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

[canidoit]

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.

@scott2000, wouldn't it better to have a high resolution balance/pan pot after the input pot so that you could adjust it whenever the tracking drifts than having to use pads?

 

[scott2000]

@scott2000, wouldn't it better to have a high resolution balance/pan pot after the input pot so that you could adjust it whenever the tracking drifts than having to use pads?

not sure. Was just thinking about an easy external deal....

Remember they also had a 3-position gain switch, which provided accurate rough settings.

woah..missed that....... thanks ... need to read up....
26dB @8/4 ohm ...

Internal three-position input sensitivity switch provides
settings of 0.775 volts for full standard 1 kHz 8/4 ohm
power, 0.775 volts for full standard 1 kHz 70 volt power,
and 26 dB voltage gain.

 

[KA-Electonics.com]

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.

If you want to make sure the power amp gains are identical feed mono tone, noise or music into the monitor path and connect an AC-responding DVM between the + speaker output terminals on the power amp to read the difference in channel levels.

Adjust one of the input level controls on the amp and null for minimum level.

When doing this it's a good idea to use only one channel of the console's monitor out and split it with a Y cable to feed both channels. That way you know the input levels at the power amp's inputs are exactly equal.

You can use the same approach at the console's line-level monitor outs to find tracking and gain errors upstream from the power amp.

Connecting a meter between wiper sections of a pot - while its driven - can also provide a quick measure of its' tracking in its upper to mid rotational range.

I use a similar trick in the DCAO-II line/headphone amp to equalize the gains of the upper and lower transistor pairs to minimize even-order distortion. The meter is connected between the upper and lower pair emitters and, when nulled, is as accurate as adjustment using an FFT.

 

[kags]

In practice, especially for project/home studios, I recommend that the user sets their monitor controller (usually part of the USB interface) to about halfway up. Then adjust the sensitivity control(s) of their amp or powered speakers to achieve a comfortable working volume in the room while playing back a finished mix/master from their DAW. Then there will be plenty of gain and headroom for almost any situation and the monitor pot will mostly stay around its "good" range of operation. It's also important to check the balance of the L/R sensitivity controls, which can easily done by ear. Simply play a mono pink noise source from your DAW, panned straight up the middle, and make the noise is centered exactly between the speakers. An SPL meter could help, but may also be confusing, as pink noise will not give a steady reading on the meter. This listening test should also reveal any polarity problems in the monitor system.

For commercial studios, we always run our amps wide open as we don't know what kind of projects the clients will bring in and if a visiting engineer is capable of maintaining a proper gain structure through the monitor path. We have clients blow a woofer a few times per year (which we charge to the client). I have only had two tweeters or horns blown in the last decade or two and those were due to unplugging a piece of gear, like a guitar, while the monitors were up really loud. The exception would be clients who still wish to work on NS-10s, on which our clients blow a woofer and/or tweeter much more often. There really is no reason to mix modern hip-hop and R&B (or much else) on NS-10s, but some people still think it's appropriate.

 

[Gavin Pursinger]

Take AC volt reading on your input signal to the amp to be sure your signal ins are matched. Then take the AC volt reading Off your amp speaker outs to be sure they are equal. I built a DPST switch for L/R with a SPST SWITCH FOR in/out of circuit so I can check this periodically. That way you could use your amp pots where you think they sound best.

 

[Gavin Pursinger]

Take AC volt reading on your input signal to the amp to be sure your signal ins are matched. Then take the AC volt reading Off your amp speaker outs to be sure they are equal. I built a DPST switch with a SPST SWITCH FOR in/out of circuit so I can check this periodically. That way you could use your a.p pots

 

[user 37518]

Let me add a bit of math to this thread.

First, lets define some terms:

Noise factor 'F' is the ratio of the signal to noise ratio (SNR) at the input to the SNR at the output. That is F=SNRi/SNRo.

Noise figure 'NF' is the Noise factor expressed in dB, namely, NF = 10log(F). The lower the value of the NF the better, ideally we would want a NF = 0dB, which means that SNRi = SNRo; in other words, an NF = 0 dB means that the amp or whatever piece of equipment we are considering did not degrade the SNR at all by introducing extra noise of its own, which of course, is not possible in reality, although we can strive for an NF close to 0dB.

Now, there is an equation called the Friis equation (not to be confused with the other Friis equation for antenas) that mathematically states what audio enthusiasts already know empirically. Friis equation tells us that if you have a series of amplifiers (or equipment) connected in cascade, the overall Noise Factor of the entire chain is given by:

F = F1 + (F2-1)/G1 + (F3-1)/(G1*G2) + ... + (Fn-1)/(G1*...*Gn-1)

Where F1 is the noise factor of the first amplifier, F2 of the second, and so on, till Fn which is the nth amplifier.

G1 is the gain of the first amplifier, G2 of the second, and so on...

So lets apply this equation to the DAW/amplifier combination. We only have two pieces of equipment, namely the DAW and the amp. So the overall Noise Factor equation will look like this:

F = F1 + (F2-1)/G1

Where F1 and G1 are the noise factor and the gain of the DAW, respectively, and F2 is the noise factor of the power amp.

We can see that the greater G1 is (i.e., the larger the DAW gain is) the lower the overall F will be, since the term (F2-1) will be divided by a larger number G1, thus making this last term smaller. Evidently the best we can strive for is that F = F1, which can only be accomplished if G1 -> infinity. So we can draw the following conclusions:

The first equipment in the chain (in this case the DAW) has to have a very small F1 and a very large gain G1 in order to achieve the smallest overall F. In other words, if you want to have the smallest F and, consequently, the smallest NF, turn the gain of the DAW as high as you can and the gain of the amp as low as you can.

There are other things that need to be considered like distortion and headroom and so on. But, if you want the lowest noise, that is what you should do.

 

[JohnRoberts]

Just what I always wanted more math....

JR

 

[Gavin Pursinger]

Wow...rocket science...brilliant dude

HUMBLY, I SUBMIT...
LADDER STYLE GAIN METERS ARE NOT as accurate as needle slingers(VU) for L/R comparisons especially in affordable converters...Volts AC of stereo sides is crucial.

I have applied much of info from this forum in my trench level world....Thanks for you knowledgeable folks time and willingness to share

 

[user 37518]

Just what I always wanted more math....

JR

What is the problem with math? You dont look to me like the kind of person who bashes at math just because you don't understand it.

 

[JohnRoberts]

Maybe you didn't see the emoticon? Suggesting I was teasing.

What is the problem with math? You dont look to me like the kind of person who bashes at math just because you don't understand it.

That sounds a little passive-aggressive ("don't understand"?). I understand enough math to have enjoyed some success in life, but being self-taught I do not appreciate complexity for the sake of itself.
===
I like to half joke that I failed calculus multiple times. The first time was in an advanced placement high school calculus class with all of seven students. Coincident to my calculus class, the girls gym class were typically meeting in the yard right outside my window doing what high school girls in skimpy gym uniforms do. I spent more time studying them than the blackboard. Then I fell short again once or twice in college, I don't remember exactly. As I recall I got the gist of it, and appreciated the power of integral calculus to realize concise solutions to problems way before we had computers to iterate us close enough using successive approximation or whatever computing techniques. What I really liked was how using differentiation and integration I could just remember one physics formulae instead of all three for use physics class, and just derive the other two formulae. Actually thinking back about it, being forced to memorize a bunch of trig identities more than exceeded my budget of attention span for that subject one time.

I recall my high school calculus teacher, pulling me aside and asking me what I was going to do with my life after failing his class....

JR

 

[user 37518]

Maybe you didn't see the emoticon? Suggesting I was teasing.

That sounds a little passive-aggressive ("don't understand"?). I understand enough math to have enjoyed some success in life, but being self-taught I do not appreciate complexity for the sake of itself.
===
I like to half joke that I failed calculus multiple times. The first time was in an advanced placement high school calculus class with all of seven students. Coincident to my calculus class, the girls gym class were typically meeting in the yard right outside my window doing what high school girls in skimpy gym uniforms do. I spent more time studying them than the blackboard. Then I fell short again once or twice in college, I don't remember exactly. As I recall I got the gist of it, and appreciated the power of integral calculus to realize concise solutions to problems way before we had computers to iterate us close enough using successive approximation or whatever computing techniques. What I really liked was how using differentiation and integration I could just remember one physics formulae instead of all three for use physics class, and just derive the other two formulae. Actually thinking back about it, being forced to memorize a bunch of trig identities more than exceeded my budget of attention span for that subject one time.

I recall my high school calculus teacher, pulling me aside and asking me what I was going to do with my life after failing his class....

JR

It did sound passive aggressive, my apologies, I didn't mean to. What I meant is that I constantly listen people saying stuff like "Math? I hate it, I used to suck at math back in achool" and they say it like it's some sort of badge of honor. I am sure that many hate it just because they dont understand: it's like Jazz, an acquired taste; unless you have an idea of what is going on you just hear random notes.

I am also aware that tons of math is not required for great analog design, Jim Williams was notorious for arriving at amazing circuits with an intuitive rather than a mathematical way of thinking. But math does help a lot to plant your feet on solid ground, at least in my opinion. In my experience, the stumbling block for many engineers is math; they have a great idea, but when it involves solving some profound math problem, they get stopped dead in their tracks, and the great idea they had vanishes away.

It reminds me of Faraday and Maxwell. Faraday's insight for experimental work and phenomena, with practically zero formal education was unrivaled. But when it came to express and materialize his ideas, his friend James C. Maxwell did all the math heavy lifting.

 

[Electrobumps]

Regardless of maths and other technicalities I’ve accidentally on a few occasions maxed out all my faders by mistake in the DAW. If you don’t have any other volume control that is gonna hurt your ears and speakers

NS-10s, on which our clients blow a woofer and/or tweeter much more often. There really is no reason to mix modern hip-hop and R&B (or much else) on NS-10s, but some people still think it's appropriate

This is an off topic bash at NS10 users, but really a reference monitor is down to the engineer. Speakers are subjective and personal choice. If you want to save your NS10’s from inappropriate monitoring levels you can always fuse them.

 

[Rowboat]

Your engineer friend was correct. From recollection, every power amp I've used in studio or PA rack I ever loaded was dialled out max.

All adjustments from the board - or, as the modern world now has it - the DAW.

I use a neat old Dangerous Music D-Box for monitoring and summing, its one-pot volume control is good enough for the passives (driven by an ancient Crown) and it presents no issues with my powered mains.

Deal is, maxxing the power amp channel volumes takes them out of the signal path. This is 'a Good Thing'.

 

[user 37518]

Your engineer friend was correct. From recollection, every power amp I've used in studio or PA rack I ever loaded was dialled out max.

All adjustments from the board - or, as the modern world now has it - the DAW.

I use a neat old Dangerous Music D-Box for monitoring and summing, its one-pot volume control is good enough for the passives (driven by an ancient Crown) and it presents no issues with my powered mains.

Deal is, maxxing the power amp channel volumes takes them out of the signal path. This is 'a Good Thing'.

Just because everyone is doing, doesn't mean it is right.

 

[JohnRoberts]

If everybody did it, we could stop putting gain pots on power amps... .

I was product manager for all power amps at Peavey for several years and our customers would never tolerate removing the gain pots, even though we could sell them amps for even less money.

Do what works for you...

JR

 

[Rowboat]

Just because everyone is doing, doesn't mean it is right.

<chuckle>

Ever see the movie 'Snatch'?
"Just because it's written.. doesn't mean it's so."

 

[Rowboat]

If everybody did it, we could stop putting gain pots on power amps... .

I was product manager for all power amps at Peavey for several years and our customers would never tolerate removing the gain pots, even though we could sell them amps for even less money.

Do what works for you...

JR

Did I suggest eliminating pots?
They have a use. Zero before powering down.

 

[totoxraymond]

Well, i think i'll add my 2 cents in there. Even though it might not make much difference.

I work in post-production and mix a lot of surround for TV shows. Also i'm freelance so i work in different studios every day. First, I like when the monitoring is referenced is dBC, this way i can be ready to go in a few minutes even if i never worked in the current studio. (Clients pay an hourly rate so they like not losing time).

Then in my opinion it's never good to attenuate a signal to fet more gain. This can only increase noise. So i guess that if you have to attenuate, you amp might have too mich power for your speaker/room? We don't need PA amp in a small/medium control room do we?

Finally, in my studio,i like to check monitor imbalance every month or so. Get the SPL meter, play pink noise in each speaker, one by one, and adjust accordingly.

Cheers,

Thomas

 

[user 37518]

<chuckle>

Ever see the movie 'Snatch'?
"Just because it's written.. doesn't mean it's so."

So basically my argument is based on sound physics and math, yours is based on what you have seen people do. Perhaps instead of <chuckling> and quoting movies, you could offer arguments as to why your point of view is the correct one.