CUSTOMAUDIO OD100

[bepone]

HI Roberto , thanks.
TO3 transistor I think is in place to limit current?

to me looks like LM338K, regulator for 12V DC for the heaters..

[sergio]

thanks very appreciated

[Littlewyan]

Interesting, so it still has the 2.7K/.22uF bypass on the 3rd stage? I thought the standard had less gain than the OD100SE.

I copy here some comments written by bnouille (Bruno Durand IIRC):

OD100 SE+ is just basically the same as the 3+ .Same clean and lead channel .The so called "crunch" channel is just the lead channel with one R value lowered for less gain somewhere ( can't remember which one cause it's been a long time since I worked on these , between second and third stage probably ) . It's always a 4 stages + CF all the time
in the same way the Classic's or ML models drive channels are just the same crunch channel ( 3 stages + CF there all the time) with a couple opto alternating two resistors values) .They also have way less filtering in the power section
Original OD and SE have a ton of filtering .It starts with 4 x 270µ in series/Parallel
Original OD 100 drive channel is different .No cold values on cathodes .it's very thick with a 100n first coupling and 1µ /2,2K on the first and second stage stage + .001 caps on second and third stages instead of two 470pf ..first stage being followed with 470k/1M and not .001/1M like the 3+ . Also 470k instead of 220k after third stage
PT 100 (original ) is a bit of a mix of all of those though there are actually 2 or 3 different versions . The PT100 SE is different with a drive channel mostly like the OD100 SE+
New PT15 is very similar on the drive channels as the original PT from 15 years ago and its clean channel is a bit of a mix of Fender layout with some Marshall values on tone stack . Not a fan at all

There was no "major" changes between 3+ and SE . Lead changed on second cathode from 15k to 10k and a serie resistor changed from 470k to 220k .. One serial resistor added on the crunch channel and both tone stack did go from 39k/470pf to 33k/220f . Interestingly Lukather still used the non SE crunch channel with SE lead channel . There was also a slight change in the EQ to make it flatter with pots on noon . So nothing I can see as a major
It never changed after 1993 except for things that have nothing to do with the Circuit itself (pots brand etc)

Some photos in attachment.

[roberto]

to me looks like LM338K, regulator for 12V DC for the heaters..

Yes, it's for DC heaters (see connections on its right).

[FUCHSAUDIO]

HI Roberto , thanks.
TO3 transistor I think is in place to limit current?

I suspect it's possibly DC tube filaments and/or relay or optocoupler DC supply regulation (or both).

[roberto]

Interesting, so it still has the 2.7K/.22uF bypass on the 3rd stage? I thought the standard had less gain than the OD100SE.

One of the lead channel I liked most was developed together with a friend on the CAE 2nd and 3rd cold stages with partial bypass. First two coupling caps were (IIRC) scaled down by a factor of 5, snubbers were reduced as well, all other stages different, but the two cold stages in series (à la Slash) were there. Power supply was tights as well (à la SLO IIRC). I've found the very old photos on my phone!