Home |
Search |
Today's Posts |
#1
|
|||
|
|||
schematic and prints for akg 451 pad?
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 |
#2
|
|||
|
|||
"Kurt Ballou" wrote in message om... 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 |
#3
|
|||
|
|||
Kurt Ballou 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." |
#4
|
|||
|
|||
|
#6
|
|||
|
|||
On Sat, 27 Nov 2004 09:34:44 -0800, "Richard Crowley"
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 ****er. 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 @/ |
#7
|
|||
|
|||
Frank Vuotto wrote:
On Sat, 27 Nov 2004 09:34:44 -0800, "Richard Crowley" 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 ****er. 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." |
#8
|
|||
|
|||
|
#9
|
|||
|
|||
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? |
#10
|
|||
|
|||
Frank Vuotto wrote:
On Sat, 27 Nov 2004 09:34:44 -0800, "Richard Crowley" 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 ****er. 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? |
#11
|
|||
|
|||
Kurt Ballou 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." |
#12
|
|||
|
|||
Kurt Albershardt 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 |
#13
|
|||
|
|||
Kurt Ballou 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. |
#14
|
|||
|
|||
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? |
#15
|
|||
|
|||
"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. |
#16
|
|||
|
|||
On Mon, 29 Nov 2004 21:40:01 -0800, "Richard Crowley"
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 @/ |
#17
|
|||
|
|||
Richard Crowley 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. |
#18
|
|||
|
|||
In article ,
Rob Reedijk wrote: Richard Crowley 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." |
#19
|
|||
|
|||
"Scott Dorsey" = public menace Kurt Ballou 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. ** There is no point in asking Dorsey *why* he believes this UTTER CRAP to be true - that would only produce even more and worse crap from this inexhaustible source of misinformation. It's time we had a word to describe rabid, know nothing capacitor paranoids like Dorsey . How about " Dielectraphobic " ??? I really recommend avoiding the things as much as possible, ** If Dorsey recommends something - then do the exact opposite ! but you can build one with a single NPO cap shunted across the capsule. ** NPO caps are ceramics and are * LEAKY* and *MICROPHONIC* !!!!!!! The only kind of caps that have low enough leakage to use for this job is polystyrene. A value of about 220 picofarads is needed for a -20 pad - connected from centre pin to case. 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. ** If Dorsey recommends something - then do the exact opposite ! But if the mike electronics are clipping, you're stuck. ** But you are * NOT * stuck with Dorsey's mad advice. ................ Phil |
#20
|
|||
|
|||
"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 |
#21
|
|||
|
|||
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 wrote in message . .. 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
|
|||
|
|||
On 30 Nov 2004 14:46:36 -0800, (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 wrote in message . .. 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 @/ |
#23
|
|||
|
|||
|
#24
|
|||
|
|||
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 wrote in message . .. On Mon, 29 Nov 2004 21:40:01 -0800, "Richard Crowley" 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 @/ |
#25
|
|||
|
|||
ok. plans are moving along to fabricate some pads. anyone know how
to dismantle a 451? |
#26
|
|||
|
|||
ok. plans are moving along to fabricate some pads. anyone know how
to dismantle a 451? |
#27
|
|||
|
|||
"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 |
#28
|
|||
|
|||
"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 |