The BA-3 as preamp build guide

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Marra

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Joined 2009
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After a couple of home goals so to speak( trimmers turned wrong way and miswired p/s) my BA3 is up and running. Fortunately nothing was damaged with my errors.
Trying ZenMods suggestion of Silmic and mkc as an output cap which sounds pretty good so far. I'm using the Salas SSLV regs set to 24V and lightly hotrodded.

Thanks once again to Nelson and Jim for this excellent build guide:cheers:
 
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Russellc

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Joined 2003
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6L6 said:
In my world that means that some values don't quite match the schematic, in order to use stuff I have on hand...

:D :D :D


I'm interested as well, as the next preamp project will be the BA-1 gain stage used as a preamp, and I have a set of Salas LV shunt PCB I would like to use. :)
Click to expand...

I've got partially (mostly) assembled "Hypnotize" and "Mezmorize" boards...seems I remember they use shunt regulation? Seems I recall a thread about just using the power supply items for other than intended pre amp?

Russellc
 
M

Marra

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Joined 2009
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A few pics of my build.











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.The stepped attenuator is a 23 pos ladder jobby from Valab on that well known auction site. Case is second hand courtesy of another forum member. Just need to make a cover for the transformer so's I don't accidently catch the exposed wire.
I have only listened for a couple of hours but think it is gonna be a keeper.
I may eventually go fully dual mono like in Torchwoods build.

http://www.diyaudio.com/forums/analog-line-level/272368-new-dual-mono-super-ba-3-a.html
 
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Russellc

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Russellc said:
Well,maybe I left a ground off somewhere, I just switched to an input that didnt have anythinghooked to it and got quite a pop and back ground hum. Switching it back seems ok and plays fine. Should selector switch have a wire to ground.

Its new and I am listening to spotify out of my computers output for a sound source...finding it a bit scratchy compared to my tube unit. Does this thing require breakin or do I need to kepp playing it and reset bias and offset. I am surprised with the gain, not that crazy high as I thought it might be.

Russellc
Click to expand...

Playing much better now with loads of gain. The popping subsided, still a little low level hum if switched to an input with nothing on it. Will be going by a radio shack tomorrow and will pick up some cheap RCAs for shorting plugs.

Nice Pre!

Russellc
 
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Russellc

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Joined 2003
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This thing gets better and better. Thanks for the build thread and all the help 6L6, Zen Mod, Hikari1 and everyone! I will post pics of it once my "fancy" knobs arrive. 6L6, the nice Gibson knobs were out of stock at Antique electric, Guitar Center shows them. I ordered a couple different knobs from Antique as well as Parts-connexion.

Russellc
 
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A

AndrewT

R.I.P.
Joined 2004
There are three small errors created by resistors, all the others are very small.
Noise
Temperature coefficient
Voltage coefficient

If the material is metal, any of the metals, then noise is pretty low.
If the operating power dissipation is well below the maximum rating then the change in resistance is pretty low.
If the operating voltage is well below the maximum rating, then the change in resistance is pretty low.

A series string of metal film resistors gets all the variations well below audibility.
That means no audible effect.
 
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