S.O.B. Limit control

Pre Recto days. Boogie modified Fenders, Mark I-IV, Dual Calibers, etc

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Bottle Rocket
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Joined: Fri May 24, 2019 2:58 am

S.O.B. Limit control

Post by zjdrummond » Fri May 24, 2019 9:03 am

I have been researching old boogie amps. Kind of like the idea of grabbing one for that loud, mean, clean thing that they can do. Came across the S.O.B. and wondered about the limit control. What was that about? Is it an actual limiter dynamics processor, or just an attenuator aimed at reducing output level to keep your super distorted sounds from blowing your eardrums out?

Mark III
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Re: S.O.B. Limit control

Post by bgh » Tue May 28, 2019 10:35 pm

I bought an S.O.B. back when they first came out. So, my memory may not be all that well.

The limit control was kind of weird. I left it on 0 most of the time. If I recall, it's purpose was to starve the PI (Phase-Inverter). At 0, it doesn't do anything. As you turn it up, it starves the PI more and more - kind of like a "reverse gain".

I don't think I ever got it sound good with the limit value off of 0.

Hope this helps.
Lefty guitars: Gibson SG standard (1977) • Gibson LP custom (1979)
Amps and such: Mesa Boogie Mark IV-B • Mesa Nomad 45 • Mesa TA-30 • Effectrode Blackbird • Kingsley Jester • AMT SS-11a • Zoom G5

Bottle Rocket
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Re: S.O.B. Limit control

Post by redrabit1 » Thu Jan 09, 2020 1:39 pm

No technical data here, but as a previous owner I can agree that nothing useful came from the LIMIT setting. I would state that the later version with a PRESENCE instead was more musical to me.

Mark III
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Joined: Fri May 04, 2018 10:36 pm

Re: S.O.B. Limit control

Post by woodbutcher65 » Mon Feb 03, 2020 10:30 am

I have an SOB. The limiter was useless. It was based on a Triac. Yank that out, bypass it, or replace it with a post phase inverter master volume control. (There's already a master on it, too. But a PPIMV is a better type so maybe bypass the first master.)

There's a .003 cap in the preamp that makes the SOB very harsh. Remove it. You'll never want to put it back, believe me. It's located near the master volume pot, bypassing a 220K resistor near the plate of V2B.

I modded mine by changing around some capacitor values so it now sounds much better than it used to. Mine is now voiced like a Marshall JTM45 but with more gain and there's a pull gain boost as well. The thing is a real terror now.

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