simple pre with offset problem

[aparatusonitus]

No, as long as input is without dc offset.

[kp93300]

I remove the 2sk 170 ,2sj74 and replace with matched set with IDSS of 10 and 10.05 ma.

I rewire the drain source orientation.
The input voltage is + 12.07 V and -12.09 V . The dc offset could be trimmed up to 0.1 to 0.14 V only for both channels ---no change.

BTW, i use LM 313 and 337 as regulators .

The pre runs very well without any undue heat in the regulator or the transisitor. I have left the thing on for 1 to hours without problem.

Do i need to match the BC 550 and 560 ?
I do not own a scope, how to check for oscillation as suggested in one of the previous post?

Thanks to all for the suggestions.

Will do further checking later.

Let me enjoy some music ! I am still very satisfied despite the dc offset.

kp93300

[juma]

kp93300, you are doing something the wrong way - please check everything carefully,it must be something with wiring or components' values.
BJTs don't have to be matched.

[Joachim Gerhard]

Interchanging drain and source with 2SK170 and 2SJ74 is posible without problem.
Try to trimm R6, R7.

[PHEONIX]

Originally Posted by kp93300

I build this circuit contributed by a fellow forum member.
I am unable to trim the dc offset to zero.
Both channels show 0.1 V dc output.
It sound very good with a output cap .
What is the solution?
Do i need to match the vgs ? can a 50R trimmer solve the problem and change the sound character?
Thanks

kp93300

Why is dc voltage of 0.1V a problem , is this stage going into a power amp.

Regards
AR

[AndrewT]

this schematic is very similar to Pass' F5.
Read that pdf for some clues on setting up.

[Bonsai]

I doubt that changing the pot from 20 to 50 Ohm will 'ruin the sound' of this pre-amp.