[FrankCooter]

With a little massaging, you could turn a design like this into an all DHT SET amp. I'm thinking: LL1630 step up, CCS loaded 826, cap/grid choke, 801 driving a 1:1.5+1.5 transformer. B+ is 580v. Pretty sure this is where I'm going next.

7403 looks like a REAL interesting tube for an application like this.

Totally agree with all the negative comments on the SRPP. I've used it several times and have always been dissapointed. Done with it.

 

[spritzer]

A DHT route would be awesome too and much cheaper to build then KG's all DHT electrostatic amp. 12 EML tubes aren't cheap and then there is the actual circuit...

 

[nattonrice]

I coughed up my left you-don't-wanna-know at the total cost once I added the teflon caps... eeep.

 

[spritzer]

It's DC coupled.

 

[techbiker]

Hey,
 
I know that this thread is long dead, however I just built a SRPP-based headphone amplifier for my brother and it is amazing! It uses a 12ax7 in combination with two ECC99's along with a negative feedback loop. While the amplifier was based on Pete Millet's SRPP design, the added NFB helps to reduce the distortion from more than 1% to a nearly-immeasurable level. It is perfectly capable of driving headphones ranging from 32 ohms all the way up to 600 ohms as long as the builder uses Sowter 8665 output transformers with multiple output windings.
 
I know that many people hate NFB, but I don't see any problem with the quality of the audio coming from my brother's ATH-m50's when compared to my custom reference desktop system.
 
Anyway, the credit for the design goes to Ian Thompson-Bell. Let me know if you are interested in more information.

 

[nikongod]

Sounds fun. Im interested. 

 

[techbiker]

Nikon,
 
I haven't yet gotten permission from Ian to repost his schematics on another website, so please see the improved headphone amp schematics on this other audio forum on post 3:
 
http://www.diyaudio.com/forums/power-supplies/203529-opinions-power-supply-ht-ripple-current.html
 
Note that the issue I was posting about in this thread was related to a mistake that I made in the placement of the heater wires. The interference from the AC heater wires was entering the amplifier board and the HT line until I moved both of these lines away from each other. The first schematic is the power supply for the amplifier. Please ignore the bottom left part of this page (only the tube gain make-up stage is part of this design).
 
Here is the original Pete Millett design:
 
http://www.pmillett.com/images/ECC99_SRPP_2.PDF
 
And finally, here is the original thread were Mr. Thompson-Bell talks about his design:
 
http://www.diyaudio.com/forums/tubes-valves/191632-improved-tube-headphones-amp.html
 
By the way, I have an oscilloscope and I will be at my house for a few more days. If you would like me to take any scope readings, please let me know and I will try to do so.
 
What do you think? I am using a pair of 50k ohm output Edcor transformers with excellent results when paired with my brother's ATH-m50's. Buying a custom transformer set is usually much cheaper than using the Sowter if you know what you will be using for headphones.

 

[tubino]

Quote:

With a little massaging, you could turn a design like this into an all DHT SET amp. I'm thinking: LL1630 step up, CCS loaded 826, cap/grid choke, 801 driving a 1:1.5+1.5 transformer. B+ is 580v. Pretty sure this is where I'm going next.

I know it has been 1.5+ years since that was posted, but... I think it's still timely!  Did you ever make one like this, and in any case, what would be a source for that transformer?  I've got many of the parts and tubes for something like this... 
 

 

EDIT:  I stumbled on Andrea Ciuffoli's STAX amp design where he uses an SET to a Lundahl 1660 @ 50ma plate current...  I like it!  But I would use some different output tube... maybe 801.
http://www.audiodesignguide.com/my/stax_amp.html