Update for Elektor Crescendo Power Amplifier 1982 - Page 4 - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Elektor

Elektor News and offers from Elektor Magazine

Reply
 
Thread Tools Search this Thread
Old 16th September 2007, 03:46 AM   #31
oodi is offline oodi  Canada
diyAudio Member
 
Join Date: Jan 2006
Location: Sioux Lookout, Ontario
I have an Elektor amp I built a long time ago, maybe 1983? I have since misplaced the original Elektor magazine (German version) that contained the schematic. Attached is a picture of the board. At the time I made a single board containing 2 channels for a stereo amplifier. IIRC the original had an individual board per channel.
Attached Images
File Type: jpg im000500_sm.jpg (81.1 KB, 1940 views)
  Reply With Quote
Old 16th September 2007, 03:48 AM   #32
oodi is offline oodi  Canada
diyAudio Member
 
Join Date: Jan 2006
Location: Sioux Lookout, Ontario
Just a closer view of mostly one channel.

And my question, would anyone still have the schematic for this amplifier? I would like to replace the 220V transformer with a 110V version. Would be nice to have documentation on the amp in case of troubles...
Attached Images
File Type: jpg im000501_sm.jpg (75.6 KB, 1829 views)
  Reply With Quote
Old 16th September 2007, 09:27 AM   #33
PMik is offline PMik  United States
diyAudio Member
 
PMik's Avatar
 
Join Date: Mar 2004
Location: Fort Lauderdale, FL
Oodi send me a PM where to send the original article

Chryslerjay
afir. i did advice you to take contact to a firm very close related to AI
If they did not offer you help, the best solution would be to have a new transformer made.
__________________
Mod is fun
  Reply With Quote
Old 17th September 2007, 01:56 PM   #34
oodi is offline oodi  Canada
diyAudio Member
 
Join Date: Jan 2006
Location: Sioux Lookout, Ontario
I think I sent you a PM, if that's what the email link at the bottom of each message does...
  Reply With Quote
Old 17th September 2007, 03:02 PM   #35
PMik is offline PMik  United States
diyAudio Member
 
PMik's Avatar
 
Join Date: Mar 2004
Location: Fort Lauderdale, FL
got it
__________________
Mod is fun
  Reply With Quote
Old 19th June 2010, 10:57 AM   #36
bitravi is offline bitravi  India
diyAudio Member
 
Join Date: Jul 2007
Pmik can u send me the same article,my mail id is:bitravi@rediffmail.com.
  Reply With Quote
Old 25th June 2010, 05:37 AM   #37
bitravi is offline bitravi  India
diyAudio Member
 
Join Date: Jul 2007
Is this amplifier OK to build.
Has any one tested it with modifications.
Attached Images
File Type: jpg crescendo-mod.jpg (76.8 KB, 1172 views)
  Reply With Quote
Old 6th March 2011, 02:08 AM   #38
holger1 is offline holger1  Germany
diyAudio Member
 
Join Date: Mar 2011
Quote:
Originally Posted by bjornagain View Post
I have lived with this 180 W amplifier for almost two decades. It has been proven to be good sounding and reliable over the years, even though I must admit a little tricky sometimes. In the posts in the www.diyaudio.com I am glad too see that the Crescendo has good reputation, and many have built it and likes it a lot. The Crescendo is still very competitive I think, and should be a contender to the Hall of Fame of diy-amplifiers, if there is one!

My guess is that everyone who built this amplifier has or had some problem with high frequency oscillations and some hum induced from the power supply. High frequency oscillations can be hard to get rid of. There have been some tweaks published in the Elektor, and some that I have collected from postings on the Internet.

My amplifier had a lot of high frequency oscillations, and the RC-chain on the output went up in smoke. But the solution was easy; a small capacitor across the bias resistor solved it! I think it should been there in the first place.

So, here is a listing of proven and unproven ideas:
This should really be a table!
|| No || What || Why || Reference ||
|| 1 || 47nF in parallel with the bias resistor P1 || HF osc || Proven effective by me ||
|| 2 || Non-inductive source resistors R27-R30 || HF osc || Recommended by Elektor and others ||
|| 3 || RC-chain R32 C16 moved from pcb to speaker posts || HF osc || Recommended by others, used in other constructions ||
|| 4 || 1 nF between n-channel source resistors R27 and R28 (alternative to no 2) || HF osc || Recommended by Elektor ||
|| 5 || Replace cascade transistors T8 and T10 BF469/470 with better MJE350/340 || Improved sound quality || Recommended and proven by others ||
|| 6 || Active DC regulation || Improved sound quality || Recommended and proven by others ||
|| 7 || Resistive collector load for the voltage amplifier (it sees a varying impedance in the gate of the mos fet's) || Improved stability || Unproven here, but used in other constructions ||
|| 8 || Different feedback paths for LF and HF || Improved stability || Unproven here, but used in other constructions ||


I still have some problems with hum, and I have rewired a lot a tried many other things. Nothing helps. Stabilizing the input section didn't. To compact housing perhaps? Left and right channel does not hum equally either, and it is very irritating!

On the other hand, one of the channels have a defective mos fet, but still works...

Anyway, I think this amplifier deserves another decade using some of the tweaks. I was a bit disappointed with the new Crescendo ME, I can't use it to upgrade the original Crescendo, and there are problems with high frequency oscillations in that one too!

I will be happy to receive comments and help to update the reference columns with links to diyAudio forums.

Best regards,
Thank your for your hints. I build the Elektor Crescendo with good success, but most of all your hints are not working as expected. I changed the design in five points:

1. Non inductive metal film resistors for R27/28/29/30.
2. Lowpass filter with 6k8 and 330pF attached to the input.
3. Better driver transistors MJE350/340 instead of BF469/470.
4. A seperate stabilized power supply with +/-80V for the pre-stages.
5. The 10 Ohm resistor R3 needs to be removed to prevent ground loops.

No hum and no noise is audible. The amplifier works stable. Since the power transistors 2SJ50 and 2SK135 are available again, the Crescendo can still be build.

Holger
  Reply With Quote
Old 18th March 2011, 02:21 PM   #39
masood is offline masood  India
diyAudio Member
 
Join Date: Dec 2010
Location: fatehpur
Quote:
Originally Posted by Bgt View Post
The original design by Elektor had some nasty switching glitches and started oscillating in the wild. After making a new PCB(by hand drawing) for it and modding it is a super stable amp. Not a powerhouse, 100W 8Ohms at +_60V), but enough. Still use them, but every 10 years change all the electrolyt. caps./wiring.
The amp.is build in complete symmetry. Crosstalk at 20Khz= -100DB. Best I ever achieved with an 1 transformer stereo amp.

Click the image to open in full size.
there is not image in ful size
  Reply With Quote
Old 18th March 2011, 02:23 PM   #40
masood is offline masood  India
diyAudio Member
 
Join Date: Dec 2010
Location: fatehpur
Default thank you

Quote:
Originally Posted by masood View Post
there is not image in ful size
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
SLN Pre-Amp - Elektor Aug 1982 GlidingDutchman Elektor 26 6th April 2013 08:46 AM
I need comments about "100W power amp. elektor april 1982" jinkuchi Elektor 78 22nd February 2011 04:15 PM
Crescendo Millenium amplifier (ELEKTOR magazine 4 2001 p.36-45)? alex0 Solid State 22 13th March 2002 09:46 AM


New To Site? Need Help?

All times are GMT. The time now is 07:18 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2