Aesthetix Io Users Group

[Tango]

Maybe the following description of different brand of tube will be useful to all. It is written by Brent Jessee. @Ovenmitt introduced me to him. He is my reliable source. I think his description is well written giving accurate picture of different tubes.


The 6SN7 tube is a medium-mu twin triode in an octal based package, usually glass, although some metal envelope types were made. In normal use it operates as a class A amplifier. It was widely used in the early days of television as the vertical amplifier, and it's use was so common in most TV chassis designs that vintage 6SN7 tubes are still fairly easy to find today. Audio designers soon found it made a great audio preamp with it's large plates, ample power reserve, and low microphonic octal package. The GTA and GTB types, having been fine tuned for demands in television chassis vertical sweep circuits, can handle up to 7 watts maximum plate power!

The demands for these tubes today are primarily in vintage and recent design audio amplifiers and preamplifiers of the high-fidelity type, up to and including the most expensive and esoteric. It seems there is a 6SN7 tube for every taste and budget, and some of the vintage versions are being hunted to extinction, especially those made for the military. I will try to explain the differences between some of these tubes, and list specifically what I have in stock. I expect some of these tubes will skyrocket in price worldwide as more and more audio designers find out that this preamp tube is a design that really can't be improved upon....and that the fine vintage tubes just cannot (and probably will not) ever be duplicated by a current production tube.

Three envelope sizes are common in the full octal base version: SHORT, glass is 1.5 inches high; MEDIUM, glass is 1 3/4 inches high; TALL or "TALL BOY", glass is 2 inches high.

6SN7GT / G:​

This is the original version of this tube. It may be found in all three sizes of glass envelope. The Sylvania Tall Boy types have two triangular shaped plates facing each other mounted high in the tube, with either a top or bottom getter. Later GT versions were in a medium glass envelope with a green label and blackplates with bottom getter, sometimes called the "Bad Boy" 6SN7, and are sought after for their excellent sonics. The Bad Boy tubes are virtually identical to the military VT-231 from the early 1950s and are currently a less expensive alternative, but this could change as the Bad Boy fad catches on! A side note about Bad Boys, there were versions with 2 rivet holes in each plate, and versions with 3 holes. Both types sound identical. Don't fall for the bogus story that only the 3 rivet hole types are the true "Bad Boys"! You will miss out on some great sound from the 2 hole type, since the 3 hole versions are more difficult to find, more expensive elsewhere, and don't sound any different! I suspect the "3-hole only" story got started by my competition to justify charging a higher price for these tubes!
The early Sylvania GTA and GTB types had a top getter and silver flashed the entire top of the tube, sometimes called "chrome tops" or "chrome domes". Many brands used this design, but the high mounted triangular plates means it most likely was made by Sylvania. An unusual twist on this design is the "Mouse Ear" Tung Sol 6SN7GT. This medium glass envelope tube has the high mounted triangular plates like the Sylvania, but also includes two large round clear mica supports at the top edge of each plate, parallel to the glass sides, looking a bit like Mickey Mouse Ears. These Mouse Ear Tung Sol tubes sound very nice and are worth seeking out. The early RCA "GT" types were usually in either a medium or short envelope and have a grey RF shield sprayed on inside the glass. The GE and KenRad types were similar, but the inner glass coating is deep black. These tubes usually have flat black plates, like large 12AX7 blackplates. The military versions of these are the VT-231 and are in very high demand today. Two rare early types worth grabbing at any price are the nickel base Sylvania 1940s vintage, and the early Tung Sol 1940s types with the black oval shaped plates, often found in blackglass. Both are very scarce and in high demand, which has depleted new old stocks. These have excellent sonics are are worth the extra price, if you find one. Tung Sol also made the SAME oval plate blackglass type for many other brands. Don't hesitate to grab these, they are the same incredible tubes!

6SN7GTA / GTB:​

This is the later improved version, and the improvements were primarily geared toward the TV chassis designers who demanded more max. plate wattage and voltage, where vertical circuits can put up to 1500 volt pulses at 7 watts on the plates. For hi-fi audio use, these improvements are meaningless. These are fine tubes, nonetheless. Most are found in the short glass envelope, but some brands like Raytheon used the Tall Boy style. Sylvania made tubes have the triangular plates mounted lower, and set at angles to each other, although some of the very earliest examples of the GTA types still used the dull blackplates facing each other. RCA used the flat black plates "sideways" to each other, and GE used the grey plates parallel to each other. The Sylvania types in demand have a large top getter patch. The earliest Sylvania GTA types have a green label and heavy top getter flashing extending down the sides of the tube. Watch for the very rare "Tall Boy" Sylvania 6SN7GTA, one of the few tall glass tubes made by Sylvania for this tube type, said to rival the military types in sound quality. The early GTB types are similar, but most have a yellow or red label, with some rare first production run tubes still out there with the 1940s green label. Watch for these tubes, made by Sylvania for other brands like Zenith, Philco, and Motorola. They are currently bargain priced and are the same fine tube as those with the Sylvania label! The versions from the 1960s have the getter just covering the top of the tube. All of these have the same black triangular plates and are excellent tubes. The GE types have a side getter and large parallel grey plates, and the RCA used both bottom or side getter. Some side and bottom getter types have 2 getter patches on top, right above the plates. This often happened during the factory gettering process with 6SN7 types that did not have top getters. It is not a sign of use, as the spots are usually bright silver and visible on tubes still sealed in the box. Most other vintage USA brands you find will have been made by these three vendors, and will be one of the above variations, regardless of brand on the label. A few were made with brown micanol bases, the RCA types being very dark brown, the GE types being a lighter, marbled brown. The brown micanol bases are most often found in military tubes, as they resist heat, moisture, and fungus/mildew growth. It was not uncommon, however, for manufacturers to repackage unsold military surplus tubes in "civilian" boxes and sell them to the general public. Many audiophiles prefer either the Sylvania chrome tops, the RCA, or the GE side getter over any others, even over the military or redbase types. These are all a great bargain now, and are sure to be rare and expensive tomorrow.

6SN7W / WGT / WGTA / VT-231:​

These types indicates a military spec tube that was not made for consumer use. These usually have extra support posts on the plate structure, heavy mica spacers, and brown micanol bases for most WGT and WGTA, black for the W and VT-231. These also have the famous triangular shaped black plates for the Sylvania made. They have been ruggedized to withstand shock, the brown low loss micanol base resists mold, mildew, and fungus growth, and they can withstand heat even if used upside down. The early Sylvania 6SN7W types from the 1940s had a metal collar around the base, then later a black base. These look internally alot like the early Sylvania GTA types listed above. Sylvania made these for other brands as well, including RCA. Easy to spot as they have the triangular blackplates facing each other in a short bottle, with a very heavy chrome top flashing extending down the sides of the tube. These are RARE and worth seeking out! The VT-231 was a radar tube, and the Sylvania version looks like the "Bad Boy" civilian type. RCA made a grey glass version, Raytheon VT-231s are orange labels, and the Tung Sol VT-231 is the famous and rare round plate type. The WGT and WGTA types all had brown bases. Only the WGTA types made in the late 70s and 80s reverted back to black bases then coin or wafer bases. These are all wonderful tubes, are long lived, and sound fantastic. No wonder they are fast disappearings from the vintage market.

 

[Tango]

ECC32 and ECC33:​

A fine European version of the 6SN7GT. These don't often turn up in the USA. The few I have seen have been British and manufactured by Mullard or Brimar. This tube is usually medium glass, large, sometimes fat, full octal base, and some have a dark grey inner glass coating which hides the plates from view. I believe nearly all ECC32 tubes are cylindrical or oval plates. These are very rare, and worth seeking out. The early 1950s oval plates with brands like Cossor, Marconi, Osram, Mullard and Brimar are awesome. They are noted for their excellent sonics in audio use. Look for the early Mullard with the distinctive late 1950s brown micanol base with the "gold dust" appearance, of sparkling mica flakes in the brown matrix. Some may be labeled with either ECC33, 6SN7GT, CV1988 or a combination of these, or even made for other European brands. Some have the BVA label, and the older versions often have the date and factory codes on the bottom of the base between the pins. Be careful when buying these! Later versions were made in Russia, but still say "Great Britain" on them! The Russian tubes have a rounded glass top, and a cup or square shape solid getter. They also often have a large, very shiny black base NOT made from bakelite but from an inferior plastic. We do not carry these types in our stock.

CV1988:​

Another fine military version of the 6SN7GT, this time from Western Europe. These don't often turn up in the USA. The few I have seen have been British and manufactured by Mullard or Brimar. This tube is usually medium glass, dark brown full octal base, and has a dark grey inner glass coating which hides the plates from view. I suspect these are cylindrical plates, as most of the European 6SN7 varieties have been this type. Sometimes Brimar from the Footscray, UK factory turn up. Mostly clearglass with flattened oval plates at angles high in the glass. These are rare, and worth seeking out. Not only do they sound as good as the best industrial 5692, but they have the higher specs of a 6SN7GTB with regards to plate current and voltage, and have the long heater life and overall ruggedness of the US military types. A winning combination!

6H8C:​

This is a rather difficult to find Russian made tube that is a direct replacement for the 6SN7. This tube can be confusing to buy for the novice, as there are several versions available. The common version has a medium glass envelope and a black plastic base, and are still in production in Russia. They are of fair to medium quality, but certainly are not worth much more than $20.00 each. I have seen these tubes sold for export to the West, labelled as 6SN7GT. THE RARE VERSION, and the one to look for is the Russian military version. This tube has a medium glass envelope, with a nickel collar around the base. It has black T-shaped plates facing each other, with small holes in the sides of the plates. There may be an "OTH" production number inked on the base, and the tube type is etched within a circle on the glass. These military tubes are rare, and are built like the Tung Sol oval plates, with spring mounted spacers at the top touching the inside glass, and heavy support rods for each plate element. These tubes have incredible air and accurate bass, kind of like what a Telefunken sounds like! They are amazingly dynamic, and at the same time delicate, and very quiet. These tubes are actually rarer than the fabeled Tung Sol oval plates, and clients have told me these sound better!

5692:​

This is the premimum commercial / "industrial" grade of 6SN7. The most famous of these are the RCA "redbase" series, with their distinctive red marbled full octal bases. These are always in the short glass envelope style, and most have four support rods joining the four corners of the top and bottom mica spacers and supporting the plate structure. These have 10,000 hour life filaments and are very resistant to shock and vibration, making them low in microphonics. The RCA versions have the "stop sign" label on the top of the tube with the number 5692 inside, and on the older tubes this was often smeared off, being printed with a chalky white paint. ALL of the redbase versions of this tube were made by RCA, regardless of the brand on the label. TungSol, GE, and Raytheon can often be found branded on the label, but RCA made them all. Other brands like CBS/Hytron and Sylvania made brownbase versions of this tube, but I suspect all were actually made by RCA, as they are identical inside. The brown and black base versions are a bargain compared to the rare red base types, and most have very similar construction and sonics. These are all really fine tubes, but have been hunted nearly to extinction. I usually only have a few in stock, but they are worth the higher cost in overall long life and great sound.

 

[Tango]

OK, SO TELL ME HOW THEY SOUND!!

A tough question if there ever was one! The best advice is to get a few types and hear for yourself the good sounds you have been missing. All of these vintage tubes are excellent, much better than the Russian or Chinese yuck that is being made today. When replacing any stock Russian, Chinese, or East Europe tube with any of these vintage NOS types, you will notice immediately that the midrange glare is gone. Gone too is that honky, boxy quality, and the tiring upper midrange screech that current production tubes are famous for. Here are some VERY GENERAL observations about some of these vintage tubes:

TELEFUNKEN, and the rare RUSSIAN 6H8C METAL BASE, NOS:These tubes are usually characterized by an impressive open "air" at the top end. The soundstage is large, even in mono applications these tubes have a great 3-D image. The midrange is ruler flat, and the bass is tight and accurate. These tubes have a fine sense of dynamics, and most are impressively quiet. These are not "warm" tubes, and to some ears their lack of midrange warmth may be heard as bright. I tend to think of them as accurate, and their clean, focused sonic image is astonishing. They are both scarce and the prices are high when found. The Russian tube must have the metal base, and has T-shape plates inside with spring supports at the top, and round holes in the sides. The black plastic base version is NOT the same and only worth a few dollars. Be careful when buying these as later versions with black bases are sometimes being passed off as the early 1980s rare versions!

AMPEREX, PHILIPS, POPE, MAZDA and other Holland/France/Belgium made NOS: These tubes are a great balance of a clean, airy top end, nice midrange warmth, and accurate bass. They are very pleasant, clean, and musical to listen to in hi-fi applications. Most often found are the military CV1988 types, and the rarer ECC33 types from the 1950s. Detailed, sweet, and very three-dimensional tubes. The rare French Mazda has the air and sparkle of the Telefunken, the touch of warmth of the Amperex, and adds a nice bit of dynamic punch to the sound.

MULLARD, COSSOR, BRIMAR, and other British made NOS: Like a warm British jacket of the finest tweed, these glorious tubes have an attractive sweet warmth in their midrange and lower regions. The top end is silky and pleasant, without being rolled-off. The best of these tubes retain a fine sense of "air" at the top, and the upper midrange is smooth and liquid. These tubes reproduce the human voice, especially female voices, with haunting realism. Found both in ECC33 and CV1988 versions, sometimes with the CV1988 types merely labeled as 6SN7GT. Very rare in the USA but a very rich sonic treat to listen to.

RCA, RAYTHEON, GE, SYLVANIA, and other USA made NOS: This group is very diverse. The Tung Sol oval plates, both made for the military and civilian use, usually get the nod as the best. They are dead quiet, accurate, detailed without being sterile, holographic sonics, and an amazing smoothness and silky depth to the sound that draws the listener deep. More often found at a lower price point, the Sylvania family of 6SN7 tubes offer a nice sparkle and air at the top, a brush of midrange warmth, and nice accurate bass. The nickel base and early "W" military types are often cited as the best, but great satisfaction can be had at a lower price from the WGT, VT231, and GT/GTA/GTB chrome dome types, whose sonics are very similar to the early military versions. The "Bad Boy" GT 2 and 3 rivet hole versions are an especially nice sounding tube for the price. The GE "side getter" is a sleeper bargain tube as it sounds great and usually all versions cost less that other USA tubes! The GE is like an Amperex: airy, light, great warmth in the mids, and a nice if rather thick bass. Finally the RCA tubes hold the fort with deep impressive bass and rich and liquid midrange tones. The top is silky. The best examples are the VT231 greyglass types, and the early GT. The famous red base 5692 types are mellow and smooth thanks to their slightly lower Gm, with a beautiful 3D soundstage. Best bargain in the RCA camp is the early GTB tubes. Same rich sonics and these are usually priced well below all other types!

 

[bonzo75]

Tang, if you want to be included that badly in this thread please get yourself an IO

 

[Tango]

Tang, if you want to be included that badly in this thread please get yourself an IO

I was just trying to be helpful for people who want to try different tubes. I thought the info give a good guideline. Tubes have their on sound regardless electronic. I put the info into this thread because they were talking tubes not because I am interested in IO.

I am interested in Mike's adventure though. That's why I follow this thread from time to time. I will go back to Shoes thread now.

 

[bonzo75]

I was just trying to be helpful for people who want to try different tubes. I thought the info give a good guideline. Tubes have their on sound regardless electronic. I put the info into this thread because they were talking tubes not because I am interested in IO.

I am interested in Mike's adventure though. That's why I follow this thread from time to time. I will go back to Shoes thread now.

If you get one and roll tubes you will be able to keep up more with Mike

 

[tima]

Every IO thread I've seen includes talk of: upgrades, repairs, break-in and mostly tubes. Like @Kcin says, with the IO it's all about the tubes. With the external power supply there is something like 24 tubes in an IO? Having used Atma-Sphere amps (19 tubes per monoblock) and A-S all-tube preamps (16 tubes) for several years, I can appreciate. If I wanted to be an IO owner, I would include the price of a good tube tester in my budget.

Fortunately? - there are only 2 6SN7s in the IO I say fortunately because top ranked quiet NOS 6NS7s from the '40's and 50's must be getting really hard to find, and pricey when you do. Ken-Rads, Sylvanias, etc. The same is true for the 6DJ8/6922/7308 family, only 2 needed in the IO?. The supply is a little better for these, but not much.

Imo,the thread on 6SN7s is here: https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/ The most knowledgeable/honest dealer for those, imo, is Andy Bowman of Vintage Tube Services . His Web pages don't always show what he currently has and suggest a phone call. For the 6DJ8 family (and probably 12AX7s), it's Brendan Biever at Tubeworld (Tubeworldexpress.com).

 

[bonzo75]

Every IO thread I've seen includes talk of: upgrades, repairs, break-in and mostly tubes. Like @Kcin says, with the IO it's all about the tubes. With the external power supply there is something like 24 tubes in an IO? Having used Atma-Sphere amps (19 tubes per monoblock) and A-S all-tube preamps (16 tubes) for several years, I can appreciate. If I wanted to be an IO owner, I would include the price of a good tube tester in my budget.

Fortunately? - there are only 2 6SN7s in the IO I say fortunately because top ranked quiet NOS 6NS7s from the '40's and 50's must be getting really hard to find, and pricey when you do. Ken-Rads, Sylvanias, etc. The same is true for the 6DJ8/6922/7308 family, only 2 needed in the IO?. The supply is a little better for these, but not much.

Imo,the thread on 6SN7s is here: https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/ The most knowledgeable/honest dealer for those, imo, is Andy Bowman of Vintage Tube Services . His Web pages don't always show what he currently has and suggest a phone call. For the 6DJ8 family (and probably 12AX7s), it's Brendan Biever at Tubeworld (Tubeworldexpress.com).

Greg of UHA tape deck was an IO dealer and tube rolling expert.

 

[Tango]

Greg of UHA tape deck was an IO dealer and tube rolling expert.

Are you trying to add value to this thread or you are itching to type something? Talk about wanting to be included badly? Look who is talking?

We both should go back to Shoe thread.

 

[tima]

One way to add value generally in a post is to include a reference or pointer to what you're talking about. Whether it is mentioning something someone said here at WBF or to 'Greg at UHA' or whatever, do your reader the courtesy of not expecting them to search for it.

 

[DasguteOhr]

You can save yourself the hunt for the Holy Grail, the ECC808 is the last evolutionary stage of an ECC 83 (developed in 1963). It is trimmed for low noise and low microphony. it has a grounded shield between the triode systems. it beats every Ecc83 / 803s on the planet. use this adapter and listen.

1PC ECC808 ECC83 ECC82 12AX7 12AU7 12AT 7 6,3 V Vakuum Rohr Verstärker Vitage DIY HIFI Audio Vacuum Tube buchse Adapter Konverter|tube diy|12at7 tubevacuum tube - AliExpress

1PC ECC808 ECC83 ECC82 12AX7 12AU7 12AT 7 6,3 V Vakuum Rohr Verstärker Vitage DIY HIFI Audio Vacuum Tube buchse Adapter Konverter,Kaufen Sie von Verkäufern aus China und aus der ganzen Welt Profitieren Sie von kostenloser Lieferung, limitiere Genießen Sie ? Kostenloser Versand weltweit! ...

de.aliexpress.com

 

[abeidrov]

I know these are not NOS tubes, but I was told that they are still better, than the stock ones: PSVane 12AX7S http://www.psvane.com/en/tseries/708.html. Do you think they are worth trying in the V1 - V6 gain stages?

Thanks in advance,
Aziz

 

[audioquest4life]

I am using Psvanes in my Octave Jubilee preamp with great results. I have not splurged on PSVanes for the Io and have not heard of anyone else, until now. I don’t see why the PSVanes won’t work. They are a decent tube.

 

[ScottB]

My adventure in Aesthetix land started with a Rhea that I bought used. Once I got it in house, I listened a bit with the stock tubes and was not impressed. The sound was dull and opaque. I changed out the 12ax7’s for Tele’s and it was better but not very good. I was going to dump it but on a whim decided to replace the Sovtek 6922’s with Tele’s. That did the trick and made the thing sing. With that sorted, I searched and found a used IO and sold the Rhea to a friend.

The IO sounded better with than the Rhea with stock tubes but still didn’t sing like it is capable of. The two key tubes are the 6922’s and the 6SN7’s – get these wrong and it won’t sound good. For me, the best I’ve heard in these positions are Tele’s for the 6922’s and Tung-sol’s for the 6SN7’s. I tried several different RCA’s and Sylvania’s but none were better than the Tung-sol’s. As for 12ax7’s, I’m all Tele’s including PS. I tried a quad of RCA’s that I got from Vintage Tube Services but they were quickly vanquished by the Tele’s. I don’t like mud haven’t heard an RCA tube that I liked. As for the EL34’s, I tried Mullard XF2’s, Genlex KT66’s and reissue Gold Lion KT77’s. They each have their strengths but have the KT77’s in the system at the moment as I like the linearity of the tube.

 

[abeidrov]

Hi, I did an IO tube rolling report in 2006 https://forum.audiogon.com/discussions/aesthetix-io-sig-tube-rolling-initial-impressions

Interesting that I still use the Sovtek LPS in the first gain stage. You are absolutely correct, no ma what tube you use, the first gain stage in the IO is the most critical for noise abatement.

Albert Porter is linked in my tube review with his listening results of NOS tubes in the IO. I have not seen many others NOS tube reviews with the IO out in the forum world.

Hi, thanks for a link to your report! This is very helpful. I am just starting my journey of IO tube rolling, so reports like yours are very valuable.

Unfortunately, the link to Albert Porter’s post is not working anymore. It somehow got deleted from Audiogon database. I found the post below by Albert. Hopefully it’s OK to quote it here:
“Responding to the request by Hungryear, a second power supply adds to the Aesthetix's sense of ease and effortlessness. There is an significant increase in both the intensity and headroom, while allowing each individual instrument ( particularly piano ) to show off all their colors and micro dynamics. This change does not appreciably alter the tonal balance, compared to the single supply. It does increase the depth of the soundstage, and with a better sense of location. This increased resolution is not the hyper variety, it does this by it untangling similar sounds, and providing a precise location within the listening space. With both my Io and Callisto running dual power supplies, this is the most dynamic and effortless presentation I have ever had. For this to make sense from a financial standpoint, all the other pieces in the system must be able to resolve this improvement. Regarding the comments by Bud and Rayhall, the 6922 Sovtek would be my first change. For additional midrange and air, try the Siemens 6922 CCa or the Amperex US Military 7308 CEP. If either of these produce too much midrange presence, try the Mullard 6922 (gold pin). Realize, that when you upgrade to one of these higher resolution NOS 6922's you are listening with more intensity to the weaknesses of the remaining (original) tubes. You are judging the replacement, plus all that it exposes downstream. If after changing to the CCa or CEP, you find that there is too much "grit" in the sound, try swapping the 6SN-7 as described in my long post. After that, if you are feeling adventuresome, trade out the first stage 12AX7 tubes (Io only). Note, these 12AX7's are the ones I warned about, get TESTED, ultra noise tubes for this position. My first choice and the most beautiful sound is the Telefunken 12AX7. Other options are the RCA 5751, a US Military version of the 12AX7. The 5751 will alter the tonal balance somewhat, as it is not an exact replacement. There will be a slight loss in gain, with improved signal to noise and lower distortion. Overall, the sound will be a bit more on the dry side. One final suggestion would be the 12AX7 French Mazda. A good sample of this will produce significant improvements in high frequency transparency, especially compared to the Sovtek. However, the Mazda has not been without problems in my experience. The samples I received are not equally reliable or equally low noise. Some will play perfectly for many months while retaining their original "voice" while other samples will develop horrible microphonics and tube noise in as little as a week. This is a situation that could lead to disappointment with the Io, when in fact, the tubes are the culprit. Unfortunately, there must be some risk and experimentation within your own system to determine what is best. All the tubes I have suggested here are expensive to buy right now and will become even more so as time goes by. You should never consider their purchase as a potential mistake. If these tubes do not work in your system now, there will come a time when they will be the perfect answer.”
There was another long post about Io tube rolling by Albert on Audiogon, I saw it quoted by another forum member, but cannot find it now. Maybe you have another link to Albert’s report?

Thank you.

 

[OGH]

From my audio log:

"When I got Io back from repair in 2017, it came with a full new tube set that I ordered from the factory.
Earlier, I had used NOS tubes in the most important positions (V1-2), but these had become noisy.
The new tube set from Aesthetix used new JJ signal tubes for positions v1-v6.
I had used Telefunken NOS in V1-2.
I quickly realised that the new JJ tubes were indeed very low noise. Plus one to Aesthetix - these were clearly selected for low noise.
Yet they weren't as musical as the Telefunkens.
So what to do.
I first reinstalled the Teles in v1-2. Living with the larger background noise. Then I got tired of it.
I invested in four Philips Herleens for v1-2, and have not looked back. Or: not so much.
The Teles may be slightly better overall, but the Herleen have a bit of "rock foot", and both are above the JJs (and Sovteks) in musicality.
So, since the Herleens are low noise (even if not quite down to the selected JJ low), I don't regret. Also, since the Teles - real low noise - are now very hard to get.
Since the Philips Herleen NOS worked well in v1-2, I also ordered Herleen 6922 in V7, and RCA NOS 6sn7 in v8 (heerlen E88CC and RCA 6SN7GTB).
These have now replaced the ones in the tube set from Aesthetix in 2017 (v7 - Electro Harmonix, v8 Russian 6HA7).
This is where the jury is out to lunch, - a rather good and extended lunch, I would say.
Does it sound better? I wish I could invite you over, to listen.
It is maybe a bit leaner and also purer than I got from the Electro Harmonix plus Russian v7-8 combo. I associate Electro H with rather limited sound, but the Russian is really a contender
from way back when, and was included in the Io tube set for a reason, I believe. However my experience with RCA output tubes are generally good, so maybe this will come to the forefront, here also.
The NOS tubes are possibly unused, and need run-in.
For reference, the tubes I try in v7 and v8 now, are Philips Herleen 6922/e88cc and Rca6sn7gtb)."

My impression from reading Albert Porter's very valuable advice, years ago, was that the best idea was to move from v1 to v2 and so on downwards (from his "long" post, not reproduced above).

First, get the Io to sing in terms of the input from the cartridge. Then, change tubes downwards in the chain. Be aware that upstream and downstream tubes tend to go together differently, some match well, some dont. So he gave quite complex advice. I don't know why, exactly, but it seems that he later changed to an Allnic phono pre.

My general impression is, even if Philips tubes from the Herleen factory aren't quite up to Telefunken standard, they are very good, and clearly above new production including Psvane, Sovtek, JJ and china (where I have tried them).

They do well in the v1-2 position - low noise, and more musical than the factory-supplied JJs.
Also, I think, in v7. I am not sure, however, if this is better than with the factory-supplied EH and russian 6ha7 in v7-v8. A bit better, clearer - maybe.

Some have associated RCA with "mud", but the impression here (v8), rather, is a more "slim" sound. I use RCA NOS in various positions, and don't agree that they generally sound muddy.

Sorry for not being more precise, but in my rack, I cannot do easy AB-testing.

 

[OGH]

Dear Io users, I have a question for you.

Is there a way to set up a fairly «objective» list of tube problems in the Io? I mean, there are a lot of tubes. How do we know, which ones are problematic, when something is wrong with the sound? I was thinking of a list with this format:

«Typical symptom -- suspected tubes» (in other words, change these, first).

But the only thing I can think of right now, which is objective beyond doubt, is:

«Symptom: background tube noise - - suspect tubes: v1 – v2.»

So for example, if I think the sound is less energetic than it should be, is there a way to know, if I should change tubes in the power supply, rather than the Io itself? Are there typical symptoms when power supply tubes should be changed?

Such a list is maybe hard to make, but it could be useful, the next time something is «off» or not quite right with the sound.

 

[abeidrov]

I’ve found that my Io is very sensitive to quality of the supplied electricity. I hear, when a ventilator is switched on and off in the bathroom or when an iPhone adapter is inserted into one of the outlets Io is powered through Shunyata Triton V2, but I want to try another power conditioner. Please, share your experience. What power conditioner works best with Io? I am thinking of trying Torus Power or PSAudio or Isotek. Maybe even Stromtank, but it’s very costly.

 

[oldvinyl]

I’ve found that my Io is very sensitive to quality of the supplied electricity. I hear, when a ventilator is switched on and off in the bathroom or when an iPhone adapter is inserted into one of the outlets Io is powered through Shunyata Triton V2, but I want to try another power conditioner. Please, share your experience. What power conditioner works best with Io? I am thinking of trying Torus Power or PSAudio or Isotek. Maybe even Stromtank, but it’s very costly.

Question: is the Io using a dedicated AC line for its power? If not, then this may be a lower cost solution. I use four 20 amp dedicated outlets for my audio gear and the sub-panel for them has two grounding rods. I also use an Audience aR12. But, the Audience is not needed to keep noise form other appliances out of the Io. When using dedicated circuits, they can be wired into the main panel so that they do not share the same AC phase as other noisy appliances.

 

[oldvinyl]

Dear Io users, I have a question for you.

Is there a way to set up a fairly «objective» list of tube problems in the Io? I mean, there are a lot of tubes. How do we know, which ones are problematic, when something is wrong with the sound? I was thinking of a list with this format:

«Typical symptom -- suspected tubes» (in other words, change these, first).

But the only thing I can think of right now, which is objective beyond doubt, is:

«Symptom: background tube noise - - suspect tubes: v1 – v2.»

So for example, if I think the sound is less energetic than it should be, is there a way to know, if I should change tubes in the power supply, rather than the Io itself? Are there typical symptoms when power supply tubes should be changed?

Such a list is maybe hard to make, but it could be useful, the next time something is «off» or not quite right with the sound.

OGH - I wish I knew such specifics! My experience has been that any tube failure can have similar symptoms.

My technique - if I recently installed a new/different tube, it is the first suspect.

After that - simple binary tree. Swap umbilicals (2 power supplies). If noise switches channels, then it is in the power supply. Swap tubes between power supplies - if noise switches channels, then it is in the power supply tube. Swap banks of tubes with good power supply. If noise follows tubes, then it is in that bank of tubes. Then switch half the tubes in the suspect back of tubes, etc. Same method for phono stage. Swap all tubes left/right channel, then swap 6SN7/6922, then swap all 12AX7s, then half of the 12AX7s etc until the culprit is found. Takes some time, but it isolates the faulty tube.