[slide4417]

Thought some readers might be interested in these notes. 
My old favorite headphone amp is an Antique Sound Labs MG head OTL.
I think it was somewhere in the neighborhood of 400 bucks...about ten years ago. 
 
I use Senn HD650 cans.
 
Recently, I picked up a Chinese headphone amp on ebay. Search on 
Class A 6xxx 12xxx 6N11 12AU7 Tube valve vacuum Hybrid Headphone Amplifier AMP
 
Cost me 40 something bucks, plus 12 or so on shipping. 
The MG head uses a 12AX7, and a pair of 6BQ5's
The ebay one uses a single 12AU7.
 
I spent a lot of time switching back and forth between the two, and my wife did also. 
Very hard pressed to tell the difference. 
I thought the big ASL sounded a bit more tight, but my wife thought the ebay one had more clarity (airey).
The ebay one with its laptop-type power supply did have a bit of hum, when the volume was cranked with no input signal, but no hum under normal listening volume. 
 
My point is...for anyone wanting to play with some hollow state hi fi...the ebay item sure is fun!
Even has a pair of blue LED's by the base of the tube to make it glow neon blue-like. Too Cool!!
 
Has a switch to allow you to play around with different tubes....6911/6DJ8, and 12AX7 ....but have not 
fooled with that yet. 
 
Cheap enough to have some fun with, or an ipod amp!!
 
YMMV, have fun!!

 

[DefQon]

See the thing about those cheap no-brand Bravo/Indeed clones is that they are usually using the cheapest components and the cheapest quality PCB available to them. Sometimes when ebay seller's state they are using popular WIMA mkp caps, Vishay resistors or genuine Mosfets, it is usually the opposite or they are fakes.
 
Not to mention some of those amp's aren't even designed with-in spec more like they grabbed a bunch of parts and just soldered it onto the PCB, sure it will work, but the durability and working life expectancy of them is a question to ponder. If they had designed it with-in spec with proper components than it will sound and function even better, but it will be another different asking price for the amp itself.
 
Those amp's do benefit from tube rolling and modding greatly though.

 

[Taveren]

Hope the TS won't mind if I ask in here. dose the number of tubes in a tube amp matter? I read some comments that if it has only one tube then I should not even be considering it. will more tubes sound better? or the single tube amps are ok for entry level tube amp experience? 

 

[DefQon]

Apples and Bananas comparison. Greatly depends on the circuit design and what role each of those tubes function as, phase splitter stage, power stage, output stage etc etc.

 

[Taveren]

Apples and Bananas comparison. Greatly depends on the circuit design and what role each of those tubes function as, phase splitter stage, power stage, output stage etc etc.

 
I see, so I should not immediately disregard those cheaper single tube amps then. thanks.

 

[DefQon]

   
I see, so I should not immediately disregard those cheaper single tube amps then. thanks.

 
Those tubes are not there for nothing. Most cases if a big amp has a large amount of tubes and multiple transformers or chokes that means and depending on the circuitry design those tubes are there to push X amount of watts into SE (single-end) or PP (push-pull) modes. PP mode is usually 30-40% increase in watts current over SE configuration. But again it varies.

 

[Taveren]

Thanks again. I ask beause I noticed the cheaper tube amps normally have a single tube and the more expensive ones have separate power tubes and driver tubes. So I was thinking the single tube will be crappy compared to the multi tube counterpart.

Then there is the hybrid and the OTL to choose from.... Sorry but the more I research the more complicated it gets

 

[DefQon]

Thanks again. I ask beause I noticed the cheaper tube amps normally have a single tube and the more expensive ones have separate power tubes and driver tubes. So I was thinking the single tube will be crappy compared to the multi tube counterpart.

Then there is the hybrid and the OTL to choose from.... Sorry but the more I research the more complicated it gets

 
Tubes/valve circuit designs can get complicated to understand, there are some DIY tube books written by qualified and experience known DIY'ers and inventors that you can learn a thing or two.
 
Single tube usually means it acts as a buffer, preamp or SRPP stage or so, sometimes it can also be a hybrid class A that works in conjunction with jets and other ss counterparts. A lot of "multi-tube" amp designs have CCS blended into the circuitry or parts using an SRPP stage. Etc etc.
 
It's a deep topic to get into. Diyaudio or the diy section here has plenty of more experienced folks and diy'ers to fill you in with the blanks.