Start up delay needed??? - 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 17th May 2010, 06:12 PM   #1
losacco is offline losacco  United States
diyAudio Member
 
Join Date: Dec 2008
Default Start up delay needed???

Just finished my first amp project, Walton audio 300b mono block and it sounds great. On power up, I get a lot of popping and hissing that goes away after 5 to 10min and would like to know if a time delay would help this? Not even sure what one is, just have done some reading on them.

Thanks
  Reply With Quote
Old 17th May 2010, 06:44 PM   #2
diyAudio Member
 
richwalters's Avatar
 
Join Date: Sep 2003
Location: Alps:Tube amp designs over 150W, SMPS guru.
Popping and hissing on startup I feel needs investigation. Whatever amp design should be without this on warmup and shutdown. Check tube sockets and anything loose.

Others agree ?

richy
  Reply With Quote
Old 17th May 2010, 06:55 PM   #3
k9swc is offline k9swc  United States
diyAudio Member
 
Join Date: May 2009
Yes... and check the tubes themselves. I've had amps that did that and replacing the offending tube cleared it up.

However, on a different note, I've always gotten into the habit of returning the volume control to minimum before turning an amp on or off - especially on. If there are any such sounds generated in the circuitry, they won't be heard - or potentially damage your speaker(s). Some amps "pop" when you turn them off...having the volume down minimizes the effect.

Bud
  Reply With Quote
Old 17th May 2010, 08:30 PM   #4
el156 is offline el156  Portugal
diyAudio Member
 
el156's Avatar
 
Join Date: Apr 2010
Location: ALBUFEIRA ;PORTUGAL
Default Delay

I think all tube amps should have a delay for the HV,only after all the tubes are warm ,the HT should be aplied ! its not good for the tubes not to do that,it shorts tubes life!
A simple way to do that is to use almost any cheap tube,and connect it in serial with a 230V relay(10 ma),connect it between the plate and ŽB+ of 350V or so! When that tube is enough warm it turns the relay ON ! dont forget the cathode resistor and grid to ground!
Silvino
  Reply With Quote
Old 17th May 2010, 09:21 PM   #5
diyAudio Member
 
richwalters's Avatar
 
Join Date: Sep 2003
Location: Alps:Tube amp designs over 150W, SMPS guru.
Quote:
Originally Posted by k9swc View Post
Yes... and check the tubes themselves. I've had amps that did that and replacing the offending tube cleared it up.

However, on a different note, I've always gotten into the habit of returning the volume control to minimum before turning an amp on or off - especially on. If there are any such sounds generated in the circuitry, they won't be heard - or potentially damage your speaker(s). Some amps "pop" when you turn them off...having the volume down minimizes the effect.

Bud
Curing "off" switch transient clicks that somehow get on the signal path can be difficult to eradicate: worse with high gain tube amps with wide audio b/w. Designing amps with input sensivities around 0dBu/0.775V or higher will help alot.
One solution is to make sure the input signal can be muted first and that needs to be quick. Reason: any DC offset caused by an SS opamp pre or line amp switching off is far quicker than the tube amp and must be "downed" before reaching the inputs. I've seen may opamp preamps and power amps go into oscillation on power down relying on the fast opening of a power relay in the LS circuit. Not an ideal solution.
It only takes a mere uV to create a click and there lies the problem. I try to avoid it, but never quite succeed.
........
K9Swc is right; in a mono amp with no feedback stuff, the tubes and hardware become the offenders.
........
El156....All commercial amps of the 1940,50,60 had no sensible HT delay.The TV business dictated a thermistor in the B+. It was the only limit,(not to brown outs) and only 1 component and was unreliable. It did spread to some audio amps but it was considered Too expensive. The only practical delay:- use an indirectly heated rectifier.
I believe the Walton audio block uses a directly heated 5U4;
This design avoids the B+ rocketing on near instant warmup as there is a large bleeder resistor from the raw B+ (450V) ext rectifier to chassis. I have to check the schematic. MAy be wrong. Rectifier/smoothing circuits have a nasty reputation ! In any case keep ones fingers OUT.

richy
  Reply With Quote
Old 17th May 2010, 09:21 PM   #6
kmtang is offline kmtang  Canada
diyAudio Member
 
kmtang's Avatar
 
Join Date: Nov 2004
Location: Vancouver
I built a few of the 300B and 2A3 with similar 6SN7 driver. It seems like there's problem from the 6SN7 driver tube.

It is important to have the 6SN7 filament potential lifted to around 70V to avoid excessive potential difference between the cathode and filament at the 2nd stage.

Remove the 6SN7 and power it up to see if the noise is gone.

Watch if there is some ARC over occurs at the rectifier tube during power up. Use 5U4G tube - they are much more robust in this amp.


Johnny
  Reply With Quote
Old 18th May 2010, 02:02 PM   #7
losacco is offline losacco  United States
diyAudio Member
 
Join Date: Dec 2008
Johnny, whats the best way to check for arc at rectifier? Also the pins on my 300b's are a little loose, that can't be normal, right?
  Reply With Quote
Old 24th June 2010, 04:02 PM   #8
diyAudio Member
 
Join Date: Feb 2010
Just found this delay circuit > http://www.nervenet.info/HT_delay/ax_aug-2001.pdf
  Reply With Quote
Old 24th June 2010, 05:08 PM   #9
diyAudio Member
 
Joshua_G's Avatar
 
Join Date: Nov 2008
Location: Small village, Israel
Lets settle the b+ on cold tubes issue!
  Reply With Quote
Old 24th June 2010, 05:21 PM   #10
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
There may be 3 reasons of popping and crackings:

1. HF oscillations

2. Voltages on cathodes in respect to filaments are out of specs

3. Bad tube, with curved/loose/naked filament that touches cathode during heat up / cool down.

Startup delay would hide such problems, like sweeping garbage under the rug.
__________________
The Devil is not so terrible as his math model is!
  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
Time delay start board for tube amps gjo Tubes / Valves 4 26th November 2008 03:23 AM
soft start needed? facundonu Power Supplies 3 5th March 2007 07:41 PM
cheap time delay relay for soft start? mpmarino Parts 0 20th January 2007 09:47 PM
Tripath sleep/mute start up delay BWRX Class D 1 25th September 2005 08:45 PM
schematic needed for audio delay mazzanet Parts 1 18th February 2004 04:30 AM


New To Site? Need Help?

All times are GMT. The time now is 04:18 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