will
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Hey Lon,
Your using different tubes elsewhere to better bring out ZRock2 tubes is always interesting. I like how you push balancing boundaries, like using a relatively powerful and warm tube in the ZRock2, and compensating with the least powerful OD3 voltage regulators, in your monos.
Having used OB3s forever in my Toriis, but using more powerful/fuller 6SN7s after years of Mullard E88CCs as CSP3 outputs, I switched to 40s Hytron OC3s in the Torii. This reduction of VR voltage counter-balanced the 6SN7 fullness and intensity enough to keep things open with good spectral balance. Then, adding signal intensity and density with the ZRock2, I went back to the E88CCs, the 6SN7s too strong for me then, but the milder OC3s remaining a nice balancer for the additional gain of the ZRock2 as a third pre stage.
Based on your telling me about OD3 revelations in another conversation, I have been trying some, first Darios. In my system they opened the inner detail and space beautifully, with a tight bass, but the detail complexity and presence was actually too strong with the tube compliment I was using, and the dynamics became a little too light. This was using a GE 3-mica JG-6829 in the ZRock2, contributing to musical dynamics, space, detail and bass before the OD3 Darios. So it made some sense that these refined and open OD3s went too far with fine detail and space even for me. Then on your suggestion, trying some warmer and smoother Tungsol OD3Ws and old RCA OD3s, the space/detail balance was good, while somehow also evening up the dynamics some...pointing once again to the context of the individual tubes used, and how they balance with others, being all important.
Related, looking at ZRock2 tubes only, I find them amazingly big players in warm/full versus an open/fine detailed equation. Since by-design the ZRock2 can have a strong effect on EQ and gain... potentially creating a very different tube sound from the same tube depending on the gain levels....talk about wildcards for comparisons. So aside from the effects from mods or not, tube combinations, and all the other choices in a system, it seems particularly tricky to compare ZRock2 tubes without some pretty good context.
When you first mentioned OD3s in your monos helping, I think you had 6414s in the ZRock2. Similar in sound and gain as the 6829 I was using with my OD3 tests, I generally find 6414 a warmer/fuller, slightly more euphonic tube than the 6829s at the relatively low-key ZRock gains I use. So I am thinking just the different characters of these electronically and sonically similar ZRock2 tubes could cause a preference for OD3s over OC3s. Added to that, your ZRock2 gain preference being higher than mine (me wanting relative transparency with a slight bass boost, and you wanting more bass enhancement and a notable treble cut), gain preferences could also be enough to give us different preferences for OD3s (or other milder tubes) in our amps.
But the fundamentals of a given tube sound still hold for me, so I think recommendations are very useful, especially if we include comparative qualities of tubes in comparison to others, making it more possible to imagine the tube tendencies in our specific context. To me, OD3s are pretty extreme since I have already toned my tubes back over time. So your loving them implied (to me) something else was amping up and warming the signal, making the open VR a good balancer. Assumptions, but still some conceptual context for helping me utilize your system balancing and tube decisions here. But even with our tonal preferences being pretty different, we still often arrive at liking a lot of the same tubes. I wonder...does this indicate that we have both reached a relatively "neutral/accurate" balance, and though yours weighs toward full bass and away from treble, and mine away from bass fullness and into very fine detail and space, the same quality tubes might be doing very similar things in both settings even though the baseline balance is different???
A little confusing to both of us, knowing OA3s put more voltage to the tubes that follow, and OD3s the least (with OB3 and OC3 between), and with more voltage, the following tubes do all they do more, bass to highs..... your finding OD3s to have better bass than 0C3s didn't make sense to us. Conceptually, the OD3 putting out less voltage would create a leaner and more open sound throughout the spectrum than the OC3. And here, OC3s acting more as expected, bigger than OD3, this caused me to think of my years of EQ experiments used to fine-tune my system and rooms.
As I explored the sonic effects of EQ, it quickly became obvious that bass modes that create standing waves and associated thickness/muddiness, boom... are not necessarily the same in each room, being pretty specific depending on low frequency wave lengths in relation to room shape and dimensions. And I found if I could locate these unmusical frequencies, and bring them down just enough (with as narrow an EQ as would work), this lowered overall bass by reducing offensive frequencies only, but the bass feel and sound got deeper and tighter... stronger, not weaker. From attenuating muddling frequencies and leaving the rest more intact, the bass became more complete and fast, less masked by muddle, so more hit, more complex, and feeling more real.
These thoughts led me to think of VRs literally as EQ devices. And OD3's lower voltage output creating more bass presence than the more powerful OC3, it may be that the OD3s reduced the power of the tube they filter just enough more to help mitigate room modes??? I also wondered if it might be that OC3 and OD3 alter the balance of the specific tube they are filtering differently. Depending on the linearity (or not) of the input or power tube they filter/power, less or more voltage might influence some frequencies more than others with a given signal tube.
Just imagining out loud....
In the current state of my ZRock2 modifications....Steve's tube filter, upgraded and bypassed signal caps, bypassing all power caps (some with bypassed bypasses), more resolving and faster input and output cables as well as the signal cables out of the EQ board .... All in all, I am finding it pretty beautiful as things settle together. Interestingly, done last, in this relatively simple component, the internal cable changes seemed perhaps the biggest overall improvement for transparency, while also opening flow and speed nicely.....
These modifications done over a few weeks, I noticed more clearly that as things become faster and more resolving, not only do we hear everything with more nuance and clarity, I also hear more of everything! I noticed this happening as I modified the Torii, CSP3 and HR-1s, that about any part upgrade can speed up and make the signal more resolving, not least of which wires and connectors. And add a bunch together, the effects can be exponential.
A pointer to this phenomena while doing previous modifications (over several years), was that I progressively liked less forceful tubes. Then this quick ZRock2 modifications cycle clarified the developing notion that more resolution and speed lets more of what the tubes do through with more complexity, grace, and nuance, but also more signal power and flow... causing me to like milder tubes in the ZRock2 too....
So I seem to be noticing more that effective mods can not only make most tubes sound better, but by reducing more and more areas of impediment, the components can become more powerful in whatever they present... and this is clearly progressive multiplied by many modifications in many components. In time this got pretty pronounced here, describing a lot of why low level listening gets better and more complete with musical clarification, but also why we might start toning things down with tubes, etc without quite knowing why. For me, I was so enamored by power supply bypass effects, not least of which speed/dynamics, though finding limits all along the way and backing off, I think I was growing overly used to a more powerful/fast signal as I worked on several components at once. Then at some point, in retrospect, my system began to be a little too fast and dynamically intense, but sounding really great, with really nice apparent balances, this was difficult to discern. And now I think I realize that intuitively I was progressively toning back mainly on dynamics and warmth with tubes, while keeping or enhancing all the rest that comes with successful mods.
In fact, once I started getting a better handle on all this, the other day, in the Torii, I replaced some extra expressive Duelund signal caps with milder Miflex copper/oils, and strategically reduced power supply bypasses to better allow for the ZRock2 in its clarified state. These Duelunds and bypasses had definitely helped at the times they went in, but after finishing most modifications, I now think these same caps contributed to an excessively strong signal. Now, having taken out the Duelunds and making the power supply a little milder, it sounds plenty fast, and equally beautiful and complex to me, but a bit more relaxed, sweeter, and gentler on the ears.
Which leads me to an overall preference lately for milder tubes in the ZRock2. More stock, I preferred 12AT7 variants here, the bigger, more open, articulate and fast tube type causing the ZRock2 to better match the rest of my system. But after "finishing" mods, I often prefer the more relaxed 12AU7 variants more.... With pretty mellow/warmish/smooth RCA OD3s in the Torii, and an IEC/Mullard 12AU7 in the ZRock2, the sound is warm but beautifully spacious and resolving, while being more touching with its sweetly relaxed nature. Having realistic speed and fine detail complexity in notable space, it does not feel soft or weak, but is more sweet, more emotionally moving. Who knows where this will go since I sometimes like some milder 12AT7 types too, but an interesting trip so far!
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