L'Amp: A simple SIT Amp - Page 41 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th January 2012, 09:21 PM   #401
generg is online now generg  Germany
diyAudio Member
 
generg's Avatar
 
Join Date: Jul 2009
Location: Near Frankfurt
And of course before I change to stereo I will do a last comparing resistor, CCS and MU follower...
__________________
and the First Wtt is......a really First Class PSS Idea
  Reply With Quote
Old 16th January 2012, 12:13 AM   #402
diyAudio Member
 
nicoch58's Avatar
 
Join Date: Oct 2004
HI

Can I ask if is possible cooking something my good old 500VA r-core ?
With 39Vdc I haved draw 2A bias,cold like a dead, probabily good for 4A....
Caps 40k for ch.
Tnx
__________________
Sic58
  Reply With Quote
Old 16th January 2012, 12:34 AM   #403
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally Posted by generg View Post
this picture was taken at about 2,9V and 2,4A and shows at least the dominance of the second harmonic and the absence of higher distortions at lower input levels....
Very high 100Hz rectification buzz plus its first harmonic and their beat though. Should be pushed down further. But no 50Hz hum, that's good. I.e. no fields or gnd loops.
  Reply With Quote
Old 16th January 2012, 05:16 AM   #404
generg is online now generg  Germany
diyAudio Member
 
generg's Avatar
 
Join Date: Jul 2009
Location: Near Frankfurt
Quote:
Originally Posted by Salas View Post
Very high 100Hz rectification buzz plus its first harmonic and their beat though. Should be pushed down further. But no 50Hz hum, that's good. I.e. no fields or gnd loops.
Yes Salas .....you are right! I was very astonished to see that 100 Hz and 200 Hz peak! Normally I have a 50 Hz peak.
Why do I get this different peak and what can I do against him and I hear no hum....!

Gerd
__________________
and the First Wtt is......a really First Class PSS Idea
  Reply With Quote
Old 16th January 2012, 05:30 AM   #405
diyAudio Member
 
juanitox's Avatar
 
Join Date: Dec 2006
mine is huming like a beast . but as i remember other big toroids amp was buzzing before i probably have DC on the main. 200W variable resistor is not
a good idea the heat is so high that the wood of my case is now broken.

long is the road....
__________________
French is not a crime.
  Reply With Quote
Old 16th January 2012, 06:12 AM   #406
generg is online now generg  Germany
diyAudio Member
 
generg's Avatar
 
Join Date: Jul 2009
Location: Near Frankfurt
Sorry to hear that !

My 13 Ohm chain consists of five 50W resistors and they make on their own heatsink as big as the one for the SK82 even more heat......

Did you build the PSU like Mike suggested? But I have nevertheless only 42 deg Celsius on the sinks surface
__________________
and the First Wtt is......a really First Class PSS Idea

Last edited by generg; 16th January 2012 at 06:16 AM.
  Reply With Quote
Old 16th January 2012, 06:18 AM   #407
generg is online now generg  Germany
diyAudio Member
 
generg's Avatar
 
Join Date: Jul 2009
Location: Near Frankfurt
Your variable resistor is nevertheless a good idea, I am still fighting to get closer to the sweet spot, even 0,5 Ohm make a remarkable deviation from the point.
__________________
and the First Wtt is......a really First Class PSS Idea
  Reply With Quote
Old 16th January 2012, 09:31 AM   #408
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally Posted by generg View Post
Yes Salas .....you are right! I was very astonished to see that 100 Hz and 200 Hz peak! Normally I have a 50 Hz peak.
Why do I get this different peak and what can I do against him and I hear no hum....!

Gerd
100Hz is double the mains frequency (as coming out from bridge rectification cycling), 200Hz is its first harmonic, 300Hz is 1st's and 2nd's beating product plus smaller ones up higher. If you can't hear any ZZZZ noise then its just something in your measuring rig. Such harmonic noise gives ''grunge'' to midbass when present making it seemingly bigger also. What you can do is increase amp's PSRR with CCS or use filtering in the PSU. Choke or capacitance multiplier.
  Reply With Quote
Old 16th January 2012, 10:25 AM   #409
generg is online now generg  Germany
diyAudio Member
 
generg's Avatar
 
Join Date: Jul 2009
Location: Near Frankfurt
Hi Salas, thanks for your answer....

I just creeped into my open baffles to the tone tubby, there is only a very very faint hum... so I suppose it is this time more the measuring rig.

At any case you had a very good look at my data.......

still waiting for resitors and the IRF you suggested.... good that only the amp is mono and not me.....
__________________
and the First Wtt is......a really First Class PSS Idea
  Reply With Quote
Old 16th January 2012, 11:54 AM   #410
diyAudio Member
 
Join Date: May 2001
Blog Entries: 5
Quote:
Originally Posted by juanitox View Post
...the heat is so high...
Way too hot inside that case, and that's probably not making your transformer happy either. Move those resistors outside or get bulbs. Have a look at my post on resistors, the ones I used are 4 times as big, and I used three for each channel.

Keep going, you're almost there.
  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
L’Amp: A Simple SIT Amp: Part 1 Michael Rothacher diyAudio.com Articles 22 5th October 2013 09:25 AM
SIT Amp Article Out Now Variac Site Announcements 0 2nd December 2011 07:55 AM
Srajan has the 1st SIT amp for Une dégustation vizion Pass Labs 131 14th November 2011 11:41 PM
SIT-Preamp VladimirK Solid State 36 27th August 2011 08:36 PM
New SIT - old problem StevenOH Parts 2 13th June 2008 10:46 AM


New To Site? Need Help?

All times are GMT. The time now is 06:50 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