Converting SOB to Mark 1 specs

Mark I's, II's, III's and the almight IV

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Mark III
Posts: 191
Joined: Tue Sep 20, 2011 11:15 am

Converting SOB to Mark 1 specs

Post by MK IIB » Mon Nov 06, 2017 2:41 pm

Hi folks.
Could any of the more knowledgeable guys on here please tell me what I would need to have done to an SOB 60 watt combo to make into a mark 1 or as close as possible?
Mine has the limit control which I never use.I would like to have a presence control added too in place of the limit control.
I'm not familiar with the differences in circuits but other than getting rid of the limit control or having it replaced with a presence control(Which a few of these amps actually had)what else would need to be changed to the pre amp to make it more like a Mark 1?
It's got a great clean sound but the overdrive(input 1)doesn't sound that great.I've tried some NOS preamp tubes.
Any help would be greatly appreciated as this is something I've been wanting to have done for a while now.

Mark II
Posts: 111
Joined: Tue Mar 25, 2014 10:14 pm
Location: New York City

Re: Converting SOB to Mark 1 specs

Post by lovetoboogie » Tue Nov 07, 2017 6:21 pm

It's relatively straight forward... PI circuit and maybe some plate voltage changes. Some SOB's have both Presence and Limiter...

This thread should give you a hand...

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