Need assistance with picking the right Edcor audio transformer - 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 2nd June 2007, 11:22 PM   #1
diyAudio Member
 
Sal Brisindi's Avatar
 
Join Date: Nov 2006
Default Need assistance with picking the right Edcor audio transformer

Hi All,
I am gathering parts to build a PP 6L6 stereo integrated amplifier with bass/treble controls and I can use your expertise/opinion.

I will only be using 8 ohm speakers so the 4/8/16 ohm transformer is not necessary unless I would use the 16 ohm tap for negative feedback. I did purchase a set of transformers from Triode a while back but I think they would be to small for this amp.

I have a nice NOS Dukane power transformer with a bias tap for this amp. Which audio transformer should I purchase? I would think either the 4,200 ohms or the 6,600 ohm transformer. You can go to Edcorusa.com for additional info on the transformers.

Thanks,
Sal Brisindi

Click the image to open in full size.

Here is a mock-up of my amp with the Triode transformers. I have since purchased a 12"x10"x2" black Hammond chassis so I won't be using the chassis shown in the photo, come to think of it, I think I will need a larger chassis with the larger transformers. The relay sockets are only used to hold up the 6L6 tubes. I would probably only use 3 12AX7's instead of 4 but that is another matter. I will also turn the power transformer 90 degrees.

Click the image to open in full size.
  Reply With Quote
Old 2nd June 2007, 11:35 PM   #2
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Sal,

6.6 KOhms end to end for 6L6s. A single O/P tap sounds better. So, the Edcor model you want is CXPP60-8-6.6K, which costs approx. $60 each.

I'll EMail you some tone control circuitry.

Wimpy 'X7s are a poor choice directly in front of 6L6s. Use a Mullard circuit with a 12AT7 in the splitter/driver "hole".



edit: added topology suggestion
__________________
Eli D.
  Reply With Quote
Old 2nd June 2007, 11:36 PM   #3
diyAudio Member
 
Join Date: Nov 2005
What voltage do you plan to run? I just got a pair of their 6k6 transformers for a 6BG6GA (6L6GC with plate cap) amp -- I'll be running 400-450V.
  Reply With Quote
Old 2nd June 2007, 11:45 PM   #4
diyAudio Member
 
Sal Brisindi's Avatar
 
Join Date: Nov 2006
Quote:
Originally posted by Eli Duttman
Sal,

6.6 KOhms end to end for 6L6s. A single O/P tap sounds better. So, the Edcor model you want is CXPP60-8-6.6K, which costs approx. $60 each.

I'll EMail you some tone control circuitry.

Wimpy 'X7s are a poor choice directly in front of 6L6s. Use a Mullard circuit with a 12AT7 in the splitter/driver "hole".



edit: added topology suggestion
Hi Eli,
Thanks for your input. I have plenty of 12AT7's, 5751's, 12AU7's, 12AX7's, 12BH7's I can use. I think you emailed me some tone circuits a few months back. I have to check my laptop.

Don't worry, your El-Cheapo will get built before my 6L6 amp.. ;-)

I am just at the gathering parts stages...

Jon,
I will post the specs of my power transformer later tonight. I happen to have a nice quad of 6BG6 tubes also.....

Regards,
Sal
  Reply With Quote
Old 3rd June 2007, 07:26 PM   #5
diyAudio Member
 
Sal Brisindi's Avatar
 
Join Date: Nov 2006
Jon,
Here is a link to the spec sheet of my Dukane power transformer. It is in PDF format. Looks like it will produce 400VDC @ 200ma

That should be enough for a stereo 6L6 PP integrated amp.

http://www.tuberadios.com/temp/dukane.pdf

Regards,
Sal Brisindi
  Reply With Quote
Old 3rd June 2007, 08:26 PM   #6
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Quote:
Originally posted by Sal Brisindi
Jon,
Here is a link to the spec sheet of my Dukane power transformer. It is in PDF format. Looks like it will produce 400VDC @ 200ma

That should be enough for a stereo 6L6 PP integrated amp.

http://www.tuberadios.com/temp/dukane.pdf

Regards,
Sal Brisindi

Sal,

Just me, I like to see 2X the DC draw as the AC RMS rating of the rectifier winding, for a cap. I/P filter PSU. If I'm reading the specs. correctly, your trafo's rectifier winding comes up short. FWIW, I'd rectify with a 5AR4 into a 22 muF. 1st filter cap., which eases the pressure on the rectifier winding, starts slowly, and gives a few extra Volts to drop in the DCR of the filter choke too. I'd also use that trafo to power only the 4 6L6 "finals".

It's no secret that I like PSUs with big cujones. The B+ PSU in "El Cheapo" can (sic) easily deliver 200 mA.
__________________
Eli D.
  Reply With Quote
Old 3rd June 2007, 08:31 PM   #7
diyAudio Member
 
Sal Brisindi's Avatar
 
Join Date: Nov 2006
Looking at the Dynaco ST-70 power transformer specs, the B+ can handle 300ma, where as my transformer can handle 200ma, might be to small for my application, any opinions on this?

Thanks,
Sal Brisindi

EDIT:
Eli, You posted your response while I was typing this post. I have smaller transformers I can use for the preamp circuit. I really don't want to spend $$$ on a new larger transformer so I hope this transformer would be just enough.. How many ma would 1 6L6 use?

PS: I received your tone circuit schematic via email, thanks.

  Reply With Quote
Old 3rd June 2007, 08:42 PM   #8
diyAudio Member
 
Join Date: Nov 2005
Quote:
Originally posted by Sal Brisindi
...I have smaller transformers I can use for the preamp circuit. I really don't want to spend $$$ on a new larger transformer so I hope this transformer would be just enough.. How many ma would 1 6L6 use?
Hello Sal,

You will probably want to draw 50-60mA per tube at idle at ~450V. If you used another transformer for heaters, you might be "okay", but right at the limit for idle -- really not a great place to be

So, I'm guessing you don't have a second Dukane transformer?
  Reply With Quote
Old 3rd June 2007, 08:56 PM   #9
diyAudio Member
 
Sal Brisindi's Avatar
 
Join Date: Nov 2006
Jon,
I don't have another Dukane power transformer. This is a set back for my 6L6 tube amp, I might have to scrap the idea....

I have other power transformers with specs on them but they are under rated for this application and other transformers without specs. I can always measure the output voltage but I will not know the current ratings..

Thanks,
Sal
  Reply With Quote
Old 3rd June 2007, 10:14 PM   #10
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Sal,

Look here for some "typical" 6LCGC operating conditions. Links to complete data sheets are provided too.

Don't give up on that Dukane power trafo. If you SS rectify and choke I/P filter the B+, enough current will be available to feed a PP amp that uses a quad of "12" W. tubes in each channel. O/P trafos usually associated with EL34s would be used. Yes, the "El Cheapo" splitter/driver will do just fine. The 5 V. winding would be used (via voltage multiplication) to feed the B- rail.
__________________
Eli D.
  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
Tubelab Simple SE - Transformer Assistance ChrisR1983 Tubes / Valves 17 7th August 2009 07:08 PM
Tube Mic Preamp - which Edcor transformer? pftrvlr Tubes / Valves 6 19th April 2009 06:43 PM
edcor output transformer advice nhuwar Tubes / Valves 3 9th November 2008 10:48 PM
Question about Edcor output transformer Captain archer Tubes / Valves 8 28th June 2008 10:31 PM
Edcor Power Transformer rudy129 Swap Meet 0 5th December 2007 01:49 PM


New To Site? Need Help?

All times are GMT. The time now is 12:14 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