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How to connect monoblocks to a single REL sub with ONE RCA input

I just purchased two Quicksilver 60w Monoblock amplifiers and a LineStage Preamp by QS.
To connect this REL 328, normally one uses connect their Speakon cable (Red, Yellow, Black ends that connect to Right+, Left+, and Ground) or a SINGLE "low-level" RCA in. But this preamp doesn’t have a single sub out.

REL’s advice is to buy a second sub and attach one sub to each monoblock. Well, maybe I’ll do that, but in the meantime, I’d like to be able to hook up what I have.

Should I orient the amps so that the speaker terminals are close enough together to attach the strands of the Speakon cables? I have been warned by REL not to hook up high level to monoblocks because it will create a ground problem.

An alternative is that I get a Y cable that will bring two RCA outputs from my Preamp into the single RCA input on the REL?

Or is there another alternative?

Advice appreciated. (But please try not to tell me to just buy a second sub.)
128x128hilde45
imhififan's avatar
imhififan
2,210 posts
 
An alternative is that I get a Y cable that will bring two RCA outputs from my Preamp into the single RCA input on the REL?
Unless there’s a resistor in series to the preamp outputs, using a ’Y’ cable that bring two RCA outputs from your Preamp into the single RCA input on the REL is a big no no!
almarg already explained to you:
connect a y-adapter to the two tape out connectors, to create a mono signal for the sub by shorting the signals on the two tape out connectors together, you would also be shorting the signals on the main out connectors together. Thus an identical summed-to-mono signal would be provided to both monoblocks.
Don’t do that!!!
REL’s response: "We would recommend connecting low level from your preamp to the R328 as the safest connection for your current setup. As long as it’s safe to use a Y splitter out of the QS preamp, this will be fine for going into the single input on the sub."
I can’t understand why REL gave you such advise.
hilde45's avatar
hilde45 OP
5,035 posts
 
@imhififan I am so very glad to have this forum. I have no idea why they gave me this advice. 

The advice you gave -- the converter box -- would NOT cause the issue of the Y cable though. Is that right? (I know you recommended it but I want to make sure that I gave you a complete enough picture at that point.)

What a headache.
hilde45's avatar
hilde45 OP
5,035 posts
 
Update from Quicksilver: "I would connect the ground wire to the right channel amp ground just as they [I believe I quoted Almarg] suggest. If there is a hum then you might have to connect the woofer to just one channel that is disconnect the left + wire. A Y connector will mono the outputs on the preamp."

daveyf's avatar
daveyf
2,904 posts
 
I was in the same position as you, owning one REL sub and utilizing a mono block tube amp. I realized that the value of having mono blocks is to completely separate the signal from the left and the right speaker, with no possible signal corruption as is possible with a stereo amp. As such, it made perfect sense to me to be able to separate the left and right signals that the sub sees into a separate left and right channel for the subwoofer! That is why i think REL suggest this set up ( dual subs with mono blocks) in the first place and it certainly works a lot better this way. I have a stereo amp ( balanced) and with that I use just one of the REL subs, it works fine, but note bass definition is definitely less in this set-up. 
hilde45's avatar
hilde45 OP
5,035 posts
 
Update from me: I tried the high level. Connected to both mono blocks. No hum. Works fine. (Will it last?)
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