Tube amp with no headphone jack — what to do??

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gurdyp

New Member
Hi all,

Apologies if this is a stupid question — I've tried to do the research, but am finding it really hard to track down a solution! I recently purchased a Reisong A10 amp — without realizing it had no headphone jack! (What a dunce.)

I can still return it, but I am really liking the sound of the amp through my speakers (my set-up being: Reisong, little bear tube pre-amp, U-turn Orbit with Grado black cartridge and Jamo s803 speakers). But I have a pair of planar headphones that I'd really like to use as well.

Does anyone have any ideas for what to do here?? Are there adapters that would go from the speaker outputs...? Should I just get rid of the A10? I'm stumped...

Thanks for any help!
 
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I think, while you've got the amp, you should measure it. Fund out what you like about it in real numbers.

Power output
Power bandwidth
Distortion.

These figures will give you a baseline of what to look for when shopping for an amplifier with a headphone jack.
Then look for something similar with a headphone jack.
 
If you can send it back, make your life easier and get something with a headphone jack. While you may be able to add one, I think you are better off finding an amp that already has the engineering worked out. If you try to add one, you might find that the modification gives you more hiss or hum than you expected...and it might make you crazy in the end.
 
I built a 'headphone interface' based on dewdude's design. It's very simple; two 8 ohm power resistors (preferably non-inductive) to provide a proper load to the tube amplifier, two smaller resistors to lower the levels to the headphones, and a dual audio taper potentiometer to act as volume control. I tweaked component values a bit based on his suggestions, and added a double-pole double-throw (DPDT) toggle switch with no center off (important!) to allow me to switch between the headphone interface and my speakers. Here is the schematic for what I built:
headphone_interface.gif
 
^ this is probably the best way to do it. I suspect the other designs are more aimed at SS amps that don't care all that much about load. Tube amps work best into their proper load. Sub the 8 ohm for whatever impedance taps you are actually using. As a bonus, this doubles as a dummy load for bench testing.


StepheK said:
Does this load a tube amp output at 8ohms?
Click to expand...
no, which probably makes it less than ideal.
 
gurdyp said:
Hi all,

Apologies if this is a stupid question — I've tried to do the research, but am finding it really hard to track down a solution! I recently purchased a Reisong A10 amp — without realizing it had no headphone jack! (What a dunce.)

I can still return it, but I am really liking the sound of the amp through my speakers (my set-up being: Reisong, little bear tube pre-amp, U-turn Orbit with Grado black cartridge and Jamo s803 speakers). But I have a pair of planar headphones that I'd really like to use as well.

Does anyone have any ideas for what to do here?? Are there adapters that would go from the speaker outputs...? Should I just get rid of the A10? I'm stumped...

Thanks for any help!
Click to expand...
You can build an adapter that fulfills the following :
- always load the tubeamp with proper loading ( 8 ohm some power )
- limits the power to the headphone, this is IMPORTANT to save your ears from any problems.

Or you can get a freeestanding headphone amp for about the same amount of money ( but less work) and connect
to the tape out jack ( or line output if you tubeamp has such )
 
Here is one that I have used for tube amps. Robinette Box.
 

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StepheK said:
Does this load a tube amp output at 8ohms?
Click to expand...
Don't think I've never seen a commercial tube amp that created an 8 ohm load when headphones were used. Some of the old HK amps relied on the phones themselves to be low-Z. If this is a necessary criteria, it would need to be confirmed that whichever amp the OP replaces this one with has that functionality. There's also the issue of drive requirements, e.g., can the amp properly drive the OP's phones, or is it designed for a different impedance? This really points to the benefit to be had from an external adapter that can be specifically designed for the system, even if the amp already has a headphone jack. Magnequest at one time offered multi-tapped transformers for this purpose (TL-404), but I think they're NLA. Not to mention that a pair would probably cost as much as the OP spent in total for this Chinese amp.

Jack
 
Late response, but I thought this might be useful. I'm going to put a headphone adapter together to use with my tube amps. Below is a snip of the diagram from my Pioneer ER-420 tube receiver's manual.
Headphone Output Diagram.JPG

Headphone Output Resistors.JPG
Note that this is a 15 WPC rated EL84 unit. I'll go with higher rated resistors for flexibility with other amps and because I can't see a real reason not to.
 
I saw one before that was similar to the ESP schematic with a voltage divider, but it used a rotary switch to select different voltage dividers so you could dial it in. Can't seem to find a schematic anywhere, but I'm sure you get the gist of it.
 
I'm not a headphone user so maybe this is a naive question... but doesn't a big series R, as seen in David_NC's schematic, affect the FR of the phones?
 
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