Update for Elektor Crescendo Power Amplifier 1982

[masood]

Originally Posted by holger1

I sent a copy of the pcb layout to your personal email address. Please note, that the MOSFETs in the output stage must be mounted directly on the pcb, with an L profile of aluminium between the MOSFETs and a decent heatsink. The schematic has been already published in this thread. Good luck!

[masood]

dear holger,
happy new year.as u mentioned that u have sent a copy on my personnel e mail i have not received such type of pcb.sorry for bother you.thanking u.
your ever masood

[masood]

dear holger1,
plz send me pcb again of your post 43.thanking you

[luigicosta]

hi, can you send me a copy?
cicciosamui[at]hotmail.[dot]com


thanks

[dungdochi1978]

Originally Posted by Kay Pirinha

Hi dungdochi,

finally here are some pics of my CRESCENDO stereo power amp. Have fun and thanks for waiting!

Best regards

So look not nice, seem almost need maintance. but i dont want it more ,now i want build up A1000 amp & F5 of nelson pass. Because it is fully class A. QUALITY. if you have more expeirient do it can send it to me.
Thank you

[jan.didden]

Originally Posted by Kay Pirinha

Hi dungdochi,

finally here are some pics of my CRESCENDO stereo power amp. Have fun and thanks for waiting!

Best regards

Very well build, looks good. Must be 20 years old or so?

jan didden

[Kay Pirinha]

Hello Jan,

I've built it in 1985 or so, using lots of components out of my scrapboxes.

Best regards!

[HumNSmoke]

Hi hot tip guys
I did it in 83/84 and used it for 10 years, then I moved in a little house where I didn't have room enough to host it... the beast is huge and heavy 30kg...
Some days ago I decided to bring it back to life after a 15 years sleep in the idea to use it as the bass amp for an active 3 ways system around a DCX2496, but I noticed after removing the dust that there was hum in the speakers as soon as I plugged in the second input, left or right. I broke the ground in one cable and also isolated the earth.... still same behaviour... the I saw R32 comes very hot when I plug the output wires (checked for short-cuts)... although, the amp works on both channel even together, and DC out seems OK on one (20mV) and the other seems to near to zero to be honest
I never watched the outputs with a scope so I asked a friend to lend me one and I saw a "nice" 2MHz sinus as soon as I plug a wire on the outputs, even with-w/o the speakers... and even with the passive filters .
My amp is a bit tweaked: I didn't wired the 470VA transfos like in Elektor. Instead I used one for each channel with the idea to be able later to have the two channels completely independent from each other.
Any advise please?
Thank you in advance.

[HumNSmoke]

R32 on left channel rosted (one whole night under oscillation condition) the CF4 24/10mm stained 70µm copper.
Added pictures of :
The supply: 4 rails 20mF/100V each (on the right bottom corner, the central and single link between left/right ground, case and earth
The CF4 side
A different build with the same heatsink (parallel instead of right angle) I never tried, more compact but harder to maintain (heat tranfert aluminium piece 4mm under mosfets and 12mm over the heatsink)

[Bensen]

Hi,

Welcome to DiyAudio!

If I see it correct, you are definitely using wirewound source resistors (0R22).
These are causing on all Crescendo's oscilation.

You should swap them to inductive free resistors (e.g. MPC71), or use 4 carbon resistors (also inductive free) as I did.


Greetz