Sub connection to CARY SLP-05 preamp

Or its better to ask in a broad manner, how is an amp with 100k better than one with only 25k, of course there are other factors for overall quality, but when speaking of input impedance level how it affects people's choice? Because at least you wont need to bother too much of insufficiency, other than that, whatelse?

Once the 10x rule is satisfied, or comes close enough to being satisfied (as in this case), then further increases in the load impedance seen by the preamp will provide no further benefit. The choice of an amp should be made based on other factors, obviously including listening comparisons if at all possible.

Another point to keep in mind, though, is that if a preamp has to simultaneously drive both a power amp and the line-level inputs of a sub, and if the preamp drives both of them from the same output stage, that output stage will see a load impedance that is much lower than either of the two individual input impedances. That PROBABLY wouldn't apply in the case of the SLP-05, which has both an xlr output and an rca output, but it would apply in the case of a preamp that provides two pairs of rca output jacks that are simply wired together inside the rear panel, as opposed to being individually buffered. That is a common situation. It would also apply in the situation where a y-adapter is used.

In those situations the combined input impedance is equal to the product (multiplication) of the two individual input impedances, divided by their sum. For example, if the power amp's input impedance is 50K, and the sub's input impedance is 25K, and both were driven by the same output stage in the preamp, the preamp would see a combined load of (25 x 50)/(25 + 50) = 16.7K.

Regards,
-- Al

Impedance is usually well wihtin range with parallel downstream loads. However, adding to the complexity, I am using the fully balanced modwright 36.5 to drive my subs and mains, and the manufacturer explicitly advises against using RCA and XLR at the same time, because it will create an uneven load on the output transformer. I presume the Cary would have the same issue. So you either use 2 RCA outputs or get a high grade XLR splitter to split your XLR output (only possible if you subs have XLR inputs of course). Purist audio design makes a beautiful XLR splitter, which is an adaptor with no cable.

Edorr,

Don't you agree what Almarg suggested about feeding a pair of speaker cables from Amp to Sub speaker level input? And also why he does not suggest to do what just say. Can you explain in case you think your way is better?

I think that the problem with tapping a DD sub off the main power amp is that (AFAIK) you can't use the RTA/Room EQ function that the sub offers in that configuration - unless I'm reading this wrong (always possible!) In my book, the Room EQ is probably the single best reason to use the sub in the first place (particularly with your speakers).

Incidentally, I assume that the 2 channel pre-amp indicates a music only system. In this case, I'd think that any roll off at the bottom of the sub's passband is unlikely to be very important, since there isn't a lot of music program info that low in pitch (and it can be EQ'd back, anyway, if you really want it).

If Cary says that running RCAs and XLRs concurrently is a no-no, I'd go the XLR splitter route described by Edorr.

Just my take.

Marty