I'm looking for some discarded MXL V63M Circuit Boards

Hey all.

I've got a few doner mics laying around I'm going to do up for my son, and some friends. Please lmk if you've got some boards laying around I could use. I believe the MXL V63M, V57M,  V250, and 2006 are all the same. 

In any case...  Please Message me. I'm in New York. 

Thanks!

E.

I feel your pain, man. I wish Poctop or someone would make available an easily-purchasable transformerless Schoeps circuit DIY board for folks who like tinkering with the lowly Schoeps circuit. It's getting harder to find donor mics with them and I'd rather build one on a brand new board than de-populate and rebuild one on an old MXL or CAD mic board. I know Scott Dorsey still has PCB's for sale, but for his own reasons he only takes payment via a paper check by mail.

http://microphone-parts.com/collections/all/products/mp-v57-pcb-kit

Disregarding the obscene price, i guess something like that is what you're looking for?

Khron said:

http://microphone-parts.com/collections/all/products/mp-v57-pcb-kit

Disregarding the obscene price, i guess something like that is what you're looking for?

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Yes that is obscene.  Thanks tho.

Wordsushi said:

I feel your pain, man. I wish Poctop or someone would make available an easily-purchasable transformerless Schoeps circuit DIY board for folks who like tinkering with the lowly Schoeps circuit. It's getting harder to find donor mics with them and I'd rather build one on a brand new board than de-populate and rebuild one on an old MXL or CAD mic board. I know Scott Dorsey still has PCB's for sale, but for his own reasons he only takes payment via a paper check by mail.

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Thanks for the tip! 

Wordsushi said:

I feel your pain, man. I wish Poctop or someone would make available an easily-purchasable transformerless Schoeps circuit DIY board for folks who like tinkering with the lowly Schoeps circuit. It's getting harder to find donor mics with them and I'd rather build one on a brand new board than de-populate and rebuild one on an old MXL or CAD mic board. I know Scott Dorsey still has PCB's for sale, but for his own reasons he only takes payment via a paper check by mail.

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Don't want to promise anything, because it will take me some time, but i think about few kits
Schoeps style circuit with some functional options is on the list.
Something à la KM84 topology for LDC is also on the list, but this one would be different than Poctop version, because it will be made with additional DC converter for higher polarisation voltage as also multi-pattern use.
Anyway i need some time for that

Khron said:

http://microphone-parts.com/collections/all/products/mp-v57-pcb-kit

Disregarding the obscene price, i guess something like that is what you're looking for?

Click to expand...

I think about much cheaper version but definately high quality

ln76d said:

Don't want to promise anything, because it will take me some time, but i think about few kits
Schoeps style circuit with some functional options is on the list.
Something à la KM84 topology for LDC is also on the list, but this one would be different than Poctop version, because it will be made with additional DC converter for higher polarisation voltage as also multi-pattern use.
Anyway i need some time for that

I think about much cheaper version but definately high quality

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Please, please, pretty please. That would be awesome. I would totally buy a Schoeps kit. Possibly several. Even if you just had the PCB's for sale.

If someone were to give me a the measurements of the boards and screw placement, I'd be happy to do a layout and share it on OshPark for the basic Schoeps circuit.

midwayfair said:

If someone were to give me a the measurements of the boards and screw placement, I'd be happy to do a layout and share it on OshPark for the basic Schoeps circuit.

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That would be great!

Does this help? Mic Parts has a template sized out to fit the V63 and other mics that use the same board. It also has a second pair of screw holes to fit the smaller Apex 435 size body format.

http://cdn.microphone-parts.com/shopify/mp/MPV57-dimensions.pdf

Wordsushi said:

That would be great!

Does this help? Mic Parts has a template sized out to fit the V63 and other mics that use the same board. It also has a second pair of screw holes to fit the smaller Apex 435 size body format.

http://cdn.microphone-parts.com/shopify/mp/MPV57-dimensions.pdf

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That's perfect. I'll try to have it done by February. Putting out a few fires at the moment.

midwayfair said:

That's perfect. I'll try to have it done by February. Putting out a few fires at the moment.

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Thank you, Midwayfair!

The easy part, drawing the schematics, is done. I added a couple small modifications:

R10 and C10 are in part as a concession to the fact that we can't get 50V 470uF capacitors inside a microphone, and the extra filtering stage makes up for the much smaller cap on the 35V supply.

The 10pF in the oscillator is just because people are more likely to have that and it works just the same.

R5 & R6: I'm not 100% sure on the values. The reason for them is to allow for corrective EQ for the capsule. Right now the values are just placeholders. This actually works better if it's a shelf EQ rather than a straight cut, in which case C5 might turn into a resistor and get disconnected from the collectors. We just want to bring the 10K down some, not cut everything above it. AudioImprov has a post about corrective EQ with excellent ideas. He also points out that C4 and C5 are actually detrimental. In any case, I've drawn them into the existing schematic so that all the original stuff is there and the changes are obvious.

I'm not sure if you want me to get fancy at all, but it would be very easy to add a single resistor from the junctions of C2/R5 and C3/R6 with pads for a switch so you can make a high-pass filter. I've used this on several builds of the Alice mic with good results. It would also be trivial to add an omni switch, but you really don't need pads for that (just route the capsule connection through the switch lugs.)

There's a bit more filtering in the oscillator schematic than the original.

Finally, these will be on two different boards. There are a few reasons for this: One is that this schematic will work for the Alice mic circuit. Another reason is that you have the option of using a different oscilllator board with minimal changes, or not use an oscillator at all. If I have room on the board (it's already going to be very tight), I will try to get capsule bias resistors on this PCB so that it could be built with only one PCB.

The transistors part numbers in the main mic can change. They're just the packages in my version of Eagle.

Once I've got the PCB layout drafted, I'll post a mask here for some critique. I'm actually thinking I should start a new thread, though. I'd like to just make the Eagle files available so people can make modifications to this very popular circuit. I might also do an open source layout for the generic FET+buffer+transformer circuitboards, like what's in the MXL v67g. Since these are common mod projects, I think it would be nice if there was a straight-up replacement PCB with basic common mods implementable that anyone can pick up, in part in case they completely bugger the existing circuitboard in a mic they're modding.

Dude! Thank you so much for taking the time to do this. This looks great! I would totally be into building this and the options for corrective EQ would be totally kickass.

In that regard, yes, if you were to put together an alt version like you said that's a copy of the generic board already in the v63, that would be really fantastic, too. I have my own set of mods I do to those boards you find in MXL's, CADs, etc that I'm already parted out for.

If you look around on Ebay, those mics with the through-hole parts are becoming more scarce and what you see are a lot of low end MXL's that are surface mount. Great options for donor bodies but with no replacement boards to put in there, there are a lot less options for modders so the ability to easily get replacement boards would be killer. Again, thank you!

My few cents from my experience of building and modding schoeps topology
C1 is completely unnecessary as also grounding of the  capsule - it just sounds worse.
R11, R12 - better to use 47uH inductors and C6, C7 put after it.
C6, C7 at least half of that value. 4.7nF-10nF is sufficient for RF.
D1, D2 better to use zener diodes as schoeps did.
Q2, Q3 - BC416 or 2N5087 are better candidates.
R7 and R8 better to be matched try here carbon comp or vintge carbon resistors - sounds good
I would use potentiometer for polarisation voltage adjustement, as schoeps did
Anyway i'm not a fan of that eq in schoeps. In direct comparison i prefer much more simplified version with cap from source (or drain) to ground.
What i discovered with schoeps topology is that few simplification, few change of values works the best.
Of course matching of some components is really important.

ln76d said:

My few cents from my experience of building and modding schoeps topology

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Like I said, I wanted to draft the stock circuit before I started improving things and I did forget to specify the 0.1% matches in the current schematic.

C1 is completely unnecessary as also grounding of the  capsule - it just sounds worse.

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Well, you have to have C1 if you're going to polarize the membrane and gate bias the FET. I assume you knew you couldn't do it with a polarized front but maybe you missed the gate trim. I will probably just move the trimmer to sub for R10. It'll save one part (I have to trim some things or this isn't going to fit on a single board without standing resistors) and I don't have to worry about noise at the trimmer's junction (and there's already a filter cap after R10). I had more or less planned to do two pads for each capsule lead, so that people could either ground the rear and include C1 or omit C1 and polarize the rear.

R11, R12 - better to use 47uH inductors and C6, C7 put after it.

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The little inductors and resistors are approximately the same size -- if someone wants to buy another couple of inductors I won't stop them. I would prefer to leave it as a resistor in the schematic. People who know better will know to make the substitution, and people who don't might not have a multimeter that can measure the inductors to match them as closely as the 47R. Maybe I'm being overly cautious but I would certainly make a note of the suggestion.

C6, C7 at least half of that value. 4.7nF-10nF is sufficient for RF.

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Worst case scenario I'm calculating way above 20KHz for those anyway. It's one less capacitor value for someone to buy if I leave it as 22nF. I actually suspect that might be why they're 22nF.

D1, D2 better to use zener diodes as schoeps did.

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Yeah. They can actually be omitted without issues, too.. If it were my mic I'd sooner leave them out than put a Zener there.

Q2, Q3 - BC416 or 2N5087 are better candidates.

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I was actually going to suggest 2N4403. They've got some of the best possible noise specs when fed a low-impedance signal. I had a measureably lower hiss even just going into my DAW when I used them in some Alice mics. I think they're also a bit more common than any of the PNP BC transistors, at least here in the U.S. 5087 are common as dirt of course and most people will probably have them in their bin.

R7 and R8 better to be matched try here carbon comp or vintge carbon resistors - sounds good

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Suit yourself, but I prefer to use resistors I can buy in 0.1% from Mouser

i prefer much more simplified version with cap from source (or drain) to ground.

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I really can't get behind this. I'm not denying it works (in fact, I did it once to fix a noise issue in an Alice build, despite what I'm about to type). A cap from the source to ground would increase the gain on the drain side. On the drain it would unbalance the circuit's frequency output. The drain cap is also identical to using the cap at the base of Q2 (C4 in my schematic at the time of this post) without the extra resistors in that the output impedance of the drain is still what determines the cutoff. If you omit its mate on the Q3 side (C5) you will have the same effect as if you did only the drain cap. You can also put a single capcitor from the base of Q2 to the base of Q3, which is marginally better than the two-capacitor solution in there currently (and certainly more effective) but it's still not 100% balanced. There's really no perfect solution to this, except to try to get two extra resistors in there and then get pretty specific (different) cap values for the Q2 and Q3 base->collector caps. That way you can match the output impedance of both of Q1's outputs AND the cutoff frequency of the low-pass on both sides.

I would use potentiometer for polarisation voltage adjustement, as schoeps did

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Done! Like I said, I was already planning on it.

Here's the first draft of the oscillator PCB layout, though I don't imagine it will change. I do need to verify the exact spacing between the screws. I may be able to get it slightly smaller but it's already less than 50x50cm, so the cheapest option from iTead, and it should be less than $20 for three of them from Osh. (Haven't uploaded it there yet to check.)



Have not decided if I can get away with a ground plane yet. It's probably a bad idea for a MHz oscillator.

EDIT: Removed D3 because the trim can set the capsule voltage and the 12V it's source from is already zener-regulated. The 470uF is probably overkill now so I might could get the board even smaller. 2K is probably not a large enough trim, probably need to go to 5K.

midwayfair said:

Well, you have to have C1 if you're going to polarize the membrane and gate bias the FET. I assume you knew you couldn't do it with a polarized front but maybe you missed the gate trim. I will probably just move the trimmer to sub for R10. It'll save one part (I have to trim some things or this isn't going to fit on a single board without standing resistors) and I don't have to worry about noise at the trimmer's junction (and there's already a filter cap after R10). I had more or less planned to do two pads for each capsule lead, so that people could either ground the rear and include C1 or omit C1 and polarize the rear.

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Yeah, but what for polarise diaphragm (except oversized voltage values) and add capacitor when you can just polarise backplate and take signal from the diaphragm?
If i understand correctly - are you worried about few volts at the front diaphragm, from gate?
If so, schoeps didn't so don't be afraid.
Some microphones have applied voltages on both. For example Violet Design Dolly have 80V on the backplate and 10V on the front dipahragm. Works like a charm.

midwayfair said:

Worst case scenario I'm calculating way above 20KHz for those anyway. It's one less capacitor value for someone to buy if I leave it as 22nF. I actually suspect that might be why they're 22nF.

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Way way above can do better work

midwayfair said:

I was actually going to suggest 2N4403. They've got some of the best possible noise specs when fed a low-impedance signal. I had a measureably lower hiss even just going into my DAW when I used them in some Alice mics. I think they're also a bit more common than any of the PNP BC transistors, at least here in the U.S. 5087 are common as dirt of course and most people will probably have them in their bin.

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If i will find 2n4403 i will try it next time  
Both mentioned types works good anyway.

midwayfair said:

Suit yourself, but I prefer to use resistors I can buy in 0.1% from Mouser

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Of course it's only suggestion, but you could be surprised how non-über-specs parts can nicely affect the final result.
Worth to try

midwayfair said:

I really can't get behind this. I'm not denying it works (in fact, I did it once to fix a noise issue in an Alice build, despite what I'm about to type). A cap from the source to ground would increase the gain on the drain side. On the drain it would unbalance the circuit's frequency output. The drain cap is also identical to using the cap at the base of Q2 (C4 in my schematic at the time of this post) without the extra resistors in that the output impedance of the drain is still what determines the cutoff. If you omit its mate on the Q3 side (C5) you will have the same effect as if you did only the drain cap. You can also put a single capcitor from the base of Q2 to the base of Q3, which is marginally better than the two-capacitor solution in there currently (and certainly more effective) but it's still not 100% balanced. There's really no perfect solution to this, except to try to get two extra resistors in there and then get pretty specific (different) cap values for the Q2 and Q3 base->collector caps. That way you can match the output impedance of both of Q1's outputs AND the cutoff frequency of the low-pass on both sides.

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Balance issue was explained many times here as also denied.
Try to measure and compare output with it and without it.
Connection of the cap to ground from source or from drain depends on how you will connect and polarise capsule, same with change of polarity at the output

Cool, I'll gice all the suggestions a think and might make two layouts. One thing I was thinking is that the gate bias setup allows someone to build the original mic schematic part for part with a couple jumpers and omissions. It's easier to hit the 4v on the drain from the 6.2v supply in the original with the trim there rather than above the drain.

midwayfair said:

Cool, I'll gice all the suggestions a think and might make two layouts. One thing I was thinking is that the gate bias setup allows someone to build the original mic schematic part for part with a couple jumpers and omissions. It's easier to hit the 4v on the drain from the 6.2v supply in the original with the trim there rather than above the drain.

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Yeah, good idea!
One suggestion for PCB layout. If you will fit somehow, try to make option with C2 and C3 for placeing radial and small axial caps.
I keep my fingers crossed

I used to offer a set of PCB's for a couple of years, but there wasn't very much interest in this.
http://www.vansteenissoftware.nl/MicPCB/

Main PCB draft. I also made some tiny adjustments:

1) The parts numbering continues from the main schematic to the oscillator PCB, since I'm confident I'm not adding more parts at this point.

2) I measured the screwhole placement in the Aurycle mics I have to verify that I had those in the correct place. These are the same body size.

3) I made an important change in the main schematic which we didn't discuss yet: I made the Zener regulator from a lower value zener and white LEDs. I had found this thread a while back when I was looking for a solution to Zener noise. Since we only need to hit 12V or less on this regulator, this seemed like a good opportunity to use it (I can't very well do so if I need a 30V regulator, for instance). Zener diode noise is extremely well discussed in many, many, many places if anyone needs to look up more info. The 6k2 should be sufficient current limiting, but you might want to take a black marker or paint over the LEDs to blot them out so you can actually see the circuit ... them things are bright. If anyone has further suggestions about this, let me know before I call this one ready to prototype.

4) I'm still not 100% sure about the trimpot value in the oscillator in this mic (I've only done voltage oscillators this month for the first time, and it was all in u87 variants), but I bumped it up to 10K.

5) I put pads on the board for the capsule, but I really suggest just doing it deadbug stye.

6) I added a high pass filter that has worked well for me in the past. Yes it changes the bias slightly, but they're matched so you should be fine. I cannot measure or hear the noise increase on my equipment (but I assume it's there). It's 150Hz but if that's too much for you just increase the size of the resistor.

7) I added a pad. I opted not to do it like the original because it would have involved an extra wire run. If you're going to use it, you can route the capsule backplate connection through the switch on the way to the PCB. It's only connected to the PCB when you've got the pad in, so the PCB resistance (which I think is about 300M for FR4) loss shouldn't be a problem.

8) As suggested, I left out the input capacitor. If it's my mic, though, I'm probably ditching the trimpot, grounding the 1G, and selecting R10 for the bias. I couldn't fit both trims and it made for a MUCH better layout to just omit the cap completely.

9) Lastly, I've opted to omit the corrective EQ for the capsule. Here's my thinking: Anyone who is grabbing one of these PCBs probably isn't satisfied with the 25mm 67-style LDCs and the capsule should be the thing they replace before touching the circuitboard. There are many better options for capsules out there. If you want to get super cheap about it, you can even just omit the oscillator completely and this works as an Alice and the transsound large electrets don't usually need EQ correction either, and frankly I think they sound awesome compared to the stock capsules that come in the 990 etc. (Though I think that the larger 67-style one that comes with the Aurylce FET kits sounds better than both and I like that in my modded 990 over the other Kx7 capsules I tried.)

I'm about ready to upload these to OSH just for a visual check, but I need some time away from Eagle. Once I'm fully satisfied with it, I'll share the Eagle files. I'm also going to move as much of this information to a new thread for shared OSH Park circuits. I'll see about getting the generic FET+emitter follower PCBs done up as well, as well as a couple +- single-transistor voltage oscillators for multipattern versions of these mics. There are still some better PCB options overall for that (e.g. Chunger's oscillator PCB, if you can find it, uses a more stable chip arrangement) but I think this would be helpful to have access to.



Really don't understand why this won't display:

https://dl.dropboxusercontent.com/u/9878279/Jon%20Patton%27s%20layouts/MIsc/Schoeps%20style%20transformerless%20circuit%20-%20PCB.png