modifying my touring amp with Dumble tone stack..Which one?

[imo1]

Hey everybody,

I've been doing a ton of reading and learning!
i got all excited about possibly picking up a Two Rock classic reverb, until I learned how backed up they are!

I started looking at building some type of similar Dumble style build in that vein, and was tossing a bunch of different designs around. Lots of cool goodies.

Realized I already have enough amps, and like my touring rig, which is a signature amp i worked on with a builder in Texas. It's a little bit blown out, sounds great when I push it into my classic lead territory, but was wanting a little more responsive "cleanesque" tone. I grew up playing blackface fenders and strats(Texas boy) and evolved my amp along with my playing from a Super Reverb into many variations of it beefed up, Matchless, then many, many amps. My style of playing tends to be single channel, think of a super reverb on 6. This seems to be prime territory for Dumble type circuit mods

This amp has some "Dumble-esque" features already. I'm considering pushing the pre-amp into more of a SSS zone. losing some gain in the first two stages(going to more traditional fender-esque 100k plate, and employing the tone circuit from the SSS, without the rock/jazz switch or the downstream filter switches. I'd modify my bright switch to two different options and include the mid deep switch

I'm also looking at copping the SSS presence as well, and possibly changing my reverb level into a send return scenario.

Would love any thoughts on different tone stacks, or any other additions that would be in that realm.

Here is the schematic of my amp. I'm basing the SSS ideas off of the SSS light file.

Right on!

Ian

[talbany]

Low Plate Classic

Tony

[imo1]

Thanks Tony! I'll do some reading.
BTW, really appreciated the posts of yours I've been reading. They have been helpful in getting a grip on what's up.
I've built a bunch of amps, but venturing into this world and trying to understand where it intersects with my playing is a major shift.

[imo1]

It seems that i could add the tone stack with extra switching and change the NFB with the existing layout I have.
If I were to add the OD that would add another pre-amp tube, doable, but need to look at where in the existing circuit to put it.

[imo1]

And, if I skip the rock/jazz switch I can also ditch the 22M resistors

[talbany]

My style of playing tends to be single channel, think of a super reverb on 6. This seems to be prime territory for Dumble type circuit mods
(going to more traditional fender-esque 100k plate,

So out of all the " Dumble tone stacks" That would be closest in sound and EQ to a Fender/ Super AB76 would be the "Classic" Stack. (100k slope/.047 mid cap/100k mid pot)

and employing the tone circuit from the SSS, without the rock/jazz switch or the downstream filter switches. I'd modify my bright switch to two different options and include the mid deep switch

If you take a look at the D-Lite Schematic/Layout he omits the R/J switch and permanently wires it in Rock mode (Search D-Lite schematic)Is that what you are talking about??
BTW... It generally depends on which SSS your talking about SSS#002 has something very similar to a "Classic" stack another reason why I referred you to it. If you like you can sub out the "Deep " switch and add the mid switch

I'm also looking at copping the SSS presence as well

OK now you are talking about output sections? Again which SSS are you talking about? The ones that use the CF driver to drive the grids has a completely different PI/GNFB circuit than the ODS? Apples/Oranges? If your not going to use the Driver I would simply modify the presence circuit in the ODS

And, if I skip the rock/jazz switch I can also ditch the 22M resistors

The 22m resistors are primarily for the preamp boost.

It seems that i could add the tone stack with extra switching and change the NFB with the existing layout I have.
If I were to add the OD that would add another pre-amp tube, doable, but need to look at where in the existing circuit to put it.

The rest is really up to you! You could put NFB on V1 0n a switch as well as opt out of the preamp boost and of course make it a single channel amp omitting the OD section and switching.
The cool thing about adding the OD section here is you can basically shift or simulate a Super Reverbs volume control on 3 and on 6 adding in that extra bump in gain without the big jump in volume. That's how I would think of it, is this a feature you could use?
Good Luck!

Tony

[imo1]

Tony,

Thanks again for your replies! Definitely gonna start with the classic stack. I'm gonna go ahead and add the jazz/rock switch.

Ive got a new PT and OT coming for this. They are both Twin drop-ins, so I should be good on power. I noticed that most folks are using seperate 6V transformer for relays. I'm getting some 5v that run on something like 40mA. The tubes total are 5.1A. The PT is rated for 5.5A. Seems like the PT would be fine. Is there some other reason to run them separately?

Interesting thing will be to integrate the OD section with my current reverb that is already on the amp. I will be adding another AX7 for the OD section. Not yet sure how I'm gonna do the layout of that part. Probably gonna have to tagboard it. I haven't read much of folks integrating all of this. I figured i could just add the OD on a manual switch for now and see how it sounds in circuit.

I'm going to physically have to move some stuff around to make the 4 6L6's and the additional AX7 fit. Thinking I might cut out a piece of an old chassis to evenly space out the Power tubes. I can move the probe points to the rear of the amp. I'll also get rid of the 6L6/6v6 switch, and probably use that space for the AX7

Looks like there is some work to do!

Ian layout.png

[imo1]

I am starting to do some of the metal work, and moving some components around to make room for the bigger transformers and additional tubes.

I'm curious as to where to tap off for the reverb. Should I tap after the V1B tube? I haven't found any OD style amps with reverb to compare to(at least schematics). The Wonderland taps right after Volume(Gain) and before V1B. The circuit has similarities to the OD so figured it might be a good template as a good sounding, working amp using an OD type circuit with reverb,

[imo1]

JM Circuit.png

[dbharris]

Have you decided if you want pre-OD reverb or post -OD reverb?

This may be of interest, see Aaron's post with block diagram:

https://ampgarage.com/forum/viewtopic.php?f=5&t=28425

-Dan

[imo1]

Thanks Dan! I haven't decided. Trying to get some perspective on what would work best for my playing. I'll check that out!

[imo1]

that is quite helpful. My current reverb is pretty similar to a Super reverb. I'm understanding the nature of the OD a little better now in terms of clean vs overdrive. The non overdrive is actually like the non vibrato channel in an old fender. i don't know why I hadn't noticed the lack of another gain stage in a Fender. The 1/2 7025 adds a bit of umph to drive the PI.

Looks like I should probably take it after the 2nd gain stage. I'm gonna try a 1M pot where my grid resistor is into the Reverb and then my 100k(which is my current 'reverb' control) will be my return

[imo1]

The journey is the thing..Right?

So, this is my backup rig. I decided to experiment with a Dumble type situation, and as I got further into it, read and learned a bit, I shifted into a complete rebuild. I know it's a bit of mid-stream shift, but I am learning a lot about the circuit, and will be able to amend and shift as needed to my playing once I get it in the field. I am pushing the space and I would prefer a cleaner layout, but as I am working with a existing board, I had to work around. If I am having issues with this layout, I will go back and create a board from the ground up. The OD circuit is the most convoluted, but I have it reasonable clean. I went back and repositioned the second cathode resistor/cap as well as heat-shrinking a couple of things.

I based this off of Rootz's TR CR model. I used the general pre and tone stack of the low plate, but put the mid boost, as well as the eq shift in the front. I'm trying the 2 tube reverb. Should have the board finished in the next week or so. I'm going out of town for the weekend, but plan on seeing what I've created some time next week.

IMG_1648.JPG

Ian CR mod.1.pdf

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IMG_1646.JPG

[Colossal]

Imo,

Note that your values for R4 and R9 are reversed on both your schematic and layout. Refer to #102...unless your values are intentional, of course...

[imo1]

Imo,

Note that your values for R4 and R9 are reversed on both your schematic and layout. Refer to #102...unless your values are intentional, of course...

Thanks Colossal. I've moved towards a low plate classic circuit. The first two cathodes are 1.5k. I think that's what you are referring to