Cable or interface suggestion needed

Rocker

I have a headphones amp with 6 MM stereo Jack output. Is it 'simply' a matter of soldering the L&R signal wires together to use a mono Jack, which will be plugged into my guitar amplifier? Or is it possible to gang two standard phono leads into a mono Jack to achieve the same purpose? Or do I need some kind of interface box to play a stereo music signal through my guitar amp? Thanks.

ICBM

We use one of these in the shop to play music from our crappy laptop through our crappy workshop guitar amp!

https://www.ebay.co.uk/itm/New-6-35mm-Mono-Male-Jack-to-2-Dual-RCA-Phono-Female-Headphone-Splitter-Adapter-/152259953633

Hi-fi it is not... but if you keep the gain low it's tolerable for listening to in the same way as an old AM radio .

Soldering the two wires together will also work if you want to do it yourself.

DJH83004

To be honest IC, I have always been nervous about joining the L & R outputs of small devices like headphone amplifiers, IPhones, Laptops together, so have come up with this contraption in the workshop, basically a cheap battery operated mixer, and the L&R outputs into two separate channels - does work quite well though 
  

Sporky

DJH83004 said:

To be honest IC, I have always been nervous about joining the L & R outputs of small devices like headphone amplifiers

Likewise. A small passive mixer or mono summing amp is a much safer approach.

Otherwise there is a risk - small, but present - of each output trying to drive the other. In poorly designed electronics (ie most of it) this can result in damage to the output stage.

ICBM

True, although I’ve never seen it do so.

ecc83

Shorting  L&R line outs together should not cause any serious problems with anything remotely modern. A headphone amp should be especially s/c proof since 8 Ohm phones DO exist! There is also every chance of a tangled cans cable being damaged and shorting.  In short (HA!) if it can't stand a short it must be 'reet ***T!"

There is one special case however. If you have a 'proper' balanced line output and un balance it by shorting one leg to ground the unfortunate IC section will generate horrendous distortion and this can crosstalk into a wanted channel.

Dave.

DJH83004

The little rig in the photo is used to connect my IPhone to a quarter jack input for testing PA / disco amps with music, I genuinely would feel uneasy shorting the L&R outputs together to obtain a mono signal - could be an expensive mistake 

Danny1969

Combining the L and R on an iPhone, iPad, Ipod etc won't damage anything, the output stage has series resistance built in and is SC proof to ground as well 

DJH83004

Thanks Danny that's really useful to know.

Sporky

ecc83 said:

A headphone amp should be especially s/c proof since 8 Ohm phones DO exist!

It certainly should, but there are plenty of power amps that are fine at 8 ohms and 4 ohms, even 2 ohms, but not at all happy at 1 ohm. A short could be even worse.

Properly designed it'd have series resistance as Danny points out the iDevices do, but there's a lot of crap out there.

ecc83

Sporky said:

ecc83 said:

A headphone amp should be especially s/c proof since 8 Ohm phones DO exist!

It certainly should, but there are plenty of power amps that are fine at 8 ohms and 4 ohms, even 2 ohms, but not at all happy at 1 ohm. A short could be even worse.

Properly designed it'd have series resistance as Danny points out the iDevices do, but there's a lot of crap out there.

Agreed but a headphone amp is not a VERY low source resistance power amp. Any 1/2 sensible design will have a series resistance (to somewhat equalize drive for the variety of H/P Zs if nothing else) and therefore a total short is not possible. I.e. the amp should be continuously rated into it own load.

If you DO have a shit H/P amp that self destructs, bin it and buy better. My 20 quid Berry HA 400 is bomb proof.

Dave.

Sporky

ecc83 said:

Agreed but a headphone amp is not a VERY low source resistance power amp. Any 1/2 sensible design will have a series resistance (to somewhat equalize drive for the variety of H/P Zs if nothing else) and therefore a total short is not possible. I.e. the amp should be continuously rated into it own load.

I do not disagree.

But for the sake of three resistors and a bit of heatshrink...