2nd Gen ODS in CE Chassis

[David Root]

Just finished this one for a customer. I have done a 2nd Gen before but not in a CE chassis, which is designed for a #124. This required some changes to suit the CE chassis.

This is a 50W #40 with a #13 tonestack, Normster’s active loop, a presence pot instead of a switch, and a 250K pot wired as a variable resistance and stacked on top of the 180K divider to ground. All in a CE 100W chassis.

I used the two spare power tube holes for two can caps, one JJ 40/20/20/20 for the plates, screens and PI (one 20 not used), the other a 20 +20 Richey Gold for the loop tube. V1 and V2 supplied by the two F&T 22 uF axials. The PS wiring is a bit more involved than I would like, but seems to work OK.

It has a '68 Bassman OT. Colossal Amps relay and PS boards, thank you Dave! Bias pots are 50K with 51K across them to make 25 K each, then in parallel to 12.5K. Just makes the customer's mismatched RCA blackplate 6L6GCs a well matched pair. 32.7mA +/- quiescent cathode draw.

B+ voltages are higher than spec on the plates/screens at about 458 or so. PI is 425, loop is 361 & 258. I have V2 & V1 set up a bit lower than spec at mid 180’s plates on V2 and low 180’s plates on V1. (B+ 287, 279 respectively). Cathodes on spec at ~1.5V. I did that on the first one I built because Tony Albany tried it and recommended it on the 2nd gen circuit. The lower plate voltage sounds very nice to me. Might possibly lack a little headroom if the amp was cranked right out?? I think if I reduced the dropping resistor from the PI to V2 from 24K to 22K I'd get the HAD spec V2 & V1 plate voltages. BTW, anyone know why HAD used a wirewound dropper between V2 & V1? I used a Mills 2K2.

All the pots are NOS except the bias pots. Mostly Clarostats from the early ‘80s. These are PCB mount lugs which I simply bent over in a U to solder to. Solder lug NOS pots seem to be vitually unobtainium these days, but the PCB mount ones are still relatively available.
All orange drop caps are NOS 4PS, 6PS or 220P, except the .1uF in the PI, which is 200V, probably all at least 40 years old. A couple of 510 pF polystyrenes instead of 500pF ceramics.
Resistors are mostly Piher and Electra/Mepco-Electra, with a few 1W Riken CFs in places where I thought they would work well, like the loop, or where I didn’t have Pihers in the required value. Also three 100K NTE MFs “because I have them & HAD used them occasionally”, what the hell.

Mismatched into an 8 ohm Altec 417B it is I think the best sounding ODS I have built. My customer is going to do some clips for me as I don't have the equipment to do that properly. It sounds good with a Tele, HBs and P-90s. Will be trying it out with the customer's beat up '74 Strat tonight.

This was a fun build with all the NOS goodies in it, I got a bit carried away with that!!

[ToneMerc]

Looks great David, the early circuits are close to being my favs.

TM

[vibratoking]

Man, that thing is pretty. One lucky customer there. Love to hear the clips.

[stelligan]

Bad-assedness. Inside & out.

[Synchu]

Looks great!
And then there's this nice cab as well.

Will be great to have your customer do the clips and post'em here.
Niki

[Structo]

Looks nice David!

[M Fowler]

Very nice looking amp David.

[David Root]

Thanx guys!

I forgot to mention the awesome cabinet is by Taylor Cox of Ampnation.com. Mea culpa, Taylor!

[lpd]

Look forward to plugging the ol' beater strat into the Dumble tonight David. Looks fantastic.

[dorrisant]

Beautiful build David! I thought that headcab might be a from Taylor. He was looking for that chassis the other day.

Tony

[aflynt]

Great job! I really need to build a 2nd gen at some point. Did CE make a chassis with 4 preamp cutouts at one point, or did you modify the chassis? Also, are those Takman Carbon films in there too? How do you like them?

-Aaorn

[Structo]

The pink ones look like Takman.

The dark blue with gold leads look like Riken.

About a year or so ago, I replaced all my carbon film resistors with Takman.

What a glorious amp it became, not.

Couldn't really tell much of a difference to be honest but I can say that it has Takmans now.

[Colossal]

That one came out killer and lots of eye candy too. Very nice all around David!

\m/ \m/

[ToneMerc]

Great job! I really need to build a 2nd gen at some point. Did CE make a chassis with 4 preamp cutouts at one point

Yes, some of the early runs included a few with four 9 pin holes.

TM

[aflynt]

The pink ones look like Takman.

The like blue look like Riken.

About a year or so ago, I replaced all my carbon film resistors with Takman.

What a glorious amp it became, not.

Couldn't really tell much of a difference to be honest but I can say that it has Takmans now.

Hah! They do seem to have nice stout leads and come in a good variety of values in 1W, though.

-Aaron