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Headphone-amp as a pre-amp?

post #1 of 16
1/11/07 at 3:35pm
Thread Starter 
Hi,

I`m interested in using a headphone-amp as a pre-amp for my speaker-system.

Of course I want to use it for my headphones as well, but since some of these amps can be used as a pre-amp as well, I find it quite attractive to use it for both.

Does anyone here use his headphone-amp as a pre-amp as well and could eventually give some impressions/experiences?

I`m especially wondering wether a very good (and maybe even expensive) headphone-amp would do a similar good job as a pre-amp, or what are the differences to a "usual" pre-amp?

Thanks for any ideas and thoughts!
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post #2 of 16
1/11/07 at 4:06pm
Antique Sound Lab Twin-Head is a great preamplifier/headphone amplifier, particulary with better tubes.

http://www.divertech.com/antiquesl.html
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post #3 of 16
1/11/07 at 4:25pm
AFAIK there are no fundamental differences in the design of a headamp and a preamp. A good headamp is usually a good preamp. Many top-shelf headamps have a preamp out in the back. A bit of searching around should turn up some good writeup of the preamp capabilities of e.g. the Corda Prehead. I have happily used my Prehead as a preamp but my speaker setup is really low-budget so I can't really comment on its qualities.

Even if your headamp does not have a preamp out you can still drive your power amp using the heaphone out and a 1/4" to twin RCA adapter. But (and it is a big but) you have to make sure that your power amp input is AC-coupled or you may end up amplifying the small DC offset of your headphone out to levels that would bust your speakers. I also believe that you can buy or build yourself an AC-coupled adapter but I am afraid I have no details to offer on that.
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post #4 of 16
1/11/07 at 5:24pm
Some definite differences. Most importantly, 3 channel and 4 channel headamps actively drive the ground, where a typical preamp doesn't (its unbalanced and ground is passive). This may not change the amp characteristics much, but it's not a given. It depends on teh actual design.

Preamps are also optimized to operate into a high impedance load, headamps into low impedance. Again, probably not much of a performance impact, but it depends on the design.
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post #5 of 16
1/11/07 at 5:40pm
Thread Starter 
Quote:
Originally Posted by calaf View Post
AFAIK there are no fundamental differences in the design of a headamp and a preamp. A good headamp is usually a good preamp.
That`s what I think as well, but then again I`m almost a retard when it comes to technical aspects of amplification, hence my question.

I was just wondering if an amp that was constructed and built as a "dedicated" HA would do a similar good job in driving power amps.
And would it still work if the power amp and the headphone are connected at the same time?

I`m interested in the general concept, making a HA the "center" of the complete rig.
I`m not so much looking for suggestions concerning a special amp (most likely I`d go for the Rudistor RPX-33 then), but more for the general aspects.

Thanks for the nice and interesting replies so far.
Further experiences and opinions would be highly appreciated!

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post #6 of 16
1/11/07 at 5:49pm
Quote:
Originally Posted by DDF View Post
Preamps are also optimized to operate into a high impedance load, headamps into low impedance. Again, probably not much of a performance impact, but it depends on the design.
Are you sure about this? I thought that lower output impedance was always good... regardless of what you are driving.
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post #7 of 16
1/11/07 at 7:25pm
Quote:
Originally Posted by philodox View Post
Are you sure about this? I thought that lower output impedance was always good... regardless of what you are driving.
You're confusing output impedance with load impedance. Low O/P impedance is usually better (the frequency response is less affected by complex load impedance) but not always. Lower o/p impedance has lower stability margin when driving capacitive cables. So, the o/p Z must be appropriate for the preamp design.

FWIW I'm using a passive preamp (10kohm) for my main rig and it sounds and measures stunning. Typical o/p Z in use is in the hundreds of ohms. Not all amps will like this, as source impedance can affect input offsets and noise of the following amplifier.

I was talking about load impedance seen by the preamp/headamp. Head amps are designed to drive lots of current into low headphone impedances (<600 ohms) preamps aren't (typically>10,000 ohms). Will all headamps have an easy time with a high impedance load? For the most part, probably, but not universally. Load impedance can impact dc o/p offsets, noise and depending on the topology, distortion.
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post #8 of 16
1/11/07 at 11:21pm


Most of that was over my head, but thanks for the explanation.
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post #9 of 16
1/12/07 at 12:40am
Quote:
Originally Posted by philodox View Post


Most of that was over my head, but thanks for the explanation.
Oops, sorry bout that.
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post #10 of 16
1/12/07 at 1:03am
The answer to the question really depends on the design. There are some products, like the Sugden Headmaster, Meier Corda Pre-head and now the new Opera, that are MEANT to be both preamp and headamp. They work well for both.

I assume DDF's comments would be in using the headphone out when using a headamp as a preamp, and then he'd be right. But the above mentioned amps have preamp outs that aren't driven by the headamp section, and they make great preamps.
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post #11 of 16
1/12/07 at 5:52am
I have had less than good results using a HP amp as a preamp. Some exceptions:

The BLAudio LP is a good HP amp with high impedance HPs (works great with ER4S and other HPs above 100 ohm impedance) that works well as preamp.

The Xian Sheng 708B is a low cost HP amp that also serves well as a preamp and does a good job doing either.
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post #12 of 16
1/12/07 at 8:21am
Thread Starter 
Very interesting views, thanks!
(some of the more technical aspects went over my head too though... )

Anyway, from what I understand, a good headphone-amp with extra pre-amp outs should perform as good in the pre-amp role, shouldn`t it?

But then again (oops):

Quote:
Originally Posted by drarthurwells View Post
I have had less than good results using a HP amp as a preamp.
Would you say that these were good amps in driving headphones, and did they have extra pre-amp outs?
Or what do you think or guess why they underperformed as pre-amps?
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post #13 of 16
1/12/07 at 10:32am
Quote:
Originally Posted by leonid05 View Post
Very interesting views, thanks!
(some of the more technical aspects went over my head too though... )

Anyway, from what I understand, a good headphone-amp with extra pre-amp outs should perform as good in the pre-amp role, shouldn`t it?

But then again (oops):



Would you say that these were good amps in driving headphones, and did they have extra pre-amp outs?
Or what do you think or guess why they underperformed as pre-amps?
The Sugden and Meier perform well as both. Can't vouch for others.
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post #14 of 16
1/12/07 at 4:43pm

What I would like ...

Is for the RSA Raptor and/or the Yamamoto HA-02 to be available with preamp outputs ... in the case of the Yamamoto it has SPEAKER outputs but no pre-outs; seems it should have been the other way around ...

I can dream!

Jeff
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post #15 of 16
1/12/07 at 4:50pm
the pre-amp in the GS-1 is a very good performer...and the headphone amp is no slouch, either.
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