Aleph 30 unmarked resistors?

[kasra]

Im intending to build the balanced input for my aleph 3.
When looking on the schematics of the aleph 30 i found that 2 resistors both called R8 was unmarked.

What values should i put in there?

thanks in advance!

 

[kasra]

Oh....
I found an tread where mr Pass wrote:

R1 is used to trim Power Supply Rejection

R8 is used to trim DC Offset

R0 is used to reduce ground loops.

----------------------------------------

However by not knowing any of those values to start with, should i leave them out or jumper them instead?

best regards - kasra

 

[Nelson Pass]

If you need to adjust these parameters, start with
very high values, say 100K and go down from there

 

[eapavant]

What value are people using for R8? I have 100k. I am getting 2.8-3.0 vdc on my output. Should I decrease R8? Or do I have a different problem?

 

[Nelson Pass]

What value are people using for R8? I have 100k. I am getting 2.8-3.0 vdc on my output. Should I decrease R8? Or do I have a different problem?

depends on the polarity of the offset.

 

[eapavant]

I now seem to have other problems. I smoked R15 and 39, and I can now measure resistance from the drain to gate on all mosfets. I guess that means that they are blown? I have no idea how I did that.

 

[mpmarino]

I understand that R8 is only used if needed and not necessary. It is used to trim for dc offset if the diff pair is not matched well....right?

 

[KevinLee]

depends on the polarity of the offset.

Hello Mr Pass,

I have an Aleph 30 (Volksamp) with -200mv of DC offset on one channel and am looking for some advise.

I currently have no resistors in the R8 position on PCB.

The other channel fluctuates from about 10mv to -10mv after a couple hours.

Cheers
Kevin

 

[juluska]

No es clase A, o al menos no clase A pura simplemente por utilizar transistores de potencia complementarios MJ15003 y MJ15004. Para clase A pura tendrías que ir a esquemas asimétricos del tipo Zen de Nelson Pass con muy baja potencia y elevadísimos consumos. Si de verdad fueran 100 w en clase A necesitaría un toroidal de más de 23kg,

http://www.passdiy.com/pdf/articles/powersupply.pdf

Supongo que, como mi viejo musical fidelity A1 debe estar un poco subido de amperaje en la polarización, con lo cual una pequeña parte de sería clase A. Mide el amperaje en los transistores de potencia, uno de ellos debería marcar algo en reposo y creo que así podrías calcular hasta dónde es clase A, es lo que hacen en esta página:

http://www.mhennessy1.f9.co.uk/mf_a1/technical.htm

 

[wengtech]

can i use trimpot for first adjust into r1 r8 n r0 ?
and when the measurement all correct then i replace them with resistors.

what do you think?

 

[Zen Mod]

yes

 

[wengtech]

thank you zen mod,
i will try 100k trimpot for those 3 empty R, and trimming down from there.

and also maybe the trimpot should not be changed into R (i think.)