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

Found schematic 50W EL34 AB. Needs help...
Found schematic 50W EL34 AB. Needs help...
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 15th April 2018, 11:52 AM   #1
CaterpilarSK is offline CaterpilarSK  Slovakia
diyAudio Member
 
Join Date: Jan 2018
Default Found schematic 50W EL34 AB. Needs help...

Hello. I found a shematic on the internet which looks promising in terms of functionality. I havent played arround with tube amps before. Only experinmenting pream stages.
I wanted to make a 50W tube Amp. Since i found this schematic and i wanted something powerfull this looked like a decent choice. I have also found a schematic for a 100W one but that would be a bit too much .
I want to make this happen. I dont know what output transformer i have to buy since there is nothing specified there.
If anyone knows that this will be 100% functional then please tell me and any kind of improvements are welcome. I want to use the amplifier as a general purpose amplifier. Music and stuff. Not for guitars.
Thanks.
Attached Images
File Type: gif 50WEL34.gif (7.2 KB, 222 views)
  Reply With Quote
Old 15th April 2018, 12:02 PM   #2
jazbo8 is offline jazbo8
diyAudio Moderator
 
jazbo8's Avatar
 
Join Date: Jan 2011
Location: In Transient
Found schematic 50W EL34 AB. Needs help...
It looks more suitable for a guitar amp, you might be well served to search this forum for much better designs.
  Reply With Quote
Old 15th April 2018, 12:09 PM   #3
CaterpilarSK is offline CaterpilarSK  Slovakia
diyAudio Member
 
Join Date: Jan 2018
Could you please redirect me to one? Im thinking of a 50W amp. If possible using EL34 since i have those on hand.
Thanks.
  Reply With Quote
Old 15th April 2018, 12:47 PM   #4
kodabmx is offline kodabmx  Canada
diyAudio Member
 
Join Date: Oct 2011
Location: Toronto
To get 50W from a pair of EL34 you need to run fixed bias. You can make 40W in AB using cathode bias.

I've drawn a schematic of the latter.

Here's the datasheet. https://frank.pocnet.net/sheets/129/e/EL34.pdf
Attached Images
File Type: png 6F12P-EL34-class-AB-Pentode.png (55.3 KB, 212 views)
  Reply With Quote
Old 15th April 2018, 01:10 PM   #5
CaterpilarSK is offline CaterpilarSK  Slovakia
diyAudio Member
 
Join Date: Jan 2018
Wow that looks simple . Will this need a pream stage? Like using something as a 12AX7 or the 6F12P pentode does everything? Is there a possible alternative to use a 12AX? Also i cant tell the difference betwee fixed bias and cathode bias could you please explain?
Thanks.
  Reply With Quote
Old 15th April 2018, 02:07 PM   #6
petertub is offline petertub  Sweden
diyAudio Member
 
Join Date: Jul 2015
Location: gothenburg,sweden
Quote:
Originally Posted by CaterpilarSK View Post
Hello. I found a shematic on the internet which looks promising in terms of functionality. <snip>
Even if this schematic uses fixed bias it will not get 50w output power with any output transformer.
You will have to get B+ > 500V if you want 50w from a pair of el34 and that will be tough on the tubes.

I'd start at the other end ; find output transformers and then a suitable schematic for those transformers. The general advise is to build as simple as possible, few stages and no frills.
Cathode bias is generally less demanding although you will loose some power, something you probably don't notice, usually 25w is achieved useing EL34 and cathode bias. The lower power also makes choice of transformers easier and cheaper.
__________________
My home is at www.tubular-well.se
  Reply With Quote
Old 15th April 2018, 02:50 PM   #7
kodabmx is offline kodabmx  Canada
diyAudio Member
 
Join Date: Oct 2011
Location: Toronto
Quote:
Originally Posted by CaterpilarSK View Post
Wow that looks simple . Will this need a pream stage? Like using something as a 12AX7 or the 6F12P pentode does everything? Is there a possible alternative to use a 12AX? Also i cant tell the difference betwee fixed bias and cathode bias could you please explain?
Thanks.

You should be able to get full power with about 1V input.
  Reply With Quote
Old 15th April 2018, 02:53 PM   #8
CaterpilarSK is offline CaterpilarSK  Slovakia
diyAudio Member
 
Join Date: Jan 2018
Quote:
Originally Posted by petertub View Post
Even if this schematic uses fixed bias it will not get 50w output power with any output transformer. You will have to get B+ > 500V if you want 50w from a pair of el34 and
that will be tough on the tubes.

I'd start at the other end ; find output transformers and then a suitable schematic for those transformers. The general advise is to build as simple as possible, few stages and no frills.
Cathode bias is generally less demanding although you will loose some power, something you probably don't notice, usually 25w is achieved useing EL34 and cathode bias. The lower power also makes choice of transformers easier and cheaper.
Looking at the datasheet its quite clear that i wont get 50W but 45 is good enough I wont tweak the thing to absolute max ratings because i dont want my room to become a RTG scanning room and neither lit red by the plates lol.
  Reply With Quote
Old 15th April 2018, 03:06 PM   #9
Kokanee is offline Kokanee  Mexico
diyAudio Member
 
Kokanee's Avatar
 
Join Date: Sep 2010
Location: Puerto Vallarta/Kooteneys
Found schematic 50W EL34 AB. Needs help...
@ CaterpilarSK,

The EL-84 Baby Huey (gingertube) thread in the Tube forum has a lot of build info and schematics. Maybe helpful

Cheers
  Reply With Quote
Old 15th April 2018, 03:32 PM   #10
audiowize is offline audiowize  United States
diyAudio Member
 
Join Date: Aug 2005
Location: Seattle
Send a message via AIM to audiowize
You don't need to run the EL34s that hard to get 50 watts, but rather you need to implement fixed bias in a class AB amp that's a bit more on the B side.
  Reply With Quote

Reply


Found schematic 50W EL34 AB. Needs help...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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Someone help: SE shematic with GK71? bezobraznia Tubes / Valves 30 24th April 2011 12:17 AM
Looking for PP 7027a shematic 807tubenut Tubes / Valves 1 21st August 2010 07:52 PM
Classe DAC-1. shematic vadimgal Digital Source 3 21st September 2006 06:53 PM
NEC A10 shematic vd-two Solid State 0 5th April 2005 10:08 AM
shematic of vincent cd s1.1 alchemy Digital Source 5 29th October 2004 01:31 PM


New To Site? Need Help?

All times are GMT. The time now is 05:05 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki