Possible impedance matching issue with subwoofer?

Al, your erudite response notwithstanding, it's unlikely ANY manufacturer these days would leave it to the user to make sure his product performed optimally ;--) I don't think Mr. Grannyring should be concerned in the slightest.

As he already said,

The system sounds very good as is, just wondering if perhaps I am onto something I have missed with possible bass performance improvement.

and so my response is, don't go looking for problems where none exist ;--)
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Thanks Nsgarch and Almarg for your comments and help.

Input impedance is stated to be 20K so the preamp sees 20K to the sub and whatever ?? to the amp, but with both in paralell if the amp was 20k as well then the overall input imp. would be only 10k and that could affect freq. response on both the sub and amp. Al is correct, and using the speaker level inputs will negate the paralelling of the signals and offer less problems. Especially if they are using a passive preamp. The only thing to watch out for with using speaker level inputs is if you have a fully differential amp and the sub ties the grounds together to form the mono signal to the woofer, but that is another issue since a good sub will use a floating ground of about 100 Ohms or so.

Koestner, thanks.

Grannyring, Koestner makes a very important point about using a fully balanced amp with a sub, and your Aesthetix Atlas is indeed fully balanced. The negative speaker-level input of the sub should be connected to a ground point on the amp, and NOT to either of the amp's negative output terminals (which put out signals, as opposed to being grounded). Connecting the negative speaker-level input of the sub to one of the amp's negative output terminals could short the signal on that terminal to ground, assuming the amp and the sub both have three-prong power plugs, and depending on their internal grounding configuration.

A suitable ground point will often (but not always) be a chassis screw. You can verify that by using your multimeter to check for continuity between a chassis screw and either the ground sleeve of an rca connector or pin 1 of an xlr connector (while nothing is connected to the amp).

Concerning the input impedance of the amp, according to the manual it is an extremely high 530K, and is therefore insignificant with respect to the issues we have been discussing.

Regards,
-- Al

Al, the builder told me if the plate amp has the negative high level input grounded or in common with another connector (left minus connected to right minus, then I would need to do a special connection from the Atlas. Connect only one phase of each channel ( presemably the plus) to the high level input.

I will look at the back plates tonight.