BA-3 As Preamp

[KevinHeem]

Jim used the PS-12 from tubecad.com which was replaced by the PS-19. Joca have you read the build guide?

 

[MASantos]

OK , I'm always for overkill , but 0A7 for programmed current for shunt per rail is ridiculous , with BA3 FE as load

as for shunt programmed current , there is simply no need for more than twice or trice of load current

remember , benefits of shunt reg aren't in wasting heat and power , but in dynamic nature of it

0.7A is the sum of of channels, it will be around 300-350mA per rail of shunt current and I am also planning to increase the bias on the output mosfets a bit above the recomended. Because why not?

 

[Zen Mod]

even for BA3 FE Balanced , it's on highish side

for unbalanced it's double on highish side

absolutely no benefit , except heat and short circuit between headphones

 

[KevinHeem]

even for BA3 FE Balanced , it's on highish side

for unbalanced it's double on highish side

absolutely no benefit , except heat and short circuit between headphones

Good thing I used two 50VA trannies, cause I like to be on the highish side.

Seriously, I used them simply because that's the smallest shielded transformer Antek makes.

 

[2 picoDumbs]

Good thing I used two 50VA trannies, cause I like to be on the highish side.

Seriously, I used them simply because that's the smallest shielded transformer Antek makes.

When it comes to transformers that's an entirely different issue.
I always just go 200VA to 300VA bare minimum assuming it's around 18V secondaries or higher since they can later be used in a poweramp if required.

If it's 12V secondaries or less then probably just go to 100VA, as they'll almost certainly not be used in amp I would be interested in building.

 

[PJN]

Hi All,

I'm finishing up a BA3 preamp to use with my F6 and soon to be completed M2. I was thinking of incorporating a volume and balance control instead of a simple ladder type pot that I have used in the past. I was thinking of using a scheme that Rod Elliot had posted on his site (see attachment below). I am looking for some advice on two questions.

1.) Do the two pots need to be the same resistance ( example : a 20K for vol + 20 k for bal) ?

2.) What resistance pot would work best for a B3/M2 combo ? (20K, 50K, 100K )

Thanks,

Paul

 

[Russellc]

Or just use two separate mono volume pots....many of those ladder pots on Ebay are available in mono.

Russellc

 

[PJN]

Thinking about is some more I doubt that the pots need to be the same resistance, the bal pot is a single pot and the resistance just would determine the "swing" between channels. So I guess I could use a decent stereo ladder pot with 1% resistors for the volume and a decent single pot(bournes, alps, ect.) for the balance.

Paul

 

[KevinHeem]

I would like to integrate a subwoofer amplifier into my system.

There's a local guy that has a pair of Gallo 3.5's for sale including the S.A. amplifier. It's possible I could try them before buying.

Is it as simple as using a "Y" connector coming out of the back of the BA-3 FE connecting the S.A. amplifier and my F5, or not so much? Attached are the specs for the S.A. amplifier if helpful.

View attachment Gallo SA.pdf

 

[42001]

Guys, do the mosfets need to mached closely in this??


Kind regards,
Sjoerd

 

[AndrewT]

I would like to integrate a subwoofer amplifier into my system.

There's a local guy that has a pair of Gallo 3.5's for sale including the S.A. amplifier. It's possible I could try them before buying.

Is it as simple as using a "Y" connector coming out of the back of the BA-3 FE connecting the S.A. amplifier and my F5, or not so much? Attached are the specs for the S.A. amplifier if helpful.

View attachment 556593

You need to add filters and maybe a bit of EQ to integrate the bass only driver/speakers with the satellites.
Most would call that an active crossover.

 

[KevinHeem]

You need to add filters and maybe a bit of EQ to integrate the bass only driver/speakers with the satellites.
Most would call that an active crossover.

Yes, the SA amplifier has dual-mono gain and phase controls, continuously variable low-pass filter from 40-200Hz and bass EQ from -3dB to +6dB.

 

[KevinHeem]

Guys, do the mosfets need to mached closely in this??


Kind regards,
Sjoerd

No

 

[42001]

Thanks!


Kind regards,
Sjoerd

 

[AndrewT]

Yes, the SA amplifier has dual-mono gain and phase controls, continuously variable low-pass filter from 40-200Hz and bass EQ from -3dB to +6dB.

And the satellites.

 

[KevinHeem]

I know this off topic but I did get to audition the Gallo 3.5's, only I did it at the guys house. The cool part was he had an XP-10 and 250.5. I so badly wanted to ask the him if we could pull the covers off, but I didn't.

 

[6L6]

It's not as cool as seeing the real thing, but -

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

 

[42001]

Wow!!!! That is very, very nice to see! Thanks 6L6!!

 

[Joca]

BA3 FE ,set to 6- 9db of gain will suffice

-say that you don't go bellow 24Vdc rails (so , after the reg)

-I'm not familiar with Store reg , but I believe that I noted it is of series type ; whatever , it needs at least 6V of headroom ( input/output difference) , considering possible 10% sag of mains voltage ....... which means 30Vdc

you'll get that , somewhat depending of xformer size ( power capability , which measn regulation factor ) with proper xformer with dual 24Vac secondaries ( or 48Vac center tapped)

if you end up with less than 30Vdc at reg inputs , just set output to little lesser than 24V ........ say 23 or 22V5

I have toroid with 100va and 2x24vac secondaries. Can i use your shunty? where do i get the pcb board?

Regards

 

[Zen Mod]

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