How many Ohm for triode strapping? - 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 28th December 2006, 07:03 PM   #1
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Default How many Ohm for triode strapping?

I have seen triode strap of 100 Ohm to 1K Ohm range on EL34 or 6L6, 6550, KT88, KT90, from screen electrode to anode. Is there an optimum sounding value? What is the difference of 100 vs 1K say on an EL34?
  Reply With Quote
Old 28th December 2006, 08:32 PM   #2
Klimon is offline Klimon  Belgium
diyAudio Member
 
Join Date: Apr 2005
Location: Leuven
Related; imo beats any value of resistor: http://www.t-linespeakers.org/tubes/triode-trick.html (contains a few errors)

Simon
  Reply With Quote
Old 28th December 2006, 08:54 PM   #3
sajti is offline sajti  Hungary
diyAudio Member
 
Join Date: Apr 2003
Location: Vác, Hungary
My experience is to use as small as possible to avoid the oscillation. I used 22ohms for PL509 triode connection, and 47ohms for 6550s.

Sajti
  Reply With Quote
Old 29th December 2006, 01:41 AM   #4
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Salas,

An important consideration in sizing the resistor is staying within g2 dissipation limits.

The screen grid in an EL34 is tough. If the anode voltage is low enough, a piece of wire is OK. 100 Ohms should be plenty even at anode voltages that approach the tube's limit.
__________________
Eli D.
  Reply With Quote
Old 29th December 2006, 02:08 AM   #5
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
There are people that recommend a 1K resistor with an EL34. Mullards own data sheet mentions this value. It was said that 1K minimizes distortion. It was in a push pull design.

I have tried everything from 0 ohms to 1K ohms in my SE designs. I prefer 100 ohms. Higher values lower the output power somewhat and don't lower the distortion. I tried JJ, Svetlana, Electro Harmonix, Winged C, and Valve Art EL34 tubes. All give similar results. Oscillation was observed near the peak of the sine wave with 0 ohms on some tubes. 5 of these amplifiers have been built, although not all of them currently use EL34's they all use 100 ohm resistors. It is a good compromise with all the tubes used (EL34, KT88, 6550, 6L6GC). All 5 amps were tested with all tube types. I use 100 ohms in triode mode and in UL mode (2 of the amps are switchable).

I was using 1/2 watt metal film resistors, but I had 2 of them die, so I have switched to 2 watt carbon film resistors. I have had no issues at B+ voltages as high as 500 volts, and I have even flipped the mode switch (triode - UL) at full power (not recommended) several times.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 29th December 2006, 02:29 AM   #6
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Thank you, I currently have 1k on EL34s PP, can It be serving 6L6GCs without being too detrimental for them? Or is it better to go 100 Ohm for across the board best sound?
  Reply With Quote
Old 29th December 2006, 03:39 AM   #7
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
Or is it better to go 100 Ohm for across the board best sound?
Everyone has their own definition of "best sound." My experiments prove that it won't hurt to try it.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 29th December 2006, 07:36 AM   #8
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Hi Tubelab.com, nice to see you again!

I wander, if you've tortured 6p14p, 6p15p, 6p18p tubes. However, manufacturers don't rate them for triode connections, but rate for intended applications. 6p15p, for example, is rated for less 2'nd grid voltage than 6p14p. However, specifying that they guarrantee less distortions than 6p14p in pentode connection. The question is, are they different in triode connections? Does it mean less 2'nd grid power means weaker grid design, or specs only?
__________________
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
Questions on Triode Strapping dsavitsk Tubes / Valves 7 3rd April 2007 11:03 AM
Are there techniques for triode-strapping on the fly? leadbelly Tubes / Valves 4 1st August 2006 08:11 AM
EL34 best for triode strapping ? percy Tubes / Valves 7 4th April 2005 07:05 AM


New To Site? Need Help?

All times are GMT. The time now is 01:52 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