Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

12AU7 internally matched triodes
12AU7 internally matched triodes
12AU7 internally matched triodes 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 16th February 2016, 10:42 AM   #1
passive420 is offline passive420  United Kingdom
diyAudio Member
 
Join Date: Jun 2013
Default 12AU7 internally matched triodes

Doing research in preparation to build the Hybrid TubSumo amplifier by Valery here on the solid state forum. Thought this is obviously the best place to ask about tubes.

The front end IPS board has a 12AU7 and Valery recommends each tube having the triodes internally matched.

My question is: Are the triodes generally matched to a degree as standard or will I have to search / ask for them to be matched. I can obviously find matched pairs but is it possible to find pairs that are also internally matched?
  Reply With Quote
Old 16th February 2016, 10:56 AM   #2
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
diyAudio Member
 
JonSnell Electronic's Avatar
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
Some companies charge a premium for a 'matching service'. Personally ECC81 - 3 have a slightly higher performance on the second triode, pins 6 - 8 by design, so any valve that is matched is not to specification. It makes no difference anyway unless you are trying to squeeze an extra little bit out of them so use a better circuit or an ECC83 for more gain or a large plate ECC82 for more current.
__________________
Support for Fender, Marshall and all Valve Equipment; Audio Innovations, Audiorama FU29, Quad and Leak. www.jonsnell.co.uk
  Reply With Quote
Old 16th February 2016, 12:05 PM   #3
Merlinb is offline Merlinb  United Kingdom
diyAudio Member
 
Merlinb's Avatar
 
Join Date: May 2006
Location: Lancashire
12AU7s are generally pretty well matched. In any case it would probably be cheaper simply to buy a few, plug them in, measure voltages, and select the one with the best balance, than to buy a vendor matched one. 12AU7 is one of the cheapest tubes you can get.
  Reply With Quote
Old 16th February 2016, 12:12 PM   #4
evanc is offline evanc  United States
diyAudio Member
 
Join Date: Sep 2009
Location: New Jersey. About 1 hour from NYC and 1 min. from the beach
12AU7 internally matched triodes
I have tried some new tungsol tubes. they seemed fine but after a couple months one developed a hum.
I have purchased from this vendor with good results.
spin4cards on eBay
The NOS tubes for me have been great.
Evan

PS. boards on their way today. Yesterday was a holiday.
__________________
http://www.evancotler.com
  Reply With Quote
Old 16th February 2016, 01:02 PM   #5
DF96 is offline DF96  England
R.I.P.
 
Join Date: May 2007
Quote:
Originally Posted by JonSnell Electronic
Personally ECC81 - 3 have a slightly higher performance on the second triode, pins 6 - 8 by design, so any valve that is matched is not to specification.
Where in the datasheet does it say that? The only difference is that one triode might have slightly better hum performance.

RFT valves have a reputation for good 'twin balance'. Many RFT valves carry other branding, including 'Mazda foreign' (often with blue printing).
  Reply With Quote
Old 16th February 2016, 01:25 PM   #6
TheGimp is offline TheGimp  United States
diyAudio Member
 
TheGimp's Avatar
 
Join Date: Aug 2009
Location: Johnson City, TN
Brimar specifically states both are the same, and equivalent to 6C4.

http://frank.pocnet.net/sheets/184/1/12AU7.pdf
__________________
If there are no dogs in Heaven, I don't want to go there.
  Reply With Quote
Old 16th February 2016, 02:30 PM   #7
passive420 is offline passive420  United Kingdom
diyAudio Member
 
Join Date: Jun 2013
Sweet Jesus now I'm getting into tubes, I wondered if this day would come... Ill never get my life back. A pair of Mullard Cryo CV491's eh?

Thank you gentlemen, I certainly know more than I did.

I read on Audiotubes.com that the ECC802 version has matched triodes.

Tubeampdoctor offers them in matched and balanced pairs:

http://www.tubeampdoctor.com/product...noFUCzy5Q3Vn42

Last edited by passive420; 16th February 2016 at 02:44 PM.
  Reply With Quote
Old 16th February 2016, 03:15 PM   #8
kmaier is offline kmaier  United States
diyAudio Member
 
kmaier's Avatar
 
Join Date: Jul 2007
The Philips datasheet shows the triode connected to pins 6,7,8 to have a more favorable hum level, but that's it, and it's only on the ECC8x tubes. I've not seen any such mention for the 12AX? tubes in datasheets from RCA, Sylvania, Tung-Sol, etc.

Other options would be the 6189 as a premium version of the 12AU7 and the 5814a which is slightly better still but with a slightly higher filament current. I use the 5814a in some of my designs and have been very happy with the results.

Regards, KM
__________________
... just because you're paranoid, it doesn't mean they're not after you...
  Reply With Quote
Old 16th February 2016, 04:04 PM   #9
petertub is offline petertub  Sweden
diyAudio Member
 
Join Date: Jul 2015
Location: gothenburg,sweden
12AU7 internally matched triodes
Quote:
Originally Posted by passive420 View Post
Doing research in preparation to build the Hybrid TubSumo amplifier by Valery here on the solid state forum. Thought this is obviously the best place to ask about tubes.

The front end IPS board has a 12AU7 and Valery recommends each tube having the triodes internally matched.

My question is: Are the triodes generally matched to a degree as standard or will I have to search / ask for them to be matched. I can obviously find matched pairs but is it possible to find pairs that are also internally matched?
It depends to a large extent what you want to be alike and what the margins are.
Is it :
- current at a specific working point
- Gm at the same
- hum
And finally, the definition of matched: how close = 1% 10% 20 % or some other value.

Good amps ( as build by the folks that know what they did) was designed so
any tube that was within the quite margins of the day would work. It's one
reason that NFB was/is so successful and universally used.

Your best bet would be to buy a few ones and measure and try them.
__________________
My home is at www.tubular-well.se
  Reply With Quote
Old 16th February 2016, 04:09 PM   #10
evanc is offline evanc  United States
diyAudio Member
 
Join Date: Sep 2009
Location: New Jersey. About 1 hour from NYC and 1 min. from the beach
12AU7 internally matched triodes
I'm in general had better luck with NOS tubes then new ones. This circuit sounds the same to me no matter what tubes I put in, except for a couple oddballs that either cause a high DC offset or hum.
__________________
http://www.evancotler.com
  Reply With Quote

Reply


12AU7 internally matched triodesHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
High voltage triodes (true triodes) synchro27 Tubes / Valves 35 21st March 2016 11:16 PM
4x10 volume control - how is it done internally? CharlieLaub miniDSP 5 27th September 2012 06:51 AM
Matched Pair Brimar 13D5 (12AU7) Mull3t Swap Meet 4 17th June 2012 01:37 AM
Shields in internally balanced equipment dashbad Analog Line Level 6 18th April 2012 11:37 AM
2-matched brimar 12au7-1 westinghouse 6v6gt RogerWilco Swap Meet 0 10th September 2005 07:28 PM


New To Site? Need Help?

All times are GMT. The time now is 06:20 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio
Wiki