Answered Using both balanced and RCA outputs from a pre amplifier.

[RMutt]

Morning all. My preamp, a CA Azur 851E, has both balanced and RCA outputs. I use the balanced outs to a pair of Chord power amps.
I would like to try a sub with my stereo speakers but the sub out single RCA on the preamp doesn’t appear to be working.
Would it cause issues if I used the spare RCA outs to the sub? It’s a powered sub that has left and right inputs. I tried the single RCA sub out to the left input but it did not work. The sub should auto detect the single and did not.
The sub did work with the spare stereo outs but I’m wary of using them long term if there might be problems.
Thanks for any advice.

 

[bencat]

To be certain I would suggest that you send a message to Cambridge Audio Technical or Customer Service department and they should give you the definitive answer . From other things I have read they are quite decent and try to answer most queries .

 

[RMutt]

Thanks bencat. I’ll do that after the bank holiday. Funnily enough it was sent to Cambridge Audio for repair during lockdown and took months because of the chip shortage. I’ve never used the sub out so didn’t realise that was bust too.

 

[MVJ]

My Esoteric Dual Mono Pre has a pair of balanced outputs and two pairs of RCA outputs which can be all be used at the same time.

I have a pair of Event Opal Monitors (active) connected to the balanced and a pair of B&O 8000 active speakers connected to a pair of the RCA.

I can use both pairs of speakers at the same time & in the menu of the pre I can select which output I want to be live or select all so they all output a signal.

I have had no issues at all I did at one point have the B&O speakers behind me as a four way speaker system with no issues at all.

Your pre may have be similar operation or could sense which output is connected and the other will be off. I can't see how it can do any harm if both are always live at the same time normally to connect to an active sub and your mono amps.

With having a dedicated Sub output it may well be an either or the other on the other outputs I guess.

 

[RMutt]

Thanks MVJ. The menu in my preamp doesn’t seem to have the facility to choose in the way yours has unfortunately.
Using the balanced outputs doesn’t switch off the RCA’s, they remain live, so to speak. I suppose I was thinking if the load on the preamp or to the power amps could cause an issue when both sets were employed at the same time.

 

[rabski]

Thanks MVJ. The menu in my preamp doesn’t seem to have the facility to choose in the way yours has unfortunately.
Using the balanced outputs doesn’t switch off the RCA’s, they remain live, so to speak. I suppose I was thinking if the load on the preamp or to the power amps could cause an issue when both sets were employed at the same time.

It won't do any damage. The 'load' is absolutely minimal and it isn't like a power amplifier, where the load could affect the output devices.

The only possible issue would be that if the outputs are directly paralleled, then the relatively long cables to the sub could add some capacitance and cause some frequency roll-off at the extremes.

With everything connected and the sub connected but wound right down, try playing music and plug/unplug the sub RCA connections (turn the volume down while you're connecting/disconnecting). If it sounds different in the bass or treble, you may have to do some more thinking. If not, it's fine.

 

[RMutt]

Thanks rabski. I’ll have a little experiment.

 

[MVJ]

It won't do any damage. The 'load' is absolutely minimal and it isn't like a power amplifier, where the load could affect the output devices.

The only possible issue would be that if the outputs are directly paralleled, then the relatively long cables to the sub could add some capacitance and cause some frequency roll-off at the extremes.

With everything connected and the sub connected but wound right down, try playing music and plug/unplug the sub RCA connections (turn the volume down while you're connecting/disconnecting). If it sounds different in the bass or treble, you may have to do some more thinking. If not, it's fine.

I thought you'd soon be along with your words of widom Richard

 

[rabski]

I thought you'd soon be along with your words of widom Richard

Me? Wisdom? I thought you'd given up the booze mate

 

[MVJ]

Me? Wisdom? I thought you'd given up to booze mate

Mybad I meant withering putdowns really

 

[simon g]

Have you set up the sub woofer output, as explained in the manual?

 

[RMutt]

Have you set up the sub woofer output, as explained in the manual?

Hello simon g. I’ve only just seen this.
I believe I do have it set correctly, yes.
The sub out is a single RCA that outputs a mono mix of the original stereo. The single connection goes to the left in of the sub.
There is an option to select flat(sub) or a low frequency filter at the preamp. I’ve selected sub because I can alter the frequency at the sub. Neither setting appeared to alter the fact that nothing was reaching the subwoofer.

 

[Strider]

Just a thought:
The single sub output from the amplifier could be an LFE output - pre equalized and dedicated for a subwoofer (home cinema etc).

Or you might need to sum the inputs to the sub, single output from the amp, phono pair at the sub input?
Cheap as chips get an adaptor* or single phono to 2 phono cable.

1 into 2

 

[Strider]

Hold on - what sub are you using? I can't see a description in the thread?

 

[RMutt]

Hello Strider. I actually knocked up a one into two RCA from an old freebie. It didn’t work.
The sub is a Mordaunt Short Alumni 9.
According to the sub instructions a single RCA into the left input should work.

 

[Strider]

Hello Strider. I actually knocked up a one into two RCA from an old freebie. It didn’t work.
The sub is a Mordaunt Short Alumni 9.
According to the sub instructions a single RCA into the left input should work.

Ah - bummer.
I'll have a look around to see if I can find anything that might be of any use..
Once I had a big MS sub (servo?) that went all unwell and made a lot of smoke!

 

[RMutt]

Thanks. The preamp did fail a couple of years ago. It took an age coming back from CA. I’m wondering if it damaged the sub output then but no one noticed.
I’ve been using big Gooodmans Magister bastardisations until lately. An aesthetic driven change means I’m now on Acoustic Energy 500’s and as you might imagine they don’t quite match the previous bass output!
All this means the sub out was never tested. I suppose there’s a lesson there actually, test everything, even if you’re not going to use it, because you never know.