heater wiring - the Good the Bad and the Ugly - Page 8 - 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 4th January 2013, 05:09 PM   #71
diyAudio Member
 
Join Date: Dec 2012
Location: Atchison, Kansas
Quote:
Originally Posted by DF96 View Post
Could be a sign of spurious RF oscillation getting propagated along the heater wiring, rather than normal hum.
Not RF, looked at it on a scope. I first tried a 100 ohm balance pot and it worked but still had a little residual hum, using the caps no hum. I also tried connecting the caps with clip leads across different tubes and the result was the same. If it was some spurious pickup the results would have varied moving the clip leads around. Perhaps someone else can try it and see if they get the same results. I first used Illinois Capacitor coupling capacitors and the results were the same, I only went to ceramic caps because they are physically smaller.
Attached Images
File Type: jpg filament_bypass.jpg (84.0 KB, 1244 views)
  Reply With Quote
Old 5th January 2013, 09:35 PM   #72
diyAudio Member
 
Join Date: Sep 2005
Quote:
Originally Posted by wiredwithtubes View Post
I've found that on filament windings with no center tap bypassing both sides of the filament line with caps works better to eliminate hum than a balance pot. I used .47uf @ 100V ceramic caps.
Hello
Thank you very much.
Great idea, I hope these work for the higher power GU50 to.. That is 12.6V but I must have to check the tube data.
I have 12.5V DC also. Is not better if I use DC for the GU50.
Again I have to take a look at the tube data what is the recommendation. Great help, thanks one more time.
Greetings Gabor
  Reply With Quote
Old 6th February 2013, 07:45 AM   #73
diyAudio Member
 
Join Date: Nov 2009
Looking for somebody who have AC heater with 300B and NO noise.
It could be possible as WE91 is ac ?

Thanks for your help.

Gilles.
  Reply With Quote
Old 10th February 2013, 02:28 PM   #74
diyAudio Member
 
Join Date: May 2008
Location: West Yorkshire
Default No noise??

Hi Gilles.

I'm getting 3.9mv and 2.9mv 100hz respectively at the terminals of my AC supplied JELabs 300B monoblocks. Nothing fancy here, just AC straight to a wirewound dropping resistor, routed around the outside and with a hum pot. I haven't tweaked it for optimum performance, just made sure the wires were twisted and placed to the outer edge of the chassis. Would be interesting to see what other folks are achieving and what measurement would be considered "No noise". (Now I've measured it I'm going to have to find out why I've got 1 mv difference. Damn!!)
Attached Images
File Type: jpg JEL300b.jpg (859.3 KB, 1088 views)
  Reply With Quote
Old 10th February 2013, 02:44 PM   #75
rongon is offline rongon  United States
diyAudio Member
 
rongon's Avatar
 
Join Date: Jul 2009
Location: Across the river from Rip's big old tree...
To echo valve5425's question, and out of my own curiosity, would 4mV of AC hum on the filaments of a 2A3 or 300B be considered objectionable?
--
  Reply With Quote
Old 10th February 2013, 02:46 PM   #76
rongon is offline rongon  United States
diyAudio Member
 
rongon's Avatar
 
Join Date: Jul 2009
Location: Across the river from Rip's big old tree...
Quote:
Originally Posted by wiredwithtubes View Post
I've found that on filament windings with no center tap bypassing both sides of the filament line with caps works better to eliminate hum than a balance pot. I used .47uf @ 100V ceramic caps.
If you wanted to use cathode bias on a DHT, but still use those .47uF bypassing caps for the filaments, where would you put the cathode bias resistor?

--
  Reply With Quote
Old 21st February 2013, 04:06 AM   #77
diyAudio Member
 
Join Date: Dec 2012
Default How's this one look lads just finished the heater and power wiring

Any thoughts
Attached Images
File Type: jpg image.jpg (296.7 KB, 990 views)
  Reply With Quote
Old 20th April 2013, 11:13 PM   #78
roline is offline roline  United States
diyAudio Member
 
roline's Avatar
 
Join Date: Sep 2010
Location: East Tennessee
Elevated twisted pair...
Attached Images
File Type: jpg spud on bottom.jpg (712.5 KB, 765 views)
__________________
SO many tubes, SO little time!!!
  Reply With Quote
Old 21st April 2013, 07:12 PM   #79
diyAudio Member
 
Join Date: Dec 2012
Location: Atchison, Kansas
Quote:
Originally Posted by rongon View Post
If you wanted to use cathode bias on a DHT, but still use those .47uF bypassing caps for the filaments, where would you put the cathode bias resistor?

--
I should think you would just connect the resistor from filament to ground. But then the .47 caps would act like a bypass and boost at very high frequencies. I'm only familiar with DHT power output tubes and on a power tube you would want a decent value bypass cap. Might be best to use a separate filament transformer in such a case.
__________________
Politicians and diapers have one thing in common. They should both be changed regularly, and for the same reason.
  Reply With Quote
Old 14th June 2013, 07:20 PM   #80
diyAudio Member
 
Join Date: Dec 2001
Location: Eindhoven
Quote:
Originally Posted by valve5425 View Post
Hi Gilles.

I'm getting 3.9mv and 2.9mv 100hz respectively at the terminals of my AC supplied JELabs 300B monoblocks. Nothing fancy here, just AC straight to a wirewound dropping resistor, routed around the outside and with a hum pot. I haven't tweaked it for optimum performance, just made sure the wires were twisted and placed to the outer edge of the chassis. Would be interesting to see what other folks are achieving and what measurement would be considered "No noise". (Now I've measured it I'm going to have to find out why I've got 1 mv difference. Damn!!)
hi

The differences may be due to the tubes. The 100Hz stems from harmonic distortion from cathode to anode. The distortion may differ, hence the amplitude of 100Hz. I wrote a bit more about this here:

http://tentlabs.com/Components/Tubea...ingmethods.pdf

The amount of DC shift wen driving the tube a bit harder is also an indicator of the 300b linearity, see:

http://ken-gilbert.com/images/pdf/2%...r%20stages.pdf

best,

Guido
__________________
Guido Tent
www.Tentlabs.com
  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
The Good. The Bad and the Ugly Car Amps boxcustom Car Audio 115 17th August 2011 01:34 AM
OPT -the good, the bad or the ugly ?? AuroraB Tubes / Valves 1 9th February 2007 11:07 PM
The good, the bad, and the ugly OTL amplifiers Original Burnedfingers Tubes / Valves 46 9th November 2006 06:27 AM
Preamp Numbers; good, bad, ugly? chris ma Solid State 4 3rd September 2002 04:49 PM


New To Site? Need Help?

All times are GMT. The time now is 04:12 PM.


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