Balanced preamp

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NBPK402

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Joined 2012
#1
I have a Pro Ject RPM 1.3 turntable that will be over 30' from my AV rack, and I have a Music Fidelity phono preamp that will be next to the turntable. I cannot run balanced from the turntable as the table has RCAs.

Question: I prefer to spend under $500 for a balanced preamp (I could go up a bit more). I have looked on Ebay and see a lot of clones (MBL and Levinson JC2), but I am not sure if all balanced preamps with XLR, and RCA jacks will convert the unbalanced to balanced audio( I say this because my Music Fidelity phono preamp will not convert). I also would prefer to not lose any audio quality with the preamp. Do I need to spend more, and buy a non clone preamp?

Will a passive balanced preamp be able to drive such a long run?
 
#4
You will need a buffer or even better a RIAA corrector with an output buffer the phono cart wont drive long cables without getting nuts with the capacitance or with the impedance of passive preamplifier. Then the output buffer will have the simple or balanced output connection you need, it can be made active or with an output transformer.
Also your current Phono preamp could be modded to accept a output transformer to make a simple/balanced output if so to speak.
 
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#5
So You have:

Turntable-Musical Fidelity-7m Cable--Av rack. Correct ?

Have You tried a good quality RCA cable yet ? If Your pre-amp outputs a strong signal in the 1-2V range it should work with the 7m cable. Can't find output specs online.

Bear in mind the pre-amps You did look don't have RIIA network, so You need to connect them after Yours, or compensate RIAA in the AV Rack.

Will a passive balanced preamp be able to drive such a long run?
Click to expand...

Does Your AV rack accept balanced inputs ?
Try a mic cable with inverting input shorted to ground at the RCA end.

If not, You will need to convert RCA to XLR & ... XLR to RCA on the other side too. That makes two converters.

You could also try some sort of wireless between the two. Bass will probably be compromised. Try an AV extender or a bodypack transmitter for a start, or even a small mixer after the pre-amp.

An inverting op-amp inside the Music Fidelity & two chassis mount xlr's or jacks...

Many options: Try & stick with what Pleases You.
 
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#6
maton00 said:
You will need a buffer or even better a RIAA corrector with an output buffer the phono cart wont drive long cables without getting nuts with the capacitance or with the impedance of passive preamplifier. Then the output buffer will have the simple or balanced output connection you need, it can be made active or with an output transformer.
Also your current Phono preamp could be modded to accept a output transformer to make a simple/balanced output if so to speak.
Click to expand...
I currently have the Musical Fidelity MX-VYNL Phonostage...it could be moddified to accept a unbalanced and convert to balanced?
 
#7
MAAC0 said:
So You have:

Turntable-Musical Fidelity-7m Cable--Av rack. Correct ?

Have You tried a good quality RCA cable yet ? If Your pre-amp outputs a strong signal in the 1-2V range it should work with the 7m cable. Can't find output specs online.

Bear in mind the pre-amps You did look don't have RIIA network, so You need to connect them after Yours, or compensate RIAA in the AV Rack.



Does Your AV rack accept balanced inputs ?
Try a mic cable with inverting input shorted to ground at the RCA end.

If not, You will need to convert RCA to XLR & ... XLR to RCA on the other side too. That makes two converters.

You could also try some sort of wireless between the two. Bass will probably be compromised. Try an AV extender or a bodypack transmitter for a start, or even a small mixer after the pre-amp.

An inverting op-amp inside the Music Fidelity & two chassis mount xlr's or jacks...

Many options: Try & stick with what Pleases You.
Click to expand...
I have the Musical Fidelity MX-VYNL Phonostage. My turntable only has RCA output. I have only triied the rca cables that came with the turntable. If I could convert the RCAs to balanced with something...then could the phono stage I have drive 30' long XLRs, or would I need a balanced preamp for the phono preamp to drive the long distance?

My AV rack currently has a Yamaha CXA5100 preamp that has a balanced XLR input, that I am asssuming my phono preamp could be plugged into if I have a balanced source from the turntable. Would the unbalanced to balanced box I posted in the 2nd post be good enough?
 
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#8
The Pro Ject tt has a rca box on it... could the box just be removed and a new box fabricated and wired for balanced? Then I would just get the balanced cable for the phono preamp...if the phono pre can drive the long cables. If the phono pre cannot drive that long of cable then I would also needma balanced preamp like the ones I posted, correct?
 
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#9
> if the phono pre can drive the long cables.

Don't be scared. Try it. Modern solid-state circuits can normally drive 30 feet cable perfectly well in a benign room (no arc-welders or elevator motors). I have even run un-balanced un-shielded for 30' of a 50' run next to an elevator and the building main power panel.
 
#13
PRR said:
> if the phono pre can drive the long cables.

Don't be scared. Try it. Modern solid-state circuits can normally drive 30 feet cable perfectly well in a benign room (no arc-welders or elevator motors). I have even run un-balanced un-shielded for 30' of a 50' run next to an elevator and the building main power panel.
Click to expand...
Thank you, I will look into some 30' cables and try them out.
 
#15
MAAC0 said:
If You insist on running Balanced cables to Your AV Rack, You can try something like this after Your Phono pre-amp.

CLEANBox Pro – Dual Channel Level Converter – ART Pro Audio
Rolls MB15b ProMatch 2-way XLR/RCA line-level converter at Crutchfield

or build one

Balanced Line Driver & Receiver
Click to expand...
Thank you for the info. I think I will get XLR cables the correct length, and then use the xlr to rca adapters on each end to make sure there are no problems, and if there are problems I will pursue the XLR mods.
 
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