How to match preamp gain to amp sensitivity?

Hi Rich, I don't know if I've mentioned it but there are attenuators on the back of my ARC D250 and I am going to try it a bit more before deciding on pre or passive. I did it for a short period but no critical a-b ing. It did prove to me that the Ayre is pretty good but it will be going back to it's home in a week or two.
My CD and phono stage have plenty of gain and I can't open up the attenuators to max position at all so I'm going to assume that they have plenty of gain.
I just got my manual for the amp and it's input sens is .8v RMS for rated output of 240 watts! This makes me think passive will work really well. Input impedance is 75K ohms and I have read somewhere that this could matter a lot. I must do some more research however.
Thank you for your replies

Alun - One easy (and not too expensive) thing you might try with your current preamp, to get a sense of what you want to look for in terms of gain, is (assuming you're using unbalanced connections) the Harrison Labs in-line attenuators. Parts Express (www.partsexpress.com) sells them in 3, 6, and 12 dB versions. In my experience, they're pretty transparent -actually better than the more expensive Rothwell attenuators. And once you have them, they come in handy for non-critical sources or secondary systems.

And in terms of overall system gain - it really doesn't matter whether it comes from preamp gain, power amp gain, or speaker sensitivity - the bottom line is, do you have good range of control on the volume adjustment, without problems of noise, etc.
Rich

If you are looking at a passive unit, I own and can recommend both the Placette products (excellent attenuator with 125 steps for volume control) and the Sonic Euphoria PLC (excellent dynamics). Both have 30 day in home trial programs.

-Rick

That makes perfect sense Eldartford. I am using an Ayre K-5x that belongs to a friend which I soon have to replace as he wants it back. It's a very nice sounding unit with about 4db of single ended gain which works pretty good with my ARC amp. I wouldn't mind a touch more gain though as the Ayre is usually operating pretty high on the scale, but as you mentioned this is probably for the better.
That said would a gain on 10 or 12db be a LOT louder with less finess in the volume setting or would say 20db be a LOT louder. I'm not exactly sure how preamp gain affects the loudness of the final product coming from the speakers. I do know that a change of 6db in speaker sensitivity is like doubling amplifier power (so to speak) but I can't be sure if it's the same for preamps and amps.
Thanks

If all you want to do is match the preamp gain to the amp sensitivity you don't need a continuous control like a pot (may affect audio quality) or a stepped attenuator (expensive). All you need is a couple of resistors (dividing network). Use some cheap resistors from Radio Shack to determine the values you need, and then substitute exotic resistors, of the same values, if you think it matters.

Don't worry about "overloading" the power amp input. Your use of the preamp volume control prevents that. The disadvantage of too-high preamp gain is that the volume control will be very low down in its range. Working near the top of its range is good both with regard to audio quality and user convenience.

Thanks again Rich, this could be a possible avenue for me.
I am thinking however that any pre that I use in my system may be only as good as the attenuators found at the back of my amp, and if these are NOT of the best quality, anything going to them may be just a waste.
I may look at them better and see if they can be bypassed or update with something like the EVS.

Hi, Alun -- I've used a couple of passives, McCormack TLC-1 (still in my office system) and EVS Ultimate Attenuators. Like many folks, I thought there was a tradeoff - excellent transparency and smoothness, some loss of perceived dynamics, especially in the bass. I also prefer to run long interconnects to my amp, which does not work very well with passives (I'd say not more than a meter or at most two). Audio Research amps generally have very high input impedance, which will help with some of the issues. I see the Placette passives on Audiogon for attractive prices, so you might give one of them a try.
Rich

Thanks Racarlson, I see what you are saying. My amp (ARCD250mkII) actually has attenuators on the back of the amp. I've tried them out using my phono stage and CD direct and they work out pretty good but not enough fine tuning.
My reason for asking is that I'm looking for a preamp and on another post have had some good suggestions but I heard once that I could overload the input stage of my amp if I use a pre with too much gain.

When running direct into the amp it produced excellent sounds. Now I'm thinking that passive is the way to go. I could NOT open the attenuators wide open so I think my input sens. is very low therefore it could be a good match for passive.

Any suggestions on this?

This is a tough problem. Several possibilities:
1. Attenuators at the amp inputs.
2. Sources (e.g., some DACs like the Benchmark) with variable output level
3. A preamp with electronic or other finely-stepped volume control (like the PS Audio PCA-2 and a bunch of others) - the big issue is usually that rotary volume controls give little room for adjustment if there is too much gain - actual input overload is rare these days.

Best bet - try the preamp with a system that has similar amp gain and speaker sensitivity to yours, and see if you're happy with the ability to adjust the volume easily, especially at low levels. When doing so, beware of the tendency to listen much louder in the showroom that you typically do at home. We've had dealers comment on how quiet we like to listen, when we thought we were playing music loudly in their showrooms!