B1 Buffer Preamp

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#2,962
If i understand correct what you want to do, then connect the relay volume pot to the input selector as you would normally do and then connect the input selector to one of the B1 input as in the picture a couple of posts before. You will then have to put jumpers at the B1 board at the place where the pot would normally connect. Jumpers can go like this: InR to OutL and InL to OutR
 
#2,963
Here 3 different version of B1 we made ...

The latest version we made ... this proto have near 1500$ just in parts ...

Mundorf Silver&Gold&Oil 1k and 10K
Resistor Vishay the top list
DACT volume control (the top list)
Battery 5000ma 22.2v LiPo
RCA Connector WBT NextGen Gold (I have Silver too but not tried yet)
Batterie connector DIN
Ground wire OCC 7N copper in one big segment
Solder Mundorf

* this is VERY good indeed!
An externally hosted image should be here but it was not working when we last tested it.


A very very good version here ... A WAY better to the original proto...
An externally hosted image should be here but it was not working when we last tested it.


Original proto (150$) including the interconnect.
An externally hosted image should be here but it was not working when we last tested it.

* Not bad but on our system, it's a bit agressive.
 
#2,964
Thanks to the simple circuit design, I was able to build the B1 with most parts from my parts bins, except the FETs. Have been amazed by how natural the B1 sounds so far, to my ears anyway.

Cheers,

Alf
 

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#2,968
tinitus said:
this 'old' LDR/buffer scheme by Nelson Pass use sk170 and sj74

wonder if anyone knows how to convert it to the B1 buffer 😕
Click to expand...

Old?
Peice of cake!
I might even have a dwg by the master himself(at home)? Basically just put the bottom transistor into a current source configuration and change it to the N type device. I guess some of the single endedness of the B1 needs to be addressed as in "symetrical B1 Buffer" thread.
 
#2,970
piece of cake?
would be nice if it were

Itsmee, current source with N device, suggested by flg, is that what you are drawing ?

no, nothing built yet
but I urgently need a preamp
and I have the fets, and matched LDR

well, I also have both "symmetrical B1" boards
but sj74 are rare
 
#2,972
ok, i'll skip the LDR
seems pointless anyway
with a source slector there will still be a switch in signal path
and resistors too
guess I can just as well use Broskies new mono attenuator

hmm, they come with print boards
maybe I can find a place for the jfets on there too 🙄
 
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