Throughly disappointed with my new Yamaha A-3000 Integrated.......

Dhpeck 12-24-2017
6. I just unplugged my Sub now as the rca cables are a bit bent up; however it didn't affect play for 2 hours yesterday without shutting off.

By any chance have you at any time had the sub connected at speaker level? 

If so, the speaker level connection could easily account for the intermittent protective shutdowns, and possibly even damage.  As you've probably seen stated in the manual the amp has balanced outputs, meaning that there is a full amplitude signal on the negative as well as the positive output terminals.  If only one sub is being used, connecting most subs at speaker level would cause the signals on the two negative output terminals of the amp to be shorted together, and would also probably connect them to AC safety ground via some low impedance.  As you may have seen, the manual specifically cautions against doing that.

Good luck.  Regards,
-- Al
 

Were you thinking perhaps the sub was plugged into the speaker connections?

I was asking if you had ever done that to make sure it wasn’t the case, because if you had ever done so it could easily account for the symptoms you described. And I suspect that the Martin Logan sub you mentioned in another thread provides both speaker level and line level inputs.

Also, perhaps pointing out that connecting a sub to the speaker terminals of this amp is a no no will prevent someone else who may read this thread and has the same amp from damaging it.

Good luck. Regards,
-- Al

Can you run a connection from the terminals on the speaker to the sub?

No, absolutely not. That would result in the same issues that would occur if you connected to the amp’s speaker terminals.

However what would probably work ok, depending on the specific design of the amp, would be to connect the + inputs of the sub to the + outputs of the amp, and connect either or both of the - inputs of the sub to a chassis screw on the amp. (I’m assuming here and in what follows that one sub is being used, rather than two, and that the sub provides inputs for two channels). That is what REL recommends for their subs when connecting at speaker level to an amp having balanced or bridged outputs.

I can’t envision a design for which that approach would cause damage. The worst thing that might happen, depending on the designs of the amp and the sub, would be a loud hum. But chances are it would work ok.

An even better approach would be to solder one or both negative wires from the sub to the ground shell of an RCA plug (or optionally two plugs, using one for each negative wire), leaving the center pin unconnected, and plugging it or them into an unused RCA input connector (or connectors) on the amp. In the case of the A-S3000 and other integrated amps providing "main in" connectors, it would probably be preferable to plug in there, rather than to an input intended for a source component, since that figures to provide a more direct path to the ground of the amplifier section.

In cases where the sub provides speaker level inputs for two channels I suspect it wouldn’t make any difference whether one or both negative input terminals of the sub are connected, as the two negative input terminals of subs which provide two input channels are most likely connected directly together within the sub.

Regards,
-- Al

@arch2
Your question is a good one. And as I indicate below a follow-up question with Martin-Logan will probably be necessary to be confident in their answer. But first I’ll mention that there are two things which make this situation different from connecting a powered sub to the outputs of the amp:

1)Connecting a single powered sub which provides + and - speaker level inputs for two channels to both output channels of the amp would most likely connect the amp’s negative output terminals for the two channels to the sub’s internal circuit ground, and therefore short the two negative output terminals together, potentially causing damage. That will not be an issue in the situation you are asking about, since the amp’s two channels would be connected to different speakers.

2)The suggestion I had made of connecting a sub’s negative input terminal to a chassis screw or the ground shell of an RCA input connector on the amp will not be suitable for this application because it would greatly reduce the amount of power the amp could deliver to the speaker’s electrostatic panel, which of course is not powered by the speaker’s internal amplifier.

3)The remaining concern, assuming that the speaker has a 3-prong IEC receptacle for its AC input, is whether or how it connects the negative input from the amp to AC safety ground. What I suggest that you ask Martin-Logan is as follows:

(a)Does the speaker have a 2-prong IEC connector (AC "hot" and AC neutral) or a 3-prong IEC connector (AC "hot," AC neutral, and AC safety ground)? If the answer is 2-prong, you are good to go.

(b)If the IEC connector has 3-prongs, is the speaker’s negative input terminal completely isolated from AC safety ground? If the answer is yes, you are good to go.

(c)If the answer is no, what is the impedance between the speaker’s negative input terminal and AC safety ground? If they are connected directly together, or are connected together through a low impedance (for example, 10 ohms) I don’t think it would be safe to use the Montis in conjunction with your amp. But if that impedance is high (for example, a few hundred ohms) it should be ok.

Good luck. Regards,
--Al