Feedback sent to Bob from eurotubes.com:
Hi Bob. The shrill is gone! The JJ Tubes arrived today here in Denmark, only six days after ordering them over the phone. They arrived in good shape and have been tested to be okay.
Thanks for the quick shipment and for marking each tube box with gain factor. Here's a short review on my first impression after installing them in my guitar amps. I am a guitarist and play all kinds of metal, so the following review is based primarily on the overdriven character of the amps.
Peavey Classic 50/50 tube Power Amp
Stereo Power Amp, factory installed with all Sovtek valves.
First thing I did, was to change the input stage to JJ's. The input stage consists of 2x ECC83 S and 2x ECC81. The shrill is gone! The quite shrill character this amp had with the Sovteks are almost gone. Sound is a tad more dark, but a good dark. The tone is more round, but still with good air and definition in the mid range. So, no frequencies are lost - the voicing character just changed to the better. Slightly more gain now. I didn't need that, but that's okay.
Then I changed the 8 (eight!) EL84's in the power stage. No output increase, that's fine. At first the low frequencies seemed weaker, but after a couple of minutes of playing, I had a pleasant smile on my face. With the JJ's, the lows are more tight and focused and the amp seems to have a quicker response and with a more firm grip. Very good. When I drive the power amp real hard, it goes a bit 'middly' now, but not too much. I have heard this mid range change from other tube amps as well and it's no big deal.
ENGL E530 tube preamp
Factory installed with 1x Sovtek 12AX7WB and 1x ENGL labeled ECC83 valve.
Changed both at the same time to JJ's (ECC83 S gain factor 110). Again, here the JJ's remove a bit of shrill from the highs, but apart from that, no big change in the overall sound. A tad more gain noticed.
I didn't expect big changes from a preamp anyway, but here comes a pleasant surprise. The E530 has a "contour" switch on the lead channel which I haven't used much, because it adds to much fuzz in the mid range for my taste. It destroys fast distorted palm muted runs by adding a noisy character and too much mud in the mid range. But with the two JJ's it's awesome!
The messy fuzz is gone and the "contour" switch now adds a perfect brutal in-your-face character to the tone, which I find very useful. Heavy overdriven solos now have more grunt / body and are projected with much more clarity in a full band mix. The notes are separated much better compared to the stock tubes. That surprised me a lot! I haven't explored the very versatile tone controls of the E530 yet with the new JJ's, but maybe there are more treasures to be found in this very good preamp!
All in all a great improvement in tone!