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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
hilde45's avatar
hilde45 OP
5,048 posts
 
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 will comment that I tried an RCA out from my Streamer and while I could hear bass, it was definitely inferior to the high level connection.

@jl35 When you say "I do use the upgrade REL cable" you mean the "Speakon" cable that clicks into the sub and has 3 wires on the other end? I assume so but these subs can differ. 

Also JL35 (and Almarg)  -- are you at all worried about some kind of damage happening to the amps? @decooney mentioned this happened to him with a Cary amp years ago.

jl35
4,048 posts
 
REL makes an upgraded version of the Speakon cable that is included with the sub...I've had this setup about a year with no issues...but I am not technically knowledgeable so can't advise
imhififan's avatar
imhififan
2,211 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
5,048 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
5,048 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."

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