[RuudNL]

How big is the difference? I noticed that the output level is somewhat depending on the FET used.

[valco]

I actually testet it further now. I finished it a bit late last night, so I tested it very quickly.

It seems to have the excact same output as the original u87. The orginal U87 is a tad duller , but that might be that the capsule is dirty.

[gearhunter]

I'm ordering the BOM and I was wondering if for C15 I can order Styroflex of 620pF 160V instead of 560pF 630V or keeping the voltage and capacitance straight on styroflexes is important

I was thinking of order them at Don-Audio instead of Mouser since they are located in Europe and I can´t find the substitutes I have for styroflexes (Wima FKP2 560p/100V/5mm,Ero KP1830 470pF/100V/5mm, etc):

560pF/630V  (Styroflex 620pF https://www.don-audio.com/Styroflex-Polystyrene-Film-Audio-Capacitors_3)
470pF/630V (Styroflex 430pF https://www.don-audio.com/Styroflex-Polystyrene-Film-Audio-Capacitors_12)
10pF/630V (https://www.don-audio.com/Styroflex-Polystyrene-Film-Audio-Capacitors_19)
220pF/630V (https://www.don-audio.com/Styroflex-Polystyrene-Film-Audio-Capacitors-220pF)

https://www.don-audio.com/Styroflex-Polystyrene-Film-Audio-Capacitors

Would these do the job?


Thanks all!

[Delta Sigma]

...
560pF/630V  (Styroflex 620pF https://www.don-audio.com/Styroflex-Polystyrene-Film-Audio-Capacitors_3)
470pF/630V (Styroflex 430pF https://www.don-audio.com/Styroflex-Polystyrene-Film-Audio-Capacitors_12)
10pF/630V (https://www.don-audio.com/Styroflex-Polystyrene-Film-Audio-Capacitors_19)
220pF/630V (https://www.don-audio.com/Styroflex-Polystyrene-Film-Audio-Capacitors-220pF)
...

Did you order your board from Dany yet? I think he has Styroflex kits for each project.

Phantom power is 48V, as long as you're well above that in voltage ratings you're good. I haven't built a U87 so I'm not super familiar with the schematic. Looking at the 1980 Neumann schematic, there's a 560pF cap for the pad. If you replaced that with a 620pF cap, you'd get a larger pad (maybe 11dB?, not much more). There's a 470pF cap that (I think) couples the HPF between the front and back diaphragms. Subbing in a 420pF cap could potentially make an audible difference.

Have you ordered the bulk of your components? Look for C0G or NP0 ceramic caps of the correct values. Swap them with the styroflex of different value and see which one you like more if there even is a difference. I use C0G caps in my builds instead of styroflex. not sure I can tell the difference between the two cap types.

56 C0G 470pF 100-200V caps in stock at Mouser:
https://www.mouser.ca/Passive-Components/Capacitors/Ceramic-Capacitors/MLCCs-Multilayer-Ceramic-Capacitors/_/N-bkrdaZ1yzvvqx?P=1z0x74kZ1yx4atuZ1yo19ldZ1yx4as7Z1ywxu2pZ1yxbokaZ1y9fee6Z1z0z819Z1z0z7l5

[jasonallenh]

Finally getting around to building my second one of these. Seems like the headroom on my previous build isn't right. It's distorting fairly easily. Am I able to re-bias without disconnecting the capsule? If so, is the ZapNSpark method the best way to go here?

[FarisElek]

Thought I'd comment a out the serious success I had today building one of these for my friends. Its the 3rd I built for a friend. This time, to keep prices low, I used a $15 Nutrik NTE10/3 transformer wired reversed and a Dachman Audio k87 that they were selling for $50 until recently. The result was fantastic! slightly rolled off low end compared to the BeesNeez capsule and aml t13 I used in the other builds. Also slightly more "air". But so very subtle. Very recommend those cheap Neutrik transformers for this build. I may find the smaller core saturates on drums or something. But for vocals they tested very well.

[btyreman]

this is such an intruiguing project, I've been saving for a long time for the 'real' thing but do not like the sound of the modern U87ai as much as the vintage one, has anyone on here used a genuine neumann K87 capsule in one of these mics? you can still buy them from sennheiser... and has anyone compared a genuine vintage U87i to one of these? if so I'd like to hear audio clips of it...

[FarisElek]

this is such an intruiguing project, I've been saving for a long time for the 'real' thing but do not like the sound of the modern U87ai as much as the vintage one, has anyone on here used a genuine neumann K87 capsule in one of these mics? you can still buy them from sennheiser... and has anyone compared a genuine vintage U87i to one of these? if so I'd like to hear audio clips of it...

If you do a search you'll definitely find what you just mentioned on this forum somewhere. I've had excellent results on all my builds which have been all beezneez capsules and most recently a Dachman Audio Capsule. Used AML transformers and recently a very cheap Neutrik and the two are almost identical. I believe I read having the original mesh Neumann screen ended up being a subtle part of the sound too. But you get pretty damn close.

[jasonallenh]

If you do a search you'll definitely find what you just mentioned on this forum somewhere. I've had excellent results on all my builds which have been all beezneez capsules and most recently a Dachman Audio Capsule. Used AML transformers and recently a very cheap Neutrik and the two are almost identical. I believe I read having the original mesh Neumann screen ended up being a subtle part of the sound too. But you get pretty damn close.

You got a part number for that Neutrik transformer??

[FarisElek]

You got a part number for that Neutrik transformer??

https://www.mouser.com/ProductDetail/Neutrik/NTE10-3?qs=jCymNF74TgXcTOWS11Yi9w%3D%3D

Must be wired in reverse. 10:1

[jasonallenh]

I have 2 lots of 20 2n3819s i bought from Mouser (Central Semi) and eBay (Fairchild... possibly),  the  Central Semis all measure between 16 and 19mA IDSS when  testing using a 9v battery and multimeter set to mA, and the eBay 'Fairchild' fets all measure between 13 and 16mA (marginally better but still nowhere near the numbers people have talked about in this thread....).

I tried the mic with one of the lowest IDSS values from the  fets from mouser and it seemed to work, although the gain required to get much volume out of it was rather a lot, and the lowest value from the ebay fets also seems to work, however when i popped a few of the fets into my transistor tester both reported as actually being jfets but the values reported by it were wildly different between the two sets of transistors - i have attached a picture of the transistors and the values the tester shows - could someone give me some insight into why the values are so different? Im assuming it might be because the 'Fairchild' fets are perhaps not what they are labelled as!

As far as the gain is concerned to get a usable level out of the mic at a regular speaking volume - i tried with two interfaces, a focusrite 2i2 - this needed the gain turned up full and still comes out low, and a Audient ID44 which gets about the same level at 3/4 way round the gain knob, does this seem right?

I can confirm this - the Central Semi parts are bad and getting worse. I built my first 87 clone about six years ago and settled for the one 2N3819 from Central that was under 13mA. I just bought a batch of 10 and I only found one below 17mA. I managed to find the rest of the batch I bought in 2014, but the best in that bunch was around 14mA. I've seen a lot of different parts pitched as alternatives, including the NTE312 and J112. Both of those *look* similar but I've not heard of anyone incorporating them into a build. You can still get ON/Fairchild J112s on Mouser, and I'm particularly interested in the NTE312 as its Idss range is more narrow (5mA to 15mA).

If you've used an alternate part, we'd love to hear from  you

[patxiplg]

I can confirm this - the Central Semi parts are bad and getting worse. I built my first 87 clone about six years ago and settled for the one 2N3819 from Central that was under 13mA. I just bought a batch of 10 and I only found one below 17mA. I managed to find the rest of the batch I bought in 2014, but the best in that bunch was around 14mA. I've seen a lot of different parts pitched as alternatives, including the NTE312 and J112. Both of those *look* similar but I've not heard of anyone incorporating them into a build. You can still get ON/Fairchild J112s on Mouser, and I'm particularly interested in the NTE312 as its Idss range is more narrow (5mA to 15mA).

If you've used an alternate part, we'd love to hear from  you

Then the key to a higher output level is to use one with a low Idss value? I'm also suffering from very low output which makes the whole system noisier... Thank you!

[FarisElek]

All U87i circuits have low output. I've built 5 and they all had ids between 9-14 and they were almost all identical. The lowest value was loudest but no more than 1-2db.

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