Headphone amp

[skyboltone]

Has anyone seen a tube guitar headphone amp scheme anywhere. I know the golden ear hi fi crowd has numerous schemes available. One wonders if the work has been done adopting these schemes to our use.

One still needs to couple the output to the impedence of the headphones. My opinion, and it's only that, is that one needs to run the OT at saturation, for that reason I'm thinking it needs to be a custom transformer. The characteristic impedence at 1 khz for a set of High End headphones is 32 ohms.

I may noodle on this for awhile. Anybody thought much about this? I've checked the archives to no avail.

Dan

[Bob-I]

I think what you'd need to do is run the amp into a dummy load and tap off a headphone output.

[krash]

Right, well sort of right.

You should use some kind of reactive load like a Weber Mass or something like that so that the amp (whatever it is, even a 1/2W amp) gets a reactive response from the speaker. Then you need to tap off of that and the best way, frankly, is to drive the "tap" (through high resistor like 1M) into a FET or something to drive the headphones. You will need active feedback loop to fine-tune the response characteristic of the headphone amplifier stage so that it sounds like a giutar speaker. It's basically an active speaker simulator at that point. Much easier and more effective to do with a DSP.

Anyway, with that said, if you're looking for the best guitar tone into headphones, your best bet is to use something like a Line6 POD or Guitarport. Speaker cab/driver modeling is a tough nut to crack and you'll never pull it off with a passive device or a simple active filter using a real tube amp. You can use a Weber Mass with a DI output, then bring that DI output into a POD, set the amp model to something like "tube preamp" or whatever and just use the cab modeling and run your headphones out. That's probably the best possible way to go.

[UR12]

This is just a thought, But Randal Aiken has a speaker emulator circuit on his site here http://www.aikenamps.com/spkrload.html Like Krash said, you really need a reactive load as a speakers impedance changes depending on the frequency and a Dummy load resistor's doesn't. Then you could install this line out circuit I attached. Buy youself a nice headphone amp (cordless might be nice) and run the line out from the amp to the headphone amp.

Replace the 2 10K resistors with a 20K and loose the switch

[krash]

the problem of course is that any decent headphone is going to have reasonably flat frequency response, and a guitar speaker is not anything like flat. So at some point you are going to have to do some tone shaping.

[UR12]

Skyboltone

After re-reading your question i'm not sure I understand what it is your trying to do. Are you wanting to use your guitar amp to drive a set of headphones or are you looking to build something using tubes to plug your guitar into to drive a set of headphones?

[krash]

Dana, in a way that may be a moot question. Under no circumstances are you going to be able to drive a pair of headphones from a cranked tube amp (to get decent tone) without blowing the headphones or eardrums. So any way we slice it, we are going to have to use some attenuator scheme.

No matter what, we run into this problem that a headphone driver doesn't sound anything like a guitar speaker. So in reality if you want anything resembling satisfying guitar tone, you are going to have to do some serious tone shaping of the signal to get it to "sound" like a guitar speaker before it gets to the headphones. That's why I suggested using a tried-and-true approach like a Line6 modeler that uses convolution algorithms to simulate speakers (it works in the time and frequency domain but not in dynamics unfortunately and also does not really do "distortion"). Using passive components or even active filters has a decades-long history of spectacular failure.

I still contend that even the best solution you might come up with on a DIY basis is not going to compare favorably with the tone from a $75 modeler like a Behringer V-Amp 2 or something like that.

[UR12]

Krash

I agree and that's why I was trying to get a clarification on what it was he was trying to do. There are a lot of off the shelf ss headphone guitar amps out there. I don't recall seeing a tube one. After reading Bob-I's response I thought he was asking how to modify an amp to get some kind of headphone out. But after rereading his question I think he meant something like a small headphone type guitar amp. Like you, I don't think he will ever get a set of headphones to sound like a 4 x 12 cab or whaterver speaker combination, but a small headphone amp (line6 or what ever), might be just the ticket for practicing.

[loverocker]

No matter what, we run into this problem that a headphone driver doesn't sound anything like a guitar speaker. So in reality if you want anything resembling satisfying guitar tone, you are going to have to do some serious tone shaping of the signal to get it to "sound" like a guitar speaker before it gets to the headphones. That's why I suggested using a tried-and-true approach like a Line6 modeler that uses convolution algorithms to simulate speakers (it works in the time and frequency domain but not in dynamics unfortunately and also does not really do "distortion"). Using passive components or even active filters has a decades-long history of spectacular failure.

I agree with most of that. I'd only add that you don't need to go digital. H&K Red Box, Palmer PDI-03, Behringer's GI-100 (not tried it yet) all do the speaker emulation (with Palmer being the 'Rolls Royce, and also 100% passive).

These give the a line level signal with the right tone shaping and all you need to do is plug that into any amp with a neutral EQ and headphone out. There are stacks of home recording widgets that fit that bill. Plus you get the added bonus of mic-free recording.

As for adding a proper headphone out to an existing valve amp, I did save a schematic from someone called 'simcha' (creator or the Moonlight amp, I think) from Ampage about a year ago. It's a load/attenuator + speaker emulator + headphone out. Again, all passive. It may still be in the Ampage archives. I've not had time to build it though.

[skyboltone]

Krash

I agree and that's why I was trying to get a clarification on what it was he was trying to do. There are a lot of off the shelf ss headphone guitar amps out there. I don't recall seeing a tube one. After reading Bob-I's response I thought he was asking how to modify an amp to get some kind of headphone out. But after rereading his question I think he meant something like a small headphone type guitar amp. Like you, I don't think he will ever get a set of headphones to sound like a 4 x 12 cab or whaterver speaker combination, but a small headphone amp (line6 or what ever), might be just the ticket for practicing.

Hi guys, sorry for not keeping up with my post. I was looking for a tube based amplifier that drove only a pair of headphones. I have read with some interest the replys here and now see it as a bigger problem than I had thought.

In the meantime I bought Roland, sand state, practice amp called the Mini Cube, that models a half dozen different amp sounds and throws in a flanger, reverb, tremelo, chorus and phaser amongst other things. It has a 5 inch speaker but sounds much better inside your head with a pair of upper end Sennheisers.


This little amp should get the fingers back in shape until I can get a real amp built and tuned.

By the way, I received my Epiphone Valve Jr yesterday and don't even have a speaker to plug it into. I've been away from this passion for some time. Anyway, I'm doing some remodeling on the boat and will take time to make an open back box for the Eminence Delta Demon I ordered last night.

Thanks for the help

[dobbhill]

I've tried the Red Box and the Behringer unit with succes, using them for line-out balanced sends to the FOH mixer. I've always used a speaker cabinet for stage sound, though. A good speaker simulated load, (Aiken's comes to mind) would be needed to play silently. You got my attention as my wife HATES my Express clone/Marshall 1960 setup in the bedroom.
I'd love to hear more on this subject.
D

[loverocker]

My favourite is the Palmer PDI-03 (which can be a dummy load, too). I run that into my PC's cheapo sound card for direct recording*, with another output to a Behringer mixer into home monitors. The Behringer has the headphone output for when the PC's switched off.

The PDI-03 is a studio staple and has been very hard to find and spendy for a long while ($800+ used), but Palmer has re-released it recently, so it's more affordable. It's still a long-winded way to get a decent headphone sound from an amp though!

* To get a rough idea of what an amp through the Palmer and into headphones sounds like, take a listen to these short sound clips:
- 5W amp: http://www.firstmail.com/clips/se5a06.mp3
- 18W amp: http://www.firstmail.com/clips/pp1806.mp3