What do you see as the downside of tubes?

Dav65mus, Be careful what you wish for, especially if you like what you presently are using. The road to audio hell is paved by folks trying to make a meaningful positive change to get only a small, or any, meaningful improvement. Different perhaps, degredation often. Buckle-up before you take this road! :-)

Dgarretson, Thanks for your input here. I had the PH2 for 6-7 years and loved it. This was the one sleeper in the ARC product line that truly was an outstanding product. I only "upgraded" to the BAT P10 as I wanted more phono gain and benefitted with a little more foundation in the bass. I can imagine that a parts update, 15 years later would open up significantly the PH2 in dynamics and clarity.

As for the TX2575 contributions in the Aria, I do not know since I did not hear one with the "standard" Vishay resistors. But if you read my lengthy (sorry) review of the Aria, 2/3 of the way down, you will see that I did a major overhaul to a Counterpoint SA-2.

When the stock SA-2 died, I discussed many options with Michael Elliot. Ultimately it was a cap in the PS that failed. I suggested that he rebuild the PS with the same parts as the Aria. And to also switch over to a Plitron transformer....in an external chassis that I found on a DIY site. I was so overwhelmed by the performance of this that I bought another SA-2. Comparing these two units, it was the Plitron that was 70-80% of the performance improvements with the rebuilt SA-2. This was easy to verify as I could swap the old and new transformers between the two SA-2s. I knew then more than ever the importance of a PS transformer, in a preamp anyway. And I suspect this has more to do with the Aria's level of dynamics and clarity (as it too uses the Plitron) than due to the TX2575 resistors.

I went onto to replace 20 resistors in the SA-2's audio stage. This was a well spent $200. The improvement in clarity went up another notch, but otherwise the sonic signature was untouched. And finally, the remaining RelCaps in the audio stage were updated to Dynamicaps as used in the Aria and the SA-2's rebuilt PS. And again similar benefits but the 3D strengths of this unit remain.

So from these experiences, I attribute the Aria's clarity to the Plitron, the very simplistic circuit design of the phono and line stages, and most definitely the TX2575 resistors ..... in this order.

As for the Aria and SA-2 excelling as tube products, I attribute this to their tube PS more than anything. Even with stock tube in the PS, the sound is quite amazing. But I have discovered 3 tubes here that take this unit to a whole new level of 3D performance. This is one area that the above updates do not affect very much. And with nearly the same tube compliment in the Aria's PS, I have found these tubes to do the same thing here.

The other major benefit is that a very high percentage of tube line stages out there are 6922 based. With the Aria, I can run tubes in the 12AU7 family. And I have found a few types that significantly outperform (it's not even close) my coveted Amperex 6922 PQ pinched waist, and at a fraction of the 6922 cost.

So yes, the TX2575 contribute to the Aria's stellar performance, but a number of other factors, mainly the Plitron and the all new designs in the audio stages, coupled with the long proven tube PS here, have far more to do with this.

Jafox, from your comments and thorough review of Aria and Counterpoint, it would appear that these products owe their distinction primarily to tube power supplies. The flexibility of Aria in accommodating extensive rolling of tube families may also be a factor. Plitron and Dynamicap may be ruled out, as these are fairly common in high-end applications, and Dynamicap IMO is surpassed by several other types, particularly teflon. On the fourth hand, there is nothing like TX2575, which has proven superiority in disparate modded components in my system(e.g. BAT VK75SE, Merlin BBAM, Atma MP-1.)

On the point of rolling the Aria line section (particularly in view of poor results obtained with 6H30) I'm curious whether in addition to the switch between filament voltages, Aria obtains the optimal operating points across so many tube types. In phono section of my modded Atma MP-1, I've been back and forth between 12AT7, 12AV7, and ECC99. Each change requires fairly extensive R swaps for optimal operating point. Of these three tubes ECC99 sounds best-- which appears to have been an also-ran in Aria. So while I respect the versatility of tube rolling, I am cautious about pronoucing the superiority of any particular tube independent of circuit, and question whether a single preamp can do justice to so many tube types.

I'll add that the modded MP-1(which like Aria has the virtue of simplicity) includes replacement of 12AT7s with matched bipolar transistors in first gain stage of phono section(an Allen Wright idea planted in MP-1 by lewm.) This was a clear step up both sonically and in terms of gain. The latest factory iteration of MP-1 adds better CCS regulation to improve 12AT7 performance, so the question remains open from this experiment regarding relative superiority of tube and hybrid in phono. (My PH-2 rebuild will press the point further into FET. BTW, I also had a long run with BAT P10. The modded ARC PH-2 is the keeper.)

Perhaps the discussion boils down to tube vs. SS power supplies. On this point I can offer little other than to add that in my schema, the latest high-voltage silicon carbide zero recovery Schottky rectifiers improve significantly upon soft recovery discrete Hexfreds(or worse, 4-pin bridges) used in SS power supplies in most top gears. Some designers will argue that a tube power supply cannot equal the dynamics and energy of SS. Schottkys also raise the bar in terms of tube-like refinement. So the jury may be out on that one as well.

We ran tube-based regulation for years. I'm as a big a fan of tubes as anybody, but when we developed a proprietary regulator for high voltage, it was **immediately** so much better than the tube circuits that there was no going back.

There are a lot of factors in a regulated power supply! Essentially the regulators behave as a sort of power amplifier that you are listening to. They have to be very linear and wide bandwidth to really work right. The problem we ran into with the tube regulators is that bandwidth is a real problem. The result is right now that our regulators function with wide bandwidth and about 2 orders of magnitude less noise than is possible with tube regulators.

I'm not saying that tube regulation is all done in, but some innovation needs to occur before it can keep up with a **properly designed** solid state regulator.

I have two systems of good quality. One SS and one Tube (DAC, Pre, Amp). The SS is in the TV room with surround sound etc. The stereo tube system is in the living room.

Although I listen to music on the SS system I experience the music on my tube system.

100% of my friends will want to listen to music on the tube system over the SS system.

Never have any problems with the tube components and I keep a good supply of tubes to roll which I find enjoyable.