I'd like to take a moment and give my opinion
(and only my opinion
) of what changes I made that I liked or not, or were worthwhile for the money/time. The speakers I've been using are the Klipsch RP600M.
First off, the change of preamp tubes to the Russian Rocket 6N2P-EV was great. Much better than the stock tubes immediately. And super value considering how much they cost for a pair. It sounded much tighter overall, but it felt like I lost some bass depth.
I next changed the rectifier tube to the Gold Lion GZ34, and my notes that I wrote to myself, I thought this change made the sound more "solid state like", faster, tighter notes, cleaner highs, and brought back my bass depth.
With COVID-19 issues, I had to wait about 2.5 months for my tube adapters to arrive from China so I could start playing around with the 12AX7's.
My opinion, the Gold Lion 12AX7's sound the best of the preamp tubes I've rolled so far. Expensive, but I feel worth it.
The Mullard 12AX7's to me, sounded like a copy of the Russian Rocket 6N2P-EV. So if you want to save yourself the troubles of getting an adapter and using these, don't. Just stick with the Russian Rocket's.
The PSVane 12AX7-T Mk II made me feel kind of... Meh. Not bad, but didn't stand out at all to me. Especially considering their cost (expensive). Of the tubes I have, this is the pair of tubes I wish I never bought. Wasted money here.
Coupling capacitors. I went a little crazy and bought some Russian PIO caps from eBay....K42Y-2 .22uf, K75-10 .22uf, and Teflon T-2 .022uf. Those K75-10 caps are HUGE! After I read and researched some more, I thought maybe I should just cut to the chase and instead of trying to make a "good value" upgrade, just buy something proven and purpose built for audio. That's why I bought the Mundorf Supreme Silver/Gold/Oil .22uf so I wouldn't be asking myself, "what-if" in the future. They're expensive as hell, but I only wanted to be messing around inside once. After 300 hrs suggested break-in, I think they sound very nice, but if I had to do it again, I'd probably just buy the Supreme Silver/Oil instead and save a few dollars. How they sound is difficult to put into words. I guess I'd say overall more smooth and rich. To me, the capacitor change was different from tube rolling. Not the highs or lows...just sort of rounded the edges slightly of the music. I would still make this change if I had to do it again. I would make this one of your last changes, when you have done everything else.
Power tubes. Gold Lion KT77 I love best! More drive, more punch, more kick. Expensive compared to other reissues. If I want to listen to the Reisong A10, I want these KT77's in there. I bought the PSVane HiFi Series EL34B's because they seemed to be a great value and have for backup. To me, they sound like the stock Shuguang EL34B. No noticeable difference and wouldn't buy again.
Final thoughts. I was impressed with the difference the GZ34 rectifier tube made. Maybe because it doesn't sag as much as the stock rectifier, but it provides a stronger power base, or overall drive that makes all the other tubes sound better. I think dollar for dollar, it's hard to beat the Russian Rocket 6N2P-EV preamp tubes. I like the Gold Lion 12AX7 much better, but I could happily live with the Rockets. Power tubes...buy the Gold Lion KT77's and forget about the others. Coupling capacitor, like I said earlier, I feel it's worth the time/money...but only after you made all the other changes and looking for the cherry to put on top of your dessert.
I've been using the A10, hooked up to Chromecast Audio, running through Schiit Modi DAC, and on the suggestion of another member here, a FX-Audio Tube-03 Preamp with GE5654 tubes. That Tube-03 preamp not only sounds great, it helps with tone controls, and adjusting the level of input to the A10....well worth the inexpensive purchase price.
Like I said, it's just my opinion. A collection of my thoughts, and what I would have loved to have read while doing my research of upgrades to this fine amplifier!
