3rd Generation Period Correct ODS 50W

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martin manning
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Re: 3rd Generation Period Correct ODS 50W

Post by martin manning »

Most folks here are very familiar with Merlin's books. They are among the best ones to appear on the subject, IMO.

All of the clean and OD triodes in an ODS are straightforward common cathode gain stages. Dumble's tone stack has some unique features, but it is basically the TMB stack used by Fender since the 50's.

What is it you are referring to as a "TRD?"

BTW, this type of post belongs in the "Discussion" section. The "Files" section is reserved for reference materials like schematics and layouts.
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Structo
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Re: 3rd Generation Period Correct ODS 50W

Post by Structo »

Yes, Goldhedge could you please take the discussion to the main Dumble section? :)

I don't have moderator ability in this section so I can't move your posts.
Tom

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

Post by Max »

Structo wrote:With the Dumble ODS style amps, people usually go with the 100w option because of tone.
Tom, AFAIK this isn't correct. Just some few examples: David Lindley used two 1st generation ODS 50W heads. Steve Lukather used a 2nd generation ODS 50W combo and AFAIR Steve Kimock a transition generation "classic" ODS 50W (#0086). Andy Brauer Studio Rentals in LA owned a 2nd generation ODS 50W combo for rent that AFAIK is on countless records and Terry Haggerty used a transition generation "classic" ODS 50W combo (#0077). More examples: http://ampgarage.com/forum/viewtopic.ph ... 06&start=0

IMO the ODS 50W amps just have a different individual character - perhaps because of their different dynamic response and because of the different flavors provided by the 50W Fender Bassman and the 100W Fender Twin/Showman output transformers.

The small volume difference between an ODS 50W and an ODS 100W IMO isn't of much practical importance anyway. So IMO it's just a matter of personal taste if someone prefers the feel and timbre of the 50W version or the feel and timbre of the 100W version.

Cheers,

Max
xk49w
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Re: 3rd Generation Period Correct ODS 50W

Post by xk49w »

I am now starting to attach wires to the assembled boards based on this layout and this schematic (both in this thread).

I sort of expect that the layout is correct. That said. the schematic appears to have some small errors. The two tube sections are reversed for V1 and V2. Maybe this doesn't matter but one couldn't lay it out without crossing wires according to the prototype mainboard layout.

Then for V3 (PI) the two tube sections are also reversed. (The layout has the 5n from the master vol going to pin 2). However. the plate resistors also appear correspondingly reversed according to the layout; the 47k should be on the inverting section's plate.

This would not be problem for folks that build from the layout but for others that don't, maybe.
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Matt J
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Re: 3rd Generation Period Correct ODS 50W

Post by Matt J »

I've been studying over this design because I'm considering using the preamp and preamp switches for a Small Special build I am planning. Considering those amps may have both been made around the same time, I figured a 2nd/3rd gen design would be the way to go.

I want to make sure I understand the correct wiring for the preamp (bright, deep, and jazz/rock) switches before I continue any further. I'm afraid I might over look something from the posted layout and schematics, so I've drawn out the switches in Microsoft Paint (Note: I am not an artist!)

How does this look to everyone? Have I missed any connections or overlooked something from the layout?

Thanks!
- Matt J.
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jelle
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Re: 3rd Generation Period Correct ODS 50W

Post by jelle »

Looks good for an ODS. But a Small Special does not have the mid cap on the board. The cap over the bass pot has that function.
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Matt J
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Re: 3rd Generation Period Correct ODS 50W

Post by Matt J »

Thanks Jelle!

I'm using some of the Small Special builds you and others have posted on here as an inspiration! Of course I will have to reverse this image since I plan on building the chassis like the original, with the tubes pointing upward.

Just working now on slowly sources the parts I need and making sure I understand the circuit (I've been working on my own layout and may post it in the Small Special section) No need to rush into things. Experience has taught me that patience pays off in examples like this!

- Matt J.
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jelle
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Re: 3rd Generation Period Correct ODS 50W

Post by jelle »

Sweet, have fun prepping! :D
Bombacaototal
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Re: 3rd Generation Period Correct ODS 50W

Post by Bombacaototal »

Thanks a lot for all the details

I am listening to "I Fall In Love Too Easily" and it sounds great!
talbany wrote:Here is a 3rd generation ODS 50W..

3rd generation made around the 1978-1979 Ser# around 60-75..
Since these alterations occurred around a 2 year time frame and more than 1 or 2 amps and for the sake of accuracy should be referenced as 3rd generation ODS and shouldn't be looked upon as tweaks or custom voicing s for a certain customer..
Changes are listed on the top right of the layout are


1 Treble: 250KA treble pot

2..005 soldered between the wiper and top of the Bass pot

3.Black RG59/U 75 ohm foam - similar looking as the Tandy Wire RG59/U 75 ohm foam in ODS #094,(see below picture) but without the "Tandy Wire" label

Although this layout wasn't taken from an actual 3rd generation specimen perhaps I'll run across one here in the future..If so I'll make another separate layout better reflect the accuracy's of that amp (3rd Generation)



3rd generation "pre-classic" clips: (Posted By Max)

http://ampgarage.com/forum/viewtopic.ph ... 117#135117
http://ampgarage.com/forum/viewtopic.ph ... 120#135120
http://ampgarage.com/forum/viewtopic.ph ... 121#135121

Clean sound of a 3rd generation "pre-classic" Overdrive Special 50W combo with 12" Altec 417-8H Series II with a paper dust cap mod

Karl Ratzer "I Fall In Love Too Easily"

Karl Ratzer – guitar
Karl Hodina - accordion

Don't miss Karl Hodina playing his accordion!
More discussion

http://ampgarage.com/forum/viewtopic.ph ... 428#138428

Here you find clips of all the ODS generations from David Lindley's 1st generation ODS up to the skyline-HRM amps in the #200+ range: http://ampgarage.com/forum/viewtopic.ph ... 06&start=0


Enjoy Tony
Last edited by Bombacaototal on Tue Jan 31, 2017 10:37 pm, edited 1 time in total.
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Matt J
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Re: 3rd Generation Period Correct ODS 50W

Post by Matt J »

jelle wrote:Sweet, have fun prepping! :D
Thanks Jelle!

Prepping really is half the fun of amp construction for me! I love getting a big pile of parts and components, then going through and doing prep work o on them: measuring out component values to make sure they haven't drifted, etc. Some more board building supplies should be coming in the mail soon, and I am very excited about the new Weller soldering station that's on its way.

Now I just need to build a new a capacitor out foil test box! I made one several years ago that worked great, but I have misplaced it some where!
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Matt J
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Re: 3rd Generation Period Correct ODS 50W

Post by Matt J »

Thinking back on this 2nd/3rd generation circuit. I know this layout and schematic doesn't show the use of a PAB boost, but has anyone consider an alternate way of remotely switching the Jazz/Rock switch? I've tried to do some searching on here about this topic, but haven't found anything that directly discusses this.

Could you wire a standard footswitch, like some reverb and tremolo units use, without having to use powered relays so that, instead of engaging a PAB, it just switched between the Jazz and Rock setting.

Just a curious thought I had. Since I'm using parts of this circuit in my Small Special build, I've been thinking over a lot of things about this design lately.

- Matt J.
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jelle
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Re: 3rd Generation Period Correct ODS 50W

Post by jelle »

I much dislike the PAB with this circuit. I wonder why some commercial builders add it...I really wonder.
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