Aesthetix IO tube rolling experiment at Area 51

What a fun and tiring day; I spent the whole day conducting some tube rolling experiments with the Aesthetix IO Signature. First off, I would like to commend Jim White and company at Aesthetix for a job well done with the Io phono stages and any of their products as a matter of fact. Straight into the power and then cabling afterwards, the IO is great out of the box. Oh, the voicing and dynamic realism are to die for. My unit is almost two years old. I have been real happy with this purchase and I plan to make this my keeper phono stage until one of us departs this wonderful world.

The stock tubes in my particular Aesthetix IO unit are:

1st Gain Stage: V1/V2 Sovtek 12AX7LP
2nd Gain Stage: V3 Sovtek 12AX7WB
V4 Teslovak E83CCS
3rd Gain Stage: V5 Teslovak E83CCS
V6 Sovtek 12AX7WB

V7 Sovtek 12AX7LP
V8 Sovtek 6SN7

I planned to do a tube rolling experiment based on availability and low costs of new tubes. I first ordered some matched sets of Mullard 12AX7’ for the second and third gain stages. I also ordered Sovtek 12AX7LPS for the first gain stage and a set of EH 6922’s to replace the Sovtek 6922. I also ordered some EH 12AX7 Gold pins to try in the second and third gain stages and some 6922’s gold pins to replace the Sovteks. So basically I am going doing a shoot out of Mullard 12AX7’s vs. EH 12AX7 Gold pins vs. stock tubes and the 6922 EH vs. Sovtek 6922.

First experiment
Replace the first gain stage V1/V2 (Sovtek 12AX7LP) with new Sovtek 12AX7LPS. I also replaced the stock Sovtek 6922 with the EH 6922. I should have done this a long time ago. I no longer have any tube rush at higher volumes, and the musicality stayed the same. This was a treat and as a bonus subtle low level details became even more apparent. I cannot believe how quiet this phono amp can be, compared to what I was living with before, it is NIGHT and DAY, and I thought it was great before, just one of those idiosyncrasies I lived with before. The silence compares nicely to some solid state designs, in this way, I mean for the absolute quietness.

NOTE: After this swap, I felt the first gain stage warranted keeping the new Sovtek 12AX7LPS in that location as well as the EH 6922. I did not conduct any further tube rolling in the first gain stage; it was great with the new tubes. A big improvement over stock tubes.

Second Experiment
I placed the Mullard 12AX7’s in the second and third gain stage V3-V6. I proceeded to allow this setup to play off and on for a week and a half; about 35 hours total playing time. The Mullard 12AX7s were detailed right out of the box and I allowed them to play both in warmed up and a first start state. The Mullards pretty much sounded the same cold or warm. After a few days, about 10 hours, I started to notice consistencies with the sound; the Mullards have a definite etched character about them. My notes are: etched sound, precise, a little dry, lacking depth, wide stereo imaging, low noise, accuracy vs. musicality (had me thinking about hi-fi and not music), not natural sounding, good bass. Somewhat articulate voices and ambiance.

Third Experiment
I swapped out the Mullards for the Sovtek 12AX7 Gold pins, these were a little challenging to get in and out due to the gold coating on the pins. I put about 17 hours on these tubes. These tubes were different then the stock tubes and the Mullards in regards to a robust upper mid freq. Notes; deep bass, robust upper mids, slight increase in background noise, voices seem ok but on some music lacking euphoric overtones, good depth, etched sound/precise, somewhat dry musical presentation, good low level resolution, narrow soundstage. I can’t finger what it is I am missing here, but there is something.

Fourth Experiment
I decided to swap back in the stock tubes in the last gain stage, V5/V6 (Sovtek 12Ax7WB and Teslovak E83CCS) and left the EH 12AX7’s
In the second gain stage. This was a great combination. The tubes seemed to harmonize, despite three different vendors of tubes in the phono amp, they had some good synergy. Notes; slightly more robust upper mid, somewhat euphonic voices with more realism, very quiet, excellent low level detail, great tonality range, great detail overall, accurate bass, balanced sounding with not much emphasis in any frequency range, except the upper mid freq bump, piano exhibits excellent decay and dynamic realism, captures ambiance of recordings, very wide stereo presentation (enveloping), excellent voice separation from microphones, NOTE TO SELF: Most musical so far, toe tapping and musical involvement, you know when you know, this is music, a great combination, more emotional feeling and exciting. Hearing music and not hi-fi. I want to keep playing records all day with this setup, but I must stop to change tubes.

Fifth Experiment
I decided to mix up the tubes again, this time I swapped in the Mullard 12AX7 in the second stage, while leaving the stock tubes in the third stage and the first stage remains the Sovtek 12AX7LPS as in all of the experiments. Notes; almost the same sound as the EH12AX7’s in the second stage, little less depth, low noise, real deep bass, slightly less musical, accuracy vs. musicality (had me thinking about it again), slightly more embouchure from trumpet heard, soundstage more up front. I can hear the orchestra on the Sketches of Spain LP, but with some instruments washed out. I am missing something here too, can’t quite figure it out. I could not listen all day with this setup.

Sixth Experiment
I decided that since I was on a tube roll, haha, well, that I might as well test how the stock tubes would sound in the second and third gain stages (V3/V4/V5/V6) with just the first gain stage replaced (Sovtek 12AX7LPS). I already had a best sounding to me experiment; I was not ready for what I heard though. Notes; extremely deep bass, dynamic impact and slam, very musical, very wide stereo, excellent close microphone vocals (multiple singers), excellent low level detail, layered depth, excellent voice retrieval (unbelievably lifelike), quiet, most natural sounding timbers, excellent tonality across frequency spectrum, best piano (especially the Steinway on Patricia Barber’s 45rpm LP’s), this is THE best experiment. The piano had excellent decay and heft, a lot energy. Voices were the most euphonic, I mean they just had that sense of realism about them, you will know it when you hear it. In comparison, experiment 5 came closest to this sound, then experiment 6. I could listen all day with this setup.

I have to mention that I used a variety of music to see how these experiments would react to various types of music. I used the Miles Davis Sketches of Spain LP (Classic 200gram) to test the embouchure of the trumpet and listen for the breaths prior to blowing into the trumpet. The better I heard this in each experiment, the better I rated it in low level resolution. I used Bad Company, Ready for Love, because the LP I own is an original US pressing with outstanding timber in regards to cymbals and excellent voices, the recording is great and demonstrates again the ability to reproduce timber accurately and the resonate sound of the triangle clanging. If I can hear this sounding natural and not tinny sounding then I am almost sure that the combination is doing something good. Steve Perry (Journey lead singer), his LP has so much emotion and the ambiance is so great that if I can’t hear any signs of the ambiance or his emotional energy seems somewhat laidback then I know something is missing. A great LP to listen to and just relax; especially if you bring your spouse into the listening room with you. Patricia Barber, Nightclub (MFSL 45rpm), especially for the Steinway piano, you know when the piano just surrounds you and envelopes your listening space, you get the feel as if the piano is playing virtually in your room, I have experienced this LP without great dynamics, and believe me, this LP is real revealing of a system to playback pianos. Doobie Brothers, It keeps you running, this song demonstrates multiple microphone playback with various singers on the right, Michael McDonald is the lead singer, but as the chorus kicks in, the other singers sing along, at this point, your system should be able to discern the different singers and hear each one, there is one that on the second chorus, the voice is really euphonic and that singer is sitting slightly higher and a tad back from the other singer, it sounds great if you can hear it. I also played Sara K, (Stockfish Records), she has a very articulate voice and her guitar is very precise, again articulation in her voice and the slight sound of lips parting or breathing are signs of resolving low level details.

In closing, as I ventured to conduct these experiments, started since 0530 this morning (Germany time), it has been a fun and exciting time. I was amazed how great the IO sounded before and never really had any issues with the sound. As I swapped in the first stage tubes and then played it back, I was really in for a shock as to what was to come. I am pretty sure that Jim White and his crew conducted tests for each one of the Aesthetix products and tube matched each one; on each tube box that came with the IO, I do see each box labeled with a technical measurement for each tube. I wonder if Aesthetix is now using the Sovtek12AX7LPS in the first stage, as this made the greatest impact for me, what a silent beautiful piece of hardware this has become because of the first stage tube swap. Since it is an experiment I conducted, I will leave the stock tubes in the 2nd and 3rd stages for a little while and go back to the EH’s in the second stage to see how they compare directly. That is for another day. I feel confident that despite what people are saying about the tubes in the Aesthetix products, maybe the first gain stage is all we need to correct in order to achieve best performance before spending megabucks on tubes that you may like or not. I respect others who have conducted experiments with NOS tubes and have had great results. My feat is more or less for modern tubes and current productions. I now have a variety of tubes to experiment with at a relatively low cost. Of course the tests were conducted on my system in my listening room so your own tests may vary. I am very happy with the current configuration. I hope these experiments help others who are interested in some low cost tube rolling for Aesthetix IO products. Bottome line, the stock tubes with the tube rolled first gain stage tubes and the buffers make the IO come alive even more.

That is all, I am hitting the sack, all of this tube rolling has burned me out. Good night.

Very nice summary of your listening experiences with all the different combinations! Thank you for sharing this.
I thought my experiences would be helpful to some people. As there were so many writeups about using NOS tubes with these products, but nothing with the newer tubes I decided to investigate for myself. The tubes I used were all matched pairs, so in each gain stage the pairs were matched.

I would suggest that anyone owning the IO replace the following tubes to hear immediate improvements:

1. Sovtek 12AX7LPS (first gain stage), mine did not come with these, but the Sovtek 12AX7LP
2. Replace the Sovtek 6922 to a matched set of EH6922

These are my comments and for my system:

3. Second and third gain stage, the suprise here, was staying with the stock matched tubes in the second and third gain stages, these tubes get it right.

4. The EH 12AX7 in the second gain stage will give you some details that I feel make the system sound much more hi-fi then musical, it does sound good, but to my ears, the EH's ranked second behind the first suggestion. if you need absolute detail, then these tubes will do it. This swap was the second best sounding to me.

5. The Mullard 12AX7's, again they sounded close to the EH 12AX7's in the second gain stage, but they exhibited some differences that I would say make them third on my list.

6. Using either EH or Mullard 12AX7's in both the second and third stages, exhibited some differences that I just nitpicked, some of these combinations will sound great to other people and in other peoples systems. For me, it was a matter of losing the musical experience, especially in regards to the fine microdynamics in voices. These combinations gave the greatest amount of details and etched sounds, however, at the expense of musicality.

The tubes that came with the IO originally have all been matched and measured at Aesthetix, so I believe that is also key to allowing these products to shine. The other tubes used in the experiment were also matched. I was careful enough to keep using the same tubes in the same locations to stay consistent with the experiment.

If for any reason, I would say that replacing the first gain stages and the buffer had the greatest impact for the better. I also learned that tubes can be like cables, tone controls for your system if you will, these various combinations will sound different to someone else, because of room and system interaction.

Now it is time to get to listening to music. Again, I hope others will be able to use my writeup as a gauge of various new tube performance vs the stock tubes.

If you enjoy transparency/liquidity/lack of coloration/frequency extension/accuracy and full sound staging: Try either the Siemens or Telefunken ECC83 from the 50's-60's. In place of the 6922's: try Siemens 7308's, E188CC's or CCa's from the 60's(grey plate under the getter support-The 70's version is too bright/edgy)
Most newer gear are designed around the current offering of tubes. I'm not surprised that the newer tubes offered something that you like.

Now, I wonder what rolling a few 5751 tubes into the mix would sound like? Hmmm...
I know people keep saying that, once you do NOS you never go back..., haha. I am keeping self control over wanting to try any NOS right now, but for how long?
I own a Callisto sig. and went the NOS tube route..... I don't want to push over the edge, but it really was a HUGE difference for me, compared to some of the other "current" production tubes I tried.