[george_k]

I'm looking to purchase a pre-amp/power-amp combo. On the pre-amp side, the units I'm considering have gains ranging between 6 - 12 db. On the power-amp side the amps under consideration have gains that range from 26 - 32 db.

I won't be buying both units at the same time (I'm limited by my budget) so I won't be able to play with both gain variables at the same time.

Is there such a thing as too little gain, too much gain, just the right amount of gain and does this have an effect on sound quality? My living room is a medium sized space.

[zybar]

I'm looking to purchase a pre-amp/power-amp combo. On the pre-amp side, the units I'm considering have gains ranging between 6 - 12 db. On the power-amp side the amps under consideration have gains that range from 26 - 32 db.

I won't be buying both units at the same time (I'm limited by my budget) so I won't be able to play with both gain variables at the same time.

Is there such a thing as too little gain, too much gain, just the right amount of gain and does this have an effect on sound quality? My living room is a medium sized space.

The short answer is yes.

How much gain you need depends on the rest of your system and is a much more complicated answer.

George

[sts9fan]

I had an odyssey amp with ~32db of gain and with a pre it was too much.  I would only go that high again if my speakers were not very sensitive.  Also if your pre is anything short of silent a amp with 32db will be a problem imo.

[Srajan Ebaen]

With my 98dB Rethm Saadhanas, I can run CD-direct into my 2-watt Yamamoto SET and remain below 50 on the CDP's display (99 max = 2V). I'm likely listening at about 1V source max. Any gain a preamp would introduce would be flat wasted, period, end of story.

With my 26dB Supratek Cabernet Dual preamp, I can drive 85dB speakers without any amplifier voltage gain, i.e. by way of Nelson Pass' F4 whose voltage gain is minus 0.5dB.

On my 91dB DeVore Nines, I need no amplifier voltage gain on most recordings with the 12dB ModWright LS-36.5 but on certain classical recordings with low median level, I can run out of gain by a few dB. By the time I switch to the 20dB Raysonic C200 preamp, I'm in fat city SLP wise and categorically need no voltage gain in the amplifier.

My room is essentially 14 x 20 with a nearly twice that open space adjoining. This by way of some real-world figures.

As your speaker sensitivity goes up, your gain requirements go down and once you're approaching 100dB for speaker sensitivity, excess gain tends to equate to noise (surf or hum without signal).

The first question you need to answer is speaker sensitivity, then desired SPLs in your listening position. From there you can figure out how much voltage gain your system has to provide. Then you can decide whether to get a low-gain preamp with a high-gain amp, the reverse, whether you even need an active preamp and so on. You can definitely have too much gain and most people in fact throw gain they paid for away in buckets by where their volume control sits when they listen...

Standard amplifier gain is 26dB, standard preamp gain somewhere between 16dB and 20dB. Add digital sources with 2V outputs (or more) and it's clear that for normal-sized rooms and 90dB speakers, there's ridiculous excess gain in the system...

[george_k]

Standard amplifier gain is 26dB, standard preamp gain somewhere between 16dB and 20dB. Add digital sources with 2V outputs (or more) and it's clear that for normal-sized rooms and 90dB speakers, there's ridiculous excess gain in the system...

That pretty much describes my system in a nutshell, 2v source outputs (squeezebox, cd player) and 90db speakers.

Light listening for me is around 70-75dB and loud listening 80-85 with peaks reaching around 90dB. I also use my 2ch setup for watching movies and I've noticed peaks (gun shots, explosions) register higher than 90db.

The preamp I'm strongly considering has 11.5db of gain, what would be an appropriate gain for the power amp?

[Daryl]

Hi George,

You wan't to pay more attention to S/N ratio and less attention to amplifier gain specs.

A power amps gain is usually set so that a standard easily achievable line voltage can drive it to full power.

Often they are set to achieve full power with 1v input.

So a 200w amplifier with a gain of 32db would need 1v input to reach full output.

With a gain of 26db, 2v would be required to reach full output which is still fine (actually I like this better).

Many pre-amps can achieve 8v or more but some folks are using passive pre-amps which have limited output capability.

The idea is that the amplifier be able to achieve full output with an input voltage that most any input device can achieve.

So you will likely see higher gains with more powerfull amplifiers but not always.

The Hypex amplifiers are all set to 26db which means full output will be achieved with 1.4v for the smallest and 2.8v for the largest.

If you noticed that the gain of a particular amplifier was unusually high or low for it's output capability you likely would want to avoid that one.

If you have high sensitivity speakers and you can only use say 20w of power into them, getting an 800w amplifier would likely also get you a higher than necessary noise level.

[george_k]

Did some searching on the net and found this:

I have found from practical experience that a combined preamp/amp signal gain of 32 dB is excellent for most systems with speakers that have efficiencies between the mid 80’s to low 90’s.  Horn speakers with efficiencies of over 100 dB can generally get by with amp/preamp gains of 20 to 25 db.  This depends of course on the level of the signal source.  A low output phono preamp could push the horn speaker system to require an amp/preamp gain over 30 dB.  A little excess gain is needed to have the flexibility to crank up the signal when desired.  That's what the volume control is for.

Source: http://www.transcendentsound.com/amp_input_sensitivity_and_gain.htm

Using the author's logic in regard to 32 dB being an excellent system gain (is 32dB a good number to aim for?):

If preamp gain = 12db then poweramp should have gain = 32-12 = 20dB
If preamp gain = 6db then poweramp should have gain of 32-6 = 26dB

How does one calculate amplifier gain when it's not specified?

I looked at two 150 watt amplifiers and they both have a different gain specified:
The Bryston 3B-SST (150watts x 2) has a gain of 23 or 29 dB depending on setting
The Ayre V-5xe (also 150watts x 2) has a gain of 26 dB

[Daryl]

Pre-amps don't have a single gain.

The volume control adjusts the gain from near zero up to maybe 12db or so.

So if a pre-amps gain is specified as 12db it's gain isn't 12db unless the volume control is set to maximum.

There is additional gain when the phono input is selected because of the low output levels of phonographs.

The pre-amp is really to reduce the gain of the system to a comfortable listening level so that you aren't driving your amp full out.

The reason the gain can go to +12db is just to insure compatibility with all situations because the manufaturer doesn't know if you have a componet with an unusually low output level or just a recording that was recorded at a low level that you might want to boost up to full output.

Gains are supposed to be set to insure compatibility between componets.

Gains usually are not a concern when shopping for gear but definately learn how to figure out how to calculate where they should be so you can flag the componets with gains that are out of whack.

Look for high S/N ratio especially with high sensitivity speakers.

[george_k]

The reason the gain can go to +12db is just to insure compatibility with all situations because the manufaturer doesn't know if you have a componet with an unusually low output level or just a recording that was recorded at a low level that you might want to boost up to full output.

Makes sense now

Look for high S/N ratio especially with high sensitivity speakers.

What would an appropriate S/N for speakers that are 90dB or say 100dB efficient?

[warnerwh]

I like to see 90db S/N ratio.  Going a little below this is fine. If your speakers are super efficient though I'd want way low low s/n. 

Those are just my opinions. I can say I've used preamps and amps with less s/n and it wasn't a concern. Get below 85 much and I'd look at the engineering. There must be exceptions.

So it depends.  Your room acoustics make more difference.