2 mono units as Stereo - age, matched, factors to consider for best stereo results?

[canidoit]

What factors are there to consider when it comes to using 2 units for stereo?

Buying a new commercial unit to match with your old unit to use for stereo, is that susceptible to stereo issues?

When building 2 DIY units, what components should be taken into consideration for best stereo matching (ie. capacitors, resistors, brand, specs)?

If you have a stereo unit, and you use the left side more often and drive it a lot like on a preamp, does that eventually affect the unit functioning as a stereo unit such as shift in image, quality differences in left and right channels?

Thank you.

 

[user 130681]

If both amplifiers are equally matched, there should be no issues.

 

[gyraf]

you need to be more specific - what exact unit..?

 

[canidoit]

For example - pre-amps, equalisers, color boxes(tape emulators, saturators), single channel 500 series units...

 

[Tubetec]

I wouldnt worry too much about any matching other than having the same decay tank , theres inevitably going to be differences in the sounds of two or four tanks , the nice thing is they tend to blend into something with a smoother decay.

I tend to use a wire wound pot of a couple of hundred ohms as an attenuator from a guitar amp speaker out , it give a huge range control over the drive , you can easily go all the way from cleanly driving the transducer to saturating it if you want ,with a whole range of colours in between . Mono drive of the tanks is usually fine , what emerges still has stereo width and depth . As you can see with the Audioscope unit on the other thread there are other ways the tone can be changed like driving or recovering the tanks either in series or parralel connection .

 

[Script]

So, your 'for example' means like anything`?

Could always feed same signal to both units, pan to mid/mono on two separate channels, and then AB. Don't hear much of a difference ? Then there isn't much of a difference. But sure could also go thru the hassle of measuring outputs for differences in dB, frequency response, phase, IMD etc. -- and this through all settings, of course...

With old units it might be different. Some units are notorious for sounding slightly different even if the exact same model and age. Also ageing capacitors in audio path can result in increasing loss in bass response (calls for a recap). Last but not least, some people even like it when two mono units do not sound exactly the same when used for stereo -- some kind of chorus-like effect, call it 'mojo' if you like.

When DIYing, I match all components related to audio path in same positions on L and R (resistors, caps, pots etc), as well as all components in compressor sidechains. I also match resistors (but not caps) on power lines.

As for compressors, there's dual mono and there are techniques for stereo linking.

 

[Tubetec]

The basic mechanical delay time of the springs will always vary to some degree , for me that adds a slightly random element which makes the space more believable and interesting . Then again if you want to try and match the delay times of springs ,why not .

 

[canidoit]

Thank you all for the replies.

So I guess based on using one channel more than the other in a stereo unit will lead to stereo differences with age? I mean, even though both channels are on in a stereo unit, driving one side harder will likely burn those circuits more and lead to an eventual difference? Or do circuit designers design it in a way that prevents this issue?

Thank you.

 

[gyraf]

no. don't expect wear from loud use - only exception maybe tube power amps

 

[iampoor1]

You really need to be more specific. "Categories" of outboard type is not enough. For instance, most preamps should be pretty close to identical but potentiometer tolerance differences can make a big difference in gain setting. The units might be identical other than 1 gain knob needing to be in a slightly different position for matched gain. I would personally say that that makes them identical but I know some would disagree

As a rule of thumb running "louder" signal through a unit doesnt cause any wear differences unless its a tube unit...and then it depends on the design

Of course vintage units...depending on condition can sound different, but plenty of new units from the factory can sound different too (for example...not all 1176 clones ae calibrated identally....ask me how I know.)

I think a good way to approach this is: set the units up to sound identical and see if you can hear a difference or not. And then if you can hear a difference...adjust the knobs of 1 unit till you get a closer match...since potentiometer tolerance differences and sometimes even the knob alignment can make an audible difference.

Anyways hope this helps!