The Amp Garage

Yeah Gil I stared at the schematic till my eyes crossed and the only thing I can think of is the power supply. My amp has been completely rebuilt(not for this reason) and still the same effect. It is pretty subtle but I do hear it. I thought I was going nuts and then Marcos confirmed a similar effe...

As far as LC's tone over the years, my favorite Dumble tones of his remain the late 80s period through the very early 90s. Regardless of the guitar used... 1st Valley Arts Strat, 2nd VA Strat, VA Tele, Les Paul Special, etc. Even with the 335, which he didn't use much at all then, he got what to me...

Gil, thank you for the report, I was thinking of trying the same thing, although I expected that it would not work perfectly. So I will have to finish my d-lator project some time. BTW for about a decade I have been using what I call the "poor man´s Larry Carlton rig", i.e. using a small solid state...

Some ideas: You could start by increasing the V1b output coupler to at least .02, which may entail changing the V2a coupler to .01 if you feel you have too much bass in OD mode. You could also try modding the amp to 3rd generation specs, i.e. 250k treble pot and losing the .02 cap on the bass pot. S...

Charlie, I have used this type of cable (which is what HAD used in my ODS) sometimes, mostly as the connection between input jack and V1 grid in Fenders, it does a little sparkle, and it was also really cheap, but as difficult to work with as you expect, stiff and thick, but it stays put once it is ...

I wonder if these treble peaking caps that are parallel to the preamp grids are there to limit the low end response to further focus the OD. Is the value confirmed to be 0.005uf? The 3rd generation circuit is very bass-heavy , so I can see the desire to reduce low frequeny content, especially if yo...

Sorry, I was wrong about the LNFB, looks like the orange drops on V1b and V2 bypass the grid stoppers. I was unable to decipher the values, anyway, something I have not seen before, wonder if this is original. Also, obviously, original e-caps were replaced . Looking forward to your contributions, I ...

Very cool, Charlie, thanks for sharing. The amp looks very familiar to me, typical 3rd generation amp with "fiunky od entrance". Right away, I noticed some differences: LNFB loop on V1b, balance trimmer in the PI section, tone stack might be 250k /250k / 1 M (T/M/B).I will dig deepeer into this when...

What surprises me is that Joe describes #14 as "more compressed" than other Dumbles he has owned. My impressions were quite different, I found the earlier specimens to be more dynamic, less compressed than the later ones (4th generation ) I played. Of course, I have never met #14, so who knows what´...

Hi Charlie, I have also noticed this phenomenon. After discussing this on the forum, I changed the wiring on my personal amp (1979 ODS) to the 80s style wiring where the OD input is grounded. I still hear a difference when connecting either a "h.f. taper" circuit, as in some Dumbles, or larger value...

Generally speaking, what's the difference by tonally between the 70's and 80's Dumble amps? All the Dumble amps I played are custom built individuals - everyone with an individual timbre, feel, playing comfort etc. Even if you only talk about one "model family" - like the ODS 50/100W e. g. - I know...

On the subject of the V2 grid stopper: HAD used values ranging from 56k to 180k, the higher the value the more attenuation of treble frequencies due to the Miller caspacitance, the higher values tend to smooth the OD a bit. I found the treble loss is quite noticable at values above 220k. The real pu...

Another idea:
If the amp has the LNFB network on V1b, try removing it.
This will add a lot of chime to your clean channel,
it will also make the OD more raw, more rock´n roll,
which may or may not be to your liking.
Good luck Marcos

Hi Timo,
HAD recommended a linear 250K pot as Treble control, although he did use
both linear and 30% taper pots in his amps AFAIK. Since the linear
type is easier to get I would go that way.
Hope this is helpful

Marcos

Here´s my 2 cents:
Instead of changing the pot,
I would try increasing the V2b coupler to .01 first,
a free experiment without soldering. See how you like it,
Marcos