Pre 3 balanced out - which sockets?

[MrKettle]

I've got a 10 year old or so Pre 3 originally built with two sets of phono outputs where it would be useful to convert one set to balanced out. Does anyone know which particular variant of minature XLR hardware works best or was used originally?

[Richard]

Morning, These came with my XL kit and I had to enlarge the chassis hole a couple of mm from the regular RCA size. They look like Farnell/CPC but if you want to be sure of getting the WD ones Matthew will most likely have them in stock

[bikerhifinut]

This is timely.
I am about to embark on the big rebuild of the EL34 power amps as a single chassis stereo amp, and one of the features I would like to include is a balanced input alongside the unbalanced, I have some matching transformers for the input so when I get along to build the transformer output pre I shall include balanced out as well as standard unbalanced. I use long leads from pre to power amps and balanced has to be the best way for the future to cut down on hum pickup i think.
A.

[John Caswell]

Hi all,
Bear in mind that you cannot use balanced and unbalanced from pre3 simultaneously, or even leave both cables plugged in, also because the pre 3 secondary may not be earthed it would be essential to earth one end of the balanced cable screen, preferably the send end at pre3. Depending on your layout you may be able to earth both ends but beware of hum loops and the like.

John

[Richard]

Morning, yes as John says. Also a bit of a nightmare to fit retrospectively. The chassis holes needs opening out and paint removing and access is not good if the relay pcb is already soldered in. Wire them back to the OPTX with their own cable + - earth screen. There is an additional build sheet for this and I have a pdf suggesting the sockets are Switchcraft. Contact me or Matthew if you need more info. Pics of mine attached.