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.