OTL Amp/Headphone Suggestions

[dustinsterk]

Hey Everyone,
I have had such a great experience with my DIY ST35 I wanted to ask anyone if they have any suggestions for a OTL amp? I have looked at the Bottlehead Crack, but it seems a little expensive for what parts are included. I am looking for a nice tube sound using headphones (still undecided which ones) at work.

Thanks in advanced!

--Dustin

[dustinsterk]

After re-reading my post...let me rephrase my question: I am looking for a new DIY project, schematics, or other OTL tube amp project similar to the Bottlehead crack OTL amp. I did do a search and found discussions back in 2010 about a Headwize OTL amp:

viewtopic.php?t=4041

I think I found what is now the dead link in that post:

http://headwize.com/?page_id=457

Does anyone have any experience with this amp?

Thanks!
Dustin

[EWBrown]

This simple OTL headphone amp design by Aren van Waarde is pretty close to the "Crack",at least in general topology:


http://headwize.com/?page_id=427



Schematics "redistributed" from the original article:

(parts list and other vital info is on the website)






HTH

/ed B

[dustinsterk]

Thank you very much! Just out of curiosity have you or anyone else built this amp before? Also any idea what he used as the transformers?

[mesherm]

I have used Aikido topology for two headphone amps for my Grado headphones. Both sounded quite amazing and started me re-listening to a lot of my favorite CDs.
The Aikido uses more tubes how ever. I have also used Aikido topology with a few changes for 300B and 2A3 SET drivers also with good results.
http://www.tubecad.com/2006/04/blog0062.htm

[azazello]

Thank you very much! Just out of curiosity have you or anyone else built this amp before? Also any idea what he used as the transformers?

I build the same /6AS7 G & PCC88 Siemens/with kenotron RV200/600, 2 years ago, sound is awesome with my Sen 580. I used PT from Russian tube TV.
Parallels C3 & C4 are not good idea, better use one C with Hi quality /my is Siemens/.
https://picasaweb.google.com/1095707775 ... 0498375714

[EWBrown]

I built the "Crack" kit when it was first released, and still at the initial lower price. The main difference from the "Headwize" is that it originally used a 12AU7A and 6080, I modded it for a 6CG7 which was a simple matter of wiring the driver tube socket filament to pins 4 and 5 (same as with the 6DJ8 / ECC88 / 6922/ 6N1P, etc)

The power transformer isn't critical, just as long as you can get 150 to 160VDC B+. DC filaments are nice, but not absolutely necessary, as the overall amplifier voltage gain is pretty low, a bit less than 30X total.
The 6AS7G / 6080 is a filament current hog, at 2.5A, the 6CG7 is 600 mA, so at least 3.1A is required, play it safe with 4 or 5 A, the filament winding (or separate 6.3VAC tranny) will run less hot. If you rectify and regulate it, then 5A to6A would be best, The 6AS7 / 6080 platecurrent is approx 25 mA per section, the 6CG7 about 4 mA per section..

I use it with Sennheiser HD600 'phones, it sounds quite nice!

/ed B

[dustinsterk]

Thanks to you all for suggestions/comments!