How can I determine if a given amplifier will be suitable for my speakers?

I hope it's not inappropriate to post this here. I am posting because I am excited to build one of Nelson Pass' class A amplifiers. However, they are all well below the specified wattage for my Vandersteen 3A speakers (Richard specs them at 100wpc, which I am currently providing).

I know I can run these speakers on less, because I have done so, with a Kenwood KA-4006 rated at 34wpc. I never hit clipping distortion with that amp in normal use. I tried turning it up until I did hit total loss of signal, but it was quite a bit louder than I would ever want to listen.

Basically, what I'm asking is this: Is there a way I can test or monitor the levels of my amplifier (either current or a DIY) or determine when it is at the limits of it's capability? I feel like I'm swimming in the dark, not sure if I'm going to run into an edge or if I'm way out in the middle.
 
frugal-phile™
Joined 2001
Paid Member
You are less worried about efficiency/poer levels in the amp than you need to be with the amplifier’s Rout.

The vandersteen has a fairly flat impedance so that becomes more or less a non-issue.

V3afig01.jpg


Also keep in mind that how loud an amplifier can seem to play has as much to do with power as it does with how the amplifier recovers from clipping.

100w is only 6 dB more power than a 25w amp.

dave
 
Official Court Jester
Joined 2003
Paid Member
max power is one thing, sufficient power completely other

it depends of your room size, SPL habits etc.

while evaluating amp (not just for power), just use your ears - when sound (going up in SPL) is no more pleasant, something is fishy - either there is too much power for spks, or there is not enough power in amp for your needs...... or amp is simply Drek (presuming that speakers aren't

if you were happy with Drek of 34W, be assured that any of First watt frame amps will run in circles around that one
 
Your Vandersteens should do well with any of the 25W class A amps. I can recommend the Aleph J and F6, which can both be run at slightly higher voltage. They hit well above their weight class.
I have an old pair of 2C speakers. They sound wonderful even with the latest VFET amp, which is only rated for 10W.
 
Thank you all, you have given me much more confidence!

To the extent that Rout is the variable I need to think about, what value, or what ratio, should I keep as a general target when evaluating a paring?

> when sound (going up in SPL) is no more pleasant, something is fishy

When this might be an issue, it's usually so loud that it's "no more pleasant" simply because of how loud it is. Should I take that to mean it's a non-issue since I've hit the limit of my desired SPL before I hit clipping?
 
Your Vandersteens should do well with any of the 25W class A amps. I can recommend the Aleph J and F6, which can both be run at slightly higher voltage. They hit well above their weight class.
I have an old pair of 2C speakers. They sound wonderful even with the latest VFET amp, which is only rated for 10W.

Wow, even the Aleph J with it's 13W into 4 ohms performance? That's really great to know.