Crescendo ampilifier elektor1982

[lineup]

Here is a better ORIGINAL Crescendo 1982 schematic scan.
I found the link by searching this forum.
http://img347.imageshack.us/my.php?image=cres1c9wn.jpg

I hope it uses same refering label numbers for resistors as danne uses.

[danne_linkinpar]

I test my Crescendo today again and i have change the resistors and tody the R15,R16 and R9 gone upp in smoke why, sombody now???

[Jay]

hi danne,

may be you put 12V zener in place of 3v9 zener? They look similar. The 12V one is slightly fatter, and has higher series number.

[danne_linkinpar]

I hav eproblem whit oscillations in my crescendo somone that can help me+?

[Bensen]

Make sure that your gate resistors are as close as possible to the gates of the MOSFET's! Put a ceramic cap of a few 100n between the + and - rail as close as can be to the FET's.

[AndrewT]

Hi Bensen,
do you mean drain to power ground? or +drain to -drain?

[Bensen]

Hi Andrew,

No I ment: just placing one ceramic cap between the power rails. And this as close as possible to the MOSFET's.

[AndrewT]

Hi,
just as done with opamp bypass!
Never seen this on a power amp.

[refosk]

I had built the original crescendo from 1982, it works fine with low volumes but when I volume it up I get strange distorsions heard like brp,brp,brp when bass is playing. And this bass distorsions are very loud. Can someone sugest me what to look for?

[joensd]

Maybe P1 is dirty/corroded and so bias current might not be set properly.
Check bias current and if you set it up turn the pot slightly forth and back (that sometimes is enough to "clean" the contacts;
if it´s too bad and current alters, change it)

Otherwise check all voltages and report back the ones that are not at least similar to the original schematic.