Thread: quick question on amplifier power + max gain

hoping to tap into the group's collective knowledge here on a basic question...

given two amps with the exact same power specs but each with a much with different max gain -- assume the amps are identical in every other way and both are put in the same system driving the same speakers as follows:

amp #1: 30 db max gain | 8 wpc into 8 ohms
amp #2: 15 db max gain | 8 wpc into 8 ohms

what would be the effective difference between these two amps?

could it be as simple as: the source volume being set at the same level, one plays louder that the other?

thanks!!!

Out of curiosity, what is 'max gain'? I don't think I have ever seen that measurement used.

Originally Posted by BlueFox

Out of curiosity, what is 'max gain'? I don't think I have ever seen that measurement used.

not 100% sure, i have seen manufacturer specs for gain stated as max gain, total gain, and gain -- but, i have only seen specs quote one figure so maybe all the variants are used interchangeably.

i do believe that bias affects gain, as well as power. for example, my tube amp has a recommended maximum 0.22 mV bias voltage which gives 18wpc power. the generally recommended operational bias voltage is 0.18 mV which gives 15wpc power. i would assume the same would be true for solid state amps.

so maybe there is something along these lines accounting for the varying terminology -- perhaps, others more knowledgeable than myself can clarify.

I think the terms are used loosely in the marketing arena, enough that it is actually quite difficult to compare two amps, unless you put them on a bench, and directly measure them with the same equipment, in the same manner. In marketing literature, it's apples to oranges.

That being said, I am not an electronic engineer, nor an audio insider, just an old man who has watched this stuff for a long time.

the first question is how much noise is in one amp at 30db of gain, verses the other amp at 15db of gain.

so gain verses noise. mostly we like more gain with less noise. all other things being equal. then when you attenuate the volume the noise is further reduced.

the other factor is the preamp, and how it performs at what level of gain. so matching the best range of each device. some preamps perform admirably at all volume levels, but those are typically the top level.

the other preamp factor is a digital volume control. typically they throw away bits of information when they attenuate. so you want to be close or at unity gain to retain all the information. this is mostly an issue with home theater processors that digitize everything. if the amp has too much gain for the digital volume control you will lose refinement. you can find devices that will lower the amp gain for better amp-preamp matching.

mostly this 'gain' issue is a matching question between amps and preamps.

Originally Posted by aKnyght

hoping to tap into the group's collective knowledge here on a basic question...

given two amps with the exact same power specs but each with a much with different max gain -- assume the amps are identical in every other way and both are put in the same system driving the same speakers as follows:

amp #1: 30 db max gain | 8 wpc into 8 ohms
amp #2: 15 db max gain | 8 wpc into 8 ohms

what would be the effective difference between these two amps?

could it be as simple as: the source volume being set at the same level, one plays louder that the other?

thanks!!!

The table is a bit confusing: what dB are they referring to?
It could mean (as you note) that one amp has a higher input sensitivity than the other (3dB) in which case, fed the same input signal, one would sound louder than the other.

What confuses me -- mind you, it doesn't take much! -- is that the dBW (watt) scale is entirely different, i.e. +10dBW corresponds to 10Watts, +20dBW -> 100Watts, etc.

thanks mike! ...very helpful in putting this into the larger picture / context -- as suspected, there are a lot of layers on this onion to peel back.

Originally Posted by Gregm

The table is a bit confusing: what dB are they referring to?
It could mean (as you note) that one amp has a higher input sensitivity than the other (3dB) in which case, fed the same input signal, one would sound louder than the other.

my impression is that manufacturers (or at least the ones i looked at for this exercise) were listing the gain as dBW. and, among those the higher gain amps did have higher input sensitivities (lower values).

so - in a magical world where all else is equal, amp #1 in my example will sound louder given the same input signal, as you note ...if i am now understanding this correctly.

Originally Posted by aKnyght

hoping to tap into the group's collective knowledge here on a basic question...

given two amps with the exact same power specs but each with a much with different max gain -- assume the amps are identical in every other way and both are put in the same system driving the same speakers as follows:

amp #1: 30 db max gain | 8 wpc into 8 ohms
amp #2: 15 db max gain | 8 wpc into 8 ohms

what would be the effective difference between these two amps?

could it be as simple as: the source volume being set at the same level, one plays louder that the other?

thanks!!!

If you want the same volume, the low gain amp will have its volume control much higher than the high gain amp. Generally speaking it's best to choose a low gain provided the highest volume you ever want remains within your volume dial range. This will keep the signal to noise ratio high.

Originally Posted by puroagave

The amount of gain expressed in db for a given power output should take into consideration the amount of gain available upstream and ultimately the efficiency of your speakers. A high gain amplifier will require less gain from the pre amp for a given output. If you combine a high gain line level pre amp to a high gain power amp you will run into noise issues with high efficiency speakers in particular. The tell tale sign is if you're using only the bottom half of the volume range before overload sets in and you're over-driving the speakers or clipping the power amp. The concept of gain matching a system is so misunderstood and rarely brought up on forums or mentioned in reviews but can be crucial in achieving the best overall s/n your system can deliver among other attributes.

Absolutely. With speakers like ours (we both have Avantgardes) we need either a low powered amp or one with a low (or better still adjustable) gain so that our listening is not all done in the bottom quarter of the volume control. This reduces noise and could protect our speakers from overload if someone puts a book on the remote and the volume goes to full blast!

I see you have a Valvet. Is this the E2se? I had one on loan for a while and quite liked its sound but it has no easily operated on-off switch, no trigger and no auto shut-down if left with no signal. This is only a problem as it's a power-hungry amp that is unkind to the environment if left on continuously. Also it makes them technically illegal in the EU though dealers seem unaware / uninterested in that inconvenient factor! Peter