Re-post My Aleph-5 problem

[dzkh63]

I finished a Aleph-5. Very thing OK. the sound great,the off-set was -10mv and -27mv stable. But I have a problem that when turn-off the amplifier, after about 1 second I hear a small CCCC......sound . at the same time the speaker's Mid-Low driver's CONE move FORWARD and returned . I have use a analog multymeter measure the speaker terminal, there is a postive 4V, and fast return to zero.
I re-post this question. Hopefully help me how to solution the problem. I want to know it will be damage the speaker and the amplifier?

[Duck-Twacy]

Nobody can say something usefull about this??

Maybe its the elco's decharging through the speakers?? Just guessing though...

[Magura]

If I am not mistaken, this effect would be a matter of the discharge of the PSU caps. This effect is quite pronounced on some topologies if the tolerances of the PSU caps are big, and the caps are in each end of the tolerance.

Magura

[stefanobilliani]

IMHO it is the mismatch of the Fets .

If you like to take a safe range for your speakers , there is a nice relay circuit that short the speaker outputs and prevents both turn on and off thumbs .
The extract comes from the Zen Lite project pdf .

[dzkh63]

Thank you for your reply.I'm long long time waiting.
My PSU used 4-68000uf/50V caps. and 2-2.2mh, AWG#14 conductors.The output cap was parallel a 20uf/400V Solen cap. and a 0.1uf/100V Wima MKP.
The FETs match as following:
3.724 , 3.728 , 3.728.
3.738 , 3.734 , 3.744.

3.712 , 3.712 , 3.710.
3.718 , 3.726 , 3.724.

The off-set was stable: -10mv ,- 20mv.
The problem was happen the 2 channels, I don't know how to check the caps. tolerance. I never find the same problem in this forums. I think may be I have some mistake. I ask help me to solution the problem. Add a protect circuit may be a last choice.
Thank you!More people discussion.

[wuffwaff]

Hi,

I just had a look at my Aleph5. It does exactly the same thing as yours. After turn off it does nothing for a short time, then 3.6V appears for a very short time.

It does this on both channels. I seem to remember other Pass amps I had at home doing the same thing.
I wouldn´t worry about this cause it certainly won´t hurt your speakers. You just have to get used to the "blub" coming out of your speakers at turnoff

William

[Netlist]

My AlephX measures a 1.5VDC peak when I shut it down. It very fast goes down to 0V. I recall having that noisy sound as well in the test phase. For some reason it disappeared in time, I think I upped the bias a bit. Bear with me, this is just an assumption. Your 4VDC is a bit high though.

What do you mean with 'Output Cap' ?

/Hugo

[dzkh63]

Dear Hugo thank you for reply. Please forgive my poor English. The 20uf Solen cap. and 0.1uf Wima MKP was parallel to second 68000uf/50V cap. ,it's located after the conductor .
Dear Willam thank you for your reply. I will no worry about this problem. This is my first DIY project. I'm satisfying the performance. More better then my Accouphase E210 integrate amplifier.
Thank you friends help.

[Duck-Twacy]

I'm also building an Aleph5 with a CLC in the powersupply (my second amp, but my first was a kit, about 20 years ago. So I also don't have a lot of experience). At the moment I don't make much progress (too many other things to do).

It would be nice to see your Aleph, dzkh63.
Maybe you have a picture you like to share?

Greetings.

[Blues]

Could it be that at power off DC volts find its way through R1, LED1, R22-R25 then accross your speakers as the PS caps discharge? Try connecting cathode of LED1 directly to ckt ground. Has anybody experienced this on their Aleph 30/60?