The BA-3 as preamp build guide

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#204
There are differences with different metals and with different constructions. But the distortion levels from good resistors are so low that virtually all of them are inaudible.

It's when we choose the wrong type of construction, or material, for the duty that we make the distortions audible.
 
#205
R101/R201 Salas BIB

Marra said:


The transformer is 50VA with 20V secondaries from Avel Linberg which with the mains where I live this gives me 22V. I had intended to use a transformer with four secs but had miss remembered what the secs were.
This feeds a pair of Salas SSLV shunt regulators running 240ma current hence slightly hot rodded then supplying +- 24V to the BA3 board.
Click to expand...

HI Marra,
I've been looking at this picture of your build and am a bit confused about R101/R201 in the Salas shunt reg. In the one channel I can see 10R resistors in the R101/201 position. In the other channel I see banded resistors Red/Blue/Black/Gold which would equal 26R in the R101/201 position.

10R would give the stock 200ma output.

I'm in the process of deciding what size resistor to use in that position.

Thanks,
Kevin
 
#206
Hi Kevin;

I can assure you that the banded resistors are 10R;I took the lid of this morning to check. You are correct they are running at the stock 200ma current. My mind was getting ahead of itself as it is my intention to increase the shunts current. I just wanted to make sure that the case was up to running hotter as the base is not very thick.

The BA3 does sound really good at the 200ma from the SSLVB.
 
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#210
Hi all

Questions about transistors
1- should 2SK170/2SJ74 be matched or simply from the same grade ?
2- if same grade, 2SK170 are available on diyaudiostore for grade A & D, and 2SJ74 are available on grade A, C & D, so is A or D preferable ?
3- for 2SJ313 / 2SK2013, is matching or same grade necessary, I see no reference to that

BR
Jean-Louis
 
#213
Trimpot

The Idss of my 2sk170/2sj74 is 7.4ma so I'm using 1k trimpots for P1 and P2, Right?

I'm using all RN60 1/4 watt resistors but 47k seems to be out of stock everywhere. I do have some RN 55 1/8 47k, would that be ok for R2 position?
 
#216
I am finally at the point of finishing several projects and am looking for some opinions from others. I have a F4 as functioning boards strapped to sinks, a DCB1 that is finally getting a chassis, and a BA-3.

My question is how to best utilize the BA-3. Is there any point to putting the BA-3 in the same chassis as the DCB1 with its own set of inputs and outputs so it could be used for a gain stage following the DCB1? Should it be built into the F4 chassis, or kept in a stand alone chassis?
 
#217
Eric said:
I am finally at the point of finishing several projects and am looking for some opinions from others. I have a F4 as functioning boards strapped to sinks, a DCB1 that is finally getting a chassis, and a BA-3.

My question is how to best utilize the BA-3. Is there any point to putting the BA-3 in the same chassis as the DCB1 with its own set of inputs and outputs so it could be used for a gain stage following the DCB1? Should it be built into the F4 chassis, or kept in a stand alone chassis?
Click to expand...

I would put it in a separate chassis. That way it is a movable pre...it will drive F-4, crippled or not. Other will become a "spare".....

Russellc
 
#219
Asking for advice / opinions. I am helping another member put a preamp together and this came up:

If you had two f4 amps and were planning on biamping would you go:

1) ba3 - b5 crossover - pair of f4 amps.
or
2) b5 crossover pair of ba3 - pair of f4 amps

number 2 would require a source selector before the b5
Thanks for the time, Evan
 
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