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I'm starting the tube rolling adventure tonite, but I have one question. You suggested I try 7308s in the 6922 position.....well I can't find a 6922 in mine??? Do I have a different version than you?
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Follow Ups:
...I found the 6922s hidden back there! So far I've got NOS Black Glass Tung-Sol 6sn7GTs, (4) Mullard 12ax7s in the rear positions, and (2) Amperex 7308s in.I have a few random pairs (not quads) of nice NOS 12ax7s laying around, but I wasn't sure which two you were talking about when you said:
"The next 2 - the one on the right is in the signal path, the other is a current source.
Ditto for the 2 12AX7's closest to the front panel."
Are you saying I could change just the tubes on the right (of the pairs) with some decent NOS and get good results (or do I need more matched quads)??
Also, I have some nice Siemens EL34s laying around, but can't find them. I'm assuming they would work well in the PS, but you like the KT66s better it seems...
The 12AX7's in the Io are in pairs (in each channel).V1 & V2 both carry the signal and are critical to getting the right sound. Low noise, low microphonics and matched pairs (for left and right channel) pay off.
The next 2 12AX7's (toward the front panel of the phono stage) are V3 & V4. With the front panel towards you, the tube on the right carries the signal and is thus more critical to have better tubes.
The 3rd set of 12AX7s is closest to the front panel. In my Io, they are not side by side due to the volume controls pots. However, like the 2nd pair, it is the 12AX7 on the right hand side to get the best tube in to.
For the power supply, the biggest difference there is to replace the EL-34's with KT-66. The bass will amaze you. The dynamics will dazzle you. The phono stage will then sing.
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Hi,Are we talking the Io?....then 6922 could be ECC88, E88CC, 6DJ8, 7308. For all intents and purposes these are the same but there are differences in current draw/capabilities that should not pose a problem in the Io.
Good luck. I tried an amperex 6922 PQ USN tube with good results in that position.
i'll second that emotion
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Yes AJ, the Io is what I'm talking about....found the 6922s I was looking for and got those changed out! Do you have experience tube rolling in the Io as well (see my follow-up post entitled: Duh...)?
Hi,I have tube rolled in the Io...and continue to do so. I'm currently running the recommendations of Albert Porter who posts on Audiogon.
I've got RCA Mullard XF2 El34's in the power supply and RCA blackplate 12ax7's in the power supply as well. I use two supplies.
The front end tubes are low noise Telefunken ECC83s followed by the amperex PQ6922 red base 5692(6sn7) I've also tried Hytrons in here aswell as Brimars. The balance of the 12ax7's are telefunkens too.
From Albert Porter on Audiogon:
I have used the Io for some time, and was the first to implement the dual power supplies. I have now done this with the Callisto as well. The Callisto is the matching preamp from Aesthetix. On tubes, I started with stock and after some break in, decided to change critical positions to improve the sound. The first four 12AX7 tubes (near the input jacks) are VERY critical, and any noise or microphonics in that position are going to make your life miserable. If you get professional help with any tube selection at all, make it these four. Other tubes that make a big difference is to replace the two Sovtek 6SN7 with the RCA 5692. The old military red base 5692 is the best, but the black plate RCA 6SN7 is a great choice as well. The Sovtek 6922 tubes used in the output of the Io are so bad, that almost any brand is better. I like the Telefunken 6DJ8, the Mullard 6922 white dot, and Amperex 7308 all nearly equal. The sound of these three sets of tubes is radically different, and the correct choice is in the ears of the beholder. The Sovtek 12AX7 tubes used in the outboard power supply, while audible, are not a good place to begin. Going to something extreme like the Telefunken 12AX7 ( as I have ) will be audible, however everything else needs to be at the limit, for this to pay off. Changing the EL34 tubes right beside the 12AX7's (still speaking of power supply) have a large effect on the sound. The two best are the MO Valve KT66 and the Mullard EL34. I have tried almost every tube that will plug in that socket, and these two are by far the best. To respond to the question of reliability, I run my Io 24 hours a day, NEVER turning it off. I pulled the Telefunken 12AX7 and MO Valve KT66 tubes from the two power supplies, and tested them against the recorded numbers from the year before. The loss in trans conductance was only about 12%. At this rate, the power supplies should run 24 / 7 for about 4 or 5 years. Upon testing the main unit, the numbers showed the 5692 (replacement for 6SN7) at about 15% loss in the first year, and the Mullard 6922 white dots (only about 6 months old now) show no loss at all. The main problem with this unit is the fact that ALL the gain is with 9 pin miniature tubes. There are no MOSfets or transistors at all to do this amplification. To make matters more volatile, the circuit uses NO feedback and is run with extremely high gain. This unit will take the .5 MV signal from a moving coil cartridge, and drive 40 feet of interconnect to amps requiring 5 volts peak to peak input signal. There is not another product requiring so much from the first few tubes in a step up stage. This simply means that some people are going to have terrible luck with plugging in tubes (especially UNTESTED) and others will have no problem at all. I think this unit fares pretty well as far as maintenance, but with the small signals from your phono cartridge being magnified with microscope like gain, care must be taken. If you have a problem or make a mistake, it will show up. The good news is that if this phono amplifier is set up correctly, it is without question the best product of it's type I have ever heard. The nearest competitor was the Magnum Opus phono from EASE. The EASE was the evolved version of the Counterpoint SA9, both units designed and manufactured by Mike Elliott. If the SA9 or Magnum Opus phono were still made today, I would tell anyone wanting zero hassle with front end tubes to give these units a listen. They are not as magic, silky or dynamic, because the first stage is a FET, but that FET resolves all the issues I spoke of concerning finding perfect tubes for the first stage. I hope this helps explain what and why and hopefully will allow others to make a decision you can live with. I would be pleased to offer suggestions as to which tubes, if a description of the current system sound is given, and a goal as to what you wish you could change about the sound and tonal balance.
Albertporter 02-01-01Hope this helps. I believe the manual does describe the function of each tube. Often current sources or cathode followers "should" have little impact on the sound. You'll go crazy with this! I did for months and just sit back and relax now. Audiogon has some good threads on the Io you should have a look.. good luck!!!
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