Neumann U47FET Clone: D-U47 FET Microphone Project PCB Build thread

[EvLoutonian]

Dan, do you know how many of us there are with the PCB's?  (ie. how many you made initially?)
This will give a better idea of how many people will potentially be looking for a transformer for their build.

Then Mark could offer a better indication of bulk price, for example?

 

[poctop]

Dan, do you know how many of us there are with the PCB's?  (ie. how many you made initially?)
This will give a better idea of how many people will potentially be looking for a transformer for their build.

Then Mark could offer a better indication of bulk price, for example?

about 40 set were sent,
Dan,

 

[EvLoutonian]

Okay, cool.  Thanks for confirming that, Dan.

So, how many of you folks with the U-47fet PCB's are interested to do a bulk buy on a nice output transformer?

I'm in for 2 transformers myself, to go with my PCB sets.  And I'm happy to go with whatever everyone else agrees on, to get the best deal, as I'm sure they'll all be very good transformers.  I am tempted to go with the SAMAR if we can get enough people interested, and we could probably get a comparable price to the others that way.  I've heard glowing reports of Marik's work on his other mic transformers, so I imagine it's a pretty special unit.

Let's hear who's looking, initially, anyway - to gauge numbers?

Keen to hear what others are gonna use for capsules, too!
I have an Equinox Q47 capsule, plus a recent Dale M7 capsule from Cathedral Pipes.  But I've already got these allocated to a couple of tube U47 projects, so I'll prob want to get another pair of capsules for these FET builds!

 

[Winetree]

Looking for 2 transformers and capsules.

 

[tomas1808]

I am in for 1 transformer.

Still no capsule.

BTW EvLoutonian, have you compared the Equinox and the Dale capsules? I know the Dale is considered to be very good, but I haven't heard much about the Equinox.

 

[EvLoutonian]

BTW EvLoutonian, have you compared the Equinox and the Dale capsules? I know the Dale is considered to be very good, but I haven't heard much about the Equinox.

Hey!

I haven't had the chance to try either capsule yet, actually.  I bought them for my two tube U47 projects (neither of which I've completed yet) and now I'll need to source two more suitable capsules for the U47fet's as well!

I'm trying to work out what's the best way to go for capsules in the slightly more affordable category to use in my U47fet builds. 

Thinking maybe RK-47 (as offered by microphone-parts) or something else along those lines? 
* For example, maybe the RK7 is their more 'even' or 'vintage' sounding capsule, compared to the RK47?
http://microphone-parts.com/rk7-microphone-capsule/

Have people had good results from these fairly affordable capsules?

I'd especially like to know ~ if anyone has tried the RK47 or RK7 capsules alongside, the Equinox Q47 capsule ~
- how do they compare to each other? 

The B-stock Equinox capsules were sort of comparably priced to the microphone-parts offerings last I checked.

Would it be worth asking Equinox for a group price on capsules?
Or microphone-parts? 

Who thinks they might be in the market for either of these capsules for their current mic builds?

Suggestions for other viable alternatives?

I noticed that Beezneez are currently offering their range of capsules at a reduced rate of $330ea (+GST for us Aussies), which I presume would be fantastic capsules, but I have already spent such a lot of dough on the parts for my MK47 (& EF47) that I don't feel that I can also afford $350 capsules for my U47fet's as well!

Can always be tempted, mind you...

 

[tskguy]

Our good friend Wave recently bought a Mparts k47 for his ioaudio 47 build and he wasnt very pleased. He described it as brittle and wasnt what he was looking for. Granted it wasnt the same circuit but you know 80% of the sound is the capsule. Anyway I am actually going to try and reskin a flea backplate, They actually sell the unskinned backplate and the outer rings as well as the screws for 100 bucks US. If it goes well I may consider reskinng the backplates if someone wants a reskinned flea k47, that being said let me give it a try first and see how it sounds.

Eric

 

[Marik]

Here is the test I was talking about earlier--comparison of two consecutive number U87, one with stock BV13 and another fitted with our replacement transformer. Of course, there is no processing of any kind, except for fade in/fade outs and cutting out all eee, mmm, and so on. The voice:

http://samaraudiodesign.com/U87VoiceStock.wav

http://samaraudiodesign.com/U87VoiceSamar.wav

And me playing some jazz:

http://samaraudiodesign.com/U87PianoStock.wav

http://samaraudiodesign.com/U87PianoSamar.wav

Our good friend Wave recently bought a Mparts k47 for his ioaudio 47 build and he wasnt very pleased. He described it as brittle and wasnt what he was looking for. Granted it wasnt the same circuit but you know 80% of the sound is the capsule.

I had good experience with m-parts K67 capsule and wanted to try their K47. I've never seen K47 to be brittle and the circuit (or even grill construction) could easily do that.

Best, M

 

[tskguy]

The Mparts capsules seem to be very good for the price but everything I have heard so far seems to be pretty un pleasing in the upper freaquency range. Thats me comparing it to other capsules in the same body and circuit (u87). Agian the capsules are very nicely constructed I just havent heard one I like yet. To each his own i guess.  Your transformers look and sound great by the way!!

 

[OPR]

Wow!... Nice work Marik!!  Sounds like you just added an extra octave to the lower end frequency response on those mics!! It's interesting to look at the wave forms on the piano files as you can even see the transients are passing through the transformer unscathed!It reminds me of you Toroidal  ribbon mic transformers when compared to other good transformers Lundahl.

 

[EvLoutonian]

The price is $109, but of course, with group buy the price will go down.
If somebody is willing to try it we can make sample transformer and send to audition.  Best, Mark

If my calculations are correct (following an email reply from Marik) he could offer us approx. the following prices on a bulk order:

Order of 10 SAMAR output transformers:  approx ~$92 ea.  (+postage)
Order of 25 SAMAR output transformers:  approx ~$82 ea.  (+postage)

I hope I got that right!

..It's just to give an idea at this stage, anyway..

I understand folks are keen to consider the various different transformer options available, and maybe also wait on some test results from this unit, as well as the new Sowter transformer, etc..  so folks, just pipe up when you wanna go ahead and order something as a group.  I'm obviously keen to get moving along on putting my mic's together (once the PCB's arrive), and that's why I've got amped up about helping to co-ordinate a purchase.
But I don't really know what's the protocol for co-ordinating such an order at this stage - and I don't wanna choke up this thread if it's not the right place for this aspect of the build.

Open to being prodded in the right direction, fellow DIY tinkerers.

 

[Marcocet]

Personally I'm most interested in the AMI transformers, but without some sort of group buy that will most likely be price prohibitive. I've heard great things about Marik's stuff as well but haven't had a chance to hear any yet. I can't wait for the opportunity! And those prices look extremely reasonable.

 

[EvLoutonian]

Personally I'm most interested in the AMI transformers, but without some sort of group buy that will most likely be price prohibitive. I've heard great things about Marik's stuff as well but haven't had a chance to hear any yet. I can't wait for the opportunity! And those prices look extremely reasonable.

I can tell you that Oliver (at AMI) recommends their T49 transformer as an economical alternative for the U47fet.
(compared to their historic spec reproductions, which cost a lot more)
 
He points out that the T49 has nearly the same inductance, and stray inductance, compared with the original.

The T49 is usually $85, but he can offer them to us for $65 ea. for an order of 10+ units as a group purchase at this time. 

Just passing the info on..

For me, spending $70 vs. $100 is not such a huge factor that it would totally dictate my decision - not as much as simply choosing the nicest transformer to do the job - but I'll be glad if we can go in together and get something for around this budget by buying together.

Goodnight!

 

[Le Roux]

I'd be in for one AMI transformer.

Neil

 

[Sredna]

+1

 

[OPR]

I had good experience with m-parts K67 capsule and wanted to try their K47. I've never seen K47 to be brittle and the circuit (or even grill construction) could easily do that.

Best, M

+1 Me too ..I have used both their rk47 and K67 types Both sound good to me ... Jim Williams also gave them the thumbs up in a Gear Slutz  thread.. Also there are also a few  comercial modders using them in there products..

 

[Steph.B]

Hello,
I've received my PCB's yesterday, thank you Dany !  8)

 

[wave]

Hey guys,
I thought that I should chime in. I didn't get the RK-47 I got the RK-7. I was looking for an M7 type of capsule for my MK47.
Since I couldn't get any response from ChuckD regarding his M7 and the Thiersch was a little out of my price range, I elected to give the RK-7 a try.
I didn't think (and I apologize to tskguy if I communicated this wrongly) that the capsule was brittle. I thought that it was harsh. When I say harsh I mean that it sounded like there was something wacky in the midrange response. Kinda like when you drive a power amplifier too hard and you start hearing the distortion @1K.

The response of the Rk-7 was as advertised. Def dark and not bright like a K67 style capsule but I just didn't like it in my mic.
Eric came by with his first new M7 style prototype on Sunday and we threw it in. His M7 sounded awesome and was what I was looking for, for that mic. I'll let Eric chime in about whether or not he will be offering his M7 commercially but if he does, we will have another great sounding, awesomely priced 100% USA made M7 option.
I had to let my MK47 burn in the other night as I had not done so yet so I will fire it up tomorrow and get some sound samples posted for everyone.

Dave

p.s. Maybe we should create new threads for organizing group buys for transformers and talking about capsules. This is Dany's build thread and I would hate to see it get hard to find pertinent info for building the DU47 FET

 

[poctop]

I am mentionning officially that what you see on the U47FET schemo is what you will get  no more no less except  that Circuit will allow Bias for the FET (2N3819) ,

To clear some confusion before it happens the Bias on the U47FET is not actually a Bias , it permits a certain adjustment to the source voltage to operates half the Rail voltage,  it also permitted me to set the FET in a consistant VDS ( about 15V in this case) condition , as i went further into this circuit design with the help of any extraordinary electronician guy who fixes stuff by wetting is finger and touch the PCB  ;D,  to understand the that FET source current is actually regulated by the transistor below and it actually feedbacking to the Drain Voltage for the change in Voltage implying the constant current source , so this design is actually AutoBiasing and regulates a predetermined idle current,  i had noticed no change in the THd Level as well at the oprating point set ,
So basically brings us over a section of the curve where there is not much change in behavior,


So for the Folks who will build, the pot is not really necessary unless you want to learn about the circuit.
if you dont install it just short the 2 used pad with a fine wire and then use R6 = 6.8K there is some extra in the bom anyway as you need a pair to match the front end , the value is not critical,

Best,
Dan, 

 

[poctop]

Validation For Alctron GT-2B Style Microphone & Railing Test
Space Left For Transformer , about Length 38mm *  width 50mm approx,  8)