Two 6J5 versus one 6SN7 - 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 3rd August 2008, 01:39 AM   #1
diyAudio Member
 
Join Date: Jul 2008
Default Two 6J5 versus one 6SN7

Is there any advantage in using seperate 6J5s as input and driver, compared to one 6SN7, other than less crowding on one socket and maybe more tube rolling posibilities ?

AB.
  Reply With Quote
Old 3rd August 2008, 07:52 AM   #2
diyAudio Moderator Emeritus
 
ray_moth's Avatar
 
Join Date: Jan 2004
Location: Jakarta
In the case you mention, I doubt there is any difference. However, if you were looking for a matched pair of triodes, you would stand a better chance of finding them with two 6J5s than with a single 6SN7.
  Reply With Quote
Old 3rd August 2008, 01:10 PM   #3
sgerus is offline sgerus  United States
diyAudio Member
 
Join Date: Nov 2005
Location: Milwaukee, WI
If you have the space and the layout of the amp looks good, I think having 2 sockets is the way to go just for the flexibility…..

And, According to the Morgan Jones book “Valve Amplifiers 3rd edition, p189” the Pinnacle 6J5GT is one of the best “6sn7’s” you can get.
  Reply With Quote
Old 3rd August 2008, 03:37 PM   #4
jeapel is offline jeapel  Canada
diyAudio Member
 
Join Date: Sep 2003
Location: quebec
hi
it s just to share my hum test with ac heater
with stereo preamp

-for the 6.3 vac heater with 6sn7

1-pin 7 to ground and pin 8 to 6.3vac
=> zero hum to right but hum to left
2-pin 8 to ground and pin 7 to 6.3vac
=> zero hum to left but hum to right
3-my final solution is:
pin 7 to 33ohm to ground
pin 8 to 33ohm to ground
=> low hum to both channel but not zero

if my test is right maybe avoid dual triode
and always ground one side heater
but wait for guru confirmation :-)
  Reply With Quote
Old 4th August 2008, 12:07 AM   #5
diyAudio Member
 
Join Date: Jul 2008
Quote:
Originally posted by jeapel
hi
it s just to share my hum test with ac heater
with stereo preamp

-for the 6.3 vac heater with 6sn7

1-pin 7 to ground and pin 8 to 6.3vac
=> zero hum to right but hum to left
2-pin 8 to ground and pin 7 to 6.3vac
=> zero hum to left but hum to right
3-my final solution is:
pin 7 to 33ohm to ground
pin 8 to 33ohm to ground
=> low hum to both channel but not zero

if my test is right maybe avoid dual triode
and always ground one side heater
but wait for guru confirmation :-)
  Reply With Quote
Old 4th August 2008, 12:09 AM   #6
diyAudio Member
 
Join Date: Jul 2008
You had to complicate things.
  Reply With Quote
Old 4th August 2008, 01:54 AM   #7
jeapel is offline jeapel  Canada
diyAudio Member
 
Join Date: Sep 2003
Location: quebec
the hum was a problem in my 6sn7 preamp
i m not a tube expert but for me there was
a hum problem with dual triode for me it s
because in 6sn7 heaters are in series not
parallel

not easy ! forget about it
  Reply With Quote
Old 4th August 2008, 02:44 AM   #8
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Quote:
Originally posted by jeapel
the hum was a problem in my 6sn7 preamp
i m not a tube expert but for me there was
a hum problem with dual triode for me it s
because in 6sn7 heaters are in series not
parallel

not easy ! forget about it
This isn't the real cause.. Almost all 6SN7 I have ever seen except for a few of the very last coin base types have parallel filaments, and I have never had a hum problem with this type with ac heating in pre-amps or power amps. Undoubtedly an issue of execution.

IMO Using two 6J5 where a single 6SN7 will do is both a waste of space and a socket. It confers no real advantage I can see. Last time I was aware the 6J5 wasn't being made any more..
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 4th August 2008, 11:14 AM   #9
jeapel is offline jeapel  Canada
diyAudio Member
 
Join Date: Sep 2003
Location: quebec
6sn7EH electro harmonix = series heaters

execution problem very possible
  Reply With Quote
Old 4th August 2008, 03:56 PM   #10
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Quote:
Originally posted by jeapel
6sn7EH electro harmonix = series heaters

execution problem very possible
I guess that is an oddball design, I don't use them as my preferred Sylvania 6SN7 is readily available on eBay for no more money and to my ear sounds much better.

I've not had hum problems with the 6SN7EH either.

I have used 6SN7 in SRPP and conventional common cathode cathode follower and transformer coupled line stages as well as LTP and drivers in my power amplifiers and I have never had a problem with hum in any of my designs.

You may need to bias up the heater supply when using AC to something like 50Vdc to assure absolute silence.

Of the many people here I would say your experience with the 6SN7 is quite atypical and the problem points either to a defective tube (design) or something not quite right in your design. Do you have a scope, other test equipment - and how much analysis have you done?
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  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
ZRT 2 way versus 2.5 way s7horton Multi-Way 5 13th August 2008 06:23 PM
Diy Versus Comercial east electronics Solid State 0 29th April 2008 09:15 AM
One speaker versus two Mos Fetish Multi-Way 12 23rd August 2005 02:07 PM
TPP versus PSE. GeirW Tubes / Valves 11 27th November 2004 08:55 AM
2.5 way versus 3 way Mos Fetish Multi-Way 1 6th April 2003 06:57 AM


New To Site? Need Help?

All times are GMT. The time now is 08:49 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