Preamp Deal of the Century

I'm using a 5AR4 rectifier in my setup, but not the stock one. I'm using a NOS GE 5AR4, the one with the copper sides on the plates. I think it sounds excellent and it is nowhere near as expensive as the Mullard GZ34 (I haven't heard those, however). You can get the GEs for ~$50 at Antique Electronic Supply.

I have been playing around with the regulator tubes since I did the Solen mod. Here are my opinions:

Stock Sovtek 5881/6L6WGC: The worst of the bunch. Sounds glary and brittle, with deficient bass

NOS Tungsol 5881/6L6WGB: I picked up a used pair at a swap meet a year or so ago for ~$30, I think. They immediately replaced the Sovtek 5881 in my setup, and have been there ever since. They sound much better than the Sovtek 5881, with more bass and without the glare on the highs. They only read about 63 on my tube tester, barely in the "good" region, but they still sound very good.

New Sovtek KT-66: I picked up a matched pair of these a couple days ago from Parts Express for $50. I like them! They have a very full sound, with killer bass, yet still retain most of the high-end shimmer and detail. I can see why Mick recommended these to people who want to tube roll. They do not get very good reviews online as power tubes, but they seem to be excellent regulators. Very beefy construction, with copper grid posts and a larger plate structure than the Sovtek 5581/6L6WGC, so they are definitely not just re-badged versions of that tube in a different bottle. The metal base and coke-bottle shape look cool as well. I'm very pleased with this purchase.

Just checked with AES - they're out of the GE 5AR4s, even though they're listed on the website. Bummer. Glad mine still have many years of life in them...

PS cap replacement - anyone tried any other options - I have done the V caps and they were definitley an improvement so I am keen on upgrading power supply ( alps RK50 pot was also very good but pricy ) - another tweak I recomend is replacing the bottom plate in both pre and PS with something more rigid and using proprietry footers - I used symonite sandwich panel ( like alucabond ) - I drilled new vent holes of course

Cheers

Experiences with GZ33 vs GZ34? I'm looking for anyone who has compared and contrasted these two rectifier tubes in a Supratek preamp. The GZ33 is very cool looking, but how does it sound versus the GZ34/5AR4?

I've had numerous rectifiers in my sauvignon and cabernet. They include the 6106, Sylvannia 5a45, Mullard GZ33, Mullard GZ37, and the Mullard/Amperex metal-base GZ34. The Mullard/Amperex metal-base GZ34 is by far the best in my preamp. The improvements have been in the areas of reduced noise, longer note sustain/decay and to a lesser degree better harmonics which has increased the timbre. I've had my GZ34 in the system for about 5 years and my system is always powered on and playing.

From what I recall about the GZ33 and GZ37 specs the heater current is a good deal more than the GZ34. I think that anyone rolling regulators or rectifiers in the suprateks should consider the impact of one upon the other. Some of the larger regulator tubes place their own demand upon the power supply.