Did you order your board from Dany yet? I think he has Styroflex kits for each project.gearhunter said:...
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)
btyreman said: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 said: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.
frasermunro said: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?
jasonallenh said: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 ;D
fsalter said:-However most of what I've seen in this thread re: NTE312s has been speculation. Can someone confirm having used NTE312s and getting equally good results?-
I have built several 87's with the NTE312's and can confirm that they all measured below 10ma and that their quality is consistent.
DT_Music said:Thanks my phone camera is pretty weak, here's another pic that I think should be a little more clear.