Reisong A10/A12 Modifications                 I completed the Skunkie modifications on my A10 and compared it with my Onkyo receiver using a Douk Audio switcher box. The A10, now an A12, sounded much better but still sounded too bright. There was still a little harshness to a female singer’s voice so that the Onkyo sounded smoother and had better soundstage. I kept stepping down the value of the resistors for Schade feedback and got a little improvement each time. I ended up with 360k for a feedback resistor and wanted to improve it some more so I ordered some more resistors and some orange drop capacitors (.33 and .47) to try for new coupling caps. The parts came in and I listened again carefully to get a good idea of where I stood before making any more changes and found out something had changed! Without changing anything, the harshness had disappeared and the soundstage had spread out. Does this mean the tubes had worn in? My tubes are all JJs except the 5AR4 which is Sovtek. I don’t have any experience with tube gear so all I know is what little I’ve read about giving tubes some burn in time. Can anyone verify that sudden improvements like this are common occurrences?  I left the Schade resistor at 360k and left the coupling caps alone because the Reisong amp now sounds better than the Onkyo SS amp. I will probably leave this amp as is for quite a while before I try changing anything else on it. It’s still a little brighter than the Onkyo but at this point that is a good thing. The Onkyo has the singer sounding a little muted and not as up front as the Reisong. I think the Reisong sounds more natural and suits my taste better. My listening position is only six or seven feet back from the Klipsch RF62 tower speakers and I keep it at moderate levels (small apartment) but sitting in the sweet spot gives me a nice soundstage which is very enjoyable. I listened to a remixed version of Linda Ronstadt’s Ooh Baby Baby and the bell like tones just blew me away. I know I’m a Johnny-come-lately and these modification videos have been out for years but the A10 and A12 are still selling at good prices and after the Skunkie mods, they are still a very good amp for cheap. Others may discover the opportunity to go this route in the future so I’m going to try to upload the spreadsheet I made to keep it straight in my head how to make the 12AX7 heater changes to achieve the scheme where the tubes can be swapped at a later date and use the unused side of the tube when it gets worn out. I added the original excel file in case anyone needs to add corrections or clarifications. I hope this is useful to someone.

Critical Listening                 Turned on new Reisong A10 and it sounded great. Initial comparisons between the tube amp and my SS amp sounded so alike that I couldn’t tell the difference. Maybe I shouldn’t be so quick to change anything on this amp. I also bought a Douk Audio VU3 switcher box but I was afraid to try it because even though it supposedly had a dummy load for whichever amp was disconnected from the speakers, I couldn’t find any reviews from anyone who had tried it out with a tube amp. I finally obtained some 220-ohm 5-watt resistors and installed one on each set of output jacks from the A10. Now with some more careful listening while switching between amps, I discovered the deficiencies of the tube amp. With certain music and voices, I could hear the harshness and thinness of the tube amp. Even my wife noticed that when switching to the SS amp, the room seemed to get bigger. OK, I’m happy and excited to find good reason to tear into the A10 and do all the Skunkie modifications. I want the modified version of the A10/A12 to sound better than the SS amp or at least as good but with that tube sound difference.                 I’m happy with the sound I already have. My signal path is a WiiM Ultra playing Tidal high-res streamed files exiting the WiiM digitally via a USB cable to a SMSL P100 which is supposed to re-clock the stream in order to reduce jitter ( see CheapAudioMan $60 hack). Then the signal travels to the SMSL SU1 DAC via a short coax cable. The DAC output goes to a Schiit Audio Freya +. The Freya has two outputs so I sent one to the Onkyo NR777 streamer box input and set the receiver to direct mode so no processing takes place (the Onkyo does double duty as a home theater receiver when not in streamer mode). The other Freya output goes to the tube amp. Speaker cables from each amp go to the Douk switcher box and then to my Klipsch RF62 tower speakers. The Klipsch speakers claim a sensitivity of 97 dB so they should perform well with the soon to be modified Reisong tube amp.                 As a retired former electrical controls person, I needed a hobby. Even though my last exposure to vacuum tube theory was in the early 1970s, the idea of studying enough to re-learn and extend my knowledge to the point where I can safely and successfully perform these modifications, has energized and excited me. Thank you, Stephe, for putting out the videos that got me going on this path.

I'm Steve, My Riesong? Reisong?, I can never remember the spelling, A10 will be delivered tomorrow. I've already ordered some of the material for the modifications. This will be fun. I remember playing a 78-rpm copy of Rhapsody in Blue on my parent's Tube amp record player. The only other tube amp I ever fooled with was in the radio of my 1956 Buick. I had to pull that monster out of the dashboard and take the tubes to the drug store tube tester and buy 3 or 4 new tubes to get the radio to work. I guess everyone has figured out I'm pushing 75 years old. I have a decent sound system already, but I want to get the tube sound as an alternative. I'm rusty on vacuum tube theory but intend to learn as I go. My career has been in electrical controls and automation programming so I'm adept at soldering and reading schematic diagrams. However, I'm more familiar with silicon controlled rectifiers, TTL chips, AC and DC large motor drives, programmable controllers, etc. than with tube circuits. Can't wait to convert this A10 into a modified A12. I told my wife that this hobby is going to take the place of the sports car I almost bought. That should help justify the expenditures. Anyway, I'm glad to join this forum because if I try to talk about amplifiers, speakers, room acoustics, etc.with anyone in my extended family, all I see is their eyes glaze over. I need others to talk to so I can learn and discuss the things I'm interested in. I'll be posting in the question-and-answer category soon. And, I bought a Skunkie tee shirt to wear while I work on the amplifier mods.