So I bought a Pro-ject Pre Box RS... (Valve suggestions?)


The Pre Box RS comes from the factory with Electro Harmonix 6922, on the output stage. All I have read about this pre has suggested a linear power supply upgrade and tube rolling gives
significantly better results, so the linear PSU is already done (19VDC from a HDPlex 200W).

I've already got some tubes I bought for my old old DAC (it's now 9 years old).
I have a pair of Amperex P.Q 6922 [VCM 163 tested], and a pair of
Phillips E88CC SQ [1109] with writing on the box [12500-12750 and 12400-12500 on the other box] What do those hand written numbers mean?

Anyway, which valves should I likely go with? (I am hoping for longevity as well as quality)



 
128x128rixthetrick
The tube codes are easy, if you can read them. Sometimes they are faint or invisible.

Top line is three characters:

tube type, tube type, change code (model or version #)

Bottom line is three or four characters:

factory symbol, year (last digit), month (A - L), week of the month.

If the codes are legible, post them and we can decipher them.
The 12500-12750 and 12400-12500 numbers are the readings from a tube tester (in UMhos).   The tubes have 2 plates in each and those are the numbers for each plate.    Without looking up what the numbers should be these seem like well matched tubes.   Each plate in each tube is the same.  And the 2 tubes are close enough for me.
Thanks delkal,
I am learning from you guys.

tomcy6,
Phillips SQ
I can make out (looks almost etched in a faded silver/grey)
7LG (then under it)
What appears to be a right angled triangle, with the hypotenuse coming from down on the left, to it's apex on the longest of the other two sides which is vertical on the right, then 1F4. Both have exactly the same markings.

AMPEREX P.Q (PQ with two stars, one between the letters up top and in the bottom of the shield)
Amperex
6922
Made in USA (funny as I purchased both sets in Australia, seem I brought them home) in silver numerals "332" and also separately below in grey
7L8 (next line under it had me puzzled)
at first the symbol under it looked like a wagon wheel, but then I realised it was a circle with the pins for the valve, and then 3F to it's right.
Elsewhere  it also has in larger white print, what I thought was a faded 405,but is in fact using both as a reference clearly 105 with a strike through the middle of the 1's, kind of like the French do with sevens. Maybe it is a 7?
With the shaft being vertical, or parallel with the 05, not at all angled to the right like a seven though.

Hope that's not too cryptic?
Thank you tomcy6