Tube rolling experience in Aesthetix Callisto Sig

After a week with the Callisto Signature line stage, I was eager to hear the potential of this unit that Albert Porter has praised the last few years. As is quite evident, Albert has put much time and effort to get his Aesthetix units finely tuned with various NOS tubes and other wire and component updates.

After a brief review of his Audiogon writings and some recent email tips he sent me, I thought I’d try some of his ideas in my Callisto. His suggestions 2 years ago, when I got the Io, was to replace the stock Sovtek 12AX7’s with Telefunkens. The result of that was breathtaking in the improvements of bloom and decay. I did not update the EL34s in the Io’s power supply at that time as I was so content with the 12AX7s and I was pretty much out of money by then. But after tonight’s experiences with swapping the EL34’s in the Callisto, I will do this very soon for the Io.

Albert’s recommendations for the Callisto was to start with the EL34s in the PS. He wrote that this would be as dramatic as the Telefunkens in the Io. This is quite a bold statement but a statement that caught my attention. He then suggested trying a few different 6922s. I sensed that his advice to replace other tubes would be beneficial but only after the EL34s and 6922s were addressed first. I looked around Audiogon and hunted down various tubes recommended by Albert and managed to find a few sets to ultimately try in the Callisto.

The tube compliment in the Callisto is as follows:

Audio Chassis:

2 6SN7
4 6922
2 12AX7

Power Supply Chassis:

2 EL34
6 12AX7

The first tubes to arrive were a quad of Amperex 7308 (6922), a quad of Siemens 6922, and a pair of Sylvania 6SN7. The EL34’s that I was so eager to receive were still to come. Rather than wait for those, I went ahead and put in the quad of Siemens. Right away I could hear a ringing sound in the left channel when raising the level. Oh nuts, microphonics! I swapped the Siemens around to determine the troubling tube but now the ringing was gone. Perhaps a tube was not fully seated. Two nights later and still no ringing, so for now, this is not an issue.

I truly could not hear much of a difference with the Siemens vs. the Sovtek 6922’s. Late into the night I went back to the Sovtek 6922s and they sounded mighty fine but I detected a slight unnaturalness to the piano overtones that made them sound a little electronic. I then put in the Sylvania 6SN7 which brought on a very slight reduction in midrange forwardness. I put the Siemens back in and ran with the Sylvania tubes for two nights awaiting the EL34s.

Finally the Amperex-labeled EL34s arrived. I went back to all stock tubes and put the EL34s in the P.S. Oh my, oh my, I was so surprised and yet I was not. There was instantly so much grain removed. Vocals and piano came out from the fog! I had dynamics like not at all with the stock Electro Harmonix EL34s. I honestly do not remember differences at the frequency extremes as I was dumbfounded by how the mids were now so incredibly clear. What a wake-up call!

After 10 minutes or so I found the sound to be too fatiguing. The new EL34’s brought on so much energy but now there was a tonal imbalance with exaggerated midrange and ringing that was not at all to my liking. But remembering Albert’s comments that changes in some places would show “issues” elsewhere until they too were addressed, I kept a positive outlook on this adventure. I had detail with the Amperex EL34’s that I simply did not want to give back!

I had not tried the Amperex 7308 (6922) so they went in next. Yikes, lots and lots of midrange warmth. It was as if I put in a Cardas Golden Cross IC between the Callisto and CATs. Now there was even more tonal imbalance with too much midrange warmth. And there was even more of a sharpness to the initial strike of piano notes that had me running to cover my ears. I could see how this would be a good tube for overly dark systems but oh my not in the Callisto here anyway. A return to the Sovtek 6922’s took the sound in the right direction but now I was more aware of this initial-strike-of-the-notes problem. I did not have this problem with the stock EL34, or at least it was not so evident.

Next up was a return to the Siemens 6922. Wow! Now you’re talkin’. Piano now sounded much less electronic. There was space between the notes. Whereas the improvement of the Siemens over the Sovtek 6922 was subtle with the Electro Harmonix EL34s in the P.S., this difference was now a significant refinement with the Amperex EL34s in the P.S. The system now had detail in the mids that had only existed before in the trebles. But there was still a wee bit of a fatiguing nature to piano notes in the initial strike rather than in the overtones. This was almost like a sharp twang. It was not serious but still noticeable. And this was not a character I had noticed of the Callisto with the stock tubes. Clearly the Amperex EL34’s brought on much dynamic and authority characterizations, but they also unmasked remaining problems elsewhere.

So the Siemens 6922 was a huge step in the right direction with the Amperex EL34s in the P.S.

Remembering the subtle improvements of the Sylvania 6SN7 when using the stock EL34 tubes, I wasted no time putting in the Sylvanias. Big big smile! Once again, the subtle refinement heard with the stock EL34s was now huge with the Amperex EL34s in the PS.
The added presence from the initial strike of piano notes was nearly gone! It was so close. But there was no denying that it was an addition to the sound that was not there with the stock tubes. Other than this very minor issue, there was a wonderful tonal balance as with the stock tubes but now with much more resolution in the mids. The music had structure and definition and placement that was not at all present with the stock tubes. And finally I noticed a little more extension in the bass. Perhaps this was because the fatigue elsewhere was now gone.

So the Sylvania 6SN7 brought me even closer to tonal and musical nirvana.

With the piano now much more out in the open, occupying more of the presentation, I was wanting more body and dimensionality to the sound. The detail was there like never before but because of this detail, the volume of space of the piano notes was a little bit reduced and lacking in presence than I would have expected by this time. But I was clearly getting greedy.

With one pair of tubes still to play with, I put in the Telefunken 12AX7s. Initially I heard no difference. And still an hour into listening, I really could not hear a difference. Finally a return to the Sovtek 12AX7 and the annoying strike of the piano notes returned! As minimal as it was, it was clearly there! I had not even noticed it was gone with the Telefunken as I was so busy focusing on the bloom issue. But indeed, when I returned to the Sovtek 12AX7 I heard a reduction in the bloom of the piano as well. It was not so easy to hear this improvement with the “step up” to the Telefunken, but a return to the Sovtek and the difference was immediate.

So the Telefunken 12AX7 not only removed another layer of the Sovtek fatigue but also brought on a little more dimensionality that I wanted.

Now I have a huge improvement in musicality like I simply could not have imagined from the replacement 10 tubes. I would be very surprised if the second P.S. would bring on the dramatic improvement in dynamics and resolution like this tube update has done.

So what did I learn here:

1) Albert was absolutely right on when he said the EL34 tubes would be THE significant change here.
2) No matter what type of tube it is, i.e., 6922, 12AX7, 6SN7, Sovtek tubes absolutely have a house sound. There is a definite fatigue in the initial attack as well as overtones in a highly resolving situation. And these tubes are not very high in terms of resolution.
3) Unless you can also replace ALL of the Sovteks tubes in the audio chassis, I do NOT recommend changing the EL34’s. The EL34 change not only brought out more of the potential of the Callisto but also brought right to the forefront the additive weakness of all the Sovtek tubes. And the result was a step in the wrong direction until corrected by changing the other audio chassis tubes.
4) There is little gained by replacing the tubes in the audio chassis as the refinements brought on by the tubes here will be masked by the mediocre dynamics and resolution capabilities of the stock (Electro Harmonix) EL 34 tubes in the P.S. Again, Albert was right: there is a definite pecking order.
5) There is much to be said about a matched set of tubes for any given product. Just throwing around NOS tubes and expecting magic to immediately happen will only result in immediate frustration.

With the audio chassis now retubed with non-stock tubes to match so well with the EL34’s, I can put the cover back on the audio chassis and not worry another minute on this for quite some time. Perhaps the replacement of the six 12AX7 tubes in the P.S will bring on some benefit, but for now, I am very pleased with the outcome.

This “updated” Callisto has all the dimensionality of before but now with dynamics and detail that would knock the socks off anyone, including JD. 8-)

A note to Guido: I think I finally found that Bosendorfer.

And Albert, I now owe you 2 deluxe strawberry cheesecakes.

Very thorough review, John. Unfortunately, that's too many permutations for my itty bitty brain to follow, and im afraid i never woud have been able to sort through the differences if i were to try the same thing. Anyway, your dedication, thoroughness and vigilance will help future callisto rollers!

There is a very, very important variable i may have missed: WHAT VINTAGE were these 6922's (and other) tubes you were rolling? It's a well known fact that the best 6922/7308/ 6DJ8's were made in the 60's and early 70's - and that anything in the mid to late 70's and beyond are JUNK. There are a lot of tubes flying around out there claiming to be one thing, but are another (mostly 80's tubes being passed off as "genuine" well they are siemens, but the production info conveniently left out).

I myself was burned on a "Siemens 7308" I had procured ata hefty price, having been told, "this is THE ULTIMATE tube for your First Sound Preamp" only to find out with some research it was manufactured in 1980. It's not all about the date either - it sounded lifeless. Clean and transparent, but nothing special, sterile and boring. I sent it back.

IF yu dont have one already, you really need a good tube source, someone who will not deceive or rob you. In my last expereince (before I sold the First Sound), I landed some REL 1960 Amperex 6922 "Pinched Waist" tubes which, as Joe of Joe's tube lore documented were simply superb. The difference between it and te 1980 Siemens 7308 was enormous, beyong comparison really.

Anyway, I'l step off the soap box now - but remember tube-children, "it's a jungle out there, buyer beware"
Excellent info John! Now I am suddenly wondering if there is such thing as wire-rolling craze in pianos, like there is tube-rolling in audio gear.
Jafox, thanks for the excellent description of your tube experiements. Now that you've found the tube complement that gives you a sound you like, take it up another notch by applying Walker Audio Extreme SST to the tube pins (very lightly - follow the directions), let the SST break in, and listen again. It's amazing how many layers of veil there are in our systems that can be lifted.

Kind regards,
really, that stuff works? for REAL? No kidding? Honestly? No joshing? You're not puling our legs? Not april fools day? you mean it? Not "opposite day"? Not pulling a fast one? Not prevaricating? Scout's honor? Cross your heart, hope to die? PINKY SWEAR?
Great info John, it sounds like you've had quite a few changes in two weeks. I will bring a couple other 12AX7's to try when we next get together.
Artg: Your concerns on "legitimate" tubes has much merit. It would be easy for many people here to misrepresent the vintage or manufacturer of a tube. But this is the case for all such audio purchases here.

I have had much success with 3 sellers of tubes here so I check out their inventory before I look elsewhere. As for the vintage of the ones I got this week, I will have to do some searches and see if I can learn an approximate date of manufacturer based on the labels painted on the tubes. If people are painting old labels on new tubes, surely there are many more prosperous counterfeit operations than profiting from the few of us tube users in the world.

As for the later tubes being "junk", other than the Amperex 7308 being too way much of a good thing (midrange presence) the remaining tubes far exceeded the stock Sovtek and ElectroHarmonix tubes. So even if we can not get our hands on those prized pre-1970 tubes, I am convinced there is much musicality to be gained by swapping out the Sovteks in some areas.

And yes I fully understand the overwhelming nature of trying so many tube permutations in these products. I seriously considered trying a pair of the Amperex 7308 and a pair of Siemens 6922 in the two groupings within the Callisto but I was very pleased with the Siemens quad.

Again, I relied on all the efforts previously made by Albert. All I did was learn for myself if these tubes were as dramatic as he claimed. He clearly did all the legwork with determining the good from the bad in the many many tubes that he surely tried in these units.

I never would have the patience to try 4 or 5 brands of each tube type. Keep in mind, I am more a "forest" rather than "trees" kind of audiophile so putting a lot of time and effort for that last pinch of refinement or perfection is not what I am after.

Like Albert's experiences greatly benefitted me, I was looking to share what I had learned in 3 nights what could very well take the efforts by someone else down to one night. And that was the purpose of the "what did I learn" summary.

So Art, don't let all the tube changes scare you. It really was rather straight forward. Now the Io is a different beast!

Guido: Funny man. Maybe Itzhak Perlman should consider string rolling as well? Cat lover here so no cat gut jokes please. Or is that just tennis racket strings?

Rushton: Where do I get this SST? I guess I can not put the cover back on the Callisto tonight afterall.
Jafox, here's the link to Walker Audio for Extreme SST:

Lloyd offers a money back guarantee if you're not satisfied and you return the unused portion in 30-days. I'm definitely a believer in the result with my Io Signature, plus every other contact in my system.
John - as always, your points are dead-on. I guess it's a matter of cost/perfromance ratios. The stock sovtek's cost X and delver a certain baseline perfromance. they's also very cheap because they're in abundant supply, so their ratio is decent. Later date (ie. mid 70-80's and beyond) NOS 6922/7308's may be better than stock, but at what price? If properly priced (there is a surprisingly large supply of what i lovingly refer to as NOSJ (new old stock junk)), then their ratio is also reasonable - maybe even a tad higher than the stocks. OTOH, if the NOSJ are being sold as "DA BOMB" at $250-$350 per matched set (which is what you might need to pay for the real deal early 60's stuff), then suddently the ratio SUCKS, dig? Reputable tube sellers will either only deal in the good stuff (e.g., Andy at , or will properly discount the NOSJ for what it is.

Anyway, i have no reason at all to believe any of your tubes were NOSJ - I was just posessed again to share my painful experience paying premium $$$ for NOSJ (in my case the 1980 produced Siemens 7308).

As for the overall nature of your analysis - i really applaud it - it was excellent, and i could see how systematically, it would be doable rolling all those babies in there. I've done some rolling on my Berning, and on my previous First Sound Preamp. Im a big fan of fine tuning sound on tubes - Bravo!

OK, Rushton, I just bought some walker extreme SST.
John, believe it or not, string players tend to be also compulsive string rollers by nature. No danger to cats though, Pearlman likely uses some newest variant of steel strings. No NOS either, a string more than a couple of years old is not even good enough to be deemed NOSJ. . . it's pure Junk. And the US Marine Corp's band sadly lacking string instruments, there is regretably no such things as JAN strings either.

For your 12AX7's try a pair of RCA 5751's 3X mica Black plates. They have slightly less gain, but have excellent focus and resolution and are grainless in comparison to most all 12AX7's..they will make a audible difference...Ken
Hi Ken, I was thinking exactly of these tubes to try in my DAC as it takes a pair of 5751 and also a pair of 7044. I have so much harmonic richness from the DAC but would like a more low end extension and maybe even a little more top-end presence. So this is the next tube rolling project. But I will try these in the Callisto because of your recommendations.

Ok Art, I almost bought the SST today but now I'm not sure to buy the regular or the premium. I will wait on a report back from you here before I make the move.

John, I have some of the regular I can bring over and we can try it before you but.
John, the regular SST is good, but the Extreme SST is actually better. For me, in my system, it was worth moving to. It's certainly worth starting with J.D.'s offer to try his regular SST and then decide from there whether you want to pursue it. I'd suggest first starting with some interconnect or speaker cables: the effect will be consistent elsewhere. The Extreme just improves on that result. Here's a link to my comments about Extreme SST from a few months ago: