[bigjppop]

I recently acquired a new EL34 based push-pull amp from Suppo Audio (Chinese company) and I'm curious as to what some of you tube gurus might have to say on he design/schematic.  I've started a thread over at diyaudio

http://www.diyaudio.com/forums/tubes-valves/160924-new-suppo-audio-el34-amp.html

but I'd love to know what some of you guys think as well.  I'm still very new to the DIY thing so please try and right your comments "for Dummies".  I'm looking for anything that jumps out at you and says "I'm an easy fix, fix me!"  I'm planning on swapping out the coupling caps (because that's always been a good fix in anything I've ever done) but am having a hard time knowing what value of cap to order as I'm still pretty green when it comes to reading schematics.  Other than that, I'm open to anything.

Thanks in advance for your help.

Edit:  Thanks for the heads up Blair.  The following link should work better.  Make sure and use the magnify button for a better view.  Added some pics as well.


http://picasaweb.google.com/jeremyrobertson1/SuppoEL34#5441802552673708930

[Niteshade]

I have seen their web site before and always wondered about them. Your schematics & other things are not available to non-members.

[bigjppop]

Thanks Blair, updated first post.  I'd love to hear your thoughts on the schematic (knowing in advance that you not a fan of PCB's in tube amps )

[Niteshade]

It looks like a good design to me. Please update us once you get it.

[JohnR]

The coupling caps are 0.1 uF. I guess what's confusing here is why you feel the need to mod it in the first place. Removing or replacing the volume pot with a stepped attenuator would be an easy tweak to do.

[bigjppop]

The coupling caps are 0.1 uF. I guess what's confusing here is why you feel the need to mod it in the first place. Removing or replacing the volume pot with a stepped attenuator would be an easy tweak to do.

Isn't that part of the addiction!  If its good stock, it for sure can be made better, right?   

A different volume pot would be a nice swap but unfortunately the pot has one of the 6N6's directly behind it and really doesn't allow for much more than what's there now.

As for th caps, I thought the .1uF caps where probably what I was looking for.  Now, do you think 400V caps will do it or should I go with some 600V caps?

[Niteshade]

Listen to it first!    If it works well, don't mess with it.

Geesh. 

[Bill Baker]

Don't put any money into it until you get a feel for it. If it sounds like crap, nothing you do to it will make it sound "right" and you will only be throwing money away. It's the old "Polishing a Turd" syndrome.

 If you like what you're hearing after spending some time with it, you can start playing around with it if you so desire.

  If you get the upgrade bug, the power supply is where I would start. The Chinese do some strange things in power supplies and this one is a bit different. But again, see what you have first.

 Enjoy and keep us posted.

[bigjppop]

Boy, you guys are just no fun!  Alright, alright... I'll listen first and then see where the world takes me.  I definitely don't want to be doing any turd polishing (which they should definitely make a smiley for!).

I'll report back soon.

By the way, you guys would make terrible crack dealers!   

[Niteshade]

Once you get it, take some close ups for us of the circuit boards.

Mods to the feedback circuit could make a difference if later tweaking is desired.

Something else: Try the 4 ohm tap instead of the 8 ohm for a different sound.

That's a voltage doubler power supply for B+. It looks to be a good design. Time will tell!

Something of interest: The bias supply can be upgraded: Bridge rectifier & slightly different filtering circuit. BUT: Printed circuits can make this a nasty proposition unless there is room in the case to add parts (properly). I wouldn't do anything at all to it unless there are issues.