?
  10. 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."
  11. 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
  12. 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.
  13. 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?
  14. 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.
  15. 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
    @/
  16. 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
    > @/
  17. 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
    >> @/
  18. 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.
  19. 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.
  20. 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."
  21. 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
    > @/
  22. 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
  23. Archived from groups: rec.audio.pro (More info?)

    ok. plans are moving along to fabricate some pads. anyone know how
    to dismantle a 451?
  24. 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
Ask a new question

Read More

Pro Audio Audio Schematic