Question for tube aficionados

The current production Gold Lions produce a sound that comes closer to the old production Philips tubes such as Mullard and even the less rich sounding Amperex.  Still many of the old 5751s while excellent in regard to tone are even better for imaging and sound spectrum profile balance  i.e. relative amounts treble to mid to bass that is partly a function of what a tube type can alter sort of a tone matter but different in my mind.  Gold lion does not make a 5751 to my knowledge but I sure would like to see them try. They do make a 12AU7.
There has been a run on whether a 6SN7 can be subbed for a dual triode 9 pin minature, and it can in some applications take the place of a 12AU7 in some applications. adapters can be bought on Ebay and elsewhere.  I am not sure whether you pre would allow the diferences betwen the 2 or not, but my understanding is that they serve similar purposes.  6SN7s are said to be very linearand there are plenty of 12AU7 bashers around on tube froums.

I owned the PV5, PV8, PV11 and PV12 over the years. Going from memory, seems the later versions starved the tubes a bit. before you start serious tube rolling, may want to measure the plate and cathode voltages and see what there are, then calculate the current going through the tube. On my PV12, there was less than a milliamp, so changed out the plate and cathode resistors to at least get the current up to a milliamp. sounded much more open and less constrained.

The PV5 I wish I had never sold...did not have the highest resolution, but was such a musical sounding piece.

best
J

If the CJ uses any 12AU7's try NOS RCA 5963. These are always a serious upgrade from your new stock 12au7's and they're a plug and play replacement. Highly recommended.

And almarg has stated an important point about the use of the 5751 variant in your CJ preamp...
Please note: The indiscriminate substitution of type 12AX7 tubes for the 5751 will seriously degrade the sonic performance of the unit.

The 5751 has lower gain, so it's recommended to stay with a 12AX7.

This comment is backward. The book is saying not NOT to replace the 5751 with 12ax7. The higher gain of the 12ax7 would overdrive the circuit, being 30% higher. That’s why it says not to indiscriminately do that.  

I have a used the PsVane with much sucess.
I have an Amp that uses the 12AX7 In that I have put Sovteks (Basically nothing more than a tube to put in a tube socket) 
Also put in Vintage Mullards and Tele's . The matched Set Psvane to me sounded better balanced, clearer and detailed.
The Mullards a little bright & the Tele's A little to creamy for my system.
 But it is always specific to equipment.
I also had a tube phono section which required both pairs. Again I tube rolled the Sovteks and
only replaced with the PsVanes. Vintage is great but they have their issues.  With the PsVanes were very quite and for the price worked great and you should have no regrets. At worst they become a very good back up set just in case your vintage choice go south. But now my vintage 12AX&'s are my back up and the Psvane are still in and working fine for well over 2 years.
Lastly give them a little time to break in. Out of the box you will know you are the right path.