modifications to compact EL84 amp - 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 13th January 2003, 04:36 AM   #1
Serow is offline Serow  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Regina, SK, Canada
Default modifications to compact EL84 amp

The following schematic is found at triode electronics :

Click the image to open in full size.
  Reply With Quote
Old 13th January 2003, 04:42 AM   #2
Serow is offline Serow  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Regina, SK, Canada
I really like the simplicity of this circuit and the EL84/6BQ5 output tubes. However, I would like help with the following modifications:

1) Increasing power to greater than 10 watts.

2) Possibly changing the driver tube. I haven't heard much about the 6C4, but I know it is out of production. How about an ECC99 or 6SN7? I read in the circuit description that it only needs to swing 11 volts.

I'll need some detailed assistance, as I'm just starting out.

Regards,
Eric
  Reply With Quote
Old 13th January 2003, 08:06 AM   #3
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
And it wouldn't hurt to lose the tone control R3 & C1 I believe.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 13th January 2003, 11:52 PM   #4
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default HOLD ON...

Hi,

Planet10 is correct,loose the tone control...

Up C4 to 470 mF,up C2 to 0.22mF and your going to have a little powerhouse.

The 6C4 should still be around at reasonable prices,check Antique Electronic supply.

All of this won't yield a a more powerful amp but the upgrade will give quite a bit more headroom and better bass performance.

Heck,I may build one for the bedroom system...

Cheers,
__________________
Frank
  Reply With Quote
Old 14th January 2003, 12:03 AM   #5
Colt45 is offline Colt45  Serbia
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Send a message via ICQ to Colt45
6C4 = 1/2 of ECC82

personally id drop the resistor splitter thing, use a 6SN7/6CG7, use 1/2 for gain, and 1/2 as a cathodyne.

bump B+ to 300v, leave Rk the same..
should give you ~17w, IIRC.
  Reply With Quote
Old 14th January 2003, 12:11 AM   #6
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default 6C4 = 1/2 of ECC82

Hi,

Quote:
personally id drop the resistor splitter thing, use a 6SN7/6CG7, use 1/2 for gain, and 1/2 as a cathodyne.
And loose the elegance in the process for what?
A dB or two?

If you need the power look elsewhere I'd say??

I dubbed this the "Tiny Penthode"

BTW,a nice compact circuit can be made using a pair of ECL86s this way...call it the "Pocket Amp"

Cheers,
__________________
Frank
  Reply With Quote
Old 14th January 2003, 12:45 AM   #7
Colt45 is offline Colt45  Serbia
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Send a message via ICQ to Colt45
what elegance?
  Reply With Quote
Old 14th January 2003, 01:01 AM   #8
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
Originally posted by Colt45
what elegance?
The passive phase splitter -- that is the whole point of this amp.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 14th January 2003, 02:26 AM   #9
Colt45 is offline Colt45  Serbia
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Send a message via ICQ to Colt45
i dont see the point though.

12AU7 is the same size as 6C4, same tube, just 2 in 1, and you could use a cathodyne instead of the funky phase splitter.

but whatever works..
  Reply With Quote
Old 14th January 2003, 03:36 AM   #10
diyAudio Member
 
Tom Bavis's Avatar
 
Join Date: Jun 2002
Location: Macedon NY
Would a ONE resistor mod retain the elegance? Remove the ground at the low end of the cathode resistor and add another 100-200 Ohms from that point to ground. The balance of the output stage will be improved. Calculation of the wattage is left as an exercise for the reader (translation...Where did that calculator go?). Of course you'll need more drive voltage - nothing is free. But it isn't hard to find a tube with more gain than a 6C4.

For more power, you'll need more than 250V, especially with the extra drop of the added resistor.
  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
5W EL84 drive EL84 SE Audio_idiot Tubes / Valves 31 31st May 2012 08:38 PM
NHT 3.3 Modifications SY Multi-Way 22 22nd June 2008 05:12 AM
DAC-in-the-Box modifications. Again. Aleksunder Digital Source 1 19th July 2007 03:10 AM
DAC modifications elaar Parts 5 29th May 2006 01:11 PM
Zen V4 modifications pro Pass Labs 2 31st August 2004 05:19 PM


New To Site? Need Help?

All times are GMT. The time now is 03:01 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