Sub connection to CARY SLP-05 preamp

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

09-12-11: Edorr
... 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.

My posts about the SLP-05 were based on the assumption that its outputs are capacitor coupled, as is the case with most tube preamps, and not transformer coupled, as is the case with your Modwright. I was also making the assumption that its rca and xlr outputs are driven by independent output stages, which is why I used the word "probably," in capital letters, when I referred to the impedance reduction that would result from driving two line level loads in parallel as "probably" not being applicable to the SLP-05.

If the Modwright drives rca and xlr outputs from a common output transformer, presumably with a grounded center tap on the secondary winding, and one end of that winding going to the rca center pin, that is a completely different story, and you were correctly advised.

Regards,
-- Al

Al, thanks for explaining.

Grandtech, probaby wise to check with Cary as Marty suggested. Regarding your other question, I'm also with Marty on using speaker level inputs. You want to use EQ with the subs if at all possible which such a setup would preclude you from doing. I am not even sure how you would use the Xover build into the DD-12 on a speaker level signal. I could be wrong here but I believe the Xover works on the line level input. This would make this a complete non-starter, since you need to apply a low pass filter.

Marty & Edorr, good points about RTA and equalization, with which I have no particular familiarity. I would expect, though (correct me if I'm wrong), that driving the sub and the power amp with parallel line-level signals from the preamp would be no different with respect to those functions than driving the sub from the power amp outputs, since in both configurations the sub has no control over the signals that ultimately get to the main speakers.

And the alternative of driving the power amp's inputs with the high pass outputs of the sub's crossover necessitates a tradeoff against the possible adverse sonic effects of putting a lot of sub circuitry into the main signal path. As well as the need to make sure that there is a reasonable impedance match between preamp and sub, which without further information on the sub we can't say with certainty.

Regards,
-- Al

I don't know how the DD-12 works, but I presume it has a separe line level input and speaker level input and the EQ and Xover can only be applied to the line level input - I could be completely wrong on this. If this is the case you cannot use the speaker level input, because your subs would run on a full range signal, which would be a complete mess with your mains.

I also would personally never run my mains with a high pass signal out of a relatively low grade Xover build into the sub. (not to mention long runs of cabling from preamp to cabling back into your main power amp.

So to me the only option would be to split the line level signal from the preamp and run parallel into mains and sub, applying EQ in the sub and using the sub xover for low pass filtering. If there are no impedance issues with this approach this would be preferable IMO. Of course, you run your mains at full range in this setup. In my (limited) experience this is not an issue, as long as you use a low crossover point for your subs.