Leaving monitor amps on max and letting DAW, mixer adjust volume - pros and cons, sound quality, etc?

[canidoit]

An Engineer once told me to leave the studio amp on max and let the mixer do the volume. I didn't ask back then why, but now since I am noticing issues with my Hafler P1500 amp I am realising he might be right.

For over 10 years I have been able to set the Hafler P1500 at the lowest volume dial (full CCW) with no issues because the volume was too loud for the room and I didn't want to put the volume dial in any other position as I did not want to deal with left and right level matching.

Lately I have noticed that my left and right image is off drastically, like it sounds 50% more to the left and I noticed that when I put the volume dial to max(unity), the problem disappears and its center again. Its possible that it becomes center again at other higher levels than full CCW.

Could this be due to the age of the amp? What usually causes this issue?

The noise of the amp does start to be prominent at the max level.

My question is, does putting amps on max sort of change the sound quality of it, similar to a Neve pre-amp, when pushed harder? Wouldn't it be better to choose 60-80% volume on the amp?

What usually is the best volume setting for an amp or even powered monitors to get the most neutral/true sound from it?

Thank you.

 

[Brian Roth]

Several "real world" issues.

With the amp cranked wide open, noise from the desk will be much more obvious.

In that situation, any accident at the desk (in terms of level) can easily "send the tweeters so they are imbeded into the rear wall of the control room" <g>.

Gain staging.....

Bri

 

[john12ax7]

Sounds like an issue with the pots in the amp not tracking closely. When you go to 100% the pots are effectively out of the circuit. Some contact cleaner could help or just replace them.

As to the ideal level question there really is no correct answer. As mentioned, gain staging.

 

[Brian Roth]

Yep, seems like the "expiration date for the milk" on those pots has been passed. Maybe twist them back and forth a few dozen times to "clean" the contacts?

Bri

 

[canidoit]

I didn't think of that! I thought maybe the capacitors or something internally was causing the issue because to be honest, out of the 10 + years I have had the amp, I probably only turned the volume knobs less than 30 times so I thought why would that be broken. I always just left it at full CCW and left it there, but occasionally touch turn it to make sure it was still full CCW.

Will definitely try that, thanks people!

 

[ruffrecords]

The trouble with most pots is their tracking is abysmal. The only place you can be sure the channel gains are the same is when they are maxed. The level pots on most amps are right at the input so they should not affect amp noise at all. Most pro desks have a big passive stepped monitor level controls so they track extremely well and because they are passive they add very little noise of their own.

Cheers

Ian

 

[Matt Syson]

Monitor pots should normally be used at around 10 dB of so 'down' from maximum so that the tracking Left to Right is at least reasonable and as you may have pots on the mixer/controller the power amp should have it's level adjusted so that it is at 'normal monitoring level' when the mixer/controller is set. Many power amplifiers are way too sensitive so will need to be 'turned down', but this may end up having the pots set fairly low where the tracking is probably not good. I would therefore recommend a fixed attenuator so that the pots can be used rather closer to 'maximum'.
Normal (and even pretty expensive) pots struggle to maintain decent tracking over a 40dB range.
Switched attenuators can of course have excellent tracking but then there are other considerations if you don't know what you are doing. The idea of having a 10K pot (or attenuator) feeding more than about 3 metres of cable makes a complete mockery of 'high quality monitoring' which is why these 'passive controller' units are not to be recommended. Using VCAs as the monitor level 'pot' can allow excellent tracking and very 'convenient' when you are controlling 5.1 or 7.1 monitor levels. There are several 'switched attenuator chips that are digitally controlled which again give excellent tracking BUT need a fair amount of support circuitry. Monitor outputs where the output is direct from a pot, without an amplifier are simply cheap and nasty. As Brian commented, having the power amp turned up full (or maybe it has no pot at all) is always a risk to the monitor speakers for those moments when you turn the desk on/off when the amp is on. The BBC desks had around 24dB range on their monitor pots and were checked at top, 'normal (centre) and bottom (which meant that 'slugged' dual track linear pots were used and then there was a 'Dim' switch (and a mute of course)

 

[iomegaman]

I've used a Behringer USB Monitor controller for this very reason for years...while the Bear-Ringer stuff often gets a bad rap this is a VCA controlled product that was rumored to be lifted from SPL's design...I ignore the USB side of things, (although it does have the same BurrBrown headphone amp used in the costlier UAD stuff), the DAC is probably "meh" but for a VCA controlled system it's pretty painless...and I think it alleviates the original idea of cranking your stuff to 11 so that you get accurate audio information in the L/R fields...

But then again I'm nothing if I'm not cheap.

 

[canidoit]

Seems to be the pots needed a bit of movement for better contact as suggested, stereo image back to normal as before.

@ruffrecords, my old Benchmark DAC-1 has pretty good tracking on the stepped pots (not switched pots) even at low levels.

What tips do you guys have for lining an amp to be center? I tried sine waves once, but find it can become easily blurry where the center is. Short bursts from kicks seems to be better.

 

[Whoops]

An Engineer once told me to leave the studio amp on max and let the mixer do the volume.

I also presented this question to myself many times.

If the Amplifier has a volume knob, and if I have a monitor controller before the amp, where should I set the amps volume control?

Also, what happens in amplifiers that have no Volume control at all? I've used the Quad 405, Bryston 3B, Rotel, none of them have volume controls.
So what happens in these cases? are these amps always running on maximum amplification and the actual level just depends on the amount of signal they receive at it's input?

 

[scott2000]

If the Amplifier has a volume knob, and if I have a monitor controller before the amp, where should I set the amps volume control?

Where the target max spl is acheived when the monitor control is all the way up? Not sure.

 

[abbey road d enfer]

Where the target max spl is acheived when the monitor control is all the way up? Not sure.

That would be correct if the amps volume control tracked well, which means better than +/-0.5dB, and if the signal level was standardized, which is seldom the case.
Actually, there must be some room for adjustment, provided by a good tracking device. Having a stepped attenuator placed right at the amp's input is as close as possible to ideal.

 

[scott2000]

Actually, there must be some room for adjustment, provided by a good tracking device. Having a stepped attenuator placed right at the amp's input is as close as possible to ideal.

Some old Crown amps have detented knobs at the input. Can't imagine they stay accurate after many years?Did they hand select them?
Could you build a little pad or 2 in front of those pots to even things out a little if needed once they were set as close to where they need to be? Could be neat to swap in some of those little smd dact type switches ...they're very accurate but I remember slightly not liking the way they sounded for some reason years ago.

 

[ccaudle]

If the Amplifier has a volume knob, and if I have a monitor controller before the amp, where should I set the amps volume control?

The ideal case would be that the monitor controller then becomes a true loudness control, and you mark it in SPL. The Dolby/THX recommendations to theater alignment are pretty clear, and provide an excellent starting point for high dynamic range music.
See the original loudness papers from Bob Katz at Digital Domain for some background reading. Let me know if you can't find them and I will get the links, but you should be able to find them at digido.com.

what happens in amplifiers that have no Volume control at all?

That would typically be a consumer grade amp, so would be setup for "typical" consumer equipment levels. Depending on generation that could be 1V for max output, but once Sony standardized as 2V max output from CD players I would expect that some amps are based around that. Equipment marketed for home theater probably follows THX guidelines.

are these amps always running on maximum amplification and the actual level just depends on the amount of signal they receive at it's input?

That is basically how all amplifiers work. Very few (none that I know of) actually vary the gain of the amplification circuit, and even if there is a level adjustment that is actually just an attenuator at the input to the amplifier circuit to control the "amount" of signal at the "real" input.

What tips do you guys have for lining an amp to be center?

High resolution volt meter. That doesn't account for speaker variation, but at least gives you a starting point to understand the performance of your equipment.

This is DIY forum, so there are a couple of choices that are in the spirit of this forum that just take a little work.
The first would be to replace the existing pots in the amp with switched resistor attenuators. You could buy switches and an big pile of resistors and do it yourself, or get something pre-fab like DACT attenuators. Either way it leaves the amp operation essentially the same, just with repeatable adjustment that tracks much better.

The second option, which is really only viable if you will always be using that amp with the same speakers, is to setup the system gain as I recommended above (i.e. THX/Katz style SPL based), then measure the settings of the amp input control needed to achieve that, and replace the input pots with a fixed resistor divider. That eliminates any issues of contact degradation over time, but locks you in to a fixed input-to-output effective gain (i.e. combination of passive attenuation plus active gain).

 

[abbey road d enfer]

Some old Crown amps have detented knobs at the input. Can't imagine they stay accurate after many years?Did they hand select them?

Even brand new, they were not particularly good in terms of tracking from an amp to an other or from channel to channel.
They were lin, not log, so the taper is rather good in the upper part of rotation, i.e. between top and about -6dB, which is typically all you need in a PA situation. Remember they also had a 3-position gain switch, which provided accurate rough settings.

 

[JohnRoberts]

An Engineer once told me to leave the studio amp on max and let the mixer do the volume. I didn't ask back then why, but now since I am noticing issues with my Hafler P1500 amp I am realising he might be right.

If amp volume control is turned down it is possible to saturate the mixer audio path before getting full power from the amplifier. Good practice is to operate the amplifier turned full up.

There are a small handful of exceptions. 1- you can reduce interface noise by padding down the amplifier and driving it hotter. 2- In multi-amp active crossover systems individual amplifier gains need to be normalized.

For over 10 years I have been able to set the Hafler P1500 at the lowest volume dial (full CCW) with no issues because the volume was too loud for the room and I didn't want to put the volume dial in any other position as I did not want to deal with left and right level matching.

In side by side comparisons louder is usually perceived as sounding better, so many amp sellers delivered more gain than needed,

Lately I have noticed that my left and right image is off drastically, like it sounds 50% more to the left and I noticed that when I put the volume dial to max(unity), the problem disappears and its center again. Its possible that it becomes center again at other higher levels than full CCW.

As others have already shared pot tracking is not well managed. Only at full up can we trust tracking and gain.

Could this be due to the age of the amp? What usually causes this issue?

Seems unlikely to be an age issue but perhaps a dirty wiper inside the pot.

The noise of the amp does start to be prominent at the max level.

This can be apparent when listening in the near field using efficient monitors. If you pad down the amp to improve apparent S/N confirm tracking, and look out for clipping the audio path in front of the amp.

My question is, does putting amps on max sort of change the sound quality of it, similar to a Neve pre-amp, when pushed harder? Wouldn't it be better to choose 60-80% volume on the amp?

It should not make an audible difference. If it does it could be a faulty control.

What usually is the best volume setting for an amp or even powered monitors to get the most neutral/true sound from it?

Thank you.

Full up eliminates one or more possible variables, but generally not a problem.

JR

 

[Gold]

You could also figure out the input gain of the amplifier. Sometimes it’s as much as 20dB. It’s usually in the specs. The gain is usually at line level at the input. If it’s an opamp stage it’s easy enough to reduce the maximum gain.

 

[JohnRoberts]

You could also figure out the input gain of the amplifier. Sometimes it’s as much as 20dB. It’s usually in the specs. The gain is usually at line level at the input. If it’s an opamp stage it’s easy enough to reduce the maximum gain.

In power amp design you don't generally locate extra gain in the front end, to maximize stability you want to put most of the gain in the amplifier stage, which simultaneously attenuates the negative feedback, improving stability.

Do not mess with (reduce) the gain of the main stage of a power amp because that could diminish stability. Just like some op amps are not stable with less than 10 dB of closed loop gain, power amps can be affected by the same mechanism.

JR

 

[Whoops]

That would typically be a consumer grade amp, so would be setup for "typical" consumer equipment levels. Depending on generation that could be 1V for max output, but once Sony standardized as 2V max output from CD players I would expect that some amps are based around that.

The Bryston 3B I don't think it fits in the "consumer grade amp" category.
I't s professional amplufuer used in many studios around the world, most of the times driving a pair of ProAC Studia 100 speakers







The Rotel (dont remember the model) and the Quad 405 are very good Hi-end Hi-Fi amplifier

That is basically how all amplifiers work. Very few (none that I know of) actually vary the gain of the amplification circuit, and even if there is a level adjustment that is actually just an attenuator at the input to the amplifier circuit to control the "amount" of signal at the "real" input.

So basically the amplifiers that don't have a built in volume control, it's like they have the volume maxed out and regulation of the speakers volume is made by the monitor controller.

Also for the ones that actually a built in volume control, changing the volume on the amp or changing it in the crontrol room monitor unit will yield the same results as both are at the input before the amplification stages.

Is this correct or am I'm missing something
Thank you

 

[ccaudle]

The Bryston 3B I don't think it fits in the "consumer grade amp" category.

And yet I found this spec for the Bryston 3B-ST:
Input sensitivity: 1V for 120Wpc into 8 ohms; 2V for full output, balanced.

That is 8 dBu for full output. I would expect an amp actually intended for use with studio or broadcast equipment to have a setting that allowed at least 20 dBu input for full output, if not 24 dBu.

So basically the amplifiers that don't have a built in volume control, it's like they have the volume maxed out and regulation of the speakers volume is made by the monitor controller.

Yes.

changing the volume on the amp or changing it in the crontrol room monitor unit will yield the same results as both are at the input before the amplification stages.

That should be true, yes.