tube matching - 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 29th September 2008, 08:45 PM   #1
diyAudio Member
 
TUBESMAN's Avatar
 
Join Date: Apr 2004
Location: New York
Default tube matching

Lets say you have a bunch of single triodes, 6J5 for example. You want to match them for use in a CCS driven Differential stage. What would you measure to establish that tube #3 is the matched pair of tube #81?

I assume that the best place to start is to place them in the circuit you plan to use at the intended operating point and measure the voltages across the tubes.

How equal is equal?
  Reply With Quote
Old 29th September 2008, 08:50 PM   #2
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Actually, if it's a CCS-loaded long tail diff stage, the matching isn't at all critical.

If you do want to match, I'd set up a jig to run the tube at the designed operating point (plate current and grid-to-cathode voltage), then match for plate voltage and gain.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 29th September 2008, 08:51 PM   #3
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Trace curves on transparent films then match them visually.

There was a project related to some geological research. One Russian computer center got an order to calculate percentage of some spots on maps of the entire Earth. Instead of loading the data into the computer a programmer took scissors and cut maps, then weighted results on precision scales. He got a premium for fast and accurate results.

__________________
The Devil is not so terrible as his math model is!
  Reply With Quote
Old 29th September 2008, 09:03 PM   #4
diyAudio Member
 
TUBESMAN's Avatar
 
Join Date: Apr 2004
Location: New York
Thanks Sy, that is about what I figured would be the case. Sometimes I ask questions so I can be sure I am as crazy as I think I am, by seeing if someone agrees with me. As far as curve tracing, I remember a few years ago an Italian (I think) company sold a microprocessor controlled curve tracer. I think they stopped making it, I think, is there a similar unit from someone else?
  Reply With Quote
Old 29th September 2008, 09:15 PM   #5
diyAudio Member
 
TUBESMAN's Avatar
 
Join Date: Apr 2004
Location: New York
[QUOTE]Originally posted by SY
[B]Actually, if it's a CCS-loaded long tail diff stage, the matching isn't at all critical.

Is it also possible that in a CCS LTP that one tube, in an extreme example, could draw 15mA and the other 5mA in a circuit set for a total of 20mA? That is why I figured I'd like to match the tubes.
  Reply With Quote
Old 29th September 2008, 10:11 PM   #6
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
You cam feed your target stage with a sawtooth and save oscillograms to compare.
__________________
The Devil is not so terrible as his math model is!
  Reply With Quote
Old 29th September 2008, 10:11 PM   #7
diyAudio Member
 
Join Date: Mar 2003
Location: Zürich
Hi tubesman

For a differential stage with CCS in the tail and matched plate resistors (which are essential conditions for a differential stage anyway) Morgan Jones recommends to match triodes by comparing plate voltages: same voltage = matched.

Erik
__________________
my surname is indeed 'de Best': neither misspelling nor snobbism! Ask SY!
  Reply With Quote
Old 29th September 2008, 10:41 PM   #8
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Is it also possible that in a CCS LTP that one tube, in an extreme example, could draw 15mA and the other 5mA in a circuit set for a total of 20mA? That is why I figured I'd like to match the tubes.
Yes, but unless you're direct coupling to the next stage, it doesn't matter much; remember, the swing is constrained to be equal and opposite. As a practical matter, it's tough to find two tubes of nominally the same type that are THAT far apart.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 29th September 2008, 10:50 PM   #9
diyAudio Member
 
TUBESMAN's Avatar
 
Join Date: Apr 2004
Location: New York
Quote:
Originally posted by SY


Yes, but unless you're direct coupling to the next stage, it doesn't matter much; remember, the swing is constrained to be equal and opposite. As a practical matter, it's tough to find two tubes of nominally the same type that are THAT far apart.
I did say it was an extreem case! I realize that unless the makers of the tubes really don't give a rats a**, they will be closer than that! I think I have an adequate group of answers to my question. Now all I have to do is buy the 100 triodes that I want to stockpile!
  Reply With Quote
Old 30th September 2008, 12:40 PM   #10
Gordy is offline Gordy  United Kingdom
diyAudio Member
 
Join Date: Nov 2006
Quote:
Originally posted by TUBESMAN
...I remember a few years ago an Italian (I think) company sold a microprocessor controlled curve tracer. I think they stopped making it, I think, is there a similar unit from someone else?
I think the old company was Sophia. For a unit nowdays look to Mr. Hagerman: http://www.haglabs.com/vacutrace.html
  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
Tube matching service - As found on Craigslist Sal Brisindi Tubes / Valves 1 17th December 2007 04:10 AM
Tube Matching and Push-Pull dsavitsk Tubes / Valves 2 23rd September 2007 12:25 AM
Tube Matching Rob11966 Tubes / Valves 11 11th September 2007 09:52 PM
Tube power Amp matching with SAE Mark M pre amp and AR18 speaker or MS 25i soultribe Tubes / Valves 1 13th August 2006 11:08 AM
tube matching fixture Original Burnedfingers Tubes / Valves 8 1st September 2003 12:01 PM


New To Site? Need Help?

All times are GMT. The time now is 07:35 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