[ULUL]

I have no idea exactly what this is called or where to find it after searching the web.  Apologies as I'm a rather newbie. 
 
Have an amp that has dual XLR out  that is left and right channel.  Need a cable that can take plut in both XLRs and then combine that to a single 1/4" female jack to plug in a headphone. 
 
Where can I find something like this?    Don't need anything exotic so I searched Monoprice but have no idea what this is called or if they even have it. 
 
Thanks,
UL

 

[Steve Eddy]

You don't want to do that. You could damage the amplifier.
 
Pretty much all amps that use dual 3 pin XLR outputs are "balanced" amps. And most "balanced" amps use bridged outputs. In other words, there's no common ground. So you can't tie together one of the outputs from each channel as you would have to do to go from dual 3 pin XLR to 1/4" TRS. Same goes for outputs that use a single 4 pin XLR.
 
What amp is it by the way?
 
se

 

[nikongod]

As steve said, building the cable you describe is a pretty rough idea. 
 
 
You could do it safely with a pair of 300:300/32 transformers  
A bit more involved than just a cable. And I don't know anyone who makes the transformers I'm describing. 

 

[ULUL]

Quote:

Hmm, the dealer of the amp said this provides the best audio.  He's right as we tested the audio.
 
The unit is the Firestone Bobby amp.  Amazon lists it though no review.  They sell a good number of these amps and I figure they know what they are doing.
 
I am not sure what you mean unfortunately as to the danger.  Is it just damaging the amp, or is there danger of electrocution?
 
Thanks,
UL
 
 
 
Originally Posted by Steve Eddy /img/forum/go_quote.gif
 
You don't want to do that. You could damage the amplifier.
 
Pretty much all amps that use dual 3 pin XLR outputs are "balanced" amps. And most "balanced" amps use bridged outputs. In other words, there's no common ground. So you can't tie together one of the outputs from each channel as you would have to do to go from dual 3 pin XLR to 1/4" TRS. Same goes for outputs that use a single 4 pin XLR.
 
What amp is it by the way?
 
se

 

[Steve Eddy]

It could damage the amp.
 
Just looked at the amp. You don't need an adapter cable. You can plug your 1/4" plugs directly into the amp.
 
se

 

[ULUL]

Indeed,  There are two outputs for headphones. Each output can take either an XLR out (single channel) or a 1/4" headphone jack (two channel).   With the two 1/4" output, one is for high impedence and one for low. 
 
BUT when one plugs in two XLRs and then combine to one 1/4" output, the audio is improved - cleaner, more sparkle.  It is slight but noticeable.  
 
There are apparently four amplifiers (not sure how that works) that drives the two outputs - two for each.  But when combined, all four drives one pair of headphone.  That's what I'm told.
 
Anyways, the shop has been running it like that for a long time. 
 
UL
 
Quote:

It could damage the amp.
 
Just looked at the amp. You don't need an adapter cable. You can plug your 1/4" plugs directly into the amp.
 
se

 

[nikongod]

Quote:

Indeed,  There are two outputs for headphones. Each output can take either an XLR out (single channel) or a 1/4" headphone jack (two channel).   With the two 1/4" output, one is for high impedence and one for low. 
 
BUT when one plugs in two XLRs and then combine to one 1/4" output, the audio is improved - cleaner, more sparkle.  It is slight but noticeable.  
 
There are apparently four amplifiers (not sure how that works) that drives the two outputs - two for each.  But when combined, all four drives one pair of headphone.  That's what I'm told.
 
Anyways, the shop has been running it like that for a long time. 
 
UL
 

 
If they have the cable, surely they can sell you one. 
 
Since there are at least 3 ways to do this, and they are all wrong for different amplifiers due to the fact that there are no standards here nobody can give you the right answer but them. 

 

[Steve Eddy]

Quote:

There are apparently four amplifiers (not sure how that works) that drives the two outputs - two for each.  But when combined, all four drives one pair of headphone.  That's what I'm told.

 
Yes, that's called a "bridged" output, and precisely why I wouldn't recommend the scheme you're talking about. What happens is that you have the output of one of the amps on one channel being connected to the output of one of the other amps on the other channel. This effectively shorts the outputs of each of those amplifiers and can potentially cause damage.
 
If that shop has been running it like that for a long time, then it just means that the amp is current limited so that it won't destroy itself. But there's no earthly reason to make such a connection. The non-shorted amplifiers will behave just as they would otherwise, but the ones whose outputs are shorted together will be distorting like crazy. If that results in "improved" audio, who am I to argue?
 
se

 

[ULUL]

I am grateful to you and all who replied.  Great forum. 
 
I picked up the amp today and confirmed with the shop that the amp was designed by the factory to function exactly like that and yes, the audio is better.  They sell a lot of these - more more to Japan and Singapore apparently where they are well regarded.    Thanks again. 
 
ULUL
 
 
Quote:
 
 

 
Yes, that's called a "bridged" output, and precisely why I wouldn't recommend the scheme you're talking about. What happens is that you have the output of one of the amps on one channel being connected to the output of one of the other amps on the other channel. This effectively shorts the outputs of each of those amplifiers and can potentially cause damage.
 
If that shop has been running it like that for a long time, then it just means that the amp is current limited so that it won't destroy itself. But there's no earthly reason to make such a connection. The non-shorted amplifiers will behave just as they would otherwise, but the ones whose outputs are shorted together will be distorting like crazy. If that results in "improved" audio, who am I to argue?
 
se

 

[nikongod]

Quote:

 
 
I picked up the amp today and confirmed with the shop that the amp was designed by the factory to function exactly like that and yes, the audio is better.  
 

 
Why not wire it that way internally then?