amp and speaker load matching...

[jaybee]

I'd be interested to hear people's views on how important it is to match the power of your amp to your speakers?

Obviously if you're running a 6 watt SET amp you're going to have to go for a super sensitive speaker that presents a stable load...

Similarly an 81dB behemoth that has huge current requiremts necessitates a tank like Kilowatt power amp...

Whither the middle ground?

let's stick to an integrated amp...

We all know that a clean, short well constructed signal path is what we want.... my instinct is that the attenuator(potentiometer?) in the pre-section is hugely important.... What I wonder is this.... Should one aim for the amp to have buckets of watts to spare... or is less attenuation preferable?

If I have an easy load, reasonably sensitive speaker and I persuade a manufacturer to fabricate two amplifiers as identical as possible but one 40wpc and one 100wpc is there a accepted wisdom (based in fact!) as to which will wound better?

Do I want the pot at 7 o'clock with buckets to spare or a three o'clock, working hard but with some still to go?

[Sligolad]

I have decidedly parked myself in the buckets to spare camp, I would rarely get to the 5 or 6 level on the pot.
Luckily the volume is not rotary dial so little chance of someone turning it up full and blowing the speakers to the back of beyond!!!

[tony]

I currently have 2 KT88 valve amps. One is 30w and the other is 40w. The 40w which is cheaper loses the plot when you go very loud.
The 30w has control at all volumes. So I think it is a hard question to answer as it depends on the quality of the amp. I think in Pearse's case one power amp would suffice for his system.Whether 2 brings it to another level as it gives so much headroom would need trying to confirm.

[jaybee]

I currently have 2 KT88 valve amps. One is 30w and the other is 40w. The 40w which is cheaper loses the plot when you go very loud.
The 30w has control at all volumes. So I think it is a hard question to answer as it depends on the quality of the amp. I think in Pearse's case one power amp would suffice for his system.Whether 2 brings it to another level as it gives so much headroom would need trying to confirm.

Let's say its a €2000 euro theoretical model...

so lets pretend that Unison Research make two, as near as they can, sonically identical models, one at 30w one at 60w....

[Fran]

There's a lot of factors in there jaybee I think, more than just the watts.

There are few enough cases where more than 25-30W are needed I think in reality. After all, if your speakers are say, 90db then with just 1 watt input, you are hearing 90db at 1m from the cone. That's pretty loud loud at just 1 watt - enough to wait for the missus to have gone out before doing it! I would guess that very very few here have ever used more than 4 or 5 watts of the available power from their amps. After that - it headroom for the very occasional short extra bursts of power needed.

There is also the load and how the amp copes with that. Some speakers are easy to drive and are very stable from low to high frequencies - and some are notoriously bad eg quad 57s. I have fried a few source resistors on my own pass amp while experimenting with the quads. So there is another element of matching there. If you have an awkward load, then the distortion can rise and sound quality can drop. Mentioning the quads, I've heard a few amps with them and the treble goes really horrible.

Lastly there is the gain. Many modern amps are now made with a gain of about 15dB or thereabouts. But in the old days, much higher was common as many sources had low output compared to your CD player. So some older amps, or amps based on older designs will have high gain.

I think the circuit itself, and its ability to cope with the impedance of the speaker, then followed by components, transformers (+++ in valve amps) are vital to sound quality.

You mentioned input pots. There are a huge variety now available from cheap to dear. The best value I have found are the gigawork stepped pots from ebay, at about €12 or so. Very clean and transparent, and miles better than the oft-quoted alps blue. My first port of call at the moment.

Enough rambling!

Fran

[tony]

[
Let's say its a €2000 euro theoretical model...

so lets pretend that Unison Research make two, as near as they can, sonically identical models, one at 30w one at 60w....[/quote]

Fran has given a detailed tech reply(Cant improve that) The 30w US theortical would more than likely be valve and 60w for the same price would be SS. As many have posted here 30w valves delivers a lot. My cyrus 8xp was 70w my new amp is 30w driving the same speakers. (spendors and quads) Really once you get to 25-40watts in valve it should suffice for most normal situations. The more inefficient a speaker ie 86db as against a higher figure 95-96 is harder to drive(needs more power).

At €2k I would be searching hard on the secondhand market as you will get a €3.5-4.5k new amp. Generally better parts(transformers,wiring,general build etc)

Of course if you go for the avantegarde speakers a leben cs300 will suffice as they are so efficient.

[jaybee]

ah if only I had 2k to spend!

this was a purely theoretical question, the 2k was just a demonstration that we were talking about a really good amp