All the way up is kind of extreem don't you think ?
You don't want to saturate the input of the amp by sending a hot signal to it and you don't want the amp at max all the time with the possible noises it'll produce.
You want to maximise both volumes to get less noises and less distortions..
My approach would be to put the audio interface to the middle and start the amp to zero, then go up slowly until you reach the volume desired.
Note that mixing at low volume with occasionnal high volume check is a better approach ;)

It depends on the quality and the architecture of your sound card, but for safety reasons, I would strongly advise against leaving the volume knob on the amplifier at maximum.

For a motherboard-fitted sound card where the level control is done digitally, the standard approach is to run the sound card at maximum and control the volume at the external power amp. In this way, you use the full digital range of the D-A converters so you don't get variations in sound quality as you adjust the listening volume. However, as pc said, you do need to check that the input of your external amp can handle the full output of the sound card, and maybe use an attenuator at the input of the amplifier if not.

If when you say "sound card" you actually mean you have a proper audio interface, then things may be a bit different. The clue to this is that you talk about "RCA cables", and computer-based sound systems rarely have RCA connectors.

For us to give you a more complete answer, you need to tell us what make and model of sound card you are using, and it would also help to know the make and model of external amplifier.

Boswell, post: 432486, member: 29034 wrote: It depends on the quality and the architecture of your sound card, but for safety reasons, I would strongly advise against leaving the volume knob on the amplifier at maximum.

To echo what my esteemed colleagues ( and friends) Boswell and Marco have mentioned, I wouldn't be running an external power amp at full balls-out, for a number of reasons; the main one being that if your amp clips and decides to send more power to your speakers than what they are rated to handle, you're gonna cook your monitors - not to mention potentially your ears, if you are in a close enough proximity - and let's be real here... most of us are generally sitting pretty close to our monitors when we are mixing - usually within 36"- 40" or so ...

It's not like this is impossible to have this scenario happen, either; all it takes is an unintentional or accidental boost in gain in your software's mixer, or your soundcard's output, and just before the coils in the speakers melt down like Chernobyl, your ears could be subjected to an un-Godly amount of distortion - and at an extremely high db level.

As Bos has stated - it would help to know which soundcard, amp ( and I would also add the type and rating of your monitors as well) that you are using.

d.

Computers are very prone to random clicks and pops as they switch drivers and device patching, so these frequently put full output onto the line outs before, they settle back to their proper level. Some programmes hog a driver until the next bit of software requests and is allowed a release - and I'd not want my speakers subjected to this. I always have a manual control in between. With computer small speakers it rarely matters, but when there are more than a few Watts on tap, clicks and bangs are not wanted!

paulears, post: 432491, member: 47782 wrote: Computers are very prone to random clicks and pops as they switch drivers and device patching, so these frequently put full output onto the line outs before, they settle back to their proper level. Some programmes hog a driver until the next bit of software requests and is allowed a release - and I'd not want my speakers subjected to this

I hadn't thought about this, but Paul is spot-on here. Intermittent and random computer noises are not all that uncommon.

In fact, I had this happen just yesterday - I had opened a project file where the SR was set at 96k; and I had another audio program running in the background set for 44.1 ... and I heard an audible "pop" when I hit "play" on the 96k project file.
I was okay, because the output volume on my DAW - and to my amp - was set very low. And because my amp's settings were also lower - they were set at about half - nothing bad happened.

But ... it very well could have. If I had had my volumes maxed, at the very least it would have been very uncomfortable, at most I could have cooked the speakers - and I very well could have also damaged my hearing.

I'm using a 300w Hafler amp, so one thing's for sure... I certainly wouldn't have wanted that "pop" to have hit my speakers ( or my ears) at full volume. ;)

Thanks for the input, I've learned some valuable bits of info. I have had that problem of pressing play and almost damaging my hearing because the sound that played was much louder than I expected. I know now to keep my amps volume as low as possible and turn up my sound card as much as I can without causing my amp to distort. I did a test. I turned my amp up fairly loud and then slowly turned up the output of my sound card and I could turn it up all the way up without hearing any audible distortion coming from my amp. So now what I will do it keep my sound cards output at 80% it's maximum and start my amp at zero and turn it up as needed. That is the best solution.

You still didn't answer the questions asked - type of sound card, power amp/rating, gain chain...