[pix] [finished] Germanium Preamp

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Thanks Kubi.
No. We're not talking 100GHz SMD stuff here.
At least I'm sure I can't hear or measure the difference.
I was thinking about hum and buzz but when you say that you can't hear it it's OK  ;)
Hope so. The preamp works for me and I assume I didn't make any mistakes drawing the schematic.
Looking good but if you have some time take a look.  :)
 
No hum and buzz in the originals right next to two open frame linear PSU.

2627895089_0bab73a32c_o.jpg

 
What's wrong, Moby? Is the signal distorted? lost along the way?
BTW: Please, use BC560 or a similar PNP-transistor instead of the ASY26, not the BC550 which is NPN.
Sorry I made typing error, yes BC560 pnp  ;D . I'm still looking for possible error, but I have just one half of amplitude at the end  :p
Maybe I made some value error, because it's stated as a list separately.  :(
 
Yes Kubi. I was too fast  :-[ I was just redrawing but left my brain somewhere else  ;D . Thanks, now it works.  :) Can you please tell me transformers ratios U used? I remember that you mentioned that circuit will work with pretty low load at output (API type). Am I right?
jensampcorr.jpg
 
I'm sure that I saw somewhere which UTC tx can be used for this pre. (input xt) but can't find it now  :-\ Can somebody refresh my memory  ;D
 
In case no one has made this clear in this thread.

All the BA71 versions wire the transformer as 1:3.2 input.

The same input transformer is on the BA73 line amps (and others too IIRC) but then wired 1:1.58

The BA71 schematics show al the options.


 
Conductor said:
UTC AR-535
( http://audio.kubarth.com/jensamp/10.JPG )
Thanks, yes I know for original one, but I'm thinking about some possible model to use like substitute. I think that somebody wrote that somewhere.... :-\
 
Hey Jens!  I'm guilty it seems.

I have a 6 transistor BA71a on a breadboard but no longer have an original RCA
output transformer because I sold all my BA71c preamps.

When I tested it with a UTC A-20 wired for 1:2 output the breadboard version sounds good but has headroom issues. It didn't have this problem with the real RCA 1:2.45 output.

What output ratios are you and Kubi using ?
 
Wow Kubi, this is great  8) How about self etching files?  ;D Or maybe it will be better to organize some finished PCB's. Volker?  ;)
 
These boards will not work inside Purusha's cases
and if he sold you a PCB, it might be faulty and will not be supported in any way!

And before this fucker sucker even asks: NO, it's not ok with me if you produce Jensamp-cases.


What the heck hapenned?
the board looks very pro BTW!!!

Altough i thing that you should do something like the Great River MP-2 pcb.
transformers outboard for more options!

Thanks Kubi.
 
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