which turntable or how to convert to balanced phono setup?

The words you quote in italics are of course correct but have nothing whatever to do with the PE505 specifically and prove nothing.  However, I finally found the owners manual on line. It is very dumbed down, but if you look at the diagrams on the right hand side of page 9 in the English language section, there is a hint that you are correct.  Also, on the page with specs, the gain is not different when you feed the RCAs vs the XLRs. This too suggests you are correct.  Note the caveat on page 9 about feeding the balanced inputs from a TT wherein the outputs are grounded to the TT or tonearm. As they say and I said, this negates the balanced operation.

lewm

... I finally found the owners manual on line. It is very dumbed down ...

I thought the same! A component such as the PE 505 really deserves a better manual.

Note the caveat on page 9 about feeding the balanced inputs from a TT wherein the outputs are grounded to the TT or tonearm. As they say and I said, this negates the balanced operation.

Oh yes, of course, absolutely agreed.

I'm glad we were able to clarify this matter for the OP and everyone else, @lewm and I wish you the best. 

More likely the RCAs ground the negative phase of a balanced signal inside the chassis and convert to SE operation. That’s what Atma-sphere does with their amplifiers, so those who have SE components upstream can stay SE in the amplifier.

@lewm Either I'm misunderstanding this or its incorrect. At no point in our amps does the signal go single-ended. What we do instead with the RCA connection is the center pin connects to pin 2 of the XLR and the RCA ground is pin 1 of the XLR. We then ground pin 3 of the XLR if the RCA is being used instead of the XLR. 

A differential amplifier, present at the input of all our circuits, then converts a single-ended signal from the RCA to balanced operation. No transformer needed. The differential amplifier doesn't care much if the input is single-ended or balanced, since it simply amplifies what is different between its two inputs. If one side is ground, so be it. 

Also, on the page with specs, the gain is not different when you feed the RCAs vs the XLRs.

If the circuit and source are true balanced, and if one side of the source is grounded or not will make no difference to the gain if the preamplifier is really balanced. The reason is the same amount of Voltage is applied to the input in either case. So if a phono cartridge has 1mV output, if that 1mV is applied to a balanced circuit via an RCA connectors (so the inverting input of the balanced circuit is not used) the gain will be the same unless the balanced circuit is not differential or having a transformer coupled input.  Since the CMRR our our phono section inputs is rather high the signal level at the output of the preamp will be unchanged whether the input is balanced or not. 

There is a common misconception that a balanced signal will be 6dB more gain but if the source is AES48 compliant that simply is false. 

In gear that really does offer both a SE and a separate balanced input, the gain claimed by the manufacturer is usually quoted as being different for the two types of input, with the balanced circuit gain being higher.  Why is that or is it a false claim?  In the PE505 owners manual, the data sheet shows the gain is the same via either input type. I took  this to mean that cleeds is correct in his assertion that the RCA inputs are hooked up for balanced operation. This can also be seen in a diagram on page 9 where they show not to drive the PE505 with a SE output from a TT, "for best results". The diagram also suggests the "ground" side of the RCA jacks is not connected to audio ground, in other words RCA hot must go to pin2 and RCA ground to pin 3. However, they never come out and say it.

On your first point, we are actually in agreement. The SE input is grounded (to pin1) in the case where an SE input is provided, like I did say, and like it is on my Atma-sphere amplifiers, except I am wrong about the need for a transformer or some other device to convert the SE input to balanced. Thank you for the correction. (I’ve never driven my amplifiers from an SE source or using the RCA inputs, but I know the circuit quite well.)

Do you know why the owners manual for the PE505 says the XLR inputs are for MC cartridges only?

You often quote AES48. What does AES48 say?

Funnily enough, I just found a good website that talks about AES48. (To read the actual original language, you have to pay AES for the text.). Here.