BA-3 As Preamp

[vdi_nenna]

My notes say:

Reduce R5, R6 and R7.
Or reduce R13.

I used standard values for as designed gain, i lowered R13 to reduce gain. I'm lazy.
ZM said in one post that R13 isn't the best way to adjust the gain because of a certain penalty, but I can't remember why. I think r5, r6 and r7 are preferred method.

I don't know what will happen if you go beyond designed gain structures. Noise or distortion?

 

[woofertester]

My notes say:

Reduce R5, R6 and R7.
Or reduce R13.

I used standard values for as designed gain, i lowered R13 to reduce gain. I'm lazy.
ZM said in one post that R13 isn't the best way to adjust the gain because of a certain penalty, but I can't remember why. I think r5, r6 and r7 are preferred method.

I don't know what will happen if you go beyond designed gain structures. Noise or distortion?

That would be for increasing the gain of the output stage. I am thinking of increasing the gain of the first stage.

 

[Zen Mod]

it's best to alter gain , when needed in greater amount , varying both degeneration resistor of input JFets and output I/V resistor

 

[woofertester]

it's best to alter gain , when needed in greater amount , varying both degeneration resistor of input JFets and output I/V resistor

Thanks. Good to know.

 

[ggetzoff]

it's best to alter gain , when needed in greater amount , varying both degeneration resistor of input JFets and output I/V resistor

Hey Chokester,

Would those be R8-R11

Pot size 10K-50K?

Cheers,

Greg

 

[Zen Mod]

ref. to enclosed schm

R5 is thingie in charge of input JFet degeneration ....... higher the value , lesser gain (of stage and overall)

R13 is thingie in charge of transforming output current to output voltage , higher the value , higher the gain (of stage and overall)

pot - yeah - 10 to 50 , being strictly in function/correlation of/with source cojones

 

[ggetzoff]

Choky,

I like the way you use cojones, especially using it on an audio forum...that’s why I like you.

I have LV shunty but could I go as low as 15v?

 

[ggetzoff]

My tube dac has output of 22k.

 

[Zen Mod]

you can ;

Her Mueller will rise uneven Hat , as you decrease rails , but with 15V you're still above verge

though , if you have it as option , to save precious volts from existing xformer , go brutal force - no regs** , just insane capacity

or simple cap multi with darlingtons , then insane capacity

**series shaving sissy amount of voltage , shunt shaving serious amount of voltage

 

[Zen Mod]

My tube dac has output of 22k.

Rout?

 

[ggetzoff]

Yes

 

[Zen Mod]

that's for sissies



you need buffer between that and any sort of volume attenuator

 

[ggetzoff]

Chokster,

I have DCB1 with pot prior to buffer. I should move it to output side?

 

[Zen Mod]

yes!

set DCB to have at least 220K input impedance ( bleeder from gates to gnd)

 

[ggetzoff]

What!?!?!?! All these years Ive had it backwards.....actually, I think I have it correct.

 

[Zen Mod]

If not Goeing , I'm not Boeing ?

 

[ggetzoff]

What’s the BA-3 pre current requirement?

My build thus far.....

 

[Zen Mod]

aroundish 100mA steereeoooo (SE) (50mA per channel)

best to use mono approach

if you're Boeing to shunt reg , , 100-150mA programmed current ........ so xformer no less than 350mA per leg

if you're Boeing for series reg , that's it ...... xformer no less than 150mA per leg

 

[ggetzoff]

aroundish 100mA steereeoooo (SE) (50mA per channel)

best to use mono approach

if you're Boeing to shunt reg , , 100-150mA programmed current ........ so xformer no less than 350mA per leg

if you're Boeing for series reg , that's it ...... xformer no less than 150mA per leg

Hilarious............

I’m going to be using the Salas LVs, so yes, mono. However while waiting for those I’m dying to try this with what I have, which is nice 24v, 150 mah supply. Sonically, it probably won’t be the best.

Bias it at 1v?

 

[Zen Mod]

bias it where Papa sez