Retubing an ARC VT100 mkll

OregonPapa, you mean you can hear a big difference after you replace that regulator pass element 6550 in the PH8 and Ref 3 Preamp? How old was the 6550 that was replaced?

Oregonpapa:
The REF3 and PH8 both use a 6550C for power supply regulation.

Are you suggesting that based on these data points, Sinaker01 should use the 6550C instead of the KT120 as power tubes? Perhaps you haven’t noticed, but ARC has replaced the 6550C power tubes with KT120s in all of its current amplifiers.

BTW Never use a KT-120 for the regulator pass element in any ARC product. It's a definite no no.

Ok, so, just finished installing and biasing (adjusted to the same 130 mV the amp recommends)a matched octect of Tung-Sol KT120's. Less than an hour playing time skipping through a bunch of artists I am familiar with(now Keith Jarrett playing J.S. Bach) and the verdict is positive so far. Can't speak to whether it can play louder than the EH6550's but they sound very good-perhaps a touch more effortless and glassy than the Electro Harmonix tubes but that could be just fresher tubes, hard to say. Mind you, the 6550 were only put in last Fall, so they were probably just at their "half life" based on my listening habits. Will keep the group informed as they break in, but good news is nothing went bang and they are dead quiet as well.

So the verdict after decent breakin time- they're pretty good. Not what I would call a flat out night and day difference but a bit more "drive" and a little less glare in the upper ranges especially when the volume is turned up. All in all I'm pleased for the $450 spent, but I will give full props to the EH6550 tubes - they were a good value. Assuming I can get 2 years out of the KT120 set, I am happy with the change over. BTW, one big physical difference is the heft and weight of the 120 vs the 6550. These things feel like they're built to last. Cheers!