Aleph 30 - noise in right channel

[Buhl]

Hi All
My trusty Aleph 30 has over the last week developed a strange habit - it would start to put out an audible crackling White noise on one of the channels after some hours of use - and it now does it on turn on - all the time. There seems to be some DC offset as the woofer moves outwards a bit and stays out.
The amp plays music "fine" - even on the noisy channel, however the noise is always present, and independent of volume - it's also present without signal input cable plugged in.

Any ideas/suggestions on where to start?

Only non-stock change is that the LTP input transistors and CCS are changed to Zetex ZVP3310 fets.

Best regards
Hans

 

[PKI]

Start with good quality under the hood photos, right, ZM? 🙂

 

[Zen Mod]

yup

or just send it ASAP to OPLDF

 

[Buhl]

Pictures, thought audio files would be more helpfull 🙂

Anywhere, here goes:

BTW - where/what's OPLDF?? 🙂

Best regards
Hans

 

[Maousse]

I would gently hit the components with a light isolated thing.
IMHO, bad solder joint or bad resistor.
R6 is badly bent, per exemple.

 

[Zen Mod]

yup

reflow

if that doesn't help - replace input side CCS ......... then LTP mosfets

Official Pass Labs Disposal Facility


😉

 

[Buhl]

Hmmm Zen Mod - I recall a document made by you, something about how to convert the sissy Aleph30 into a less sissy Aleph J? Think it might be good excuse now I have to change the Little Black input fuses after all...?

However, the search gives no result...

Best regards
Hans

 

[Zen Mod]

it feels oldish , as from previous life 😉

NB that 43R source resistors are typo

4R3 is right ( I had bunch of them ) ........ use anything between 2R2 and 10R

 

[Buhl]

Thanks Zen Mod..... just what I needed.....

But fooob*r! - My amp is A30 - and has 3 pairs of FETS in the output stage, so I guess I'll have to look at replacing the old fets 🙁

Best regards
Hans

 

[Zen Mod]

same thing - 3 deep or one deep as in Babelfish J - pretty irrelevant for input LTP

what you mean by "replacing old fets" ?

 

[Buhl]

I just wanted to follow your Humble advice: "replace input side CCS ......... then LTP mosfets"

So, if I use a 109-double-JFET - will it be able to drive my A30 output stage with 3 pairs of IRFP240?!?

 

[Zen Mod]

yup