Setting volume om amp?

[Cberg88]

Need advice and to straighten out something about amplifiers!
Where my colleague and I are in a disagreement!

In the "old days" I was told to never run a amp on 100% volume, and instead leave volume at 90-95% and this was to not run the amp to hard and to have more headroom?

Is this still applicable? Or is it just a myth?

My colleague thought that I was wrong in setting our new RCF TT 08-A II speakers att 100% yesterday when setting up a job, and the discussion started if this was wrong or not..
My beliefs are that this is not applicable in modern (Class D) amps, does anybody else have any other input on this?

Some powered speakers of course have printed at the volume knob where eg. 0db Line signal should be set, but for example the TT 08 only has the markings "-∞" to "MAX". 

 

Best regards
/Christopher

[J Pearce]

On most analogue amps the 'volume' control is a simple attenuator, not a gain control. The amp still retains its full voltage gain, it will just need a hotter input before it achieves clipping. 'Unity gain' is usually achieved by running the amp with the attenuator at full. 

Digital amps all vary, especially those that are specific to a manufacturer's speakers (d&b for example), and those who have speaker specific DSP models. Some Class D amps just have a passive attenuator on the front end into the amp, some use a digital 'volume control', some have very sophisticated processing available with gain limiting, voltage limiting, impedance monitoring, and lots of other fun ways to lose a day.

Powered* speakers vary, the upper end models tend to have only a single line level input as you describe, but there are many models that have a mixer built in with multiple inputs some of which can be at mic level etc.

I tend to run my analogue amps at full - though in one of our venues I run them attenuated for reasons of gain structure (oversized rig in a smaller venue, so with amps wide open we'd rarely exceed -30dB out on the desk). Powered speakers I usually run at whatever 0dB is.

I like to get my amp/powered* speakers 'volume' controls set to something repeatable, so either on a detent or a clearly labelled position. 

*[unneccessary detour on powered vs active]
Active speaker is an annoyingly blurry term:
Some use it to mean 'uses an external crossover and multiple amp channels' - a synonym for bi-amp.
Some use it to mean 'has an amplifier within the speaker cabinet' - a synonym for powered.
Just to further confuse matters there are lots of powered speakers that are bi-amped.

I avoid using the term 'active speaker' for all of the above reasons.

[Cberg88]

Quote

I like to get my amp/powered* speakers 'volume' controls set to something repeatable, so either on a detent or a clearly labelled position. 

Exactly what I was after in this case also. 

We do a lot of jobs with our RCF NXL 24-A where we once landed on "10min over 12 o'clock" was about right for that job.
And on some bigger jobs I can feel like I don't have that headroom anymore on the mixer, since I have to go above 0 on faders sometime. 

It would be much easier to just MAX them out on the speaker, and don't worry about whether me or my colleague checked that the volumes are the same, and of course just adjust the Main in the mixer.. 

I sent RCF a message about this and asked them also. Will be interesting what the have to say about it. 

/Christopher

[sleah]

There isn't a black & white right or wrong answer. There is of course 'best practice' for best quality and efficiency.

Setting an amp control to say 50% won't stop the amp being max'ed out. The 'user' can simply push the faders/master to max, even the trim pots. Which could easily max out the amp not to mention introduce a ton of distortion. A skill many DJ's have....

My take is to first set gain structure up to the amp (keeping amp at minimum initially) - I tend to go for 0db or 75/80% ish fader level for both channels and masters (to give a little head room), set input trim pots to give a similar level on VU meters (depends how they are marked) then look at amp controls to set the maximum volume in the particular space.

This based on using analogue amps that don't have built-in limiters etc or using anything else between mixer and amps. Even using extra kit be it limiter/compressors or crossovers, the principal for gain structure and result of getting it wrong and over driving speakers is the same.

Edited April 26, 2023 by sleah

[sandall]

4 hours ago, sleah said:

My take is to first set gain structure up to the amp (keeping amp at minimum initially) - I tend to go for 0db or 75/80% ish fader level for both channels and masters (to give a little head room), set input trim pots to give a similar level on VU meters (depends how they are marked) then look at amp controls to set the maximum volume in the particular space.

Exactly that. Mixer channel & output faders at about 75-80% (on many small mixers this will be marked as 0dB on channel faders & -10db on master faders), adjust input trim pots to give something sensible on the meters, THEN lift the amp's level control(s) to give the volume you require in the space. As a rule of thumb (assuming I've picked the right gear for the job) I tend to run amps at about 70%, but for speech this might need to be as low as 30%; for rock it might be nearer full.

[J Pearce]

Probably worth adding that I usually have a system processor betwixt desk and amps, so do my attenuation there, or at the D-A converter coming out of the processor.

[David Morison]

The only thing I'd add to the above is to consider how likely unauthorised interference may be after you've set your preferred levels.

If there's any chance at all of a "well meaning" muso or similar monkeying with the amps, then I'd make sure they're set to max so that at least there won't be any unwanted increases in volume.

That does mean accepting the penalty of potentially less convenient master levels out the desk (if no DSP in between) unfortunately.