interesting headphone amp, 100 dollar tube option....

[pucho812]

I been thinking of a headphone amp for some time as the built in solutions I had on my uad converters were nothing stellar.  After  extensive looking I picked this  as the price was nice. $100.00 It has balanced inputs  1/4" headphone and 4 pin headphone connections,  and tubes. all made in china not chino. 
the circuit is a hybrid of tubes and 5532's.  Specs are not bad. So I get it in the mail today and fire it up.  First impression was it was nice especially for the price tag. The tubes run warm so looks like they are more for then show.  The stock tubes sounded o.k. and I was lucky to have  subs lying around that were a jan stock so I swapped them and got more pleasing results to my ear.
While I am  enjoying things,  this seems like the race to the bottom as far as electronics.  Perhaps I shall release a 99.00 dollar 1073 clone and really screw up the market.

https://www.amazon.com/LOXJIE-Balance-Amplifier-Headphone-Power/dp/B07H5JLD2Q

 

[scott2000]

What headphones are you using?

 

[pucho812]

What headphones are you using?

bayer dynamic dt770's are the bench test..

 

[pucho812]

test number two with sennheiser  280 and 300's as well as audio technica headphones. Compared to the stock UAD one in a UAD silver face, yes it was lovely.  At 99 dollars, it's very lovely. at 99 dollars and JAN tubes a total of an extra 20 dollars, was  well beyond what I expected.  I don't think I could DIY anything for less $$ with specs they tout. While I doubt the specs are as quiet as they say they are, it's more then close as there is no real hiss or anything of the sort.  over all very impressive especially for the price.

the race to the bottom is happening.

 

[gyraf]

;D Schematics, or it didn't happen...!

 

[pucho812]

;D Schematics, or it didn't happen...!

https://www.amazon.com/LOXJIE-Balance-Amplifier-Headphone-Power/dp/B07H5JLD2Q?tag=viglink25540-20

 

[user 37518]

I remember seeing a similar headphone amp which used 5532s as VAS and a simple 12AX7 in a cathode follower configuration, If I remember correctly it sounded better without the tube with medium and high impedance headphones :

 

[pucho812]

Jakob,

here ya go.  8)

the ribbons go to the front panel lcd display and circuit board with volume control

 

[scott2000]

Kinda sexy.... They even splurged on the caps???

 

[pucho812]

Kinda sexy.... They even splurged on the caps???

I know right.  8)

 

[gyraf]

here ya go.  8)

the ribbons go to the front panel lcd display and circuit board with volume control

Thanks!

No schematic then? Is this an original design?

Driving 64 Ohms from the 6N3 without transformers  would be a no-no, so tubes are probably some kind of an input/distortion stage..?

Jakob E.

 

[pucho812]

Thanks!

No schematic then? Is this an original design?

Driving 64 Ohms from the 6N3 without transformers  would be a no-no, so tubes are probably some kind of an input/distortion stage..?

Jakob E.

I have not obtained one yet. 

 

[living sounds]

Wow, insides look really nice, too. What's the B+ voltage? Is this a transformer to step up the voltage for the tubes?

 

[pucho812]

Wow, insides look really nice, too. What's the B+ voltage? Is this a transformer to step up the voltage for the tubes?

I'll take some measurements,  I assume the transformer is to step up for proper or close to proper b+

 

[PRR]

Driving 64 Ohms from the 6N3 without transformers  would be a no-no, so tubes are probably some kind of an input/distortion stage..?

There's 18 pins of tubes, and over 130 pins of chips. Looks like the tubes do less than 13% of the work.

The line of 8-DIP JRC chips next to the 1/4" jack suggests a chippy output. I can't read the types, but surely 30mA/amp, so 120mA peak to load, or over 200mW@32r dead-clean buffering. JRC makes even beefier opamps at low price.

 

[pucho812]

There's 18 pins of tubes, and over 130 pins of chips. Looks like the tubes do less then 13% of the work.

The line of 8-DIP JRC chips next to the 1/4" jack suggests a chippy output. I can't read the types, but surely 30mA/amp, so 120mA peak to load, or over 200mW@32r dead-clean buffering. JRC makes even beefier opamps at low price.

the line of 8 dip are all 5532's

 

[alexc]

What I like about some of these affordable headphone amps, is using them  in differential mode ... 

ie.  driving with out of phase inputs, such as the 'hot' and 'cold' phases of a well-behaved balanced output  ....    to the hphone amp's L and R channels, then driving a decent sized low Z transformer in push-pull.

It really can give some impressive measurement figures, albeit by reducing stereo unbal to mono bal.

But for the money, the perf can get stonkingly great in a 'bal line amp' context. It's a good way to use up those 'low Z' traffo's lying about  ;D