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Old 26th July 2013, 08:54 PM   #1
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Post Help finding a new tube headphone amp

Hello,
I am new to this forum, and in the market for a new tube amp after suffering from a chronic case of upgradeitis. I have some kit building experience (I can put parts together off a schematic and solder well), but I don't have enough experience/knowledge to design an amp. Most of the tube kits that I have seen have either been hybrids (like the Project Sunrise II I have) or for speakers (which I don't have). I would like to DIY if possible, but there are some requirements that I am trying to meet. However, I am not sure if all of this is possible.

1. Low output impedance--I have pretty efficient cans (32-50ohms), that also happen to be power hungry.
2. Lots of power--My main headphones right now--modded Fostex t50rp--are happy at around a watt at 50 ohms and can take up to 3 watts. Most headphones that I am looking at eventually upgrading to are notoriously hard to drive (LCD-2s He-500s).
3. Options for later upgrade. I would like to have the amp be able to power headphones from 30 ohms up to 600.
4. Not too expensive. Broke university student here, so I don't have that much money to throw out on audio gear.
5. Tube rolling ability. I have a bunch of 12au7s for the Sunrise II and love tube rolling.

Out of that list, Power and upgradability are the primary objectives. I have been searching around for quite a while and have not been able to find an amp that can do all of that (technically the Project Ember can, but it is a hybrid which I want to try and stay away from. Plus it is a little expensive.).

Right now, I have the Project Sunrise II, and am planning on also getting the O2 and Odac soon as well. My headphones are the:modded Fostex t50rps, Denon D2000 and modded Grado SR125i.

Thanks for reading, and I appreciate any help!
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Old 27th July 2013, 02:19 AM   #2
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Quote:
Originally Posted by HollowState View Post
The little Bravo headphone amp seems to be all the rage these days. It's a very nice sounding and inexensive amp as purchased. It is also a perfect platform for modification and everyone seems to be doing just that. RCA clear top 12AU7, better FET, capacitors, analoge PS, improved heat sinking and more. Rockgrotto has a nice thread on these amps. And I think we even have one here at diyaudio.

A friend of mine in the New Jersey Audio Society has worked out a very extensive modification for this amplifier. It even works great as a preamp. He is calling it the "Bravissimo".

Edit: Well, I see that the Sunrise amp is similar to the Bravo. I suppose I should have looked at one first before mentioning this one.
Thanks for the reply.
I actually already had the bravo. It was my introduction to tube amps. There are just some issues with it and it offers pretty limited choices as far as headphone upgrades. Changing tubes make a difference, but there is no way to bais them. The stock mosfets are alright, and modding does make a difference, but not huge.

The biggest problem is with headphones that are hard to drive--like the Fostex. The bravo has 35db of gain, but just can't supply the power. The Sunrise just does everything the bravo does, but much better.

I am looking for something like an OTL or transformer coupled tube amp. I primarily want to see if powering the tubes at a full 100-300v will improve the sound. One of the main complaints against hybrid amps like the Sunrise is the tubes are just running off a standard 12.3v or 6.3v. Offering baising is a step up, but it isn't the WA6--which it seems I might just have to save up for.
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Old 27th July 2013, 02:43 AM   #3
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Hello DuMont,
Yea, I pulled my post down because it didn't answer you question or really help you. I should have researched it first, but didn't. Actually I have in my head an idea to build a small headphone amp around some nos UTC-H23 plate-to-line transformers I have. It will be a simple push-pull output with small dual triodes like 12AU7s or similar types 12FQ7, 7119, 7044 and others. Since I never write anything down, draw schematics or simulate, I just build from what I see and work out in my mind. I've always done it that way. I just have to get psyched, take the time and do it.
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Old 27th July 2013, 07:59 AM   #4
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Location: Holt, Norfolk
Check out my improved tube headphones amp here:

Improved Tube Headphones Amp

I have been in discussion with someone who wanted more power out of it to be able to drive several sets of headphones in parallel so the design can be tweaked. Even in its basic form it should be able to drive a 98dB sensitivity headphone like the Fostex to 120dB SPL which should be loud enough for anybody. With the Sowter transformer, almost any impedance headphone can be driven.

Cheers

Ian
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Old 28th July 2013, 09:26 AM   #5
regal is offline regal  United States
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Powering orthos especially Hifiman's is difficult with a tube amp. Its more expensive than building a tube speaker amp. I have found and others have measured that many ortho headphone's true efficiency are much lower than the published specs. You are going to want at least a low distortion 2-3W amplifier and as we know tube distortion rises with output. Before you jump into building something under-powered take a hard look at a hybrid, they make the most sense economically for orthos. For DIY the EHHA is a great bang for the buck but there are also a few commercial hybrid amplifiers that make a lot of sense for these phones.

If you want to spend a lot of money and time see my DHT SET amp thread, a lot of good info in there.
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