Recommend a monitor controller—rack mount ideally

[Dr Huge Longjohns]

Indeed. Wonks is officially a scholar and a gentlerabbit.

[Dr Huge Longjohns]

but it's usually easy enough to hook up an external meter of some sort.

I was intrigued by this, Hugh, if you're still following. How does this work in practice? A rackmount meter of somesort? How does it get wired in?

[Dr Huge Longjohns]

https://www.youtube.com/watch?v=V_6_ek8V1-A

This is interesting. Shows how a cheap Mackie passive controller skews the stereo image by 1dB. About 3 mins 50 in.

[Hugh Robjohns]

but it's usually easy enough to hook up an external meter of some sort.

How does this work in practice? A rackmount meter of somesort? How does it get wired in?

Rackmount meter, or freestanding meter... it matters not. The feed depends on the controller. Really good ones -- like my Crookwood -- provide a buffered output specifically for metering post source selector/mode switching but pre volume control. Some provide a record output which can be used. Or you could use a spare artist headphone output... there's usually a way on all but the most basic.

H

[Hugh Robjohns]

This is interesting. Shows how a cheap Mackie passive controller skews the stereo image by 1dB. About 3 mins 50 in.

This channel tracking problem afflicts most monitor controllers that use standard rotary potentiometers for the volume control. It doesn't matter whether they are active or passive, cheap or pricy... it's a fundamental problem of the design of a pot. The tracking error is almost always at its worst when the control is in the bottom half of its range. More attenuation generally gives worse tracking accuracy between channels.

That's one reason why it is recommended to set a reference monitoring level with the control around 2 o'clock where the tracking accuracy tends to be pretty good.

More expensive controllers tend to use more expensive (often conductive plastic) pots which tend to have better stereo tracking accuracy, but the only real solution for guaranteed stable imaging at all volume settings is to use switched matched resistors, either wired around a rotary switch, or with relay switching.

H

[Dr Huge Longjohns]

Most fascinating. I note in your review of the Audient unit you say "Unusually, rather than the traditional ganged potentiometer, the main speaker monitoring volume knob actually controls a stereo electronic stepped-attenuator chip, specifically chosen to ensure perfect channel matching at all level settings — so there can never be any wayward image shifts. On my bench tests (see below) I found the channel matching was within 0.1dB throughout
the entire range, with completely inaudible 0.25dB steps, and a maximum attenuation of 105dB" I confess I didn't know what you were talking about here, but I assume this issue is precisely what you were referring to?

In your Drawmer CMC2 review you say "The volume control features the same four-gang potentiometer arrangement as the MC2.1, which helps to maintain very close stereo channel-tracking" which again refers to this issue I guess.

Thanks very helpful.

[Dr Huge Longjohns]

Or you could use a spare artist headphone output... there's usually a way on all but the most basic.

Wouldn't this just read the level from the headphone out at the level its volume control was set to?

[Hugh Robjohns]

I confess I didn't know what you were talking about here, but I assume this issue is precisely what you were referring to?

Yes. Electronic attenuators can offer very good channel matching at all settings, but potentially raise the distortion figures slightly, and can impose some gain-structure issues for the designer. Audient did a very good job with theirs, though. Drawmer took a typically sideways approach to minimise the problem by effectively averaging the channel mismatches across multiple pots.

Both of these solutions are a lot less expensive than 24-step (or more) rotary switches with matched resistor chains, or relay-switched resistor chains.

H

[Hugh Robjohns]

Or you could use a spare artist headphone output... there's usually a way on all but the most basic.

Wouldn't this just read the level from the headphone out at the level its volume control was set to?

Yes...so you need to set the artist H/P volume control appropriately to calibrate the meter as desired.... Which is actually quite a useful facility if working with a VU meter.

H

[Dr Huge Longjohns]

How would you do that, then? Match it to a meter elsewhere in the chain?

[Hugh Robjohns]

Yes. That's what line-up tones are for!

[Dr Huge Longjohns]

So how would you do that in practice? And what's a good external vu meter?