Your experience is normal. Rectifiers “set the stage” for how the amp will sound. In my experience and system 5AR4’s give a richness and thickness. I prefer the 5u4 family as it has the tonal balance I like. If I wasn't running speakers with 8 15" drivers I might prefer the 5AR4's

This can be misleading! All the tubes in the amp change the sound. Currently in my Torii MKIV I’m running 60’s RCA 5U4G, Westinghouse 0A3, RCA 0c2, EH 6922 and GL KT77’s This is perfect for me and I don’t want to tube roll. A few weeks ago I had a KT77 get noisy, as I was waiting for a replacement, HK (another forum member) suggested I try the 7027A’s. I happened to have a quad that I used with a loaner ZMA I had. The 7027A’s were too lean in the current setup. I could have tried a 5AR4 to richen up the sound. It might have sounded very close to what I had with the 5U4GB and KT77 combo.  As I had a replacement KT77 on the way I waited a few days and popped the KT77’s back in.

What I suggest is get a feel for how different tube families effect the sound. Then it’s a bit of alchemy to create the sound that’s right for You, your system and room.

It then get’s even more complicated as cables can also change the sound significantly. I have a few extra power cables to help fine tune the sound along with tube rolling. In the above case where I thought the sound was too lean with the 7027A tubes, I swapped out my Cottonmouth Signature PC with the Cottonmouth Gold PC on my DAC this did end up richening up the sound a bit.

Better than the 5AR4? Others on this forum are more qualified on 5AR4’s.  I do like the new production TheTubeStore.com Preferred Series 5AR4. different tubes in the 5AR4 range will sound different. Not as dramatic as going from a 5u4 to 5AR4.

My understanding is the 5AR4 is a “softer” start than a 5u4.

The ZROCK2 also is a good tuning tool, after changing tubes in your amp revisit the ZROCK2. I like to bypass the ZROCK2 and listen for a bit after swapping tubes. I’ll then set it at 12 o’clock and listen. After a little bit I’ll slowly start spinning the magic dial, I also will back it of just a smidge after I find a position I like.

+1, absolutely rectifiers make a big difference. And what is more (at least in my UFOs, so FWIW/YMMV) they make some combinations of input/power tubes sound better than others. In other words some tube combos that sound meh with one rectifier will sound great with another, and vice versa. The combinatorics can be a little crazy making. You've been warned

Lots of info on tube-rolling on the forum as Will points out. . . and it's been my experience that the varying tubes are experienced pretty similarly in the differing amplifiers and preamps. I rolled rectifiers a lot but I really am addicted to the Aqua 274B and I find that I roll regulator tubes for the output tubes more often now, mostly between three different pairs of 0C3 that I have, each having quite a pronounced effect on the sonic nature of the amplifiers.

It can be a maddening endeavor at times so I don't recommend embarking on it until you have quite an experience with the basic sound of the stock tubes and how they present the signature of the amplifier. And then taking baby steps and stand in that spot for a time to get acclimated.

These amps Steve designs and builds are so revealing and so expressive. . . everything eventually matters and you can spend periods on and off exploring and enjoying. Heirloom material!

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I think the short answer is all bets are off until the speakers are fully broken in. Once you have a hundred or more hours on them then reevaluate.

I think that's a great question - why are Jazz/Vocals sounding so incredible and Rock/Reggae etc not as grand.

I think it has to do with bass response? I get the sense that when music has a lot of mids and treble, everything shines. When the music is "thicker", more complex? is where it's falling short to my ears.

The system is sounding better as time goes by - I still think it shines in mid to upper and wish they were a bit more fuller with bass but this may be changing as I put more time on them - obviously time will tell.

I haven't kept track but I don't think I have more than 50 hours or so. Some people are saying I need 100 hours or more - I'll have to wait and see. Using the Zrock2 has helped tremendously, I have the control dialed almost all the way up. This may be a case where I just need to be patient and let the speakers break in more. I find myself listening to genres that let the system shine more than R&R but am hopeful this will change.

Thanks to all for your thoughts and help.

Stay safe!

Warm regards

I agree, time will tell, and it might take 100 or so hours to start to more fully hear your speakers, and more to hear your amp potential more fully. Perhaps around three hundred the speakers will have reached a nice stride, and your amp burnin probably long enough to be evening up and resolving more sonic potentials, making everything better. Especially bass seems more obviously unresolved during burnin in general, and I have even had some power tubes need 200-300 to resolve more fully, especially the bass!

But patience with softer, less defined bass in contrast to more articulate mids and highs in particular, is not easy for me, and may indicate other problems.

Bass being off could be from the system/room having poorly fleshed out and/or masked bass defining qualities... perhaps bass that is otherwise good, but lacking the leading edges, space, and harmonic complexities needed to sound like real bass instruments. When these defining qualities are not there enough, and/or masked behind too much softer and less defined bass qualities in the balance.... all the bass level in the world won't solve it. In fact, in my experience more bass makes this particular situation worse.

Whereas, as I mitigated thickening, undefined bass aspects over time, and increased the definition aspects over time... my bass has progressively become much stronger feeling. And it took both efforts here, reducing the smearing frequencies that overwhelm bass clarity and articulation in my setup, while finding ways to get better resolution, better speed, clarity, and dynamics down low. With more defined leading edges and all the other subtler bass attributes, I got a more natural, impactful and powerful bass feel. But measurement wise, there likely would be notably less quantity of some low bass frequencies here, though they sound stronger because you can actually hear them well from being in balance with the rest.

I can't say if this is part of the issue there, but it may be. And positive changes from a GZ34, one of the faster, more defined rectifiers bottom to top, and extra good at big, but faster bass articulation... and from your ZRock2, a gain stage designed for EQ adjustment, but as much, being tuned to better articulate resolution and speed for the bass as well as the rest..... in a lot of settings, these two together could notably help define bass better, so improvements from them may point to this issue.

But it is still hard to figure out what is what without more tests, and it may be something that goes beyond waiting for the speakers and amp to wake up more.

If this is the case, less bass overall, can increase the impact and power of the bass that is there by helping to reduce inarticulate low bass dominance, and hopefully reveal more of the dynamic contrasts and sound complexity needed for a strong, natural bass to be better heard.

So if you want to try to find out, it might be informative to try a few tests. One might be to listen to a few favorite tunes that sound a little off with the speakers wherever they have been. Then especially if that location is close to the wall or corners, where low bass stuff can built up more, it could be interesting to move the speakers out about 4-5 feet, and then listen to the same tunes. And if that helps, you may well be experiencing what I am pointing to.

Another easy test that became a lasting one here, and is easily tunable, would be to leave the speakers where you like them best, listen to some test tunes.... then carefully plug some of the little spaces between the speaker cabinet proper and the thick bottom plate, the "plinth." This can be done smoothly and easily with some "caulk backer rod" - closed cell round pieces of foam....or if on hand, other weather stripping that is a good size so that it goes into the space without too much force, but on expanding, fits in the space tightly enough to block sound some.

I carefully press it in with the blunt end of a small chop stick or similar, and just enough into the space to clear the outside cabinet edge a bit. This way it looks pretty low key, and I avoid the passive bass diaphragm tucked away in the bottom of the cabinet.

In my case I ended up closing the back space all but two ± 3/4" spaces left, one on each side between the foam and the wooden spacers on the sides of the plinths. And in front, I ended up reducing the space using two pieces of foam that are maybe 2 - 2.25" inches long, leaving open space between, and on each side of the foam pieces. This or similar may be a good starting point to test to see if this method improves your sound as you continue to burn in the amp and speakers. And if this shows promise, then playing with how much plinth space blocking you find best, along with speaker placement experiments could be rewarding.

There are quite a few other things you can do if this is the issue, including trying a rectifier with similar traits as your GZ34, but with a little less power push, so faster and less full/thick. But I think these would be good tests to more easily find out what is going on, while hopefully increasing musical enjoyment!