What is a Parallel Single Ended Amp?

[olddawg]

How do you get 20 watts out of a class A parallel single ended amp using EL84s? Is it analagous to four 5 watt Valve Jr circuits in parallel for 20 watts? Any schematics out there?

[Amp Kat]

A parallel single ended amp is basically two cascaded power tubes wired to a single ended OT. I believe the AX 84 project is a two EL-84 SE amp and would be around 20 watts or more depending on how you biased it fixed or Cathode.

This one is actually a EL-84 and 6V6 design by a fellow Ampager Albert Kreuzer who used to post here frequently and still prolly does.

[tubeswell]

I did one a couple of years back.




Soundbytes of this amp (with my strat and a Celestion G10)

Super AC4 - Big Muff 4.mp3

Super AC4 - Bigg Muff 3.mp3

Super AC4 Big Muff Trem.mp3

[JoeM]

....
This one is actually a EL-84 and 6V6 design by a fellow Ampager Albert Kreuzer who used to post here frequently and still prolly does.

I guess you didnt see this thread:

http://music-electronics-forum.com/t24687/

[olddawg]

The new Laney 20 watt amps use 4 EL84s in what they call a Class A parallel single ended configuration. How is that done?

[Tom Phillips]

The new Laney 20 watt amps use 4 EL84s in what they call a Class A parallel single ended configuration. How is that done?

Basically just imagine 4 tubes in parallel using the same methods as the schematics earlier in this thread show for two tubes in parallel.

Actually, the description describes what they are doing.
Theoretically you can just keep adding tubes to obtain more power.
Practically you need to compensate for the change in load impedance and eventually a tone change may be noticeable because of increasing load capacitance at the input to the power amp.

The Laney may not put out exactly 20 Watts but I don't see why it could not. Just depends on how they set it up and the usual liberties that manufacturer's take when they set specs.

Make sense?
I remember that parallel single ended topology is described in the TUT books.
The second iteration of the Two Stroke amp uses a two tube parallel single ended power section.
There are probably other examples too.

Regards,
Tom

[olddawg]

Basically just imagine 4 tubes in parallel using the same methods as the schematics earlier in this thread show for two tubes in parallel.

Actually, the description describes what they are doing.
Theoretically you can just keep adding tubes to obtain more power.
Practically you need to compensate for the change in load impedance and eventually a tone change may be noticeable because of increasing load capacitance at the input to the power amp.

The Laney may not put out exactly 20 Watts but I don't see why it could not. Just depends on how they set it up and the usual liberties that manufacturer's take when they set specs.

Make sense?

Regards,
Tom

Yes, pretty much what I thought and thanks. The reason I have asked is because I love the sound of small EL84 single ended amps in saturation. I also gig with 18 watt Marshall clones. Instead of building another clone I was considering building a higher power class A amp. I thought I might use the iron out of an old 4x EL84 stereo amp. I don't usually use channel switching so I thought it might be a simple build. Of course I would have to use a different OT rather than one of the 2 OTs on the doner chassis.

[Austin]

Yes, pretty much what I thought and thanks. The reason I have asked is because I love the sound of small EL84 single ended amps in saturation. I also gig with 18 watt Marshall clones. Instead of building another clone I was considering building a higher power class A amp. I thought I might use the iron out of an old 4x EL84 stereo amp. I don't usually use channel switching so I thought it might be a simple build. Of course I would have to use a different OT rather than one of the 2 OTs on the doner chassis.

It might be cool to have a stereo guitar amp too, just get two se air gapped output transformers. You could run them both at the same time and still be single ended with double the power. Or play an mp3 player through it in stereo.

[olddawg]

It might be cool to have a stereo guitar amp too, just get two se air gapped output transformers. You could run them both at the same time and still be single ended with double the power. Or play an mp3 player through it in stereo.

Yeah... I thought about that. But with a stereo tube amp I think it would be to easy to hook up only one load and trash it. I am really intrigued with building a 20 -25 watt class A single ended amp.

[Austin]

Yeah... I thought about that. But with a stereo tube amp I think it would be to easy to hook up only one load and trash it. I am really intrigued with building a 20 -25 watt class A single ended amp.

You know that you can bias push pull in pure class A right?

[olddawg]

You know that you can bias push pull in pure class A right?

Yes, and there is that old argument about whether 18 watt Marshalls and Vox AC 30s are Class A and when. I was more curious about a higher powered single ended design. You don't see it implemented often. Now I see a major manufacturer doing it and calling it a tone monster. Four EL84s in Class A to get 20ish watts. I wonder if it would double as a BBQ grill.

[Amp Kat]

I guess you didnt see this thread:

http://music-electronics-forum.com/t24687/

Thanks for that Joe I wasn't aware but it is sad as Albert was a great poster here. RIP Albert Kreuzer

[Austin]

Yes, and there is that old argument about whether 18 watt Marshalls and Vox AC 30s are Class A and when. I was more curious about a higher powered single ended design. You don't see it implemented often. Now I see a major manufacturer doing it and calling it a tone monster. Four EL84s in Class A to get 20ish watts. I wonder if it would double as a BBQ grill.

The idle current for el84 is around 50ma so x4 you need a opt that is rated for 200ma dc. I am pretty sure you would get more than 20 watts out though..

Here is one for 80 dollars http://www.edcorusa.com/p/464/cxse25-4-1_25k

They have a cheaper one that would work fine for a guitar amp for 30 bucks.
http://www.edcorusa.com/p/496/xse25-8-2_5k

[Tom Phillips]

The Edcore transformer line looks interesting. The advertizing says they are "mathmatically designed" and "wound with the finest virgin copper magnet wire." We could have some entertaining discussions about what that means. I wish these companies would ditch the marketeer hype. Maybe they hired some people away from MM.

[Enzo]

Mathematically designed - we got out a calculator and figued the turns ratio.

Virgin copper wire - we bought new wire, we didn't unwind an old transformer and resuse the wire.