OK, I finally had some time to sit down and compare 2A3's this afternoon and evening.....
Let me recap the test conditions, Phillips SACD1000 with WireWorld Equinox 5's feeding a 1998 Audible Illusions Modulus 3A preamp with 6H23neb tubes in the linestage. From the AI to the Paramours I use a 2.5m length of Cardas Twinlink 5-C cable. This is normally a speaker cable, but it is 15.5ga Litz wire, shielded, and makes a pretty decent interconnect that doesn't pick up noise. On the preamp end there are Cardas SRCA plugs, on the amplifier end there are the Cardas right angle GRNO plugs.
The Paramours are not stock. I doubled up the Speco output transformers. They have Caddock and Holco resistors, the C4S kits, Panasonic TSHB filter caps and TSHA cathode bypass caps. The coupling cap is a Cardas. The Parafeed caps are 4mfd @ 330VAC CDE motor run caps. The TSHB's are bypassed with a set of 3mfd @ 440VAC motor run caps. I used the original coupling caps to bypass the rectifier diodes.
I added the BCP-15 plate chokes and took the stock chokes and added them to the power supply.
Internal wiring was done in the signal path with Cardas 21.5ga Litz, power wiring was all mi-spec Belden Teflon insulated silver plated copper.
I'm using Mullard CV4024's in the 12AT7 position with IERC tube shields.
Power cords to the Paramours are Shunyata Sidewinders. To the Audible a near clone of the Shunyata Diamondback. Another homebrew power cable is on the Phillips and it is plugged into a OneAC isolation transformer plugged into the digital AC outlets of a Tice SoloAV line conditoner. The Audible is plugged into the Analog section of the Tice and the Paramours are plugged into the Amplifier outlets.....no ground loop hums! I have crappy 47year old wiring in the house, but a Pass and Seymour 5262A outlet that's been cryo'ed that the Tice is plugged into.
I did the first full assembly of the amps, minus the C4S kits and oil caps, the first weekend of June. I put the Parafeed oil caps in back in the beginning of August and the power supply bypasses have been in about a week and a half. I leave the amps on most of the time, so they have quite a few hours on them and all should be broken in.
Here's a pic of the underside of the left amp before oil caps and C4S kits:
Here's the right one with the oil caps:
The Paramours are connected to a set of Third Rethm loudspeakers by a 2 m length of Cardas Cross speaker cable. The Thirds have the Lother DX55 drivers. I turned the subs off to make the comparisons to see if there was much difference in the bass delivery of the tubes....well, at least within what bass the Thirds try to put out!
So, now with all that fooferall outta the way, what were the results? Sovtek, EH Gold, or RCA?
Well, I started with the EH's as that's what has been in the amps since I got the tubes...they sounded pretty darn good, so I swapped in the Sovteks...they sounded very similar but a little less refined and maybe a little more grain in the high end, but is a very similar sounding tube. It does all the nice 2A3 stuff well, it's just that the EH's are a little better.
Then I plugged in a set of '50's vinatge RCA biplates.
Well, the sound quality went up a notch again. Things like plucked guitar strings seemed to have more definition in the pluck, the vibration of the string, the harmonics of the note, and in the decay of it's sound. There was a greater refinement in the depth of the soundstage and overall sound quality, and the texture of the music seemed to be portrayed to a greater degree. All this and they seemed smoother but more detailed!
As far as the bass goes, let me state that the Thirds do not do bass...Nope, that's not part of the job description, bud! You want bass, you gotta look elsewhere! (At least in my room!) But, what was there was very similar between the three sets of tubes with the same qualitative differences between them as in the higher end. Bass was the most tuneful with the RCA's, next came the EH's, then in a not too distant third place, were the Sovteks.
Overall, the RCA's were, in my system, the best performers. If one were able to buy new sets of RCA 2A3's at the price of either the EH's or the Sovteks, they would be a must have! But, at the price the RCA's seem to command today, it's really hard to justify their price. I would really like to hear a set of the TJ mesh plates in my system and just see how well they compare...perhaps if you are willing to spend the money for NOS RCA's the TJ's would be a better buy, I won't know until I hear them in my amps, in my system. At the prices for the EH's and the Sovteks, though, you really can't go wrong.
Looking at the internal construction of the Sov's vs. the EH's, they look like the same tubes. The EH's, though, have none of the blue gas glow that I see in the Sovteks. Plus, their ceramic base and polished pins are just a step above the quality level of the Sovtek's. Both brands of tubes are substantially better built than the RCA's which seem almost flimsy in comparison! The glass on the RCA is much thinner than that of the EH's or the Sovteks, and the RCA's pins are also a slightly smaller diameter. The EH's plate structure is also aligned better inside the tube than the Sovteks....so, it looks like the EH's are a "blueprinted" set of Sovteks, they've been ported 'n polished, and bring a higher level of refinement to the tube than is present in the Sovteks.
Ar they worth the street price increase over the Sovteks? I don't know, but either one is better than what I heard from the stock Chinese tubes by a good degree... So, I guess I'll leave the EH's in for most of my listening and break out the RCA's when I really want to sit back and enjoy the sounds....
One of these days, though, I'm gonna get my hands on some mesh plates and then..........but for now, I've got a set of Cardas Neutral Reference interconnects to break in and then next week it will be the Equinox 5's vs. JPS Superconductors (Original) vs. Goertz Tourmaline vs. the Neutral References.....I'll let them all sit for at least 100 hours on the DuoTech Cable Enhancer before comparing....more fun!
Anyhow, hope this wasn't too long, but time now to go stick "The Two Towers" into the DVD player and relax the rest of the evening!
Rick