The BA-3 as preamp build guide

[MEPER]

Yes, I have read the article now. I think I understand more and more about JFET operation. Also good to see that output mosfet does not need huge heatsinks. So the 15 K/W I have may work if I just run them at normal bias.

 

[Russellc]

I have ordered an octet. He writes that they are in the 7 mA range.....should be OK I guess (hope)…….

I did the same thing, just discussed it with him first, the "7ma range" he has has some sets closer to 8ma, so I noted for those. I think original article called for 10ma, and a few resistor/pot changes can make a wide range usable. he has them marked on package what measurement they are.

Russellc

 

[Russellc]

Yes, anything BL grade will work.

Yup, "These JFETs were chosen at Idss
figures of 10 mA (Idss is the current that flows when the Gate and Source are at the same
voltage). If you get lower values, you may want to consider higher values for P1 and P2, say
1 Kohm. They are best matched, but P3 can be adjusted to compensate for some mismatch".

I like to get around 8, everything worked with standard values....

Russellc

 

[vcec]

ZenMod:
article , here , if you want addendum
Burning Amplifier BA-3
addendum - -look down at comment #15 , by Mighty Moi :
Burning Amplifier BA-3


Thanks ZenMod - just what I was after!
Cheers

 

[ggetzoff]

BA3 FE is really at its best when mated with BA3 OS , so working in full gain/swing mode

when adjusted to work as line preamp , it's somewhat constipated

so , it's really best to make it as part of power amp , then use anything simple as line stage - even just decent pot or pot plus buffer will work as charm

Or as Papa hints in the BA-3 article, just make it a power amp itself. The Toshibas are good to 25W.

 

[Zen Mod]

I would leave heavy duty work for output buffer , still

leaving Toshibas in happy realm

 

[meanie]

http://www.diyaudio.com/forums/attachments/pass-labs/585216d1481462524-ba-3-preamp-build-guide-p-bagsn-1v20-schematic_2_.jpg

May i know Q3 in above diagram is 2SJ313 or 2SK2013.
I searched around and some site gave confusing P and N diagram for above devices.

In final stage of completing the BA3FE for my ACA V1.6.

Thanks

 

[novanta00]

Q3= j313
Q4= k2013

 

[meanie]

Just wanna share the good news, my BA3 preamp is alive !
Now driving the twin bridged ACA v1.6. I have never hear stuff that came out of my current speakers till now, very musical, much improved clarity and smooth treble.

I m very happy, thanks to Nelson Pass for sharing his design and all whom had contributed in this journey.

 

[MEPER]

Does the large voltage swing of the BA-3 match well with the ACA's?
I have also the BA-3 PCB and they were intended for the MoFo…….but good to hear they also match well with the ACAs……..

 

[meanie]

I m using 50k Alps volume pot, comfortable listening position with the knob at 11 o’clock position.
After about 2 hours, how come the 4 heatsinks on the mosfet are cold ? Not even a tad warm, bias set at 1v over the 22ohm resistors.
Did I do something wrong ?
But it sounds fine to me musically.

 

[dabenza]

Just wanna share the good news, my BA3 preamp is alive !
Now driving the twin bridged ACA v1.6. I have never hear stuff that came out of my current speakers till now, very musical, much improved clarity and smooth treble.

I m very happy, thanks to Nelson Pass for sharing his design and all whom had contributed in this journey.

Any photos?

 

[meanie]

Here it is...

An externally hosted image should be here but it was not working when we last tested it.

 

[Zen Mod]

try smaller pic

 

[meanie]

I have found in store that i have a 100k and a 250k volume pot which i uses them for my ex tube preamp, remembered paying a lot for these pots.
Can i replace them with the current Alps 50k ?

Will i get any improvement sonically ?

 

[6L6]

The 100k will be fine and sound great.

 

[meanie]

I was brought up the old school way where all signal line/path has to be shield/screened.
But i can't help noticing that alot of the members here built their amp using just twisted pair unshielded wires as input for both preamp and power amp.

Is unshielded method better ?

 

[6L6]

Shielded is likely better. Most people are just using what wire they have.

 

[meanie]

An externally hosted image should be here but it was not working when we last tested it.

Trying out 100k pot.

 

[Enochrome]

Will two boards be required for balanced? I would like to use this with a J2?