MA1 GERMANIUM mic pre support thread

[ppa]

thanks for the photo,

basing on your photo the AC126's pins are as follow:

1=emitter

2= base

3=collector

these AC126's pins should be connected to the PCB holes E,B,C of Q1 (same your photo):

1=E
2=B
3=C

 

[Pliplo]

Awesome, thanks! And should i cut the trace between C4 and C8 and do the solder joint like the pictures?

Also, im a little lost, i dont have a 220pF for c31 or 1uF poliester in the kit... all i got left is 2 ceramics labeled 47 and 27 and a little blue one labeled 271... Is any of these ok or should i go get what the bom says?

 

[ppa]

Awesome, thanks! And should i cut the trace between C4 and C8 and do the solder joint like the pictures?

yes, you should cut the trace between C4 and C8 and do the solder joint like the pictures.
this joint has the function to connect the ground plane to star ground. 

 

[ppa]

Also, im a little lost, i dont have a 220pF for c31 or 1uF poliester in the kit... all i got left is 2 ceramics labeled 47 and 27 and a little blue one labeled 271... Is any of these ok or should i go get what the bom says?

regarding the zobel net for capi input trasformer, that with C31=220pF  R22=10k is not the only used, this is that suggested by Jeff Steiger for its trasformer in Classicapi pres.
With MA1 i prefer  C31=270pF  R22=10k, but the differences are very closed to zero. For this reason I add a 270 pF NPO cap and a res of 10k inside the kit, but however these two ones should be external to kit because the trasformers are not included inside it too. 

Regarding the 1uF cap I have included in some kits cap of 2.2uF , but even here seems that the sound look differences are near to zero.

 

[ppa]

just an image of AC126 with labels on leads

 

[Pliplo]

Has anyone tried different germanium transistors? I have a friend with a ridiculous amount of NOS stuff... AC128s, MP39B's, MP25B's, A lot of Mullards and a lot of russian ones... Could it be worth it?

 

[ppa]

I have designed MA1 to use several/many germanium transistors.
I have tested the AF127 and the AC126 that are very different between them,
I have not seen russian germanium transistors but they seem to have too low performances for MA1

BTW MP39B cannot run inside MA1, with MP25B maybe that MA1 has a too low high frequency cut off freq at very high gain as >50 dB , for example 15khz of fc

edit: ac128 should run good (at 95%).

 

[Pliplo]

Finished my build, pretty straightfoward. Got a sweet bass drum sound with a B52 and tested it on a guitar cab with great results also. Gonna test bass DI on saturday's session

 

[berkleystudios]

Finished my build, pretty straightfoward. Got a sweet bass drum sound with a B52 and tested it on a guitar cab with great results also. Gonna test bass DI on saturday's session

could you post your results? very interested in adding some to my studio but i havent heard any sound samples yet

 

[Winetree]

A while ago I built 4 of these pres. Must have been some of the first 8 released.
"yes, you should cut the trace between C4 and C8 and do the solder joint like the pictures.
this joint has the function to connect the ground plane to star ground."
What pictures? Did I miss something.
As far as the sound ( Haven't use them much because of a total studio equipment rebuild and which I always find hard to discribe) is the 70's transistor, transformer sound.
Full, warm, closed, almost self compressed ( based in inital tests with vocals and D.I. bass)
All in a good way that's unlike the other pres I have.
 

 

[ppa]

A while ago I built 4 of these pres. Must have been some of the first 8 released.
"yes, you should cut the trace between C4 and C8 and do the solder joint like the pictures.
this joint has the function to connect the ground plane to star ground."

your version does not need this mod. This mod is only for the second version's PCB

thanks very much for comments and the question

Pier Paolo

 

[ppa]

here a file from a recording studio in Rome

the bass is connected to the MA1 DI input:

http://home.teletu.it/APPSI/BASS-FENDER%20PRECISION%20DIRECT%20MA1_2.wav

 

[ppa]

another file from DI input with a guitar:

http://home.teletu.it/APPSI/AC%20GUIT%20DIRECT%20MA1.wav

(not so bad)

 

[buildafriend]

Thanks for taking the time to post those.

What mic is being used?

 

[dogma]

I'm still yet to buy transormers for my two ma1's. I was looking at ed andersons Utc-012 remake and thinking it would be a giid fit sonically? Have you pier, and I've a feeling you may some lying about, so if you have time your impressions of it would be really useful to me and others as you can still buy them at jeffs shop.
Thanks pier - I keep checking them postbox 3 times a day like a madman!

 

[ppa]

Hi Matt,

the UTC-012 cannot be used for MA1 for its too low ratio.
My post office said me that the parcel will arrive likely to your address for the next week.
MA1 can use several trasformers so you should tell me what type of sound you need, please.

thanks
kind regards
Pier Paolo 

 

[sr1200]

Got my boards!
Question regarding C6 and C3  the BOM says 470u 25v the caps that were sent are 16v.  I have some Nichicon 470u 35v's left over from a previous project.  Should I use the 35v or are the 16v caps that were in the box ok?
Thanks! Cant wait to get these running!  Classic API is out of the input transformer at the moment, but should have them back by next week.

 

[ppa]

Got my boards!
Question regarding C6 and C3  the BOM says 470u 25v the caps that were sent are 16v.  I have some Nichicon 470u 35v's left over from a previous project.  Should I use the 35v or are the 16v caps that were in the box ok?
Thanks! Cant wait to get these running!  Classic API is out of the input transformer at the moment, but should have them back by next week.

470 uF 16V is good, I have forgotten to upgrade the BOM , only the first 4 kits had the 470uF 25V.
thanks for the question.

kind regards
Pier Paolo

 

[sr1200]

Last question,  If im using the EA transformers from classic API, the values of the two resistors and the cap should be what?

 

[ppa]

R21= not used
R22=10K
C31= 220pF