ODS #102 "Mystery Cap"

[David Root]

I searched but did not find.....anyone know what are the materials of composition of the .01 uF cap shown in the ampgarage layout as "Unknown Composition". Since the amp was built in '82 I am assuming it's mylar, but...???

Also, most people who have this amp say it's too bright without a D-Lator. If I build it with Normster's internal buffered loop do you think that would suffice?

The musician I will build it for uses primarily a '63 Strat and he loves my #124, which was I believe originally built for a Strat player. That of course has no buffered loop. He also likes the tones of my Bluesmaster HRM, which is a high plate design like 102.

[brewdude]

I have no idea about the cap composition. However, I can say that I saw Roben Ford at the Napa Valley Opera House (a small theater with great acoustics) last year and it was painfully bright and loud. The audience was heavy with local guitarists and most were complaining about his tone. I thought it sounded just like expected RF to sound. I had a great time.

[Structo]

I think it is mainly due to the bright cap (68pf) on the master volume.

The other thing about the Dumbleator, is that he ran long cables to it from the amp, adding capacitance.
If you build the D'lator onboard then you will have to address the brightness some other way.

Other than that it looks pretty much like a lot of other ODS amps.

Also a 2.2uF presence cap.

The overdrive pots are shown as 100K, changing those to 250K can thicken up the OD.

I saw the RF trio in 2011 with his tan Dumble and I was surprised that he didn't blast us out because I had heard that he was loud.

They were loud but not painfully loud.

[brewdude]

Oh yeah, at the show I saw RF did not use his dumbleator.

[David Root]

Thanx Gents, One of my amp building pals told me he thinks this cap (see pic) is the mystery cap, so I bought three of them on fleabay. It's about the right vintage given HAD's liking for old stock/surplus parts. Probably Mylar but definitely film/foil.

I plan to leave the 68pF brite cap out. If my customer likes it without I won't put it in. I think I will use a 12AX7 in the on board buffered loop as it might cut some highs, higher plate resistance,

Also curious about tonal effect of changing the snubbers to 330 or 390pF, and/or using polystyrene instead of ceramic. Polystyrene are smoother than ceramic but this may not apply in the snubber application, what do you think?

[hitchcaster]

if it were me, id go external dumbleator.. use brite cap.. i think 68pf sounds good with the whole rig..
the disk caps sound better on the snubbers.... no idea why they sound better but they do... move them around too, lead dress on them does interesting things... i think i remember i have the two close to each other above the tube... have fun!