Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: johnnyreece on April 22, 2026, 02:16:51 pm
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I'm thinking of diving in to high gain territory, but I don't have much experience in that are. Logic says to take a proven design and work straight from that. Unfortunately, the parts I have say that's a big fat no. I'm wanting to do a lower-power SLO with russian tubes (62NP and 6P1P). I'm also using a chassis that's got much less room than a traditional SLO would have. I've tried trimming what I can, and I *think* I have a reasonable start to a layout. I've included a copy of what I have so far, as well as the schematic I cobbled together to work from (and I've highlighted what I've got on the layout). One example of a concern are the vactrols; I've never used them before! Stuff like that is what I'd like to sort out before I get much further on the layout. I do plan on using shielded wire at least early on in the preamp. Also taking any general recommendations from the high-gain folks. I really appreciate anyone taking the time to take a look!
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Vactrols work fine, though my personal preference are the low voltage Omron relays. If you do use the VTL5C1's, XVive is a really good imitation of the original Perkins-Elmer units from ages past -- there are other cheap knockoffs that are not reliable in my personal experience.
There are versions of this circuit which use relays.
The problem with Slo builds is that layout really matters. The high gain nature of the beast makes it so, even a low power version. A small chassis might give you trouble. Or maybe not, but it did for me in my few high gain adventures. Only one way to find out. Just build it.
Use shielded cable in the signal path until you can't . . .
I'm having trouble reading your schematic because of the yellow.