That kind of generalization about the 90s amps is really a birdseye view, as per my experience. It's true that people here built HRM amps to "that one" original schematic, which tends to sound not so great in OD without the PAB. That schematic was so widely distributed that there are now statements such as "Dumble intended for the 90s amps to be used that way," as if it were the Gospel.dogears wrote:90's amps use PAB in OD mode so the pot taper on the stack is moot. The older 80s amps with the Skyline stack had 30% taper. I had one measured.
But that simply can't quite be the case. For example, I tried another 90s amp here in L.A., which a couple of other locals (from TGP) have tried as well, that sounded very different from at least my build of the 90s circuit -- which, of course, is the same one that everyone else used when building their clones as well, with the low gain input to the OD, etc. This other amp had a lot more gain on tap and didn't seem to be bass heavy at high gain settings and without the PAB on. So the tone stack thing may not be a moot point if one is willing to consider the possibility that there exist other schematics of 90s amps, which of course has to be the case. [ Furthermore, if RF's amp is a HRM -- the million dollar question! -- then his amp is definitely different; it sounds really good in OD without the PAB. RF tap dances on his pedalboard and uses all four possible combinations of channels and PAB, and the sound of the amp is always "the" RF tone.
]As for The 80s amps that I have seen in person, which were later converted to Skyliner by Dumble, they used Alpha pots for the treble (250KB) and the Bass (500KA) slots. Easy to check with the pictures of 124 I took and posted, for instance, as I have some very detailed close ups of the backs of the pots. There is one amp I have pictures of, nevertheless, which I've never seen in person, that was built as a Skyliner from the get go and that has what looks to be either Alpah pots or C TS with shiny backs all the way around, but there is not enough detail in the pictures to be sure. Those may as well be 30% taper all around, for all I know.
Needless to say, I am not suggesting the one 80s amp that someone else measured and told you about didn't have a 500KA 30% taper pot on the bass slot. I am stating that is unlike what I've seen myself, and since I've seen a few amps, those two pieces of information -- mine and your contact's -- make any generalization invalid out right of the bat.
If anyone has a chance to measure pot tapers of more amps it would be really cool, however, since that necessiates unsoldering one lug on all pots except the "middle," I wouldn't expecte for there to be many volunteer owners.
Cheers,
Gil
