headphone amplifier to drive 6 ohm phones

Archived from groups: rec.audio.pro (More info?)

Hi,

I am looking for a headphone amplifier that will take 4 (or more)
inputs and drive 4 (or more) 6-ohm phones through indepenedent
channels. Thanks for all suggestions.

Regards,
Sumit

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> In article <1125234480.531461.255160@g14g2000cwa.googlegroups.com>,
> <s-dhar@northwestern.edu> wrote:
> >
> >I am looking for a headphone amplifier that will take 4 (or more)
> >inputs and drive 4 (or more) 6-ohm phones through indepenedent
> >channels. Thanks for all suggestions.
>
> WHERE are you finding 6-ohm phones? And why?

Some really cheap headphones - the old 70s style closed plastic boxes
measure 8 ohms or so.

> There are a bunch of companies making multichannel amplifiers for zone
> paging or for home theatre applications. Parasound makes a 6-channel
> home theatre amp that would drive three sets of headphones with the
> right cabling and can handle a 6-ohm load.
>
> You'll find most "headphone amplifiers" will be unable to deal with
> such a low load impedance.

Indeed.


Graham

Archived from groups: rec.audio.pro (More info?)

Well! I needed some ultra linear, ultra flat (upto 20 k Hz) drivers for
a research project and have decided to use MB Quart 13.01 HX tweeters.
The drivers also needed to be small enough so that I could put them in
small boxes and mount them on people's heads. Hence the wierd need for
such an amp.

Regards,
Sumit

Archived from groups: rec.audio.pro (More info?)

Well! we are getting off topic here.... but just to keep the
conversatino fuelled, the goal of the project is to try and overcome
the calibration problems you mention. We have started using a reference
probe microphone placed at the eardrum to estimate the SPL. We then use
correction factors to "equalize" the drive voltage and try to create a
flat response at the ear drum. So yes, your point is well taken; and
yes, we have thought about it!!

Regards,
Sumit

Archived from groups: rec.audio.pro (More info?)

<s-dhar@northwestern.edu> wrote:
>Well! we are getting off topic here.... but just to keep the
>conversatino fuelled, the goal of the project is to try and overcome
>the calibration problems you mention. We have started using a reference
>probe microphone placed at the eardrum to estimate the SPL. We then use
>correction factors to "equalize" the drive voltage and try to create a
>flat response at the ear drum. So yes, your point is well taken; and
>yes, we have thought about it!!

I think you're going to need small power amplifiers in that case. If
you don't care about phase response, the Crown D-60 will do. If you
care about phase response, the Adcom GFA-535 can probably be found used
at a reasonable price. These are all 2-channel amps, so you are going
to need to rack up a stack of them for multiple channels.

There _are_ multichannel paging amp units out there, as I said, but I
don't think the price per channel is really that much better.

Your alternative is to put a breakout resistor in series with the
driver. This will change the damping. Is this significant? I don't
know... if there is a probe microphone normallizing the response, it
really shouldn't matter if the driver response is off. On the other
hand, if you need accurate impulse response for transient signals, this
may not be a good approach. But a 50 ohm resistor in series with
the 6-ohm driver gives you a 56-ohm load that anything can drive. Sure,
you're throwing away the vast majority of power in heating up the
resistor, but who cares? You don't have to be very loud anyway.

Do note that all of these dome tweeters have a huge number of narrowband
resonances in the top octave, and you're going to have to sort out which
are ear canal resonances and which are driver artifacts. I don't have
any real solution for this, and if I did I'd have patented it and become
a rich man.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.audio.pro (More info?)

we gang 3 old cst decks, put in rec mode.

ea deck has phones out, rec level is phone's gain...

"Tim Martin" <tim2718281@ntlworld.com> wrote in message
newsb3Re.76$84.26@newsfe2-win.ntli.net...
>
> <s-dhar@northwestern.edu> wrote in message
> news:1125234480.531461.255160@g14g2000cwa.googlegroups.com...
>> Hi,
>>
>> I am looking for a headphone amplifier that will take 4 (or more)
>> inputs and drive 4 (or more) 6-ohm phones through indepenedent
>> channels. Thanks for all suggestions.
>
> What power do you need for the phones? I'd have thought it would be
> pretty
> low, so maybe you could build a simple emitter-follower amplifier for each
> set of phones (4 capacitors, 4 resistors, and two transistors and
> heatsinks
> for each pair of phones, plus a pair of potentiometers if you require
> volume
> control; all can share a common bench power supply at 5 volts, and that
> would deliver about 200 milliwatts per ear.)
>
> Tim
>
>