My XPP OTL Headphoneamp

[Radioman62]

Hello folks
I have hesitaded a bit to present this building because of all the competing yardsticks and so forth...
But because this is the worlds most visited place for DIY works I had to take a chance

I want to share my design and I also accept all the criticism I can get. Thats the rules, I know.
I Also want to share because I think this is the best forum out there, there is.

This is the shcematic of the amplifier:


This is the schematic of the PSU:


The story of this amp is on one of my homepage sites:
Ove's XPP OTL HeadPhoneAmp

I would be glad for any comments

[Radioman62]

oops, Im sorry.
I just fixed an error on the PSU schematic. R14 and R15 should go to the bridge instead of the same side of the transformer.

Schematic above is updated, please reload/update your browser.

[Radioman62]

Hi all
It's summer and I have a low profile with electronics.

Anyway, there must be some problem with my languish or my delivery of this project..
Please tell me if my languish are to bold or if you see the advertising for my small "at the side " company... which is in it's infancy ( not cashing any money at all ) or any thing else that I, with my poor english isn't aware of..

I think this is a very good project, at no cost, for an intermediate DIY audio addict to test.

Sincerely // Ove

[ikoflexer]

Thank you for sharing, looks nice. Sometimes you have to be patient with this forum, don't be easily discouraged.

[Gordy]

No, nothing wrong with your language!

The project looks interesting. How much power into 30 Ohm 'phones?

[Stixx]

No problem with your language!

For those who are less educated (which includes me )... can you give a quick rundown of the details/advantages of your schematic ?

[Radioman62]

Hi all and thanks for looking.
A quicky before you go in deapth reading the links I refer to

It has no output transformer.
The endstage is symmetrically built, X push pull Class A. The more load the less distortion is significant for this amplifier.
The use of common cathode amplifier as the gain/front stage is overlooked. Gives low distortion and very high bandwith.
No global feedback, just some small local feedback at the frontstage, where the smart option to also have a "soundstage control" resides.
Easy to build PSU. Gives very clean stabilized Voltage without any large iron and inductances (big coils).
No special "boutique" components. Instead rather inexpensive and readily available components, including the tubes, allthough the PCC88 is beginning to be more pricey lately.

This amplifier has actually been built exactly as the schematic on my homepage. I'm actually using it in the livingroom to my own delight.

[ikoflexer]

Hi, what is the approximate current drawn by each channel?

[Radioman62]

Originally posted by Gordy
The project looks interesting. How much power into 30 Ohm 'phones?

I havent measured that because I mainly use 60 ohm or 300 ohm. I have a pair of 32 ohm Sennheizers though, that I have used to test with and they give more then enough for any ear

It's also possible to tweak out more current if necessary out of this design, if you allways run it with really low loads. Or parallell more 12B4's to drive even speakers ... in a very inefficient way though

[Radioman62]

Originally posted by ikoflexer
Hi, what is the approximate current drawn by each channel?

60mA
10ma in each common cathode triodes and 10mA trough the two PCC88 endstage triodes and the last two 12B4's takes 30mA.