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 6th August 2011, 10:11 PM   #1
diyAudio Member
 
mariner4's Avatar
 
Join Date: Mar 2011
Location: New York
Default Noisy volume pot with some tubes but not others

Hi, guys!

I built a version of Andrea Cuiffoli's no-compromise headphone amplifier (pictures in the picture thread). Schematic at HeadWize - Project: No-Compromise OTL Tube Headphone Amplifier by Andrea Ciuffoli

I have the following small problem:

When using a WE 417A as voltage gain tubes, the volume pot is silent when turned. When I replace them with JAN-Raytheon 5842 tubes (recommended for this amp), I hear noise while adjusting the volume. The sound is great with both tubes and the amp is very quiet when the pot is not being turned.

Can someone with more experience than me help analyze this situation? It's not really a big deal, but it's something I don't understand.

Thanks!
  Reply With Quote
Old 7th August 2011, 02:02 AM   #2
diyAudio Member
 
Join Date: Apr 2003
Location: Portland,Oregon
Blog Entries: 4
Send a message via AIM to DigitalJunkie
The pot is being used as the grid-leak resistor,running DC through the pot.
To get rid of that,you could add a coupling cap,and a new grid-leak resistor on the input grid to ground.
  Reply With Quote
Old 7th August 2011, 02:34 AM   #3
diyAudio Member
 
mariner4's Avatar
 
Join Date: Mar 2011
Location: New York
This makes sense. When I was constructing the amp, a friend was skeptical about DC coupling of the input, but I ignored his advice since it worked so well with the WE tubes.

I guess this means that the Raytheon tubes have stronger grid leak than the WE... I will measure it.
  Reply With Quote
Old 7th August 2011, 03:25 AM   #4
diyAudio Member
 
mariner4's Avatar
 
Join Date: Mar 2011
Location: New York
And, of course, thank you for the reply!

Quote:
Originally Posted by mariner4 View Post
This makes sense. When I was constructing the amp, a friend was skeptical about DC coupling of the input, but I ignored his advice since it worked so well with the WE tubes.

I guess this means that the Raytheon tubes have stronger grid leak than the WE... I will measure it.
  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
Preamp noisy - 100K pot?Relays? Tex Houston Solid State 46 2nd July 2013 10:37 AM
Noisy pot... nickds1 Solid State 2 1st January 2011 05:48 AM
Noisy volume pot bulgin Parts 12 31st July 2007 03:09 PM
Noisy Input Pot : Lexicon Reflex yekuku Digital Source 2 13th December 2006 10:22 PM
Volume control : - pot' or pot' variable feedback resistor (gain) ? ash_dac Solid State 5 1st August 2006 05:07 AM


New To Site? Need Help?

All times are GMT. The time now is 09:08 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