BA3 preamp hiss

[fwt1712]

I have got my BA3 preamp up and running (into peter daniels gainclone and then original spendor sa1 speakers) and am very happy with the music it is producing - way better than anything else I have used (audio synthesis passion passive mainly). It has added way more clarity, depth, power, precision but it is a bit hissy(er) than I would like. Basically I can hear a hiss/whooshy sound from a meter when not playing music and occasionally on very quiet sections. I have followed the build guide and used what I think are good bits i.e. all dale rn60s, mundorf evo oil output caps etc, alps blue 50k pot and tubecad input selector and ps19 bipolar supply. It powers up nicely with no thumps or bumps etc. and is biased pretty much bang on 1v as specced. I am just a bit perplexed at what I think is just a bit too much hiss. It doesn't vary with change of volume control from min to max (with no music of course) and even at max volume there is only the slightest hint of hum - and none below it. Any ideas on where to look - or even confirmation that this is to be expected with a no feedback design would be appreciated.

thanks in advance,
Nigel.

 

[Zen Mod]

what's ps19 bipolar supply ?

 

[Dennis Hui]

what's ps19 bipolar supply ?

I believe it's this:

GlassWare PS-19 Bipolar Power Supply Kit

 

[Zen Mod]

besides possibility that LM chips are not worthy knock-offs (so hissing) , there is a fact that LM317/337 reg is not worthy of BA3

shoot me , I'm biased .... and I like it that way

 

[2 picoDumbs]

I agree. Not worthy.

 

[2 picoDumbs]

On something like the BA3 front end, that draws no more than 60mA (per channel) I would use a shunt regulator circuit.

 

[Zen Mod]

what else ?

 

[2 picoDumbs]

what else ?

I am biased towards shunt regulators when practical.

 

[Bare]

Find... 4 Enerloop AA cells = 4.8 v (ooops Bipolar means 8 cells?)
Whatever, still cheap and trustworthy.. use those for the power supply... even if only experimentally.
Then you will know if the PS is the culprit.

 

[Russellc]

I used that PS in my second BA3 pre. VERY worthy, mine is dead silent. 6L6 used the previous model in his build. Sorry guys, problem is elsewhere.

Russellc

 

[didiet78]

Any ideas on where to look - or even confirmation that this is to be expected with a no feedback design would be appreciated.

thanks in advance,
Nigel.

Pictures of your build maybe would help

 

[Zen Mod]

I used that PS in my second BA3 pre. VERY worthy, mine is dead silent. 6L6 used the previous model in his build. Sorry guys, problem is elsewhere.

Russellc

worth trying , in case that any of LM chips is dude

and believe me , plenty of them around

regarding LM vs. decent shunt reg .......... to each his own

as always , YMMAMV

 

[Russellc]

worth trying , in case that any of LM chips is dude

and believe me , plenty of them around

regarding LM vs. decent shunt reg .......... to each his own

as always , YMMAMV

Oh no, you would be right as to superiority of shunt reg...well known fact. I'm just saying that particular power supply isnt doomed out of the box.

I have a populated mezmorize and hyponotize board I would like to use as such...also your shunty which is my next project. ( will try to get it working before tackling the Pumpkin, all in good time ) May be missing the smarts to implement in BA3, but for now the 317 power supply works fine. Maybe he should try different pieces of those parts.

My other BA3 FE has a power supply built on Peter Daniels board, I forget which regulator it uses...

Russellc

 

[Russellc]

Pictures of your build maybe would help

Or all here can illustrate a nice shunt reg and its implementation to BA3, I will definitely be following along in Betty Crocker fashion! Somewhere I have someone's notes on implementing shunty to another device, Pearl 2 maybe...I am digging.

Russellc

 

[Zen Mod]

if speaking of Shunty , all we need to know is rails voltage and Iq of BA3 stage

 

[Russellc]

if speaking of Shunty , all we need to know is rails voltage and Iq of BA3 stage

I will begin in earnest to assemble shunty....

 

[drpro]

The Salas shunty plays very nicely with my BA-3.

 

[Russellc]

The Salas shunty plays very nicely with my BA-3.

Is there a link to it?

Russellc

 

[drpro]

http://www.diyaudio.com/forums/power-supplies/192625-sslv1-1-builds-fairy-tales.html

Teabag has boards and partial kits available.

 

[Russellc]

http://www.diyaudio.com/forums/power-supplies/192625-sslv1-1-builds-fairy-tales.html

Teabag has boards and partial kits available.

Thanks