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-   -   Recommendation plz: an inexpensive tube (or hybrid) can amp for hi impedance cans (http://www.diyaudio.com/forums/headphone-systems/170300-recommendation-plz-inexpensive-tube-hybrid-can-amp-hi-impedance-cans.html)

Wikkid 16th July 2010 01:29 AM

Recommendation plz: an inexpensive tube (or hybrid) can amp for hi impedance cans
 
Hello and thanks in advance!

I have a pair of Koss Pro-4aa headphones that I just had
reconditioned by Koss.
(cost of shipping only, due to their excellent lifetime warrantee!)
Had 'em as a kid in the 70s and had beaten them to death,
but now they're brand new again and I've always and (still)
really liked them.
I hadn't listned to them at all, nor any others hardly at all
in decades, but the moment I tried out the recon'd Koss
and especially after some break in I'm real into spending
some time with them.
My current amplification (old receiver) is disapointing.

I'd really like to build an inexpensive (and simple) tube or
hybrid amp for them, and would be greatful for recommendations.

The Koss are high impedance... 260 ohms IIRC?
In that neighborhood in any case.
I don't know if I'll ever use any other cans with the amp,
but so much the better if it were flexible...
Though the priority is for optimal use with the Koss.

Easily available, not rediculously expensive tube compliment
would be nice too.
Likewise a low stress BOM and other sourcing situation would
also be a blessing.
Maybe even a ready made PCB?
Ok, ok... now I've gone to far........

Thanks again!
Greg

Gordy 17th July 2010 08:40 PM

Greg, have a look in this thread...
http://www.diyaudio.com/forums/tubes...phone-amp.html

My recomendation is in post #5

BoilermakerFan 30th July 2010 03:52 PM

A Cavalli Audio EHHA is a great hybrid with excellent support via the cavalliaudio.com web site and forum threads on Head-Fi. A full kit is available from Class Jar Audio for the MOSFET version.

I'm planning to build the BJT output version over the winter with 2238/968 BJTs, but the MOSFET version will be an easier build for you since it's available as a kit.

qusp 3rd August 2010 06:51 PM

thats a pretty common range for headphone impedance at least as well, so if it works well with your koss, the power output at least should be fairly well suited to some beyers (DT880 250ohm) and HD600/650/800 (300 ohm) I can second the Glass Jar Audio kits as well and the EHHA I heard recently was pretty nice (dont know the version)

Wikkid 11th August 2010 12:14 AM

Eureka!
 
Well Gents...
Thank you all so much!
I think I've found my amplifier.

The EHHA seems the best bet for me... in several regards.
Price range, completeness of kit (makes it so much easier for me), and
I'm sure the sound quality will be fine... I'm either unwilling or unable
to do something vastly more sophisticated.. particularly for a first go.
SQ however IS important to me, especially given that transducers
are so close to ears.
This seems like the best combination of virtues, given my circumstances.

I also like Glass Jar Audio.
I like the way they do things... and the choices they make, and offer.

Oh.... what about the PS?
Just go with the one Glass Jar offers?

Now, on to do my reaserch/learning and get down to it!

Thanks so much again!
Greg

PS: I'd luv to see pix (for encouragement) by any of you who've
decided to proceed with the EHHA !

BoilermakerFan 11th August 2010 02:23 AM

The GJA Sigma 22 PS kit is certainly a worthy PS and it makes your order process much easier. I would get the 100VA version, simply because you can upgrade to 2-1/2" heat sinks on the EHHA for a few bucks each and then run higher bias levels on the MOSFETs and it will have the reserves to deliver more peak power for those transient responses.

BoilermakerFan 11th August 2010 02:34 AM

Quote:

Originally Posted by Wikkid (Post 2269011)
Well Gents...
Thank you all so much!
I think I've found my amplifier.

The EHHA seems the best bet for me... in several regards.
Price range, completeness of kit (makes it so much easier for me), and
I'm sure the sound quality will be fine... I'm either unwilling or unable
to do something vastly more sophisticated.. particularly for a first go.
SQ however IS important to me, especially given that transducers
are so close to ears.
This seems like the best combination of virtues, given my circumstances.

I also like Glass Jar Audio.
I like the way they do things... and the choices they make, and offer.

Oh.... what about the PS?
Just go with the one Glass Jar offers?

Now, on to do my reaserch/learning and get down to it!

Thanks so much again!
Greg

PS: I'd luv to see pix (for encouragement) by any of you who've
decided to proceed with the EHHA !

Here's a good, but long thread on the EHHA:

Cavalli EHHA Embedded Hybrid Headphone Amp - Head-Fi.org Community

As I said earlier, I haven't built an actual EHHA yet, but I am building some of Cavalli Audio's commercial release prototypes. I can't share pictures of those amps, but feel free to PM me with any questions or join Head-Fi and post in the EHHA thread. There are some great builders supporting that thread and we'll get you squared away. Worst case, I'll ask Alex Cavalli directly for you as it would be beneficial to me in the fall too when I build my BJT version.

backefel 25th August 2010 09:40 AM

How does the SOHA II compare to EHHA? The EHHA uses 6GM8 tubes which, from what I heard, is getting harder to come by. Isn't more wise to choose an amp with tubes that's still in production?
Its not that I dont think it's a good amp..more like a heads up. Also, I think there's a rev a of the EHHA amp on its way with integrated psu (still 6gm8 though). Might be worth looking into :).

One more thing, Jeff might still have the kits for the soha if you were to change your mind (he still makes m3 and ck2iii kits even if they're not on his site).

dBel84 6th September 2010 02:06 PM

Pics first

EHHA

http://i246.photobucket.com/albums/g...EHHAlatest.jpg

SOHA II

http://i246.photobucket.com/albums/g...aiifrontsm.jpg

sound : Both superb amplifiers with "audiophile" sound attributes. Ultimately EHHA has greater control ( probably due to it's greater power output and speed ) Some feel the EHHA is a little bright , I never did feel that way but it does resolve a lot of the microdetail which could be interpreted as bright in the upper registers. The SOHA II can be tweaked by adjusting bias currents, tubes etc , the EHHA ( original - note that a revision is in the pipeline ) can be tuned to suite individual preferences - closed loop NFB adjustment can emphasize bottom end vs top end. ( ie more bass vs more sparkle )

there has been a lot written about both amps over on HF , I have yet to read an opinion where anyone thought either amp was a disappointment.

..dB


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