Have anyone built this 6V6 amp? - Page 5 - 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 31st October 2010, 07:14 AM   #41
diyAudio Member
 
Join Date: Apr 2008
Quote:
Originally Posted by Joku View Post
First about using a ECC82 LTP.. Could the lower gm be compensated by using larger resistors at anodes, and by using cathode follower drivers? Or does the ECC82 suck so hard that they aren't worth using even if you have them at hand?

And how about ECC85, E88CC or E188CC?
I would use a 6CG7 here personally, if you're cool with a mu of 20.
  Reply With Quote
Old 31st October 2010, 01:20 PM   #42
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Look carefully at the "El Cheapo" schematic. Please notice that it's an "integated" amp. The high μ, high gm, low RP 12AT7/ECC81 provides sufficient gain to drive both the "finals" and the NFB loop, when only a CDP is "upstream". The other types mentioned can't do the job. Another point in favor of the 'T7 is powerful synergy in combination with PP O/P tubes. Its skewing of the HD spectrum towards 2nd order blends very well with the internal even order HD cancellation of PP "finals".

Like a bad penny, the 12AU7/ECC81 keeps turning up. JMO, there are only 2 audio jobs the 'U7 is any good at: cathode follower and "concertina" phase splitter.
__________________
Eli D.
  Reply With Quote
Old 31st October 2010, 09:59 PM   #43
Joku is offline Joku  Finland
diyAudio Member
 
Join Date: May 2009
Quote:
Originally Posted by Miles Prower View Post
Edcor's have a pretty good reputation.
Yep, but the El Cheapo uses global negative feedback.. so just wondering what happens if you use an XPP transformer (rated at 70Hz min), and it runs out of 'oomph' at bass frequencies..
  Reply With Quote
Old 1st November 2010, 12:33 AM   #44
diyAudio Member
 
Join Date: Dec 2006
Location: Southwest Chicago Suburbs
Quote:
Originally Posted by Joku View Post
Yep, but the El Cheapo uses global negative feedback.. so just wondering what happens if you use an XPP transformer (rated at 70Hz min), and it runs out of 'oomph' at bass frequencies..
What's wrong with NFB PROPERLY done?

If you look carefully at the schematic you'll see an input cap that is designed to limit the low frequency bandwidth in case a cheap OPT is used. The value there in the schematic was for the guitar OPT originally spec'd. With a change to an Edcor or Dynaclone that cap can/should be increased in value.

Adjust that cap value to what's appropriate for the OPT you choose.

Let me reinforce what Eli said about the 12AT7. You CAN'T look at the tube in isolation, you have to look at the entire circuit. The 12AT7 not only offers enough mu/gain to allow the amp to be driven to clipping with line-level sources, coupled with the P-P output stage and the low/moderate NFB it provides low THD that is NOT dominated by odd-order products as is often the case in P-P amps. No other tube I know of has the combination of attributes needed to make the El-Cheapo sing. People who've built it (especially with Dynaclone OPTs) found it to be really good, way beyond what they expected.

Last edited by Jim McShane; 1st November 2010 at 12:35 AM. Reason: Correct typo
  Reply With Quote
Old 1st November 2010, 02:45 AM   #45
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Edcor's XPP25-8-7.6K should do, as long as you stick to triode mode "finals". That trafo's 25 W. rating means sufficient magnetic headroom is present to cope with the NFB induced deep bass error correction signal. Even at 56 nF., the high pass corner lies below the lowest note a double bass can produce. High pass filtering infrasonic noise, along with properly employed GNFB, allows "budget" O/P trafos to sound pretty darned good. Of course, the better the "iron, the better the amp. Built with DynaClone Z565s, an "El Cheapo" is a very good amp.
__________________
Eli D.
  Reply With Quote
Old 1st November 2010, 08:43 AM   #46
Joku is offline Joku  Finland
diyAudio Member
 
Join Date: May 2009
Quote:
Originally Posted by Eli Duttman View Post
Edcor's XPP25-8-7.6K should do, as long as you stick to triode mode "finals". That trafo's 25 W. rating means sufficient magnetic headroom is present to cope with the NFB induced deep bass error correction signal. Even at 56 nF., the high pass corner lies below the lowest note a double bass can produce. High pass filtering infrasonic noise, along with properly employed GNFB, allows "budget" O/P trafos to sound pretty darned good. Of course, the better the "iron, the better the amp. Built with DynaClone Z565s, an "El Cheapo" is a very good amp.
Hmm.. I was thinking about using ultralinear mode and maybe even paralleled 6V6s as output (using XPP-16-7.6k as OPT). Maybe that's just asking too much.

Quote:
Originally Posted by Jim McShane View Post
What's wrong with NFB PROPERLY done?

If you look carefully at the schematic you'll see an input cap that is designed to limit the low frequency bandwidth in case a cheap OPT is used. The value there in the schematic was for the guitar OPT originally spec'd. With a change to an Edcor or Dynaclone that cap can/should be increased in value.
Yeah, you are right, should have looked at it more carefully..

Last edited by Joku; 1st November 2010 at 08:45 AM.
  Reply With Quote
Old 13th January 2011, 07:56 PM   #47
diyAudio Member
 
mark02131's Avatar
 
Join Date: Nov 2005
Location: Boston, MA
Quote:
Originally Posted by lawbadman View Post
Thanks for the suggestion Eli.
What are the voltages (or range of voltages) for B+, B2+ and B-?
I would like to get this question answered. I would like to know the voltages for each the B+, B2+ and B- in the El Cheapo amp.

eli-duttman If you happen to have those values that would be great.
  Reply With Quote
Old 14th January 2011, 12:21 AM   #48
Ian444 is offline Ian444  Australia
diyAudio Member
 
Join Date: Nov 2008
Location: Brisbane QLD
Try post 35 of this thread, might find some info there
  Reply With Quote
Old 13th March 2012, 06:07 AM   #49
diyAudio Member
 
Join Date: Nov 2009
Location: pleasanton ca
Guys, no need to put in an additional trannie for the bias. Just AC couple a voltage doubler to the secondary then filter it and you are good to go. Adjust the value of the cap to get the desired voltage. With all due respect to Mr Prower I adhere to the late Charlie Kittleson's motto 'USE A TRANSISTOR GO TO JAIL'
  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
Trouble with amp 6V6 Tachyon Tubes / Valves 12 13th October 2008 05:25 PM
new 6V6 amp sorenj07 Tubes / Valves 7 11th September 2007 02:09 PM
6V6 guitar amp... Guiness Tubes / Valves 3 24th November 2003 08:31 AM
6V6 Guitar Amp SHiFTY Tubes / Valves 2 5th August 2003 02:10 PM


New To Site? Need Help?

All times are GMT. The time now is 09:56 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