symphonic Line RG4 III vs RG4 IV?

I haven't heard the latest Mk IV amps but when I got the Mk III version (That I still have), I was told by a long-time Symphonic Line dealer that the midrange on the Mk II version was better than on the Mk III 'cuz the Toshiba output transistors in Mk II were better than the Sanken transistors in the Mk III.
Looks like something similar has happened bwtn Mk III & Mk IV.
Seems like one gets the extension at the cost of richness. There is a person here who claims that he can modify my RG4 Mk III to have even better sound. Maybe I will take him up on his offer. The modified sound might approach the Mk IV sound???

Gregm,

I can share w/ you what this person told me over the phone re. modifying the RG4 Mk 3.

He told me that most of the work would go into the power supply mod. Swap out the present rectifier diodes for Fairchild HEXFRED diodes. These rectifier were "soft recovery" (that's what I remember, I think!). Replace the power supply electrolytic caps w/ computer grade Panasonic caps. He felt that the present p.s. caps had done their time w/ several on/off cycles. Then, he was going to change all the signal path caps w/ Blackgate caps, which he felt were the best. He said that he was not going to touch the power amp electronics as that was biased the way the designer intended. Neither was he going to touch the internal cabling.

So, w/ all these mods he felt that the amp would be more transparent, music would flow more easily & bass response would improve. However, he told me that this was a double-edged sword in that once I heard the "truth", it was possible that I "could not handle the truth!".

Tell me what your opinion is.

Gregm,

Thanks for your feedback.
Right now I'm dragging my feet on the mod, big time! I'm apprehensive that I might lose a good thing. I like the sound of the amp the way it is (it's not the be-all & end-all of amps but it's very, very good as-is). I have a feeling that a call to Klaus might be in order if I decide to go ahead w/ the modification.
I'll keep you posted.

Yes, the Toshibas are reputed to have a better midrange than the Sanken equivalents. I understand from a long-time & Symphonic Line experienced dealer that the RG 4 Mk 2 (used Toshibas) had a better midrange than the Mk 3. Oh well....