Junction box with balanced configuration?

Junction box with balanced configuration?

Postby fsonicsmith » Tue Oct 03, 2017 10:21 am

Forgive me if this has been covered before, but most of us know that phono cartridges are inherently balanced. Nowhere is hum and EMI/RFI freedom more needed than from cartridge to phono stage. So, why doesn't VPI take advantage of this and offer a junction box with a DIN female output and if necessary (I am not sure that it is) balanced wire configuration in the tonearm? It so happens that my beloved Manley Steelhead does not have balanced circuitry and not many phono stages do, but it would sure be nice to have the option. Perhaps if more turntable manufacturers offered the option, more phono stage manufacturers would also offer the circuitry.
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Re: Junction box with balanced configuration?

Postby mmai » Tue Oct 03, 2017 10:33 am

VPI does offer balanced junction box, although in conventional 3-pin XLR only (which I prefer over DIN).

http://www.vpiindustries.com/accessorie ... m-ivjncdwp
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Re: Junction box with balanced configuration?

Postby Brf » Tue Oct 03, 2017 10:58 am

Since the majority of phono stages and pre-amps are single ended, VPI's default configuration is also single ended. As mmai mentioned above, VPI offers a balanced phono interface box as an option.
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Re: Junction box with balanced configuration?

Postby fsonicsmith » Tue Oct 03, 2017 12:01 pm

Don't I feel dumb.
But as long as we're on the topic, this is what Manley has to say as to why the Steelhead is single ended only;

Yes the Steelhead is entirely a single-ended design. The circuitry uses single-ended topology. In order to be able to provide balanced outputs we would have to convert the signal to balanced using something like some IC's or transformers. Both these options would add more "stuff" to the signal and be certainly audible detracting from the pure sound the Steelhead provides. If you are driving a balanced preamp or balanced amplifier with the Steelhead, check to see if you also have unbalanced inputs, change your cables and go with that. You might be pleasantly surprised that they too added extra audible "stuff" in order to provide balanced inputs and the RCAs that don't have that extra "stuff" in the signal path actually sound better. (Depends on a given unit's specific design.) Or use some RCA to XLR adaptors. Most balanced gear has no problem being driven single ended but check with the manufacturer if they are going to want the negative pin 3 of the XLR grounded or floating. Transformer-coupled XLR jacks always can be driven single-ended by running HOT into Pin 2 and grounding pin 3 to pin 1. Some IC coupled XLR inputs will want pin 3 floating, others will require it to be grounded when running single-ended into it. Check with the manufacturer of your gear to see how to hook it up single-ended


I trust in Manley's engineers but I do wish I had the option of at least trying balanced inputs since I do have a hum problem I have been unable to eliminate so far. So Brf, what do you think about this, should you happen to have an opinion; is balanced circuitry in a phono stage inherently compromised?
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Re: Junction box with balanced configuration?

Postby Letsmakeadeal » Tue Oct 03, 2017 2:46 pm

My 2 cents...If your phono preamp and preamp are truly balanced circuit topology there are only upsides IMO....You have to be sure however that the unit is a balanced design. Most units are not due to the expense involved. They will sometimes use an opamp or other inexpensive splitter to allow for a balanced input and output but many will suggest that this approach degrades the signal. This is arguable as I am sure there are some designs that use this approach and still sound fine. True balanced designs double the parts count in the unit which usually doubles the cost....You can be successful with either a single ended or balanced approach however noise and hum are less likely and generally eliminated or drastically reduced in a truly balanced set up. One caveat...You have to make sure your pre has enough gain for your cartridge else you have real connection issues if you have to use a head amp or SUT in a balanced circuit since few are available that are balanced designs.
Last edited by Letsmakeadeal on Tue Oct 03, 2017 2:58 pm, edited 1 time in total.
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Re: Junction box with balanced configuration?

Postby Brf » Tue Oct 03, 2017 2:57 pm

Letsmakeadeal wrote:My 2 cents...If your phono preamp and preamp are truly balanced circuit topology there are only upsides....You have to be sure however that the unit is truly balanced. Most units are not due to the expense involved. They will frequently use an op amp or other inexpensive splitter which many will argue can degrade the signal. True balanced designs essentially doubles the parts count in the unit....You can be successful with either approach however noise and hum are generally eliminated or drastically reduced in a fully balanced set up. One caveat...You have to make sure your pre has enough gain for your cartridge else you have real connection issues if you have to use a head amp or SUT in a balanced circuit since few are available that are balanced designs.


Letsmakeadeal sums it up nicely. I own the Manley Steelhead which is single ended and a Cary SLP-05 which is a true fully differential-balanced design. Both sound excellent. It is not the design topology that dictates the sound, it's how well the circuit design is implemented that matters.
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Re: Junction box with balanced configuration?

Postby Stringreen » Wed Oct 04, 2017 7:43 am

I'm using xlr balanced out into Ayre electronics. The phono is DEAD quiet.....other than an occasional click from a scratch or similar it seems to be the same as CD (though better sounding)
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Re: Junction box with balanced configuration?

Postby Jim » Wed Oct 04, 2017 11:33 pm

Since the layout of my system required relatively long cables (2 meters) from my Classic 3 to my phono stage, I ordered my TT with an XLR junction box and, like Stringreen, have had no issues at all with hum or other extraneous sounds in playback.
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Re: Junction box with balanced configuration?

Postby Mat » Wed Oct 11, 2017 12:49 am

Yes, XLR is the best way to go if you are having any noise issues! :)
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