Dear Sbrown, Was just passing by and saw this old thread. With regard to your chosen tube complement, just be certain that the "second gain stage" does not lie within the RIAA network, because the electrical characteristics of the 5751 are not identical to those of the 12AX7. Thus using a 5751 would alter your RIAA correction. (But perhaps this has had a sonically pleasing result, by chance.)
Aesthetix can tell you whether this is an "acceptable" tube substitution. |
When I first started to play around with the Rhea, I liked the all Telefunken route. It was good enough to convince me that I needed an IO which I did purchase.
I did find another tube set I like better and it's cheaper to boot. In the first gain stage (v1 & v2), NOS EI's from vintage tube service. In the second gain stage, GE black plate 5751's and for V5, a Telefunken 6DJ8. |
After several testing sessions I would also like to share a solution I am very happy with. Minimum noise, excellent transparency while keeping a full bodied sound with huge soundstage:
Single Ended stages (2): Telefunken ECC83 smooth plate
Phase converter stage and amp stage before 6922 (2): Telefunken ECC 83 ribbed plate
Buffer: Siemens ECC88 gold pin. |
Just wanted to share the tube compliment I came up with. DEAD quiet, nice sparkle on the top, holographic soundstage and very nice air around the instruments.
V1,V2 & V3 - Sylvania 12AX7
V4 - Brimar 12AX7
V5 - Amperex 6922/6DJ8 (1961)
All NOS, matched pairs. Took a few months but worth the challenge. |
Stew
Thanks for the information. I appreciate it. |
Foo:
Its been awhile, but to the best of my recollection I replaced V1,2,3,4 with Telefunkens (12ax7) & V5,6 with Siemens (6922). Noise floor dropped considerably and sound was much warmer and more natural. A worthwhile upgrade in my opinion. |
Hi, I have been watching the drama unfold from the sidelines. I am considering a purchase of the Rhea and this is of great interest.
I have a question for Stew...
In the end, what did you end up with in your Rhea after swapping the tubes? If possible a list of the replacement tubes in each position would be extremely helpful.
Thanks in advance
Foo |
Thanks, Stew. I was contemplating a cartridge upgrade but I might do this first instead. Probably a cheaper tweak than a cartridge. |
No, Dan. The first thing I swapped out was the 12AX7LPs which are at the first gain stage (V1 & V2 in each channel). The improvement in soundstaging and three dimensional layering was nothing short of spectacular. The swap did not, however, kill the tube rush. Next I swapped out the Sovtek 12AX7WBs for EH 12AX7 gold pins. Perhaps slightly warmer sound, but still no improvement in tube noise. The last tubes to go were the Sovtek 6922s in favor of the Siemens 7308s. Thats where I lowered the noise floor considerably. I can now listen virtually as loud as I dare and tube noise, although still present, is not audible from the listening position and that is at two gain settings higher. |
Stew3859,
So did you only replace the 6922's? |
Glad to hear this, Stew! Congratulations on finding a solution, and thanks for sharing the results. |
Rushton:
I am pleased to report that I have lowered the noise floor significantly by replacing the stock Sovtek 6922s with Siemens 7308s. I was able to raise the gain setting from 50 to 62 on the Rhea, which is a two-step jump and at this higher setting I can now listen virtually as loud as I dare to without hearing any tube noise from the sitting position. The ringing is gone as well. Before receiving the Siemens I had swapped out the Sovteks with a second set of Sovteks I had in an old Audible Illusions Modulus and the noise was still present. So I'm quite certain the Siemens are responsible for the improvement. The 6922s in the Rhea operate as an output buffer. I encourage all Rhea users to try a vintage NOS 6922 or a 7308 in lieu of the stock Sovtek if you are experiencing excessive tube noise as I was. I am very happy at this moment. |
Stew, imo you're not going to get it quieter by replacing the stock tubes. This is particularly true of the 12AX7s, and most particularly true of the first gain stage. Jim White has gotten the "low noise" issue pretty well nailed with his selected stock tubes. You WILL change the sonic character of the Rhea by swapping the various tubes, but you won't make it quieter in the process (except to eliminate the ringing if that's an intermittant tube problem).
FWIW, I've spent the past two weeks swapping vintage tubes into my Aesthetix Io and listening to the result. Tonight I pulled all of them and went back to all stock. The sound changed with each change of tube, but not for the better overall in complex orchestral music. I may play with this again later and change my mind, but with our local audio group coming to my house this weekend for a listening session, I wasn't about to leave the system with the sound I'd gotten thus far. And, clearly, others have had different experiences.
. |
OK, the Telefunkens arrived today. Now mind you, the Rhea has been consistently quiet so it came as no surprise that I did not hear the ringing which I had been hearing when the Telefunkens went in. What I'm a little disappointed with is the fact that in terms of tube rush, I do not find the Telefunkens any quieter. At a certain volume level, which I consider moderate, at the listening position, I can hear the rush of air coming from the speakers. Its not a ringing and I accept this noise as being entirely normal. I never thought tubes would be silent or even whisper quiet, but I did think from all I read and heard that the Telefunkens would be quieter. Not so. I understand that Jim White hand selects the Sovtek 12AX7s he puts into the Rhea for low noise so either he does a very good job, or the design of the Rhea is just a high gain unit which is prone to a fair amount of tube rush. Anyway, my question is this: I replaced the 4 12ax7s in the first input gain stage. I'm still aclimating myself to the Telefunkens, and at most I hear a slight warm and bloom in the midband. Rhea tube complement (each channel) is V1 & V2 (12AX7LP—factory graded low noise), V3 & V4 (12AX7WB) and V5 (6922). Do you think I can get the unit to run quieter by swaping out the 12ax7WBs or the 6922. The folks at Musical Surroundings which distributes the Rhea said some people have had good luck with GE 5751s. I'm wondering if I go with 5751s in V1 & V2 and the Telefunkens in V4 & V5, do you think it will lower the noise floor. Should I swap the Sovtek 6922 with a Telefunken or Mullard 6DJ8? Any ideas where to go from here in terms of improving the performance of the Rhea be it to have it run quieter or richer? Thanks. |
Patrickamory, I had earlier spoke with Jim White about the power regenerator and he simply suggested I try listening to the unit plugged directly into the wall because of the size of the transformer. I do not have it plugged into one of the regenerated ports and, in any event, I tried to go directly into the wall, but it did not solve the problem. Also, the Rear Projection TV does not seem to have any effect on the unit. The other night when I had friends over, the TV stayed off. I intend I calling Jim White if the replacement tubes don't do the trick. |
Some time ago I had a problem with a socalled "dimmer" from a strong light in my living room.
Depending how "close" it was, the more hum and buzz I had. |
Also... I don't know what an RPTV is, but if it's a TV, that could be causing tube interference too if it's turned on?
Patrick |
I wouldn't assume the power regenerator eliminates the possibility of interference from some other electrical equipment. If I were you, I'd still explore the possibility.
I agree it seems unlikely, but it is possible that some component within the Rhea is failing and causing intermittant problems (e.g., some component within the power regulation circuitry). If replacing the tubes does not resolve this, I'd recommend contacting Jim White at Aesthetix directly to see if he has any ideas.
. |
Stew,
What does the manual say about plugging into a power regenerator? I know that the Io manual specifically warns against plugging into any kind of AC conditioner or regenerator and says to plug directly into the wall.
May not be true for the Rhea, but it's a thought. |
I have the Rhea plugged into a PS Audio P500 power regenerator, as I do virtually all of my components. I tried going directly into the wall receptacle, but that did not kill the noise either. I guess the Rhea, which is my only piece of tube equipment, might be more susceptible than the others to RF, but I have my RPTV plugged into the P500 and it plays fine. Hopefully the tubes come tommorow and we will know more. If its any help, the ringing when it comes is present even when I switch inputs, gain settings, load settings, mute, and when I power up/down the unit. Would you agree with me, since the unit performs flawlessly on certain nights, like tonight, it is something external to the unit itself? |
Stew, I don't have an answer for you. Could be you're getting some sort of power line interference or RF interference. That would account for the intermittance and for hearing it simultaneously in both channels. The interference could be coming from some other appliance running, such as a furnace motor or freezer compressor. One way to check that would be to start turning off circuit breakers the next time you have an occurrence of the ringing.
. |
Rushton, still don't have the new tubes but perhaps you can explain why I would be getting ringing in both channels on some days but not others. For example, last night I had a few friends over to listen to the system. Of course, the ringing was present when I turned the system on and stayed all night without abating. Tonight I'm alone and I turn on the system and other than the usual tube rush one might expect to hear, all is quiet. The night before last quiet too. Like you say, the only way we'll know if its the tubes is to swap 'em out. At the moment, I only plan to swap out the 12AX7s in the first gain stage. Any reason to think these might not be the culprits? This is just too strange. |
Sounds like a tube (or tubes), Stew. Only way to know is to swap 'em and see. Let us know how you make out once you change them.
. |
The intermittent noise I've been hearing I think might best be described as tube "ringing", a high pitched microphonic whistlelike sound. I thought I had the noise licked, but it resurfaced today. It can only be heard at moderate to high volumes. I'm expecting 4 NOS Telefunken 12AX7s this week so I hoping that will wipe out the problem. Any ideas gentlemen? |
Hi Thomas, thanks for sharing your similar experience. It could also be that there was some break in occurring in the tube sockets. I've heard of this happening with a new unit where the connection of the sockets and the tube pins needed some burn in time.
. |
"Hi Stew, glad to hear the hissing sound was not present last night. In my experience, tube noise can be intermittent - from one listening session to another. It can be a little unnerving. I've made a practice of taking a deep breath, powering down the system, and coming back a few hours later or the next day. Sometimes the noise completely disappears, sometimes not. I once lived with a really irritating noise in a driver stage tube of my amplifier for a couple of weeks, then it completely disappeared and never came back. What you're hearing is more likely an intermittent problem with a tube than a problem with the unit itself."
I had the same experience with my Callisto.
From the beginning I had a noise ( hiss ), but after some hours of tube burning it went away ( after a few days of use. Possible, that one or the other tube can be very sensitive at the beginning.)
Later I ordered NOS tubes and these worked fine from the very first moment. |
I had what might be a similar situation with my Rhea. From time to time I would hear a short duration hissing or rushing sound, but only from the right side. Of course my first reaction was to suspect tubes. During one night of experimentation I changed from XLO to Quatro-fil interconnects between my Rhea and pre just to see how this might change the sound from my turntable. I have not heard the noise since and it has been almost a month. Kind of interesting but probably not what you're experiencing.
I do have some Mullards on my list of tweaks to buy in the coming year. |
Hi Stew, glad to hear the hissing sound was not present last night. In my experience, tube noise can be intermittent - from one listening session to another. It can be a little unnerving. I've made a practice of taking a deep breath, powering down the system, and coming back a few hours later or the next day. Sometimes the noise completely disappears, sometimes not. I once lived with a really irritating noise in a driver stage tube of my amplifier for a couple of weeks, then it completely disappeared and never came back. What you're hearing is more likely an intermittent problem with a tube than a problem with the unit itself. Good luck, I'll be interested to hear how your journey progresses. "...since I can't imagine a tube going bad then miraculously repairing itself." And, funny thing here... The system is sounding better late last night and again tonight with the Telefunken 12ax7s still in place. Maybe the 15 hours of playing time leading up to a "critical" comparison listen was not enough break in and the additional 10-12 hours is making a difference for the better. We'll keep an open mind and see how things play out. . |
Rushton:
Thanks for your thoughtful and detailed response. Oddly enough, the noise I was hearing was not present last evening. I would not think this so strange, except the hissing sound was heard on at least three consecutive days before that. I'm almost scared to go home tonight and see whether it has emerged again. Of course, the noise did not go away before I ordered a quad of Telefunken 12AX7s off ebay. I haven't decided whether I'll swap them out as soon as I receive them or if I'll wait for the problem to present itself again. I'm beginning to wonder whether the problem is with the unit and not the tubes, since I can't imagine a tube going bad then miraculously repairing itself. I did not listen for very long last night, so the problem may be heat or thermal sensitive. I should have a chance this evening to give the Rhea a decent workout. I am curious to see what change the Telefunkens will bring. BTW, the people at Musical Surroundings wrote back to me indicating that some people have had good results replacing the 12AX7LPs with GE 5751s. Might try that if the Teles don't do the trick. Anyway, I'll keep you "posted". |
Stew, if your Rhea is less than a year old, check with Aesthetix about replacements. They guarantee the tubes for a year. The first gain stage will be the place to first hear some noise as the tubes age. These first gain stage tubes are very critical given the extremely high gain being delivered by this phono stage, and the stock tubes for these positions are hand selected at Aesthetix for low noise. If you decide to try vintage tubes for the first gain stage, be sure to get some help from one of the better dealers who can match for very low noise, like Andy Bouwman at Vintage Tube Services. I own an Aesthetix Io Signature and have been running it with stock tubes for the past four years. Many people suggest Telefunkens for the 12ax7s in the Io, and I suspect the same would apply to the Rhea given the similarity of the circuits. Others have liked the French Mazda long plate tubes. Both are fairly expensive. Just last week, I finally tried rolling the 12ax7s in the Io's second and third gain stages, just to see what a set of Telefunkens would sound like there. I'd used Telefunkens in a previous phono stage and liked them there. So far with the Io, the jury is still out: mostly a negative change for me in terms of resolution, transient response and tonal balance. I'll additionally try changing out some of the other tubes (a 6922 and a 6sn7) before taking out the Telefunkens, but at this point I don't have nearly the great sound quality that I did have with the stock tubes. One truism about rolling tubes: you WILL get a different sound. May be improved sound, may not be. And I still want to experiment with the vintage tubes because I believe some combination of vintage tubes is highly likely to sound better than many of the current manufacture tubes, as described once again by Albert Porter in a recent post on the cost of NOS tubes. . |
