Audio Research 75 SE

Ditto David12. When I asked, ARC was somewhat tongue-in-cheek about the circuit changes and parts that go into the SE upgrade.

Having said that, I doubt that ARC would charge $5000 to do an SE upgrade to my Ref 150, where the retail price of the tubes (8 KT150s 4 6H30s) being approx. $1800 and the balance (or, $3200) relating to snake oil.

OTOH, all that being said, ARC has at times described certain improvements or new models as "being in another league" or "in a different class" and so forth. That has not been my personal experience in a number of cases (e.g., Ref 3 to Ref 5 (not SE); PH-7 to PH8). Just my opinion.

So I am waiting to read comments from Carey and Oregonpapa.

BIF

I'm also interested in hearing how much of the upgrade comes from the tubes vs. the circuit changes (one obviously is much cheaper than the other).

Rrolack ... I just dropped 2 quads of KT-150s into my Ref 150. Sound is better, but not transformational. So I wait to hear back from Oregonpapa and Carey1110.

I actually found the KT-150s to be a huge step up in the Ref 75, particularly in the bottom end. Best money I ever spend in audio.

That said, I'm also super curious to hear how the upgrades change things.

According to my source, the KT-150 tubes account for about 40% to 50% of the improvement in the SE amps.

On the KT-150s ... they take a good 100 hours of break-in to start sounding their best.