Connecting pre to bridged mono power amps

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Trumpet Warrior
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Connecting pre to bridged mono power amps

Postby Trumpet Warrior » Wed Aug 28, 2019 9:44 pm

Hi there,

Technical query for those in the know.

I'm currently using a Tom Evans Vibe pre into a Belles 150A Reference Mk2 power amp for my amplification with single ended RCA interconnects. For some time I've been wondering whether having 2 in a bridged mono arrangement would be a step forwards (as has been suggested in some reviews in the past). As luck would have it, an identical amp has appeared locally which I'm interested in, but there is a slight catch... to connect the Belles in mono requires XLR interconnects, and my pre-amp only has RCA outputs. The instruction manual also mentions balanced interconnectors when indicating how to connect up 2 amps in mono.

My question is whether I could use an unbalanced interconnect with RCA connectors at one end and XLR at the other, or does it have to be a balanced cable? I've emailed the manufacturers directly, but not sure how good they are in responding to queries.

Thanks for your input.

Paul

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Re: Connecting pre to bridged mono power amps

Postby hifinutt » Thu Aug 29, 2019 9:12 am

fantastic , i have had 3 tom evans vibe amps , beautiful . also had some lovely belles kit

firstly , what speakers are you running that need all this power ? , the belles is a very powerful amp .

there are 2 great guys with regards to cables who could advise , paul coupe at RFC components who has been making cables for years and may be able to advise on a suitable solution .

http://www.referencefidelitycomponents. ... nects-xlr/

and tony at coherant who has been into belles amps for years and probably knows more about them than anyone in UK
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Re: Connecting pre to bridged mono power amps

Postby Trumpet Warrior » Thu Aug 29, 2019 11:28 am

Thanks for your suggestions.

I'm using Sonus Faber Cremona Auditor stand mounts.

It wasn't really the added power I was interested in, but the supposed sound quality improvement of mono blocking. When I had Cyrus Smartpowers, there was a noticeable improvement going to monos and I was wondering whether with relatively modest outlay (used 150A seem to be reasonably priced, though rare) I could achieve a similar sound upgrade. The review below suggests they felt there was a significant sound upgrade. (There aren't many reviews which include the amp used in mono).

http://www.soundstagenetwork.com/revequ ... erence.htm

Is this realistic or sensible do you think?

I'll have a chat with Tony to pick his brains too.

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Re: Connecting pre to bridged mono power amps

Postby Trumpet Warrior » Fri Aug 30, 2019 12:32 am

Trumpet Warrior wrote: I'll have a chat with Tony to pick his brains too.


Spoken to the guys at Coherent today - very helpful with some good advice regarding the likelihood of a positive improvement in sound quality. It seems that pseudo-balanced interconnects (XLR to RCA) will work fine although they may not have quite have the same overall effect as fully balanced cables due to the reduced ability to handle noise.

Will try and source a pair of pseudo-balanced cable if I'm able to secure the used 150A.

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Re: Connecting pre to bridged mono power amps

Postby Ianmac » Fri Aug 30, 2019 8:03 am

This issue is familiar and we have discussed it in the past so there may be something in the archive.
Connection of unbalance to balanced amplifier input is covered in detail by Hypex in their input configuration of the hypex N Core with clear diagrams as to how to wire the interconnect cable. This available on Hypex website, if you cant find it drop me a pm and Ill email a pdf.

The issue re noise is theoretically correct whether it would have any impact is largely dependant in the length of the cable between the amp and pre output.
In my main installation Im about 18 feet so there is good reason the run balanced
In my office system its 1 foot so,as I am in the same situation as you, I can run with an unbalanced to balanced cable.
If you have a short cable run an unbalanced to balanced cable will be OK

Im building a pre amp with a balanced output right now, but this does get a little involved dependant on what input sources you have that are balanced. My phono pre is balanced out so im looking at at true balanced pre amp.
It is relatively simple to convert Unbalanced to Balanced electronically and many pre amps use that route thus the confusing term of psuedo balanced
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