"fisss" on the 6C33C-pp - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 30th July 2006, 05:53 PM   #1
felixx is offline felixx  Romania
diyAudio Member
 
felixx's Avatar
 
Join Date: Feb 2005
Location: in center
Default "fisss" on the 6C33C-pp

I finish my project ...an pp with 6c33c....this is the schematic:
http://translate.google.com/translat...schreibung.htm
But...I have a problem....the noise...is not "humm"....is "fissss".
I replace some C's.....more close to 470uf/450V and the little "hummm" was disappeared.....but I still have that "fisss".All the ground wires was strictly the same like in the original project.From each plate is only one single ground wire,exactly like is in the pictures,and all connected in only one point,to the chasis.
That "fisss" is hear by some 7...10cm from the speaker(an 85db/m speaker).....and it's fine ........but when I connect an 96db/m speaker,the situation is not so good.The noise is detectable from about 1,8 meters.It's only "fisss" but it is and is not depend from volume level.
So ....do you have any ideeas how can I remove that ?
Many thanks.
__________________
"I'm glad I can build my own mistakes."
https://picasaweb.google.com/115586837612433686520
  Reply With Quote
Old 30th July 2006, 06:40 PM   #2
Giaime is offline Giaime  Italy
diyAudio Member
 
Giaime's Avatar
 
Join Date: Oct 2004
Send a message via MSN to Giaime
Are you sure you are using metal film resistors all the way? Standard carbon film resistors (or worse, carbon composition) DO have higher hiss (by the way, "hiss" has some deeper technical explanation, maybe this is interesting for you).
  Reply With Quote
Old 30th July 2006, 07:01 PM   #3
felixx is offline felixx  Romania
diyAudio Member
 
felixx's Avatar
 
Join Date: Feb 2005
Location: in center
I removed all the "humm"...simply by replace some values of filters and "pi" filters but that not reduce the "fisss".That noise is not a problem for the 85-87db speakers......but for the 95-100 db is a pain in the a**.
Tomorow I want to work a little on the 400V power supply ...to replace regulator with fast switching diodes with parallel 4,7nf.....and see what happens.
If you have any experience in that issue please explaine.
I know .....the problems with noise rezistors.....but maybe that power supply was not sufficient filter....
Any ideeas.......?
__________________
"I'm glad I can build my own mistakes."
https://picasaweb.google.com/115586837612433686520
  Reply With Quote
Old 30th July 2006, 08:24 PM   #4
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Put a wide-bandwidth oscilloscope on the output with the speakers connected. You might have ultrasonic oscillation.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 30th July 2006, 08:25 PM   #5
felixx is offline felixx  Romania
diyAudio Member
 
felixx's Avatar
 
Join Date: Feb 2005
Location: in center
So what do you think was that cause?.........the output trafo?
__________________
"I'm glad I can build my own mistakes."
https://picasaweb.google.com/115586837612433686520
  Reply With Quote
Old 1st August 2006, 03:29 AM   #6
wfmali is offline wfmali  Europe
diyAudio Member
 
Join Date: May 2003
Location: G-U
Did you run it without the pre-tubes? Did it still "fisss"? The power supply for the final stage looks fine to me-quite some effort here for PP - but maybe you hear some "switching" noise from the rec diodes?
Anyway - would also eMail Ernst directly and ask him, if nothing else,
cheers,
Marcus
  Reply With Quote
Old 1st August 2006, 05:14 AM   #7
felixx is offline felixx  Romania
diyAudio Member
 
felixx's Avatar
 
Join Date: Feb 2005
Location: in center
I run it without the pre-tubes.....the "fisss" is gone.So....the pre-tubes plate may be the cause.
I write to Ernst Roessler ....the owner .....but nothing.
__________________
"I'm glad I can build my own mistakes."
https://picasaweb.google.com/115586837612433686520
  Reply With Quote
Old 2nd August 2006, 04:27 PM   #8
felixx is offline felixx  Romania
diyAudio Member
 
felixx's Avatar
 
Join Date: Feb 2005
Location: in center
What do you think about this filter?
Do you think that make some good results for tube amps?
Attached Images
File Type: jpg filter.jpg (21.5 KB, 220 views)
__________________
"I'm glad I can build my own mistakes."
https://picasaweb.google.com/115586837612433686520
  Reply With Quote
Old 2nd August 2006, 08:41 PM   #9
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
In regards to the input noise you are experiencing, are you using high efficiency loudspeakers?

Is it just a simple hiss (more or less white noise) or does it include lower frequency rumbling, burbling, popping and the like?

If you are using carbon resistors as plate loads you may want to reconsider.. MF and non-inductive wirewound are much quieter.

Also some 6SL7 are quieter than others, so you may want to try some different brands.

I have rarely used a commercial rfi filter that did not seem to have a negative impact on the sound, (And I'll admit I don't know why) yet by the same token similar devices I've built or borrowed using air core inductors and low esr/esl film caps seemed helpful in electrically noisy environments.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 3rd August 2006, 06:39 AM   #10
felixx is offline felixx  Romania
diyAudio Member
 
felixx's Avatar
 
Join Date: Feb 2005
Location: in center
Yes...I have 97db speakers.The noise is clean ...no pups or everything.
I replace some rezistors but not all from the tubes plate and the noise(that fiss and a little 50hz from the mains) is detectable only from 25cm between ear and speaker.Is a poor noise but is.From 30cm distance the noise disappeared.I tryed with 86db speakers and is hard to hear that noise...only 1 or 2cm from tweeter.
Also I replace 6sl7 with other brands and yes.....some of them are quieter then others.
I think ...to every tube amp is that noise...more or little but is.
Put your ear close to the speaker and tell me from what distance is the noise detectable.

Do you think that noise from mentioned distance is normal?
Thanks.
__________________
"I'm glad I can build my own mistakes."
https://picasaweb.google.com/115586837612433686520
  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
What makes an amplifier "bright", "warm", or "neutral"? JohnS Solid State 51 13th December 2009 06:42 PM
Some final pics of "Stacks" revisited and "Askew" with stand Andy G Multi-Way 2 3rd February 2005 06:07 AM
Anyone used Scan-Speak's "Flow Resistors" or "Aperiodic Vents"? Ignite Multi-Way 3 18th November 2001 08:42 AM


New To Site? Need Help?

All times are GMT. The time now is 02:08 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