New test data comparing different 7591's - 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 13th April 2011, 01:29 AM   #1
diyAudio Member
 
Join Date: Apr 2009
Default New test data comparing different 7591's

Hi,

Just wanted to let you know that an addendum with new test data has been posted on the Tronola article comparing various 7591 tube types, including JJ's and EH's. You can find it at:

7591A tube comparisons

Please understand that these tests results are just a humble attempt to present data we measured on a small number of tubes. They are hardly a rigorous scientific evaluation. Yet they are better than nothing. Comments are welcome.

All the best,
Steve L.
Tronola DIY Electronic Projects and More
  Reply With Quote
Old 21st October 2011, 01:46 AM   #2
diyAudio Member
 
Join Date: Mar 2005
Location: Texas
Steve,

I enjoyed your analysis on these tubes. I am a Ham Radio fellow, and I use a pair of 7591's in RF service. I have tried old "Fishers", the EH's, and the JJ's. There is no contest; the old 40 year old tubes I have from an old Fisher AMP are by far more linear, and produce more power.

These are good RF tubes since they have low inter-electrode capacity (0.25pf G1 to P), and dual G2 terminals at the base. I use them from 160m to 20m (1.8 Mhz to 14Mhz).

I use these in class AB2, grid driven (from a 1/2 12BH7 cathode follower), with a plate voltage of 550V (@ 150ma), G2 voltage is +375 from a 6W6 series pass regulator. I use an adjustable TL431 to set the G1 bias at about -19v to set the per tube idle current to ~ 25ma.

The "Fisher branded" RF power on 80m (3.8Mhz) is about 70 watts carrier, or 80 watts PEP single sideband. They also do 20 watts AM where at 100% modulation the PEP power is also 80 watts. The EH's show about 5% less power, but have to be driven harder (well into class Ab2) for max power. The problem with the EH's is poor linearity as seen on the AM trapezoid pattern. The Fishers are near perfect whereas the EH's show a kink as we go into grid current. There is also a bit of a slight 'S' in the trapezoid walls. I haven't looked at the JJ's in a while, but they are down at least 10% from the EH's.

If anyone is interested I could compile some data and post some pictures.

Regards,
Jim
WD5JKO
  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
7591's in the Simple SE Anchan Tubelab 3 22nd October 2010 03:57 AM
Test data for 6H30PI & Hickok 539?? Zero Cool Tubes / Valves 1 12th March 2010 11:37 PM
OPT test data? Ty_Bower Tubes / Valves 2 22nd March 2009 12:17 AM
211/VT4C test data for TV-7 / TV-10 Doctorcilantro Parts 0 24th October 2008 06:41 PM
Need help with tube test data - fast HugoR Tubes / Valves 15 7th November 2005 09:24 PM


New To Site? Need Help?

All times are GMT. The time now is 04:17 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