Where to set power amp volume?

[Mark411]

Hi--I'm a new member--chiming in from Seattle--and am happy to have found you all! I really appreciate the open-mindedness of the group and your interest in jointly exploring the world of hardware, audio science, and human perception without being so darned dogmatic about everything like some other sites.

My question: I have a pre-amp feeding a Fosi v3 stereo amplifier, which powers my passive speakers. Both the pre-amp and the Fosi have volume controls. The Fosi V3 does not have the option of selecting a fixed volume or of bypassing the volume control like more expensive units. My assumption is that, for best sound, I should set the Fosi at max volume and leave it alone and use the pre-amp to adjust the system volume. Is that correct? (Sorry if this has been addressed already on other threads, but I did try to find the answer myself before posting this.) Thanks. --Mark

 

[Doodski]

Set the Fosi volume at a range where you will go to max volume with the speakers and then use the pre-amp for control. This ensures if you have a accident with the pre-amp control that you have the Fosi limiting the power. Or else just set the Fosi to max and be very careful.

 

[kemmler3D]

without being so darned dogmatic about everything like some other sites.

Welcome! I'll say we're not dogmatic about much except evidence and what needs its support.

My assumption is that, for best sound, I should set the Fosi at max volume and leave it alone and use the pre-amp to adjust the system volume. Is that correct?

In theory you should probably set the upstream device to the point where SINAD and noise in particular is optimized, which will tend to be pretty high, then attenuate with the downstream device.

In practice, if you try and can't hear noise coming from the speaker when no music is playing, you're fine and you should just do what's convenient.

 

[Chrispy]

Generally the higher source volume can limit amplified noise...

 

[Rednaxela]

Set the Fosi at a level where the pre amp at max would be a hair too loud for regular listening but not damaging so. Then leave it there, and use the pre amp as your daily volume control.

 

[Mark411]

Thanks, everyone. Of course, this makes me wonder what "volume level" is hard-wired into the majority of power amps that do not have a volume control? I always assumed that the "volume" of one of those power amps was internally set to full blast and then the listening volume was set with the preamp. Or are amps like the Fosi V3 that have actual volume controls different from "regular" power amps in that one might want to dial them down for optimum performance?

 

[kemmler3D]

this makes me wonder what "volume level" is hard-wired into the majority of power amps that do not have a volume control?

It varies, but a typical gain is around 24-26dB, it can be a few dB higher or lower.

I always assumed that the "volume" of one of those power amps was internally set to full blast and then the listening volume was set with the preamp.

Pretty much yep, "full blast" is usually defined by the maximum voltage the amp can put out.

Or are amps like the Fosi V3 that have actual volume controls different from "regular" power amps in that one might want to dial them down for optimum performance?

Usually optimum performance is somewhere in the middle or upper 2/3 - 3/4 of the operating range of the amp (based on my personal eyeballing of graphs around here only) but that's not just where you set the volume knob, but the actual output level of the amp, which in turn depends on the input level. So they aren't different in that way.

 

[Mark411]

Thanks!

 

[Nopiano]

Thanks, everyone. Of course, this makes me wonder what "volume level" is hard-wired into the majority of power amps that do not have a volume control? I always assumed that the "volume" of one of those power amps was internally set to full blast and then the listening volume was set with the preamp. Or are amps like the Fosi V3 that have actual volume controls different from "regular" power amps in that one might want to dial them down for optimum performance?

As you say, most power amps have no volume control. They run full tilt from switch on until you turn them off. They run full preamp selects which input you gear, and what volume you listen at.

The Fosi v3 isn’t really a power amp, but neither is it an integrated amp (as typically understood) as it only has one input. It’s really a desktop amp, for one source and a single pair of speakers. Nutty enthusiasts like me bought one and inserted them into ‘normal’ systems for fun, to see how remarkable a tiny box can be at powering large speakers effectively.

I ran mine at just past 3 o’clock on the volume knob as that matched the gain I was used to with my Pass power amp and Linn preamp. But flat out is absolutely fine as long as your preamp has a usable range of volume adjustment available. Enjoy!

 

[Mark411]

Thanks, Nopiano. You may laugh as I am doing something similar. I am actually using my NAD C399 DAC/AMP as the preamp (using its preamp outs) for the Fosi V3 and using the Fosi to drive my KEF LS50 Meta speakers. Obviously, I don't need the Fosi as the NAD, which uses Hypex nCore, sounds awesome with the KEFs. I just became intrigued by these recent tiny amps and wanted to hear what they sounded like. So far, I'm very impressed! When I'm done experimenting, I may install the Fosi as an amp for the stereo system on my sailboat using a Victron 12v to 48v DC-DC converter to power the Fosi and a car stereo head unit as the preamp. But that's probably a new thread. Thanks again.

 

[Chrispy]

Thanks, Nopiano. You may laugh as I am doing something similar. I am actually using my NAD C399 DAC/AMP as the preamp (using its preamp outs) for the Fosi V3 and using the Fosi to drive my KEF LS50 Meta speakers. Obviously, I don't need the Fosi as the NAD, which uses Hypex nCore, sounds awesome with the KEFs. I just became intrigued by these recent tiny amps and wanted to hear what they sounded like. So far, I'm very impressed! When I'm done experimenting, I may install the Fosi as an amp for the stereo system on my sailboat using a Victron 12v to 48v DC-DC converter to power the Fosi and a car stereo head unit as the preamp. But that's probably a new thread. Thanks again.

Have you found a particular difference other than volume you can achieve or ?

 

[Mark411]

Nothing obvious. But I’m not set up to do AB comparisons while keeping final sound level the same between different combinations of volume settings on two devices.

 

[Chrispy]

Nothing obvious. But I’m not set up to do AB comparisons while keeping final sound level the same between different combinations of volume settings on two devices.

So what drives you in this direction particularly?

 

[Timcognito]

Maybe I have different slant, I set my amps (3) at level I will rarely listen, no more that way there are never any accidents with my speakers or startling others. And since I want a single dashboard on my tablet running everything, the BluOS and Roon in three rooms, for streaming, internet radio and NAS stored content, I set each from my NAS which seems slightly lower output than the other sources. Surprisingly internet radio seems to all over the place volume wise station to station. Having only my digital sources going at full bore seems safest to me. Not saying anything wrong with other schemes, just ease of use.

 

[Mark411]

Chrispy, I think I misunderstood your original question, so here goes again: Between using the NAD C399 as the speaker amp and using the Fosi V3 as the speaker amp there is definitely a difference in maximum sound level, although both get the speakers plenty loud for me. My clear impression is that the NAD sounds better. But part of that could easily be "motivated thinking" since the NAD costs over 10 times more than the Fosi so it better sound superior, right? I'd love to try a blind AB comparison if I had the ability. That said, I'm just amazed at how good the Fosi sounds with the KEFs for being such a tiny amp, at least with the casual listening I've been doing with it.

Here's another data point: When I upgraded my amp from a Marantz AV receiver to the NAD, the improvement in stereo sound quality was very obvious. To the point where, when my wife came into the room after I'd made the switch, unaware of what I'd done, the exclaimed, what did you do to the stereo, it sounds GREAT! But when I swapped the NAD for the Fosi, there was not a similarly obvious downgrade in sound quality, if that makes sense.

As to what caused me to try out the Fosi? Just nerdy curiosity about how it would work and sound. It's not a permanent replacement, I'm just fooling around.