BA-3 As Preamp

Jump to Latest
R

Russellc

Member
Joined 2003
Paid Member
KevinHeem said:
I had a hard time telling them apart at first. I'm starting to get a handle on their differences. I think they are both pretty neutral, really letting the cartridge and Pearl II shine through. I think the Joule is a little more sweet, the BA-3FE a little more transparent. Of course my bias leans towards the one I built. Although I've really enjoyed the Joule preamp, I'll be showing it the way to the door (helping to fund new projects).

Yes, looking forward to seeing how P3 affects the sound. I guess I would start with 1 turn on the 25 turn pot (which is centered now), but in which direction do you think I should start?
Click to expand...

There is a post somewhere (this thread maybe?) in regard. I remember that each side turns opposite of each other, one left, one right. The thread referred to "turning towards a resistor" that is on the board.

Others piped in that it wasn't as simple as all that, as they found while measuring it wasn't linear, but the shift from 2nd harmonic to third and vice versa may occur several times. The writer of the thread (who escapes me just now) noted that one way tended to sharpen and draw in the stage, the other blew it up larger but that is got somewhat fuzzier.

I am trying to search for that. I am searching my posts, as I remember inquiring, since I have both BA-3 FE and BA-3 Power amp, which I should start with and so forth, the pre, the amp, or both.

Russellc
 
H

Hikari1

Member
Joined 2012
Russellc said:
There is a post somewhere (this thread maybe?) in regard. I remember that each side turns opposite of each other, one left, one right. The thread referred to "turning towards a resistor" that is on the board.

Others piped in that it wasn't as simple as all that, as they found while measuring it wasn't linear, but the shift from 2nd harmonic to third and vice versa may occur several times. The writer of the thread (who escapes me just now) noted that one way tended to sharpen and draw in the stage, the other blew it up larger but that is got somewhat fuzzier.

I am trying to search for that. I am searching my posts, as I remember inquiring, since I have both BA-3 FE and BA-3 Power amp, which I should start with and so forth, the pre, the amp, or both.

Russellc
Click to expand...

I think I wrote that thread....and yes, for my the adjustment was not linear. You can't go 5 turns this way on one channel and 5 turns that way on the other to get the same result. Also, midpoint may not be a happy medium. But it depends on your jfets and mosfets and matching,etc. perhaps the best way to set it (assuming the jfets are well matched) without a scope or software is to measure the values of the resistor network effected by p3 and get them even channel to channel. If that makes sense. At least then you have a starting point for measurement and tweaking by ear. I preferred to 2nd and third harmonic about even...not 2nd dominant. Others with different rooms or speakers might disagree.
 
H

Hikari1

Member
Joined 2012
I raised the bias on my ba3 front end today, went from 50ma to 75ma. Nice improvement, a little better bass and more liquid sounding. To bad the boards don't allow for easily mounting bigger sinks. For those of you who can take the heat I'd try more bias...Nelson says up to 100ma is fine in the article. Iam pretty much maxing out my sinks at 75ma though.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
They are basic models anyway they didn't follow the datasheet curves that well when I traced them in Spice. They are OK on Vgs to roughly know the DC bias with the practiced resistor values though. You would get the same THD figures with basic IRF models of analogous parasitic capacitances.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
Looks like SSLV basic topology. Not enough mA with DN2540 though for feeding BA-FE in full swing plus allowing some good spare to keep Zo in spec.
I don't know when linked with individual K170 is a good thing for high mA polarities swinging also. Maybe alright for op-amps.
 
Zen Mod

Zen Mod

Official Court Jester
Joined 2003
zenmod.in.rs/
Paid Member
brianco said:
What do you think of this?;

http://www.diyaudio.com/forums/power-supplies/286425-shunt-regulator-15v.html
Click to expand...

if you ask me , I don't need to think anything , having Shunty (or two) around

:clown:

besides that - having Toshiba JFets in (any) kind of reg is ok for Papa Borbely , as Demonstration of Force and Trademark thing , but for others .....

one can make proper reg with peanut butter parts , so why not - that's proper and honest engineering

I have stashed myriad of obsolete parts , as result of my own naivety ; these days is much easier just to enjoy having them on shelves while using common variety ones
 
Last edited:
You must log in or register to reply here.
Top Bottom