Neumann Vintage U87 Clone : Build Thread.

[chipss36]

Found this interesting, using current bom, ordered 40 jfets, using matadors methods to test for idss, out of 40 had a range of 5.80-4.60 ma, using a fluke 83v , sure seems off from the mean of what others have found.  May redo this with a resistor and measure voltage drop.

 

[Wordsushi]

Had read in this thread c5 , increased will increase bass, c6 to say 330 pf may help as well, that’s the high cut cap.

Thanks Chips! I read somewhere that Stam also changed C6 to 330 for their SA-87 to get their sound. Personally, I like the highs with the standard 220pf. I'm more curious about dialing up a bit more low end.

Now I'm curious to know what people have changed C5 to? Anyone out there with a recommendation as to how large to go with that C5 change?

 

[Wordsushi]

Now I'm curious to know what people have changed C5 to? Anyone out there with a recommendation as to how large to go with that C5 change?

No takers on the "is there a way to add more low end" question? No worries. Moving on...

Okay, new question. I'm planning on building one for a friend of mine and he asked, kinda to my dismay, if there was a way to add an LED in the headbasket like the Cathedral Pipes mics. So my new question for y'all is where the best points on the board to wire in an LED would be? Specificity appreciated.

 

[R1 Studio]

Hey Guys! First Time Long Time. About the D87 build. So the 2.2k resistors need to be matched within 4%. Does that mean 2.19 and 2.23? or Does that mean like 2.191 and 2.195? Is it 4% of the hundreds place or 4% something else? How close do they have to be? My multimeter, like most cheap ones, only measures only close enough to see 2.19.

I did see another post in which someone said it didn't matter, that he has no problems with his, but his resistors could be matched anyway.

Do I have to make a wheatstone bridge? How does that help if I don't have two matched resistors to start with?
Thanks,
Z

 

[dreadheaded]

The closer R18/R19 are matched the better, The mic will work with those but it could be quite noisy

 

[ln76d]

Hey Guys! First Time Long Time. About the D87 build. So the 2.2k resistors need to be matched within 4%. Does that mean 2.19 and 2.23? or Does that mean like 2.191 and 2.195? Is it 4% of the hundreds place or 4% something else? How close do they have to be? My multimeter, like most cheap ones, only measures only close enough to see 2.19.

I did see another post in which someone said it didn't matter, that he has no problems with his, but his resistors could be matched anyway.

Do I have to make a wheatstone bridge? How does that help if I don't have two matched resistors to start with?
Thanks,
Z

Naumann shows +/-0.4%. Believe me or not, but not every orginal U87 fit these specs at this position.
Buy a ten 1% metal resistors and find two close to eachother.
Or just buy 0.1% metal resistors and forget about measurement

The closer R18/R19 are matched the better, The mic will work with those but it could be quite noisy

Why do you think it could be quite noisy?
Worst case scenario in the 1-4% difference is lower voltage at some parts of the circuit, but it's not so huge difference

 

[RuudNL]

A difference in resistance will cause a DC offset between the two signal wires.
As long as this DC voltage is not too big, this isn't a real problem, although transformer coupled microphone inputs may not like this. Electronically balanced inputs are much more forgiving.

 

[dreadheaded]

I made exactly this mistake when first building a D87, couldnt understand why when I tried to Bias it there was this offset on the scope, and why there was a consistent power noise coming though, got R18/19 matched to within a few Ohms and the problem disappeared

 

[Wordsushi]

FWIW, attached below is a quick and dirty, (i.e...non-scientific) side by side graphic comparison of the AMI T-13 vs CineMag CM13113 in two identical D87 builds. The AMI is on the left and the CineMag on the right. Both mics were built from Dany's BOM ordered from Mouser on tapered PCB's in CAD GXL2200 donor bodies with identical 3rd party single-sided capsules.  I originally built the first one with the CineMag and after reading how so many folks here were using the AMI, I just had to build another to know what the difference was.

Recordings were spoken word, done in a well-treated vocal booth, recorded consecutively at the same distance, speaking the same sentences. Preamp used was the UAD SSL with no EQ or compression.

I finished the mic with the AMI T13 this morning. So far, to my ear, for my purposes, the Cinemag may have a slightly more detailed sound, but I mean slightly.

The graphs of course, don't tell the whole story, but the one thing I learned from this experience is that, at least for my purposes (VO), there doesn't seem to be enough difference between the two transformers for me to pick a clear "winner". However, which one I pick for any future builds may just come down to current price, with the Cinemag costing $46 (purchased directly) vs the AMI at $95 from Zen Pro. 

 

[ln76d]

FWIW, attached below is a quick and dirty, (i.e...non-scientific) side by side graphic comparison of the AMI T-13 vs CineMag CM13113 in two identical D87 builds. The AMI is on the left and the CineMag on the right. Both mics were built from Dany's BOM ordered from Mouser on tapered PCB's in CAD GXL2200 donor bodies with identical 3rd party single-sided capsules.  I originally built the first one with the CineMag and after reading how so many folks here were using the AMI, I just had to build another to know what the difference was.

Recordings were spoken word, done in a well-treated vocal booth, recorded concurrently at the same distance, speaking the same sentences. Preamp used was the UAD SSL with no EQ or compression.

I finished the mic with the AMI T13 this morning. So far, to my ear, for my purposes, the Cinemag may have a slightly more detailed sound, but I mean slightly.

The graphs of course, don't tell the whole story, but the one thing I learned from this experience is that, at least for my purposes (VO), there doesn't seem to be enough difference between the two transformers for me to pick a clear "winner". However, which one I pick for any future builds may just come down to current price, with the Cinemag costing $46 (purchased directly) vs the AMI at $95 from Zen Pro. 

There are some circuits which are really fragile to output transformer and there are some which are not
Try also 3UAudio, which is almost half of cinemag price - you can be surprised even much more
As i always writing  - all is matter of testing, it's for me at least, more interesting than following marketing hype

 

[Wordsushi]

So I just finished my first multi-pattern D87 and the only problem I'm having is that in Fig-8, the backside of the capsule isn't working. It works in Omni, but in Fig 8, I'm just getting the front diaphragm and it's kinda noisy. Any thoughts are appreciated.

FWIW: I am using a dual-backplate capsule. I checked with a DMM for continuity to make sure they're not connected.

 

[Wordsushi]

Okay, another problem has arisen. I re-flowed the joints on the back of the main board to try and get Fig 8 working (see above) and now I'm not getting any signal in cardioid. I measured my drain voltage and it went from 10.9 to 2.4. I then tried to upwardly adjust it with the pot and it topped off at 6.7v. After the adjustment, I'm now also seeing that same 6.7v at the gate as well. Could I have cooked the FET while reflowing the joints? Or maybe when reflowing the wire connected between G and GG?

 

[Wordsushi]

Okay, luckily I have another working D87 so tonight I used voltage readings from that one to track down that I must have cooked the FET on this one, so I replaced it. Mic is working again, in cardioid and omni, but still no Fig-8. There's some signal from the front of the capsule, but nothing from the rear.

I'd use the other D87 to track this fig-8 problem down too but the other one is single-diaphragm and no switches. I was thinking it was a cold solder joint here, but I reflowed them all to no effect.

Again, any thoughts on the matter will be received with gratitude.

 

[ln76d]

Make few pics of the circuit, maybe then will be easier to catch the problem

 

[R1 Studio]

Okay, so I am able to trim the fet drain to 11.5, but I am getting nothing from my Peluso Capsule. I am aware that it is a little different to wire up. I know the tab in front represents the opposite backplate. I have read all over the thread how to wire it, and I have tried it backwards and forwards.

I am kind of having a nervous breakdown since I had a screw break off on in the backplate. I cannot get it out to save my life. Would this cause the capsule to not work?

Does anyone have any experience returning capsules to Peluso? How much would I have to mess up the capsule before a capsule maker would not take it back? I also put the tiniest nick on the 6 micron thick circle of plastic on the diaphram as I was trying to fuss with it.

How do I trouble shoot a capsule? What values should I see with my multimeter?  I see nothing.
Thanks,
Z

 

[Wordsushi]

Make few pics of the circuit, maybe then will be easier to catch the problem

 

[Wordsushi]

#2

 

[Wordsushi]

#3

 

[Wordsushi]

#4. Sorry it's so many posts. I can't get the IMG tag to work.

 

[R1 Studio]

If I am able to bias the fet to 11.5, and I am getting know sound, does that mean that my problem can only be with the switch pcb or the capsule?

Also, if a screw breaks off in the backplate of a capsule, would that keep it from working?