520v in PP UL...? - 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 18th April 2009, 12:55 PM   #1
JandG is offline JandG  United States
diyAudio Member
 
Join Date: Jan 2005
Location: Washington State
Default 520v in PP UL...?

I have re-freshed a pair of el-34 Ampex monoblocks with SS voltage doubler PS & B+ & g2 is about 510-520'ish range w/ 300ohm cathode resistor & 100 ohm bias pot. I am just wanting a reliable output tube that will handle 520v in UL without problems. I am seriousely thinking of fuseing the HV somewhere to protect the OT's. This is a ef86/12au7/el-34 affair, that sounds pretty good, but red plates my old mullard el-34's. I need good tough toob.If I need to change cathode resistor that I will do .
Joe
  Reply With Quote
Old 18th April 2009, 07:53 PM   #2
wfmali is offline wfmali  Europe
diyAudio Member
 
Join Date: May 2003
Location: G-U
You might want to try KT77 - they are supposed to stand the > 500V g2. I personally would not run El34s UL at that voltage level if you are looking for something reliable...
Marcus
  Reply With Quote
Old 18th April 2009, 10:25 PM   #3
diyAudio Member
 
Join Date: Apr 2003
Location: Portland,Oregon
Blog Entries: 4
Send a message via AIM to DigitalJunkie
If you can use 6L6GC's,some of the Chinese tubes are pretty robust.I've some running at ~640V(!) in UL,and they haven't melted down....yet....They are able to withstand a bit of spec-busting.
Unfortunately I don't have a good idea how they sound yet,I haven't been able to listen to the amp much yet,as everything is in storage atm.

http://s199.photobucket.com/albums/a...t=PICT0083.jpg
  Reply With Quote
Old 18th April 2009, 11:59 PM   #4
JandG is offline JandG  United States
diyAudio Member
 
Join Date: Jan 2005
Location: Washington State
Nice........amp. What the heck ya got your bias set at..? I got some 5881 popped in one block & they seem to do o.k.. Nothing bad yet. I am not pushing my luck till I get proper bias resistors. They have a 300ohm resistor in there now from 1959. They still had to be running about 500v, this puts everything in the very hot department. I think I will up that cathode resitor to something a little more sane. KT-77's I will try.I really like 6l6 tubes & might experiment with some. That is a great pictorial of your amp...love the red plate gig..
Joe
  Reply With Quote
Old 19th April 2009, 03:11 AM   #5
diyAudio Member
 
Join Date: Apr 2003
Location: Portland,Oregon
Blog Entries: 4
Send a message via AIM to DigitalJunkie
LOL,yea..Doing some Tubelab style 'testing'.
The bias was roughly set to about 45ma in one channel,and 55ma in the other for initial testing,as you can see,the tubes get pretty roasty at the higher current. They seem to cope with 40ma bias 'okay' at this voltage.Like I said,I haven't been able to do much testing with the amp yet,I need to tweak a couple of resistors to get the bias range a bit lower..I'm also looking into lowering the B+,even if it involves a new/custom power trans.
Those Chinese 6L6GCR's are pretty tough tubes.
  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



New To Site? Need Help?

All times are GMT. The time now is 05:07 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