stereo equalizer balance/phase issues

[heavenorlasvegas]

hello sos, hope all is well.

I have 2 stereo equalizers. One is the tapco 2200, the other is the infamous ashly sc-66.

I'm trying to use these tools for mastering, but it seems the respective channels for each unit arent perfectly matched, causing balancing and phasing issues between the two channels.

How can I ensure these units channels are as identical as possible? thanks all.

[sonics]

I'm trying to use these tools for mastering, but it seems the respective channels for each unit arent perfectly matched, causing balancing and phasing issues between the two channels.

I suppose you need to get them serviced, but they'll still have limitations compared to better gear and software.

Is there some reason you're using those units?
I guess you know that you will get better results with a (free) plugin?

[Hugh Robjohns]

...it seems the respective channels for each unit arent perfectly matched, causing balancing and phasing issues between the two channels.

How can I ensure these units channels are as identical as possible? thanks all.

Since they both have separate controls for the left and right channels, adjusting them by ear to maintain stereo balance nd EQ response shouldn't be difficult — assuming you have a decent monitoring setup.

You could also try setting one channel, then listening to the stereo difference signal for best null (on centred sources) while dialling in the second channel.

Ideally, the equalisers should be serviced by a competent technician. Aging components will drift from their original specifications, resulting in different gains, curves and frequency tunings.

[The Elf]

How are you feeding these equalisers? If you send mid/side to them then precise matching is less of an issue.

But I agree with the above that a plug-in would be a simpler, and arguably less compromised option.

[heavenorlasvegas]

...it seems the respective channels for each unit arent perfectly matched, causing balancing and phasing issues between the two channels.

How can I ensure these units channels are as identical as possible? thanks all.

Since they both have separate controls for the left and right channels, adjusting them by ear to maintain stereo balance nd EQ response shouldn't be difficult — assuming you have a decent monitoring setup.

You could also try setting one channel, then listening to the stereo difference signal for best null (on centred sources) while dialling in the second channel.

Ideally, the equalisers should be serviced by a competent technician. Aging components will drift from their original specifications, resulting in different gains, curves and frequency tunings.

Thanks, Hugh.

Any idea what might cause a loss of low frequency performance in one channel, or an overall lack of sonic performance from a channel?

Would this be the electrolytic capacitors? Thanks again.

[Wonks]

Which equaliser? You've got a graphic and a parametric.

[heavenorlasvegas]

Which equaliser? You've got a graphic and a parametric.

Well, either or i guess.

I have two units, both graphic and parametric and both of them are suffering from a channels loss of low frequency and/or overall performance.

Thanks again.

[Wonks]

And have you swapped input and output cables over on the channels to make sure it's the units and not a cable or problem with the mixing desk channel(s)?

[heavenorlasvegas]

Yes.

[Wonks]

In that case it could be a capacitor, though capacitors in the circuit path aren’t usually electrolytics, the type most likely to fail. But a DC blocking capacitor that has lost capacitance over time will certainly start to block higher and higher frequencies and you’ll loose bass.

But there are lots of other things that could be the cause, so it’s a case of going through the equipment methodically. A signal generator and a scope would make things easier, and the circuit diagram is pretty much essential.

You can check component values between the two channels, with the fully working one as the reference. Someone may have done a repair with the wrong value component to get it working, and the right value one has never been fitted.

Also look for dry joints and corroded connectors.

But following the signal path through with a scope should tell you quickly which section the fault is in, especially with the other channel as a reference.

[James Perrett]

In that case it could be a capacitor, though capacitors in the circuit path aren’t usually electrolytics, the type most likely to fail.

I guess you've never had to fix an early Korg piano. In the one that I fixed, just about all the coupling capacitors were surface mount electrolytics which had failed or were failing. Electrolytics are commonly used as coupling capacitors in low/medium impedance circuits but they aren't usually highly stressed so will last for a long time if they aren't one of the types that are known to go bad.

However if the problem is common to both units, I would suspect wiring or other gear in the chain rather than the eq units themselves.

[Hugh Robjohns]

In that case it could be a capacitor, though capacitors in the circuit path aren’t usually electrolytics, the type most likely to fail.

Every sound mixer I've worked on, as well as most preamps, tape recorders, and outboard signal processor has used electrolytic signal path coupling/ DC block capacitors. They pretty much have to be to provide sufficient capacitance to maintain a low frequency time constant in the single Hz, given the typically low impedances involved in solid-state circuitry.

However, there's usually very little DC across them and they rarely fail, in my experience.

[Wonks]

I’m normally good at finding decent tech references on the internet but that skill seems to have failed me recently.