threshold SL10 - DC output

[pjmont]

Hello, i have a Threshold SL-10 preamp and a threshold TA300 poweramp, now i have a problem with the preamp :

Only in the left channel i have found one DC of 0,12V, this cause a problem with the poweramp (only the power amp without the pre is ok), and so my left woofer have a strange and unusual movement, even if sound the same one.
What's it? a any broken transistors?

Thank you
Pierluigi (Italy)

 

[Nelson Pass]

I am posting the schematic of the high level stage, which
(hopefully) shows a direct coupled output whose DC offset is
adjusted by an op amp. The op amp could be bad, or the
capacitor could be leaking, or some other component could
be failed sufficiently that the op amp can't make the correction.

 

[pjmont]

Ok many thanks Nelson.
Bye
Pierluigi

 

[tfender]

I am posting the schematic of the high level stage, which
(hopefully) shows a direct coupled output whose DC offset is
adjusted by an op amp. The op amp could be bad, or the
capacitor could be leaking, or some other component could
be failed sufficiently that the op amp can't make the correction.

Hello
I take an interest that try out , Pre SL-10 , this , I want to know position value aforementioned , and the circuit , Supply ,

Thanks

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

 

[Zen Mod]

search

it's there

 

[juanitox]

i really love the sound and look of this preamp , the only thing is the hi level stage gain , too much gain for nowadays sources and amp . is there a solution to reduce the gain of this stage without affecting too much the sound ?

i have already put a 30k resistor in series with the volume pot but it is the max i could had before affecting the sound..

any idea ?

 

[Zen Mod]

didn't I already told you (somewhere ) - just cut that 18K2 in half , for 6db gain reduction

gain is roughly 18K2/750

 

[juanitox]

hey zen guy sorry it was not me , can you explain how to cut ? i have the scissor ready

 

[Zen Mod]

either solder another one 18K2 across existing one , or desolder existing one and solder 9K1 instead

 

[juanitox]

you are a killer.. thks

 

[Zen Mod]

nope

I'm Manu's Padawan

 

[juanitox]

i'm small , i'm an ant... do you know what is for the 5K pot in parralel with a 3.3K res on the schematic? because i dont have it i just have a 1.3K res on both channel . is for the sweet spot or DC offset?