Does anyone have a spare face plate or photos

20 Studio, 50+, 50PA, 50R, L100, B100, L120, L120PA, L120R, 120 SLAVE, B120, B150, L150, L200, B200, Concord, and SMF

Re: Does anyone have a spare face plate or photos

Postby DaveW on Thu Apr 04, 2013 6:16 pm


Feel free to use it, if you drop me an email address (PM it to me), I will send you a hi-res pdf version to use.

Once the power and power supply are done I will mail these as well as the part numbered schematic to link to for reference.

Glad you liked the Powerpoint idea.

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Re: Does anyone have a spare face plate or photos

Postby Papa Dog on Thu Apr 04, 2013 6:54 pm

Mr. Foxen is right in that there is no "standard layout" for many Sound City products. The 120 and 200 both went through a couple or more interations and some circuit changes in the Mk 4 era. Especially during the DA to DMI conversion/transition period. And again when manufacturing was moved to New Jersey, USA.

You may be on to something about those 1 meg resistors causing noise. However, since the 120+ is the one most noted for noise, I think it is a design flaw in the filtering. The 200+ usually does not have the noise issues, unless some of the cheap components have drifted way off spec. If you look at the schematics, both DA and DMI as they appear on you will notice that the pre-amp and tone circuit ( can't really call that a tone stack) are only different in one regard. That being where, for the first pre-amp tube on the 120, there is a dual 32mfd cap, and on the 200+ there is a 200mfd and a 32mfd...mine is running 220mfd and 30mfd. Better filtering at that stage would, IMHO, have killed most of the noise in the 120+ before it got back into the tone circuit or beyond. Of course I could be wrong, and YMMV, etc, etc. It just seems to make sense to me.
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Re: Does anyone have a spare face plate or photos

Postby Mr. Foxen on Thu Apr 04, 2013 10:28 pm

Definitely found replacing al the carbon comps in the SC120 preamps lost a load of hiss. There's a bunch of other noise sources though.
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