Ayre amplifier to Subwoofer connections

So if you were to connect the two sides of a balanced output into a single-ended input, and both components had 3-prong ac plugs, you would be grounding one of the two balanced signal outputs. Depending on the design of the output circuit, that could conceivably cause damage.

To clarify my statement a little further, if both amp & powered sub had 3-prong power cords, the path by which the negative (black) output of the amp would be grounded is: Amp black to sub chassis ground to sub ac safety ground to safety ground pin on sub power plug, then via ac wiring to ac safety ground pin on amp power plug, then to amp chassis ground.

Also, I'll add to my previous comments that another way in which sub signal ground could conceivably become common with ac safety ground is if an internal short were to occur within the sub amp. That is very unlikely if it is well designed, but if a short were somehow to develope between its signal ground and the neutral prong of its 2-prong ac power plug, that would create such a situation since ac neutral and ac safety ground are tied together back at your ac service panel.

Regards,
-- Al

Al,

You are very good at explaining things! you must be a physics teacher or something. I am familiar with how balanced connections work to cancel noise by summing inverted signals. Your explanation has helped me to understand the issue of the interaction with grounds.

Since I have also done home wiring, I also get your point about the possibility of the negative lead going to common ground through a short of the amp.

I think it makes good sense to use chassis ground (per Ayre's recommendation). It is helpful for me to understand why this is so. I don't think the 6db drop will be a problem.

thanks alot Al - I have seen some of your other posts and appreciate your involvement in the Audiogon community.

drew.

the sub leads should ideally be connected at the amp end of the speaker cables, not at the speaker end. That way the current drawn through those cables by the main speakers, and any consequent voltage drops that might result from interaction of that current with cable impedance, will not affect the signals to the sub.

This is as debatable as the long interconnects vs. long speaker cable argument, as there are pros and cons to each approach. While a technical argument can also be made for connecting the sub the speaker's binding posts, simple logistics makes the strongest argument.

almarg,

A follow up on this.

I connected my r/l speaker outs to the sub, red to speaker positive input and black to chassis ground. The sound was good but not what I expected from the Ayre, the soundstage was compressed into the center and some harshness in instruments such as trumpets etc. As I listened to more music, I definitely felt as though something was not right and started swapping cables. I found that with the either input pulled from the amp, I still got sound from both speakers. Connecting the negative speaker leads both to chassis ground created crosstalk (at about -6b) and so I basically had a very expensive mono system.

So I changed to connecting negative to black speaker input and now everything sounds as it should - which is terrific: great bass, expansive soundstage, space and transparency of instruments (the Ayre is a very musical amp).

Seems to me that the only option is to make sure the sub has no common ground (ground lug on the plug) and connect to the speaker terminals unless I am missing something.

Drew.

Hi Drew,

Not sure what you mean by "with either input pulled from the amp, I still got sound from both speakers." Are there two subs, or one? I assumed there is only one sub, and its amplifier has inputs for both the left and right channel outputs of the main power amp, which it sums together to feed a mono signal into the sub's driver. The left and right main speakers are separately connected to the left and right amp outputs, and I assume are unaffected by whether or how the sub is connected. Correct me if I'm misunderstanding the situation.

If my understanding is correct, my suggestion would be to try connecting sub left red to amp left red; sub right red to amp right red; and one and only one of the two sub amp black inputs to amp chassis (leave the other sub black input unconnected).

Regards,
-- Al