I believe that the 202A is quite similar to the 502A/B amps - the former being EL34 based & the latter 6550/KT88 based.
I used to own a 502A on which I had several mods done. I found the original amp to be very dark & lacking bass clarity. The amp sounded like I was listening to it in a bathroom stall. LOL!
I had the bridge rectifier diodes, power supply caps replaced. Most of the el-cheapo resistors, coupling caps were upgraded to Kimber Kaps (IMHO this amp did not deserve Cardas coupling caps, which were my 1st choice at the start). The decoupling caps for the tubes were also upgraded to Panasonic TS series. The driver stage tube was given a constant current bias stage using solid-state devices. I had the balance pot removed. Upgraded the volume pot to a Noble which was much better (Again I did not think that this unit deserved anything better).
After all of this, the amp did open up quite a bit.
If memory serves me correctly there was a design flaw in the bias of the driver tubes - the voltage on the plate (or cathode) was too high OR there was too much AC on it. In my particular unit this manifested itself as the amp eating driver tubes (if I remember correctly it was a 12AT7 tube) like crazy.
Another thing I did not like was there was a fair amount of global negative feedback in the design. Plus, the whole amplification chain has huge amounts of gain - something like 36dB, if I remember correctly.
The other thing I did not like about my integrated was that it used pentode tubes in ultra-linear mode. It sure gave me bass heft/slam but it was missing that sweetness. In contrast, I used to own AES Sixpac power amps that also used (EL34) pentode tubes BUT in triode mode - what a difference for the (much) better.
I usually used this amp as an integrated but one day, just for the sake of it, I connected it to my tube preamp - Jolida on full volume & preamp controlling signal amplitude - it sounded simply superb! Beguiling would be correct word to use here.
Anyway, this hopefully gives you some info re. mods.
I used to own a 502A on which I had several mods done. I found the original amp to be very dark & lacking bass clarity. The amp sounded like I was listening to it in a bathroom stall. LOL!
I had the bridge rectifier diodes, power supply caps replaced. Most of the el-cheapo resistors, coupling caps were upgraded to Kimber Kaps (IMHO this amp did not deserve Cardas coupling caps, which were my 1st choice at the start). The decoupling caps for the tubes were also upgraded to Panasonic TS series. The driver stage tube was given a constant current bias stage using solid-state devices. I had the balance pot removed. Upgraded the volume pot to a Noble which was much better (Again I did not think that this unit deserved anything better).
After all of this, the amp did open up quite a bit.
If memory serves me correctly there was a design flaw in the bias of the driver tubes - the voltage on the plate (or cathode) was too high OR there was too much AC on it. In my particular unit this manifested itself as the amp eating driver tubes (if I remember correctly it was a 12AT7 tube) like crazy.
Another thing I did not like was there was a fair amount of global negative feedback in the design. Plus, the whole amplification chain has huge amounts of gain - something like 36dB, if I remember correctly.
The other thing I did not like about my integrated was that it used pentode tubes in ultra-linear mode. It sure gave me bass heft/slam but it was missing that sweetness. In contrast, I used to own AES Sixpac power amps that also used (EL34) pentode tubes BUT in triode mode - what a difference for the (much) better.
I usually used this amp as an integrated but one day, just for the sake of it, I connected it to my tube preamp - Jolida on full volume & preamp controlling signal amplitude - it sounded simply superb! Beguiling would be correct word to use here.
Anyway, this hopefully gives you some info re. mods.