AtmaSphere Upgrade from Mk 3.1 to Mk 3.3

Thanks for that info.
I really wish I had done it while it was in the shop.
Oh well, something to add to my upgrade list...
Bob

I had already had the Caddock resistors installed in a previous upgrade.

@honest1 ,
I am glad you posted your experience. I am also glad that you found it a significant upgrade.
BTW, did you get the Caddock Resistor upgrade?
Bob

Well, I did it, upgraded my Silver Series from 3.1 to 3.3  Having the amps back for a while now, I can say I'm very impressed with the results, and that the upgrade gave me a significant helping of the sound I was looking for. The sound after update is much more open and dynamic. I'm quite shocked at the difference. I thought the amps were pretty good already. The increase in dynamics seems to be due to a reduction in noise floor, rather than an increase in peaks, if that makes sense. Sounds seem to stop more completely, leaving tiny gaps between notes, rather than blurring them together.  The same is true of complex passages, where different instrumental lines can be heard more distinctly from each other.  The system is more satisfying when played at low volumes now. Bass also seems more controlled and tighter. The overall impression is that the music sounds more powerful and vivid across the spectrum. More detail can be heard from the very deepest bass through the highest frequencies, but without being fatiguing. I did notice an increase in high-frequency extension, which I was surprised at. In my case it worked out well. My speakers have a switch to help match the speakers to the amplifiers. I had it set in the position that boosts highs a bit. Since the update, ti sounds more natural with the switch in the normal position, and now sounds better than before with the switch in the other position. The increased resolution is not a result of simply boosting the highs, but is a real improvement across the board.

@

The update causes blacker backgrounds with a smoother and more detailed presentation. The new Constant Current Source (CCS) has nearly 2 orders of magnitude greater performance- and results in greater differential effect in the voltage amplifier. All the updates from the Mk3.2 level are included in the Mk3.3 level; the Mk3.2 has measurably lower IM distortion, which is audible as smoother sound.

My friend had his MA-1 amp upgraded last year and he was very pleased with the sonic improvement.  Sorry, I don't know what changes were employed, but he was also given a new 3-year warranty which is a really nice added bonus.

I see that he is very enthusiastic about his upgrade, but he doesn't get very specific about what the changes were, technically or sonically.  What should I expect from the upgrades, sonically?  I understand the 3.3 upgrade replaces the CCS tube  with a solid state device, and uses its position for a 3d amplification tube.  I don't know what the 3.2 change does, or what effect it might have on the sound. 

There is a member who picked up a set of MA-1 Silver Editions and had them updated to Mk3.3. They were previously at the Mk3.1 level, so his comments are exactly about what you are asking:

https://forum.audiogon.com/discussions/atma-sphere-updates

I only have experience with the 3.3's, but when I was looking at buying a non 3.3 Ralph and Adam have told me, it is a very big upgrade- sound and rebuild-wise(hence, the cost. If I recall, it also affect tube performance. 
Hopefully, others will chime in. I just want to give a quick response.
Bob