Using my Adcom as a headphone amp

[Erik M. Korte[_2_]]

Hi folks.

I have an Adcom GFA-535 L (It's a 4 channel - 2 stereo A & B) power
amps.

I use the A channel for my nearfields, and I'd like to use the B
channel for my headphones. There's a handy switch on the front to
power A, B or A and B.

I'd like to buy a box to take the speaker level outs and provide an L
Pad before the sound gets to me.

Any recommendations?

Many thanks!
Erik

[Scott Dorsey]

Erik M. Korte > wrote:
>Hi folks.
>
>I have an Adcom GFA-535 L (It's a 4 channel - 2 stereo A & B) power
>amps.
>
>I use the A channel for my nearfields, and I'd like to use the B
>channel for my headphones. There's a handy switch on the front to
>power A, B or A and B.
>
>I'd like to buy a box to take the speaker level outs and provide an L
>Pad before the sound gets to me.
>
>Any recommendations?

The Telex cheapies that Markertek sells are serviceable. They are kind of
flimsy but actually hold up surprisingly well in a studio environment.
Make sure you specify the stereo ones and not the mono ones.

The next step up for headphone distribution boxes would be Whirlwind and
Masque Sound and the increase in price is substantial but the quality of
construction is much better too.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Erik M. Korte[_2_]]

On Aug 31, 3:52*pm, (Scott Dorsey) wrote:
> Erik M. Korte > wrote:
>
> >Hi folks.
>
> >I have an Adcom GFA-535 L (It's a 4 channel - 2 stereo A & B) power
> >amps.
>
> >I use the A channel for my nearfields, and I'd like to use the B
> >channel for my headphones. There's a handy switch on the front to
> >power A, B or A and B.
>
> >I'd like to buy a box to take the speaker level outs and provide an L
> >Pad before the sound gets to me.
>
> >Any recommendations?
>
> The Telex cheapies that Markertek sells are serviceable. *They are kind of
> flimsy but actually hold up surprisingly well in a studio environment.
> Make sure you specify the stereo ones and not the mono ones.
>
> The next step up for headphone distribution boxes would be Whirlwind and
> Masque Sound and the increase in price is substantial but the quality of
> construction is much better too.
> --scott
> --
> "C'est un Nagra. *C'est suisse, et tres, tres precis."

Thanks Scott.

For the life of me I can't find a stereo version of this box on
Markertek's site.
Any model # in particular? Will it take +/- 60watts in and turn it
into something usable ?

I had no idea this was such an odd item. My Google skills are failing
me today.



Thanks!!

[Scott Dorsey]

Erik M. Korte > wrote:
>
>For the life of me I can't find a stereo version of this box on
>Markertek's site.

It's in the paper catalogue... or you can call them on the phone. I have
never used their website but they don't really seem to promote the things.

>Any model # in particular? Will it take +/- 60watts in and turn it
>into something usable ?

They are all just series pots (not real L-pads) with 1/4" jacks. They
won't take 60 watts, but they'll take as much power as typical headphones
will need.

>I had no idea this was such an odd item. My Google skills are failing
>me today.

This is the kind of thing most studios used to have as permanent
installation hardware.
--scott

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

[Erik M. Korte[_2_]]

On Aug 31, 10:06*pm, (Scott Dorsey) wrote:
> Erik M. Korte > wrote:
>
>
>
> >For the life of me I can't find a stereo version of this box on
> >Markertek's site.
>
> It's in the paper catalogue... or you can call them on the phone. *I have
> never used their website but they don't really seem to promote the things..
>
> >Any model # in particular? Will it take +/- 60watts in and turn it
> >into something usable ?
>
> They are all just series pots (not real L-pads) with 1/4" jacks. *They
> won't take 60 watts, but they'll take as much power as typical headphones
> will need.
>
> >I had no idea this was such an odd item. My Google skills are failing
> >me today.
>
> This is the kind of thing most studios used to have as permanent
> installation hardware.
> --scott
>
> --
> "C'est un Nagra. *C'est suisse, et tres, tres precis."


Well,

I called Markertek. They recommended the Rolls PM52 (which looks to be
the same as the ART HeadTap). This looks exactly like what I'm after.
One question though.....

The input (from my Adcom's speaker level outs) is 1/4 TRS. This seems
odd for a stereo input no?
How would one safely wire this? Left + to tip / Right + to Ring and
Both - to sleeve?

Links if needed:
Rolls PM52 - http://www.rolls.com/product.php?pid=PM52&PHPSESSID=bd512dcab0da7a793340caa7bec46dbd
ART HeadTap - http://www.artproaudio.com/products.asp?type=90&cat=13&id=63


Thanks for your help!

[Scott Dorsey]

Erik M. Korte > wrote:
>I called Markertek. They recommended the Rolls PM52 (which looks to be
>the same as the ART HeadTap). This looks exactly like what I'm after.

Problem is that they only have one level control. The Telex boxes have
four or eight of them with independent controls.

>One question though.....
>
>The input (from my Adcom's speaker level outs) is 1/4 TRS. This seems
>odd for a stereo input no?

It's a headphone thing.


>How would one safely wire this? Left + to tip / Right + to Ring and
>Both - to sleeve?

Right. You need an amp which has an unbridged output and shares common
return on both channels. The Adcom is that way. Make up some cables with
18/3 SJ cable from the hardware store.


This is the sort of thing I was suggesting:
http://www.markertek.com/Audio-Equipment/Audio-Processing/Headphone-Distribution/Califone-International-Inc/1214AVPS.xhtml

There's a Telex model that is like this also.
--scott

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

[Mike Rivers]

On Sep 1, 10:57 am, "Erik M. Korte" > wrote:

> The input (from my Adcom's speaker level outs) is 1/4 TRS. This seems
> odd for a stereo input no?
> How would one safely wire this? Left + to tip / Right + to Ring and
> Both - to sleeve?

The two input jacks are in parallel. The intent is that if you need
more sets of headphones driven from the same power amplifier, you buy
more boxes and daisy chain them together, with the second input jack
on the first box in the chain going to the first input jack on the
next box in the chain and so on. It saves you from having to make Y
cables or hook a bunch of boxes up to one set of speaker outputs.

The jacks are wired with the tip and ring as the left and right
channels. To go to the terminals on the back of your amplifier, you'll
need a cable with a TRS plug on one end and stripped leads on the
other. Since the ground on your amplifier is common to both inputs,
you only need three wires. Connect the tip and ground to the left
speaker terminals and the ring to the hot right speaker terminal. Put
the switch in the Stereo position.

Alternately, you could use a TRS-TRS cable and just plug it into the
headphone jack on your amplifier.

[Erik M. Korte[_2_]]

On Sep 1, 11:29*am, Mike Rivers > wrote:
> On Sep 1, 10:57 am, "Erik M. Korte" > wrote:
>
> > The input (from my Adcom's speaker level outs) is 1/4 TRS. This seems
> > odd for a stereo input no?
> > How would one safely wire this? Left + to tip / Right + to Ring and
> > Both - to sleeve?
>
> The two input jacks are in parallel. The intent is that if you need
> more sets of headphones driven from the same power amplifier, you buy
> more boxes and daisy chain them together, with the second input jack
> on the first box in the chain going to the first input jack on the
> next box in the chain and so on. It saves you from having to make Y
> cables or hook a bunch of boxes up to one set of speaker outputs.
>
> The jacks are wired with the tip and ring as the left and right
> channels. To go to the terminals on the back of your amplifier, you'll
> need a cable with a TRS plug on one end and stripped leads on the
> other. Since the ground on your amplifier is common to both inputs,
> you only need three wires. Connect the tip and ground to the left
> speaker terminals and the ring to the hot right speaker terminal. Put
> the switch in the Stereo position.
>
> Alternately, you could use a TRS-TRS cable and just plug it into the
> headphone jack on your amplifier.

Thanks for the information.

I really only need 1 to power one set of headphones.

The Adcom amp I have has no headphone jack. Just 2 pairs of stereo
outs.... to feed 4 speakers.
I thought the convenience of being able to A/B between my nearfields
and my cans would be nice. Especially since there's a switch on the
front of the Adcom.

Mike said: "Connect the tip and ground to the left speaker terminals
and the ring to the hot right speaker terminal."
So no need to jumper a wire to the right ground?

The fella at Rolls just wrote me back and stated:
"The wiring depends on whether your outputs share a common ground, if
so, your suggestion (Left + to tip / Right + to Ring and Both Left and
Right - tied together to
sleeve) will work, if not you will burn out your amp."

So should I now assume the Adcom shares a common ground.

Whew I'm sorry. Sorry if my OCD is in effect this morning.

1000 Thanks,
-Erik

[GregS[_3_]]

In article >, "Erik M. Korte" > wrote:
>On Sep 1, 11:29=A0am, Mike Rivers > wrote:
>> On Sep 1, 10:57 am, "Erik M. Korte" > wrote:
>>
>> > The input (from my Adcom's speaker level outs) is 1/4 TRS. This seems
>> > odd for a stereo input no?
>> > How would one safely wire this? Left + to tip / Right + to Ring and
>> > Both - to sleeve?
>>
>> The two input jacks are in parallel. The intent is that if you need
>> more sets of headphones driven from the same power amplifier, you buy
>> more boxes and daisy chain them together, with the second input jack
>> on the first box in the chain going to the first input jack on the
>> next box in the chain and so on. It saves you from having to make Y
>> cables or hook a bunch of boxes up to one set of speaker outputs.
>>
>> The jacks are wired with the tip and ring as the left and right
>> channels. To go to the terminals on the back of your amplifier, you'll
>> need a cable with a TRS plug on one end and stripped leads on the
>> other. Since the ground on your amplifier is common to both inputs,
>> you only need three wires. Connect the tip and ground to the left
>> speaker terminals and the ring to the hot right speaker terminal. Put
>> the switch in the Stereo position.
>>
>> Alternately, you could use a TRS-TRS cable and just plug it into the
>> headphone jack on your amplifier.
>
>Thanks for the information.
>
>I really only need 1 to power one set of headphones.
>
>The Adcom amp I have has no headphone jack. Just 2 pairs of stereo
>outs.... to feed 4 speakers.
>I thought the convenience of being able to A/B between my nearfields
>and my cans would be nice. Especially since there's a switch on the
>front of the Adcom.
>
>Mike said: "Connect the tip and ground to the left speaker terminals
>and the ring to the hot right speaker terminal."
>So no need to jumper a wire to the right ground?
>
>The fella at Rolls just wrote me back and stated:
>"The wiring depends on whether your outputs share a common ground, if
>so, your suggestion (Left + to tip / Right + to Ring and Both Left and
>Right - tied together to
>sleeve) will work, if not you will burn out your amp."
>
>So should I now assume the Adcom shares a common ground.
>
>Whew I'm sorry. Sorry if my OCD is in effect this morning.
>


Don't assume anything. I would think the Adcom has unbridged output,
but you can use a bridge output IF you only use one output and common
ground, IF thats available.

greg

[Mike Rivers]

On Sep 1, 12:21 pm, "Erik M. Korte" > wrote:

> The fella at Rolls just wrote me back and stated:
> "The wiring depends on whether your outputs share a common ground, if
> so, your suggestion (Left + to tip / Right + to Ring and Both Left and
> Right - tied together to
> sleeve) will work, if not you will burn out your amp."

I think that what he's telling you is to be cautious about tying the
left and right (-) together if they aren't tied together internally in
the amplifier. I didn't suggest that, I suggested just connecting one
of your choice to the sleeve. And even if they aren't tied together
internally, I doubt that you'd burn up the amplifier, you'd just not
get one channel.

A quick and simple test is to connect only one speaker to one channel
as you normally would, leaving the other channel open. Then move the
hot wire to the hot terminal of the other channel and if you still
hear the audio that's on the other channel, then the low side is
connected together internally.

> Whew I'm sorry. Sorry if my OCD is in effect this morning.

Some lawyer probably got $500 to tell them to write that. ;)