3rd Generation Period Correct ODS 50W

Dumble schematics, designs, pictures. Only members may post files here.

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sonicmojo
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Re: 3rd Generation Period Correct ODS 50W

Post by sonicmojo »

In the interest of contributing some information back to the community, here is a 3rd gen BOM that I've been working on for several months now. I used it for a 50W build that worked out very well and I'm working on a 100W version that will hopefully have similar results. Aside from a few nuts and bolts, I feel this is accurate to the layout. Your sources and pricing may vary (the prices on this list are not entirely accurate since often I have to order parts in multiples) but hopefully it can help jumpstart anyone starting up their own new 3rd gen build. Thanks Tony and Mark for your layout and schematic, they helped me greatly!
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boldaslove6789
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Re: 3rd Generation Period Correct ODS 50W

Post by boldaslove6789 »

Sweet, Thanks man!!! :D
telentubes
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Re: 3rd Generation Period Correct ODS 50W

Post by telentubes »

Greatly appreciated!!!! I'm just beginning to gather parts. This will save LOTS of time.
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sonicmojo
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Re: 3rd Generation Period Correct ODS 50W

Post by sonicmojo »

In the process of building my 3rd gen FET, I noticed a missing ground connection on the layout. Here is a revised picture of the FET area. It works for me. The connections are noted with the purple line. it also applies to the 2nd gen if we want to revise the layouts. Also, I am using an NTE459 which is the NTE replacement for the 2n3823. I am sure you can use NTE452 and other options as well.

Thanks,

Bryan
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azatplayer
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Re: 3rd Generation Period Correct ODS 50W

Post by azatplayer »

Nice tones!
telentubes
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Re: 3rd Generation Period Correct ODS 50W

Post by telentubes »

In the layout, I think the .01 cap on the manual switch gets connected to the top and middle lugs, as opposed to the top and bottom lugs (?).
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sonicmojo
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Re: 3rd Generation Period Correct ODS 50W

Post by sonicmojo »

telentubes wrote:In the layout, I think the .01 cap on the manual switch gets connected to the top and middle lugs, as opposed to the top and bottom lugs (?).
You're likely right since I just checked the one picture that shows it under the 2nd gen thread. I've wired mine like the layout though and haven't had any issues with switching. If you use a bat toggle switch instead of the old style slide switch, be sure to reverse your orientation from the layout.
---------
Bryan
Goldhedge
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Re: 3rd Generation Period Correct ODS 50W

Post by Goldhedge »

Hi all, I've been lurking. This is a fabulous site!

I understand one must have good 'iron', but haven't found where that is defined.

What, makes good iron and who makes it?

edit... maybe the mods should move this to the technical forum? Sorry
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Structo
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Re: 3rd Generation Period Correct ODS 50W

Post by Structo »

Welcome to the Amp Garage.

You'll find this is a pretty relaxed and unorganized forum. :lol:

A lot of guys swear by "seasoned" or vintage iron usually taken from old Fender Blackface amps.

Especially the output transformer.

Not sure about that since I haven't tried any but there are several options for new iron.

First decide what power tube you will run and how many.
That will determine the primary impedance and power handling specs.

For instance a 100w Overdrive special running 4x 6L6GC's will like a 100w, 2K ohm primary.

I used the Magnetic Components ClassicTone # 40-18013 output transformer on my ODS clone.
It has 16, 8 and 4 ohm secondaries for flexibility.
http://www.classictone.net/40-18013.html

Some guys like to run the 100w 4 ohm OT.

Other brands are Mercury Magnetics, Hammond, Edcor, etc.
Tom

Don't let that smoke out!
Goldhedge
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Re: 3rd Generation Period Correct ODS 50W

Post by Goldhedge »

Thanks!

I guess I'm going about this backwards? I have an EV SRO12 8 ohm speaker and I want to put a quality amp behind it.

I also have 2-12" SUNN speakers from an old 412 cab I might give a try, but I think the EV is going to blow them away.

I'm considering the 50W ODS. I don't need all that much power. If they made a 30W that would suffice. Deciding which version is the fly in the ointment.

It looks as if Ceriatone has the best prices even if it's over seas - as long as you buy local iron.

Is there a tube reverb kit that will fit?
Goldhedge
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Re: 3rd Generation Period Correct ODS 50W

Post by Goldhedge »

I've been looking over the schematic and this one thing pops up that I've never seen before in electronics. I understand the ground, but what's with the loop around the wire?

Ground shielded wire?dd

Edit: After checking numerous layouts it looks to be coax.
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Last edited by Goldhedge on Fri Jun 15, 2012 3:54 am, edited 1 time in total.
Teleguy61
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Re: 3rd Generation Period Correct ODS 50W

Post by Teleguy61 »

Yes, that is the symbol for shielded wire, always grounded only at one end.
Do a lot of research here before going forward. This is a great resource.
I have built a Ceriatone kit with old Twin iron which came out really well, but I am in the process of scratch building, now tweaking a D'Lite based amp.
If you have ampbuilding experience, the scratch building experience can be,
and it has been for me, very rewarding and instructive.
Read and learn here-this is the place.
Good luck.
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Structo
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Re: 3rd Generation Period Correct ODS 50W

Post by Structo »

Goldhedge,

With the Dumble ODS style amps, people usually go with the 100w option because of tone.
These amps have good master volumes and can basically sound good at any perceived volume.

Another thing is, I think most here would agree that a Dumbleator (tube buffered effects loop) enhances the tone of the amp besides acting as a great effects loop.

The Send and Return jacks on the amp are simply preamp output and power amp input.

With the Dumbleator setup you can use the output pot on it for your overall master volume, that way you can have the pregain and master on the amp up where the tone lives.
Tom

Don't let that smoke out!
Goldhedge
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Re: 3rd Generation Period Correct ODS 50W

Post by Goldhedge »

I've been reading...nearly every thread. :D It's all I do...anymore!

I'm interested in the 100W as long as I can play at "in the house volumes"... and it appears I can...

I think the Dumbleator ckt should be included (from what I've gleaned). Can it be installed in one chassis?

I condensed the BOM to a specific item order sheet instead of being spread out over the layout sections. That way I just order once and hopefully don't miss something.

The 'red' highlights I have questions about. Are these parts all the same, or is there really a difference? The cap, won't the 500 pF work here?

Please review and advise and I will correct. Also if you see anything I missed (Dumbleator parts, for example, I haven't gotten yet)?

Thanks
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Goldhedge
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Re: 3rd Generation Period Correct ODS 50W

Post by Goldhedge »

I found Merlin Blencowe's "Designing Valve Preamps for Guitar and Bass" in my ramblings across the net. Copied the pdf's and have studied the common cathode triode gain stage. He certainly makes subject come alive. I recommend getting the book if serious about designing amps!

I've been reading and attempting to analyse the pre amp and tone stack section.

I think what I'm looking at is a common cathode paraphase inverter design (see attach)? At first, I had thought it was a DC coupled cathode follower, but the output isn't on the cathode. Kept searching and found the PI.

In the ODS, after the valves are properly biased, the input 'B' TRD feeds the tone stack which feeds the 'A' TRD and eventually the overdrive/clean circuit and on to the inverter/power tubes section.

I've figured out that the tone control section changes the AC voltage that the TRD 'A' triode grid sees. The Rock/Jazz, and Deep switches change the resistance of their respective pots. The capacitance alters the Hz seen by the 'A' TRD grid which in turn determines treble, mid, bass.

I'm guessing that Dumble's contribution to this set up is the tone stack biasing as the amp design is a fairly simple setup in that it's a 'standard' design found all over the place. Am I close?

I'm still exploring, but it's pretty cool so far. Now, it's on to the OD triodes!
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