el84/6bq5 PSE - 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 17th August 2008, 12:41 PM   #1
diyAudio Member
 
Join Date: Aug 2005
Default el84/6bq5 PSE

Shalom, y'all!! First post but not first tube amp build. I've made about half a dozen low-powered, "traditional" single-ended and PP amps using 6V6, el84 and ecl82 tubes and I'm pleased to say that I've become addicted. I now have a nice chassis with two octal sockets and a 9-pin socket that I acquired from that auction site with the blue, red, yellow and green logo. Instead of making a single-ended, stereo amp with two 6v6's and a ecc83 I want to attempt a PSE with two 6dz7's and a ecc8x. After searching the forums I've come up with the following assumtions:
1)the opt primary must be half the impedance of single-ended(2500 vs. 5000)
2)the circuitry for the the output section must be duplicated for each pentode(i.e.- 2 SE circuits coming off each triode section)
3)due to the shared screen grids there is no possibility of UL operation
4)obviously the power supply must be strengthened to supply the extra current.
This all seems fairly straightforward and easy to implement, however, as with just about everything in life I'm sure that there's more to it than that. Can anyone fill in the blanks for me before I do any damage?
  Reply With Quote
Old 17th August 2008, 01:34 PM   #2
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Isaac,

A look at the 6DZ7 data sheet provides some clues. Not only is the g2 connection common, the cathode connection is also common. You don't have access to some techniques that correct imbalances between sections. You have to rely on the tubes being made to very tight tolerances. Use either cathode or combination bias. Pure "fixed" bias will exacerbate the enevitable differences between sections and result in current hogging.

6DZ7 drive voltage requirements seem modest enough. Have you given thought to the O/P trafos that will be used? If you have stuff made to order, a tertiary cathode feedback winding is a very good idea. OTOH, if "off the shelf" O/P "iron" is employed, the "plate to plate" NFB technique, along with an outer global loop, is in order. Pentode mode "finals" require substantial amounts of NFB in order to obtain a satisfactory damping factor.

Regulate g2 B+, to maximize open loop linearity.
__________________
Eli D.
  Reply With Quote
Old 17th August 2008, 09:05 PM   #3
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Unless you've got 'em already the 6DZ7 is pretty rare. Would not be my choice ever regardless of how good they sound. And they are decent sounding in PP amplifiers - their linearity might not be the best for SE applications however.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 17th August 2008, 09:37 PM   #4
diyAudio Member
 
Tom Bavis's Avatar
 
Join Date: Jun 2002
Location: Macedon NY
6DZ7 was a GE design, and they characterized it as a dual 7189.
  Reply With Quote
Old 17th August 2008, 09:58 PM   #5
Jaime is offline Jaime  Uruguay
diyAudio Member
 
Jaime's Avatar
 
Join Date: Apr 2004
Location: Montevideo
This is an 6DZ7 amplifier abouth te Gary Pymm 47PP.

http://www.audioasylum.com/forums/tu...12/124726.html
__________________
I write in English worse than Tarzan
  Reply With Quote
Old 18th August 2008, 03:29 AM   #6
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
I had what I think was a Stromberg Carlson 20wpc stereo power amplifier that used them for a short time (20yrs ago) and locating a reliable supply in those days was difficult, and I'm not sure how much better the www has made that situation. They weren't widely used in that earlier heyday of tube audio and I don't know of other vintage amplifiers that used them.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 18th August 2008, 12:18 PM   #7
diyAudio Member
 
Tom Bavis's Avatar
 
Join Date: Jun 2002
Location: Macedon NY
The Stromberg used the Sylvania 6DY7 - closer to a dual 6L6, though it's the same pinout as the 6DZ7. These are pretty much unobtanium - I've yet to see one for sale except for a few used ones on eBay.

Heathkit had a SE stereo amp that used one 6DZ7 for both channels.
  Reply With Quote
Old 18th August 2008, 02:27 PM   #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 Tom Bavis
The Stromberg used the Sylvania 6DY7 - closer to a dual 6L6, though it's the same pinout as the 6DZ7. These are pretty much unobtanium - I've yet to see one for sale except for a few used ones on eBay.

Heathkit had a SE stereo amp that used one 6DZ7 for both channels.
Hi Tom,
Thanks for setting me straight - in fact that is true and the 6DY7 was unobtainium and 6DZ7 were substituted by the previous owner with an adjustment to the bias supply to compensate. The 6DZ7 were very difficult to get as well. They did not sound good compared to the 6DY7 even with much tweaking probably because the loading was not close to optimum for this type.
__________________
"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
El84/6bq5/ecc83 + Ef86 = Dc Pp jackinnj Tubes / Valves 10 8th February 2014 07:01 PM
6BQ5\EL84 line amp amp_guy Tubes / Valves 5 3rd February 2010 05:26 PM
FS: 3 Matched RCA 6BQ5 EL84 mrdon Swap Meet 1 25th April 2008 02:30 AM
WTB: Matched Quad EI EL84/6BQ5 mrdon Swap Meet 0 26th October 2006 01:50 PM
6bq5/el84 yanamps Tubes / Valves 4 25th August 2002 09:53 PM


New To Site? Need Help?

All times are GMT. The time now is 01:12 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