Looking for some Single Ended Ideas

[ncusack]

Hello Everyone,

I have a few spare transformers im looking to do something with. The PT is a Hammond 270EX and the OT is a Hammond 125ESE. I also have spare 6L6 I could use in the power section.

What im looking for is a few different suggestions of what to build. Aside from the usual ax84 and fender champ stuff. 

I'm a relatively novice builder. I've done a few champ and tweed Princeton builds and an 18W Lite and im about to start a 6V6 based Spitfire. I think something a little more high gain might be in order but all suggestions are welcome.

[tubenit]

Take a look at this IF you are open to considering an EL84.  This would be my personal choice.

The sound clips are phenomenol.


http://www.el34world.com/Forum/index.php?topic=9149.0

http://ampgarage.com/forum/viewtopic.php?t=13854

With respect, Tubenit

[Geezer]

Take a look at this.  This would be my personal choice.

http://www.el34world.com/Forum/index.php?topic=9149.0

http://ampgarage.com/forum/viewtopic.php?t=13854

With respect, Tubenit

And take a listen to this> http://soundclick.com/share.cfm?id=10455845
It's the same amp referenced above by Tubenit.....fantastic tone! Mat's playing is quite intoxicating.....I've listened ~~20x today!

G

[ncusack]

That amp sounds great but the PT doesn't really match up. The mini-HRM uses the 269 which is 190-0-190 and the 270 is 275-0-275 thats a pretty hefty voltage difference. Though if that could be designed for use with the 6L6 im sure the voltages would be right in the ball park. Im no designer though

[tubenit]

You could easily make that work with 275-0-275 PT from my perspective using a 5Y3 for around 300v on the EL84.

Then use larger dropping resistors on the B+ rail.   It's the preamp and EF86 voltages that would need to be the same, IMO.

The 190-0-190 PT is using a solid state rectification for 266v.


With respect, Tubenit

[ncusack]

I suppose your right in that logic since it is a single ended amp so what rectifier you use shouldn't really make a difference other than the voltage out. sag is a push pull thing not single ended.

[DummyLoad]

perhaps this might help? just doodling - have not built this - built something similar w/ 6AQ5 output recently. output stage and CF are shoot-from-hip.

 

--DL

[Fresh_Start]

I don't see why Mr. Cusak can't take the miniHRM preamp and simply run it into an EL-34 or 6L6.  Just get the preamp voltages right and away you go.  It might not sound exactly the same but I'll bet it would sound great (especially if you can play as well as Mat does!)

Just a thought,

Apparently not a good thought based on comments Mat made over on AMPAGE. 

Chip

[tubenit]

IF your heart is set on a 6L6 type amp, you could consider this one?

This is strictly a DRAFT idea that used the basic topology of a proven SE amp but with significant component value changes.

I think it might be a great sounding amp, but I do not know that to be true?

With respect, Tubenit

[LooseChange]

The only thing I would change would be to rearrange to have a gain stage after the tone control and before the power tube. This helps drive the power tube.

[tubenit]

The DRAFT idea came from this.

http://yeomansinstruments.blogspot.com/2008/06/schematic-for-my-champ-to-wreck-mods.html

With respect, Tubenit

[Fresh_Start]

The only thing I would change would be to rearrange to have a gain stage after the tone control and before the power tube. This helps drive the power tube.

My first reaction was exactly the same, but then I looked over at some of the AX84 circuits.  Almost all of them have the tone stack right before the power amp - which is just the power tube in an SE design.  Surprised me too.

BTW there are a heck of a lot of single-ended designs over on AX84 - Classics, Associate Projects, Building Blocks.  I know the OP said he wasn't interested, but there sure are a lot of ideas there.  sewatt.com might be a source of inspiration as well.

Hope that helps,

Chip

[ncusack]

Do any of you guys have experience with the Soldano Atomic preamp? I know this is normally mated to a push pull el84 output stage but do you think it could work in a single ended design? What im mainly thinking about is the PI in the push pull vs no PI in a single ended design.

[tubeswell]

I recently did a SE amp where the PT had 280-0-280 and 350-0-350 HT taps.  On the 280-0-280 tap it sounds good with a 5U4G and a 6L6  - The 6L6 only runs at about 300 on the plates IIRC. The design has switchable cathode resistors for running a hotter bias on low voltages. (NB The attached schematic shows the higher HT voltages with a 6L6).

[Fresh_Start]

No experience, but if this is the circuit you're talking about it looks interesting for sure:
http://www.el34world.com/charts/Schematics/files/soldano/soldano_atomic16.pdf

Sometimes there's a design "problem" when trying to use a push-pull circuit's preamp with the tone stack right before the "power amp".  This is a perfect example.  The Atomic 16 uses negative feedback and has a presence control in the feedback loop.  The NFB and Presence control certainly affect the tone and distortion of the amp.  So how do you replicate them in a single-ended amp?

If I knew the answer to that question, someone would be paying me to design amps! Sorry - I'm not trying to be a PITA.  It's just that I've looked at a number of push-pull circuits that I liked and asked myself the same question.  One possibility would be to add a gain stage between the tone stack and the power tube.  That would give you a point to apply NFB, but getting it to sound like a fixed bias, push-pull amp with a LTPI is way above my pay grade.

I tried to find sound clips of the Soldano Atomic 16 and failed.  Anyone know where a sound sample might be?

Cheers,

Chip

[DummyLoad]

start with fender champ plan - build from there. 

[firemedic]

Not to butt in but when I did my SE amp I was similarly undecided. So I started with a SE Princeton topology, using a 5879 for an input tube, Fender T/B tonestack and a paralleled 12AX7 for the 2nd stage, into a 6V6. It sounds good with a 6L6 too. I love this little amp. I posted the schem. somewhere in the forum as "5879SE".