will
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Steve,
Weird, the noise you are getting..."hissing and roaring!"
Makes sense that it could be the higher gain increasing it, but I hope you can get to having little or no noise to amplify.
From your earlier post:
"Interestingly I thought one of the Mullard rectifier tubes was bad because there was a sound like air leaking out of a balloon that seemed consistent with one of them. But the sound mostly went away when I swapped out the input tube????"
I had a sound that may be like this, but only on initial warm up in my Torii. Can't recall exactly, but think it was sort of like a pulsing spiral, starting in a midrange frequency (along with harmonics), and spirally pretty quickly up the frequency range to nothing, it went away. I asked Steve about it, and he said it was oscillation, and from how I described it, it might be a weak connection between the input tube pins and socket connections. With difficulty, I very carefully bent the springy socket connector parts tighter, and it did not change. I can't find it in my notes, but I think it was when I replaced the electrolytic caps it went away, but that job meant re-soldering one or both sides of many power supply bypasses too, so I was not sure what was the exact culprit, but it was in the power supply if I am remembering correctly.
Since yours got better changing the input, if it is oscillation from a weak connection, but you still have quieter noise...this makes me wonder if the new input is connecting better, but not fully. Maybe check the pins and carefully straighten them if needed? If not that, if you feel comfortable with this idea, the top of the input tube on a CSP3 stays pretty cool. I wonder if you could very gently grab the tube while the CSP3 is playing, a thin piece of cotton rag to protect your fingers and tube, supple enough to feel the tube well… Holding the input tube perfectly upright, then very gently and briefly "twist" the tube just a touch in the socket, hoping to slightly increase pressure between the tube pins and one side of the socket connectors. If a pin or two are not fully tight, this might create a more complete connection. Then, if the noise gets better, it would seem the tube socket connectors need tightening.
Alternate thoughts:
Beside trying different ICs, I wonder about plugging the CSP3 output into a different pair of Allnic RCA inputs just to rule that possibility out.
Do all RCA connections feel tight?
Did you try removing the CSP3 altogether, running your source directly to the same Allnic inputs you had the CSP3 plugged into? Turning the Allnic way up might reveal issues with the source or that particular set of ICs.
If still noisy, maybe try different Allnic input RCAs, still no CSP3...
If you have verified good ICs and connections, it also might be interesting to take the Allnic out of the chain altogether, only connecting the source through the CSP3 and see what happens.
If you can't sort it out, then I would call Steve.
I think the Siemens and Sophia will be good tests and possible solutions. And if you commit to the CSP3, having a nice range of tubes to play with can be fun. With several quality and sonically varied tubes for each tube position, you may find you can use all, or most of your tubes to make up varied and beautiful tube sets. I really enjoy different tube sets every so often as a means to change up how I experience the music, variations of the beauty waking up my listening.
Tubes are big time for CSP3 tuning, but if you get things good for your system, the 25th mods will take it all deeper. If you call Steve about the noise, or just to find out about mods, it will be interesting to find out what makes up the standard mod set, and what "extras" he thinks might help. If you have not talked with Steve before, you will find he is very helpful, with a real desire to help us get good sound.
But back to tubes.
If after testing to resolve noise, you are still experiencing too much darkness/bass emphasis, I think the Siemens may well shift that, Siemens generally being notably clean and solid tubes. Then it will depend how much thickness/density was from your input, the outputs, or rectifier. Or was it just too many strong/warm Mullards. Though I ran all Mullards in my CSP3 for a very long time, the input was a PCC88, outputs were parasol getter E88CC, and the rectifier, a GZ32. So my input and rectifier were both lower key than those in your set. A milder tube in one or more positions could open things up nicely...perhaps a worthy experiment.
I just put in a used pair of Sophia 274B with "less than 350 hours." I am not sure they had that much, as they seem to be opening up as I listen.
First impressions in the Torii, all things set the same, the Sophia 274Bs replacing Telefunken RGN1064s, the Sophia weighs toward the bottom in balance. Notably bigger and warmer, it still offers quality detail, spacial information and definition mids down, making it an interesting tube. A more intense signal, low down clarity causes bass-to-midrange spacial and textural information to read warmly but well. More euphonic than veiled, the bass/warm emphasis shifts the balance, but does not veil the sound like many “warm” tubes. But...with no adjustments, it does off-balance the top. Very fine detail and top harmonic information is present, but the low end proportionally overwhelms the top end information some, leaving the tube less neutral and completely transparent than I prefer. Putting more energy low down, and less high up, midrange ambience takes more sonic space, I think part of the sweet euphonic quality. It is not quite sugary, but full and a little dreamy. Personally I miss some high range spaciousness and harmonics, the warmth overpowering this part of the presentation a bit much for me, but I find it a compelling tube!
This leads me to tuning with pre and amp gain balancing.
Not only a good test for the noise issue, since you find the Allnic pretty transparent, I think a good way to optimize the CSP3 as an addition might be to pull the Allnic from the signal path, and focus on optimizing the CSP3 on its own. If you have an attenuator on your amp and can use it for volume rather than the CSP3, you could adjust the CSP3 tubes and gain pots only for the best spectral balance, dynamic balance, complexity and lucidity. This might be informative, while optimizing the CSP potential in the mix.
Then, by adding the Allnic back in, still using your amp for volume rather than the Allnic, I would try to balance Allnic gain to match and compliment the optimized CSP3. This shifts the pre emphasis to source improvement more than amplification, and may or may not make you want to adjust how you use your gains. Either way though, this could be an informative exercise.
My pre stage attenuators adjust much more than just volume, making them less than ideal volume adjusters for me. More importantly for me, they adjust source signal voltage, which adjusts tone, drive, dynamics, clarity, etc. If we use a pre stage that notably adjusts signal voltage into the amp, as a volume, we are also adjusting tone, power and dynamics. Whereas, the amps I have had reveal source much more neutrally throughout the gain range, making their volume a notably more consistent sonic foundation.
My DAC is supposed to have a very transparent pre/gain stage, but I find it to create a slight veil so I leave it wide open...
All in all, this led me to using the CSP3 for adjusting the quality of the music more than volume. With a fairly narrow gain range that is optimized for over-all best system sound, moving the master up or down a bit fine-tunes focus, lucidity, bass, weight, etc...things that can be easily increased or decreased with signal voltage changes, and used to refine varied recording qualities.
My ZBIT is similar in effect, but only has a gain adjustment, yet I definitely find a given attenuator range on it best for my overall sound also. Then I can use one or both for tuning recordings, using their individual characters to improve each other. Your CSP3 also a bit more colored, and Allnic more notably uncolored, might work well together in similar ways….perhaps worth some experimenting anyway.
This brings me back to the Sophia. Since its character was a bit intense, colored, and demanding for my desired balance, I started playing around with gain balancing. At some point, finding I was consistently keeping the output tube pots on the CSP3 the same, only adjusting the input pots, I measured the resistance of the output tube pots where I liked them, and replaced the pots with quality resistors, doing roughly the same attenuation, but with improved transparency. So I have only the input pots and master.
More recently I replaced the CSP3 input tube pots with some small Chinese-made attenuators with surface mounted resistors. Though I had to "finesse" these into the small space of the old carbon pots, increasing plate hole sizes just so, they fit. When I had tried them in the output position before, I found them too brittle and lacking in nuance. But with the current, slightly warmer state of modifications, and in the input position, they are really nice...more revealing, fast, and articulate. Interestingly, this change showed I was getting some noise from the old carbon pots. Also, the new attenuators somehow allow greater voltage applied to the signal with less tendency to distortion. So I am still finding the new potential.
Anyway, with the Sophias tendency to overly strong bass, warmth and euphonic qualities (as my system was set up) ... I would normally lower the CSP3 some to lean down the bass and open mids. But I found that by raising the CSP3 input pot gains two notches (Like going from 8-9 on the stock pots), with this particular tube, running the tubes higher created more articulation throughout, including bass, and without becoming too intense. But still with a too deep bottom, then lowering the CSP3 master pot, the bass having tightened, it became less deep. Raising the gain on my ZBIT typically makes the signal stronger fairly neutrally, too high generally just being too intense across the spectrum most times. And with the Sophia, more was better....raising it from about 3 o'clock to about 4 o'clock, the increase in signal power further increased articulation, and without getting too bassy or intense in the mids. The combination tightened and reduced bass depth, cleaned and defined mids and highs, and increased speed and space... This tube has a lot of gain adjustment latitude it seems, and now, with a balance I really like. I still need to work on it for my needs, but is very nice.
The Sophia 274Bs, though a bit warmer and more euphonic, are now quite similar across the spectrum to the late 30's Telefunken rectifiers I have been using for a few years. I have to get to know them better, but sweet and smooth, in some ways they seem better, and some a little worse. But this test illustrated to me that there is always something to learn with the lively nature of tubes, and the power of gain adjustments. Now the Sophia is becoming a tube I would like to explore further.
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