"Devolving" an ODS Circuit...

[BTF]

After reading the various posts in this Dumble area, and listening to a few audio clips, I have decided to try my hand at building a rackmount Dumble ODS-influenced preamp. I only want to use it as a lead preamp, with no effects loop or switching. Therefore, I want to derive a simplified lead preamp from one of the schematics so kindly placed on this site.

My question is this: The various schematics seem to show very different topologies between ODS circuits. If I want a generalized Dumble-type setup, which of the schematics would be best from which to "devolve" the circuit?

My thanks for any input offered, as I am pretty much a Dumble neophyte!

Regards, BTF.

[Zippy]

Are you saying that you want only a lead channel with preamp boost and overdrive engaged?

Do you have any preferred Dumble sounds? If you cruise the clips within these pages and associate sounds with settings, you're there!

[boldaslove6789]

Like this...

[BTF]

Thanks to both of you! Yes, bold, if I understand that the preamp you picture is a single channel preamp, that is similar to what I'm contemplating.

Zippy, you've got it. What I have is a single space rack chassis and power supply. It's currently doing duty as an acoustic preamp which I earlier built, but I've been mulling over building an ODS lead channel instead.

One problem is that I really have no clue on Dumbles. The schematics for the ODS amps seem quite different, and I didn't know if one in particular exemplified the Dumble overdrive sound.

Neat rack, bold. I'm still a rack fan, even if that time has passed me by.

Regards, BTF.

[boldaslove6789]

BTF

Nah its not a single channel preamp. Its a clone of Tags Dumble ODS 183' made by Shad @ Quinn Amps (has both clean & Overdrive) Skyliner NON-HRM. with ftsw'able FET and Master bright cap push/pull for use with high pF cables in the loop.

I'm using it with the power amp of my 100w Mill Creek Bluesmaster, with both preamps on a switching system.


AFAIK if you want the OD don't you need the clean too. If you're going to build a preamp wouldn't you need to build both the clean side and OD side because the clean cascades into the OD, correct me if I'm wrong though.

[John_P_WI]

A lot of good info in this thread.

https://tubeamparchive.com/viewtopic.ph ... sc&start=0


Look at page 2, Ontariomaximus has a TIF posted with the schematic and page 3 has tweaking tips.

This is about as simple as you will get.

John

[BTF]

Thanks so much for your kindness. I'll have a look at that, JPW. I've never heard of a Dumblelite.

Thanks again.

[jaysg]

hmm...to narrow things down, you need to poke around the mp3's for the different amps. The 183 preamp without the Clean/Lead relay would be a good piece. I would still recommend the PAB and Mid-Boost on footswitches. Are you trying to eliminate footswitches? (note that the Mid-Boost on a footswitch is not a standard feature.)

You need to know what guitar(s) you will use. There are multiple tone stack options, most of which favor humbucking pickups. I prefer the "Classic" tonestack for a strat. ymmv...183 has the Skyliner tonestack.

[Zippy]

AFAIK if you want the OD don't you need the clean too. If you're going to build a preamp wouldn't you need to build both the clean side and OD side because the clean cascades into the OD, correct me if I'm wrong though.

What you could eliminate is the switching and relays - for that matter, you could also eliminate a lot of front panel knobs if you use trimmers and a set-it-and-forget-it mentality.

I've seen some discussion here that, for at least some period, Larry Carlton played his amp always in OD mode and controlled clean-to-OD transition by adjusting his guitar's volume control - and, of course, his touch.

[Structo]

I'm not entirely clear on what you want.
Do you want an authentic ODS preamp?

That would be four stages of preamp and the phase inverter.

The overdrive is two stages cascaded onto the clean stages.

You can have front panel switching or preferably, a footswitch to change between clean and overdrive.

Look in the files section.
The #124 ODS was one of if not the first ODS reverse engineered.
It has 100K plate load resistors along with 1K5 cathode resistors so it is along the lines of a Fender amp gain wise.
But they use smaller bypass caps to keep the bass manageable.

For a bit more modern sound the amps with what are called high plate amps use 220k/150k plate load resistors along with 3K3/2K2 cathodes.

You will want around 195-200v on the preamp plates and 285-300v on the PI plates.

[BTF]

Thanks to all for the posts. Actually, I'm not sure what I want either! I'm going to research some of the Dumble posts here and try to suss out just what I want to go for.

I don't have a problem with the build, as I've built rack equipment since the 80's. However, it's all been acoustic instrument, Marshall, Fender, HiWatt and Vox-oriented. I never even noticed Dumble until I joined this forum. I had only seen an article in an old Guitar Player on the fellow (he was called "Howard" then).

I'll try to figure out (with the helpful posts you fellows offered) what I'm going after. Structo actually answered a question I had, but which I had not posted. That is, the difference in the pedigree of the "High Plate" and the older-style circuits.

I'm also interested in perhaps building a Boogie-style preamp. As I have only played an old Mark IIb, I'll similarly have to try to "Youtube" some videos on those as well. I'm looking for a kind of American high-gain, Jazz Fusion type of sound.

Thanks again for all the help! Bill.

[Structo]

You must not belong to The Gear Page forum then, eh?
There have been a gazillion Dumble threads there over the years.
They can get quite heated as the haters try to spoil the fun for others.
The crowd is split 50/50 or so, some hate to even seen the D word while others are fan boys.

Sure most if not all of us could never afford the real deal so we build our own.

I'd say the majority of the guys here really like the amps and the versatility they offer.

[tubedogsmith]

I'm also interested in perhaps building a Boogie-style preamp. As I have only played an old Mark IIb, I'll similarly have to try to "Youtube" some videos on those as well. I'm looking for a kind of American high-gain, Jazz Fusion type of sound.

Thanks again for all the help! Bill.

Honestly, stick a loop box in the effects loop of an old Mark I or Mark III and you can get it to sound very, very dumbley. That American high gain Jazz/Fusion deal you talk about.

[BTF]

I've never visited the Gear Page, but I'll have a look.

Actually, tds, I've been mulling over trying a Mark I build. I've never played one, only an old IIb (it's been ages, and I must not have cared for the tone since I didn't buy it- the store wanted $350 US for it!). I checked out Ford's tones as he's one of the main Dumble players. It was a nice tone, but not exactly what I had in mind. I've heard George Harrison using a Mark I, and I suppose Santana used one of the originals. I'll have a look and see.

Thanks again!