BA-3 As Preamp

[vdi_nenna]

I received my boards from the site today. : )

Thanks for the volume control info!

 

[6L6]

oh, are these the same burning amp 3 boards sold here on diyaudio.com?

Although buzz's boards are a bit different, they are basically the BA-3 front-end (or 'Driver' board) from the store.

 

[merlin2069er]

Thanks. So where do you get the bias and output boards for the ba3?

 

[6L6]

Bias is now on the output boards - so you choose either single-ended or complimentary output. Add the FE to that and you have an amp.

You can get it from the DIYaudio store.

Or, you could use a BA-3 (or the other BA front end), or Pumpkin preamp, or Impasse Preamp to drive the BA-output stage directly.

 

[tinitus]

Bias is now on the output boards.....

I suppose you mean the small bias board is with the output boards ?

 

[6L6]

Actually I said it from memory, and don't remember if it's separate or on the same physical board as the outputs, or on the FE board...

(goes and looks at BA- page...)

Yep, you are right, the bias section is a separate PCB that is packaged with the output boards. (It didn't used to be that way, the first BA had the bias on the Front-End (gain) stage.

All this talk about BA-amps makes me want to build a 6-pair/channel complementary amp...

 

[buzzforb]

THis enough?

 

[Zen Mod]

make them double sided all , except gate route

 

[buzzforb]

For current capacity, I assume. You know I probably want use that many. Will probably split in half and this will be one whole channel.

 

[6L6]

Looks good! How long is the PCB? It seems huge...

 

[buzzforb]

17"

 

[Zen Mod]

For current capacity, I assume. You know I probably want use that many. Will probably split in half and this will be one whole channel.

you assume well

good plan , regarding splitting them

however - you don't need SE resistors going from both rails to output

 

[buzzforb]

(-)!
This is prototype

 

[Zen Mod]

hopefully - in unfinished state ....... or it will not work , without missing traces

 

[buzzforb]

Didnt feel like correcting it after exporting it.

F5
You know me. Everything is always partially finished.

 

[buzzforb]

Closer

 

[tinitus]

BA-3 FE onboard lytic are not really supply caps, are they ?

 

[buzzforb]

Nope. Level shifters like in normal BA3b. They are necessity, I believe, as the FE is heavily degenerated. Lower degeneration, add a cascode device, and you are probably ok. This v1 in a series of variations. Youll notice the cap is gone. I was going to use single supply, but since I cannot finish today, I will do a second. Go ahead and setup for dual mono final setup. CM and FC output are future revisions.

 

[tinitus]

Nope. Level shifters like in normal BA3b. .... Youll notice the cap is gone.

so your onboard lytics are supply caps

 

[buzzforb]

No. They are level shifters. Only difference between this and BA3b is feedback, allowing me to drop the output caps.