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DYI Headphone amplifier

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Anonymous
February 24, 2005 4:33:46 AM

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

I'd like to build a small headphone amplifier for my AKG 240M's (600ohm
impedance). I would like it to be powered by a 9V battery. Any schematic
recommendations?
Anonymous
February 24, 2005 4:33:47 AM

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

In article <_9aTd.1069$TB.176@edtnps84>, H <mshoganREMOVE@dal.caREMOVE> wrote:
>I'd like to build a small headphone amplifier for my AKG 240M's (600ohm
>impedance). I would like it to be powered by a 9V battery. Any schematic
>recommendations?

No.
Not unless you're willing to live with a big matching transformer in there.
9V isn't anywhere near enough voltage swing to drive those phones.... you
maybe could build a DC-DC converter but that would get ugly fast.

I think if you want to drive those phones you're going to need a real amp
with a real power supply. A 9V won't cut it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
February 24, 2005 4:33:47 AM

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

"H" <mshoganREMOVE@dal.caREMOVE> wrote in message
news:_9aTd.1069$TB.176@edtnps84...
> I'd like to build a small headphone amplifier for my AKG 240M's (600ohm
> impedance). I would like it to be powered by a 9V battery. Any schematic
> recommendations?

What about consider buying the AKG 240 STUDIO version (55 ohm impedance) .
It doesn't require a headphone amp - you can use them for portable use.
http://www.dolphinmusic.co.uk/page/shop/flypage/product...
Related resources
Anonymous
February 24, 2005 7:27:49 AM

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

i was wondering if i would need a transformer... but just to clarify, i
want this device to go in between the headphone output of say a mixer
and my headphones.

is 9V still no good?


Scott Dorsey wrote:
> In article <_9aTd.1069$TB.176@edtnps84>, H <mshoganREMOVE@dal.caREMOVE> wrote:
>
>>I'd like to build a small headphone amplifier for my AKG 240M's (600ohm
>>impedance). I would like it to be powered by a 9V battery. Any schematic
>>recommendations?
>
>
> No.
> Not unless you're willing to live with a big matching transformer in there.
> 9V isn't anywhere near enough voltage swing to drive those phones.... you
> maybe could build a DC-DC converter but that would get ugly fast.
>
> I think if you want to drive those phones you're going to need a real amp
> with a real power supply. A 9V won't cut it.
> --scott
Anonymous
February 24, 2005 7:27:50 AM

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

"H" wrote ...
>i was wondering if i would need a transformer... but just to clarify, i
>want this device to go in between the headphone output of say a mixer
>and my headphones.

Makes no difference.

> is 9V still no good?

Still no good. Even the headphone output in your mixer is
powered from 2x to 4x that much voltage. High-impedance
headphones are just a bear to drive from low voltages.
Anonymous
February 24, 2005 7:27:51 AM

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

What about the portable little amps that Headroom makes like their airhead
or coda le BS or whatever it is? portable, battery powered and apparently
sound good......of course these can't compare to a "real" hi-fi headphone
amp that actually plugs into the wall and weighs a ton, but at least it's a
better gain stage than most consumer and prosumer equipment provide,
especially in the portable world.

http://www.headphone.com/layout.php?topicID=3&subTopicI...
0001
http://www.headphone.com/layout.php?topicID=3&subTopicI...
0500

there we go, i knew i had that link somewhere....the coda actually looks
like a nice unit, too bad it's sold out....sound devices also makes a great
portable batt powered headphone mixer w/ 3 outs (HX-3) and a single channel
headphone amp and mic pre (MM1)...i think it will even do 48v phantom but
don't quote me

--

Jonny Durango

"Patrick was a saint. I ain't."

http://www.jdurango.com



"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:111qn7n8nb1mr1c@corp.supernews.com...
> "H" wrote ...
> >i was wondering if i would need a transformer... but just to clarify, i
> >want this device to go in between the headphone output of say a mixer
> >and my headphones.
>
> Makes no difference.
>
> > is 9V still no good?
>
> Still no good. Even the headphone output in your mixer is
> powered from 2x to 4x that much voltage. High-impedance
> headphones are just a bear to drive from low voltages.
>
Anonymous
February 24, 2005 7:28:18 AM

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

too late. i already have the 240M's.

marc wrote:
> "H" <mshoganREMOVE@dal.caREMOVE> wrote in message
> news:_9aTd.1069$TB.176@edtnps84...
>
>>I'd like to build a small headphone amplifier for my AKG 240M's (600ohm
>>impedance). I would like it to be powered by a 9V battery. Any schematic
>>recommendations?
>
>
> What about consider buying the AKG 240 STUDIO version (55 ohm impedance) .
> It doesn't require a headphone amp - you can use them for portable use.
> http://www.dolphinmusic.co.uk/page/shop/flypage/product...
>
>
Anonymous
February 24, 2005 10:51:28 AM

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

"H" <mshoganREMOVE@dal.caREMOVE> wrote in message
news:9JcTd.3480$TB.1840@edtnps84
> i was wondering if i would need a transformer... but just to clarify,
> i want this device to go in between the headphone output of say a
> mixer and my headphones.
>
> is 9V still no good?

The problem is the specific headphones you mentioned in the OP -AKG 240M's
(600ohm
impedance.

Conventional wisdom is that these specific phones require a ton of drive
voltage. I believe there has been discussion of driving them with headphone
amps with something like 50 total volts of DC supply.
Anonymous
February 24, 2005 11:20:19 AM

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

In article <9JcTd.3480$TB.1840@edtnps84> mshoganREMOVE@dal.caREMOVE writes:

> i was wondering if i would need a transformer... but just to clarify, i
> want this device to go in between the headphone output of say a mixer
> and my headphones.

If you need a headphone amplifier for that (unless you're talking
about one with multiple outputs, then you either have some very
insensitive headphones, a mixer that has a notoriously low headphone
output, or your hearing is defective and you should be seeing a
hearing specialist.

A mixer's headphone output IS a headphone amplifier.

Or did you just "say" a mixer because you're not really using the
headphones with a mixer, but with something else that doesn't have a
headphone output?



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
February 24, 2005 12:16:57 PM

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

In article <9JcTd.3480$TB.1840@edtnps84>,
H <mshoganREMOVE@dal.caREMOVE> wrote:
>i was wondering if i would need a transformer... but just to clarify, i
>want this device to go in between the headphone output of say a mixer
>and my headphones.
>
>is 9V still no good?

You still need to put 40V or so into the headphones. You cannot do that
from a 9V battery. You could do it from a bunch of 9V batteries in
series.

If you just want to match impedances, you can use 70V PA system transformers
as step-up transformers to drive the headphones. But you wind up with a
fairly big and heavy box and your low end will be affected a bit. And it
still is going to require a decent headphone output to drive them because
now you will need something that can sink substantial current into the load
rather than substantial voltage. Transformers just let you trade one for
the other.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
February 24, 2005 12:49:57 PM

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

In article <sKWdnfzzoYSi44DfRVn-1Q@comcast.com>,
Jonny Durango <jonnybush_from_officedurango1@comcast.net> wrote:
>What about the portable little amps that Headroom makes like their airhead
>or coda le BS or whatever it is? portable, battery powered and apparently
>sound good......of course these can't compare to a "real" hi-fi headphone
>amp that actually plugs into the wall and weighs a ton, but at least it's a
>better gain stage than most consumer and prosumer equipment provide,
>especially in the portable world.

They sound pretty good, but they won't drive the AKGs to much volume.
They are just wonderful for low-Z phones like the Grados, though.

The 600 ohm standard was a perfectly reasonable one back in the day
when balanced lines were all 600 ohms as well, and when most phones
were being driven off of tube circuits. But it's a different world now.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
February 24, 2005 1:07:05 PM

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

"H" <mshoganREMOVE@dal.caREMOVE> wrote in message
news:9JcTd.3480$TB.1840@edtnps84...
>i was wondering if i would need a transformer... but just to clarify, i
>want this device to go in between the headphone output of say a mixer and
>my headphones.

What is the objection to driving the headphones directly from the headphone
output of the mixer? As I recall, that's why it's called a "Headphone
Output." :-)

I'm not familiar with your AKG phones, but it might be a good idea to look
up the sensitivity in db at 1 mW.

Lastly, Radio Shack has something called a Boosteroo that might be just the
ticket, if you find that you don't have quite enough output from your mixer.

Norm Strong
Anonymous
February 24, 2005 4:21:55 PM

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

<normanstrong@comcast.net> wrote:
>"H" <mshoganREMOVE@dal.caREMOVE> wrote in message
>news:9JcTd.3480$TB.1840@edtnps84...
>>i was wondering if i would need a transformer... but just to clarify, i
>>want this device to go in between the headphone output of say a mixer and
>>my headphones.
>
>What is the objection to driving the headphones directly from the headphone
>output of the mixer? As I recall, that's why it's called a "Headphone
>Output." :-)

The headphones are very inefficient and they are 600 ohm loads. The
headphone drivers in most consoles today cannot drive anywhere near enough
voltage into them. They sound just fine from the headphone jack on a
Collins broadcast console with a cathode follower output designed for
a 600 ohm load, though.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
February 24, 2005 4:32:34 PM

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

<normanstrong@comcast.net> wrote in message
news:I-ydna14p4tUioPfRVn-1g@comcast.com

> Lastly, Radio Shack has something called a Boosteroo that might be
> just the ticket, if you find that you don't have quite enough output
> from your mixer.


While I'm an advocate and happy user of the Boosteroo in many applications,
this isn't one of them. The Boosteroo only uses a 3 volt supply (2 each AA
cells). I jazzwd mine up to run off a battery eliminator made out of an old
Comcast Cable modem power supply and a couple of dowels and brass screws.
But then I'm cheating - I'm getting almost twice the voltage before
clipping. However, that would be spit in a bucket for the OP's AKG 240M's
which are 600 ohms and more importantly, relatively insensitive.
Anonymous
February 24, 2005 5:28:47 PM

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

"H" <mshoganREMOVE@dal.caREMOVE> wrote in message
news:CJcTd.3487$TB.2189@edtnps84...
> too late. i already have the 240M's.


Symetrix 304. Around $100 used on Ebay for four channels worth of no-frills
headphone amplification, designed to drive both low and hi-impedance
headphones.

I'm using a 304 with my AKG 240M and it sounds clean and ballsy, noticeably
better than the Behringer Powerplay Pro with all its bells and whistles.
Occupies half the space (9,5"), but uses an external power adapter. A single
adapter has enough power for two units from the 300-series.

Predrag
Anonymous
February 24, 2005 5:49:20 PM

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

>
> A mixer's headphone output IS a headphone amplifier.
>

Yes of course I know this.

> Or did you just "say" a mixer because you're not really using the
> headphones with a mixer, but with something else that doesn't have a
> headphone output?
>

I'm using them with a mixer, MBox, iPod, my computer, my portable CD
player, etc etc.

I wanted a device to amplify the output from the "headphone output" of
one of these devices so I could make it louder. For example, I can
barely hear the mix coming from the MBox when I'm playing acoustic guitar.

-Mike
Anonymous
February 24, 2005 5:49:21 PM

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

"H" <mshoganREMOVE@dal.caREMOVE> wrote in message
news:QPlTd.15928$9a3.8275@edtnps91...
>>
>> A mixer's headphone output IS a headphone amplifier.
>>
>
> Yes of course I know this.
>
>> Or did you just "say" a mixer because you're not really using the
>> headphones with a mixer, but with something else that doesn't have a
>> headphone output?
>>
>
> I'm using them with a mixer, MBox, iPod, my computer, my portable CD
> player, etc etc.
>
> I wanted a device to amplify the output from the "headphone output" of one
> of these devices so I could make it louder. For example, I can barely hear
> the mix coming from the MBox when I'm playing acoustic guitar.
>

Something tells me that you picked the wrong model of headphones. I advise
looking around for a pair of 62 ohm phones. They will more nearly match the

Norm
Anonymous
February 24, 2005 10:58:41 PM

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

Arny Krueger wrote:
> The problem is the specific headphones you mentioned in the OP -AKG 240M's
> (600ohm impedance.
>
> Conventional wisdom is that these specific phones require a ton of drive
> voltage.

.... so just use a speaker amplifier?

It should sound pretty clean, only having to drive a fraction of the
current it's designed for.

--
Anahata
anahata@treewind.co.uk -+- http://www.treewind.co.uk
Home: 01638 720444 Mob: 07976 263827
Anonymous
February 24, 2005 10:58:42 PM

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

anahata <anahata@treewind.co.uk> wrote:
>Arny Krueger wrote:
>> The problem is the specific headphones you mentioned in the OP -AKG 240M's
>> (600ohm impedance.
>>
>> Conventional wisdom is that these specific phones require a ton of drive
>> voltage.
>
>... so just use a speaker amplifier?
>
>It should sound pretty clean, only having to drive a fraction of the
>current it's designed for.

That's normally what people do with them in the studio these days. They
use a standard power amp, often into a breakout box with dividing resistors
so a bunch of people can plug into the same feed.

Thing is, those amps..... they won't run on 9V batteries.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
February 25, 2005 7:01:26 PM

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

"Scott Dorsey" <kludge@panix.com> wrote in message
>
> Thing is, those amps..... they won't run on 9V batteries.
> --scott

Of course they will. A whole bunch of them in series and parallel.

geoff
!