Dirty Little Monster

[Zippy]

2Tone: I understand. Could you throw us a bone and tell us what pre's are similar to the DLM?

BTW, some of us are working with the transformer companies that Ken dealt with and they are being very generous in sharing the specifications so the trannies may be easier than you imagine.

I agree that there still exists the possibility of wide variation. Heck, what are my chances of nailing the sound of your amp if I never hear it?

Mark, I'll work with RJ to do a DLM build and some initial tweaks. What I don't know is just how much gain was in the original vs prototype vs III. We're hearing from Derek that Ken favored single coil pickups so does that mean that the DLM should have more gain? I dunno.

Consider this one as coming off the back burner and getting some attention as the next build. There, RJ, I just commited you!

[M Fowler]

Zippy,

Thanks that would cool if you two could do that. Looks like 2tone said a hot rodded JCM type circuit so thats a start.

Mark

[RJ Guitars]

Schematic updated 2/28/09 to Rev. 1B

Thanks to all of you for starting this tread on the DLM, it is just what I want to build as well.

Anyone with better skills than me, would you please draw up a JCM front end to SE and spec which trannies that I should used, RJ, Zippy anyone?

I would greatly be indebted to you.

Mark

Mark,

Please make a big note to self as you read the "Unverified Draft" part of the attached schematic - I don't really know if this is a good idea much less a build-able amp. On top of that it's probably got a few mistakes and there was a lot of shooting from the hip... so proceed with caution!

I'll probably start out with something like this but I can say that it's really similar to the DLM. It has a lot of plexi to it but I dropped the "B" input. I've also added a gain stage just before the master volume and note that I used a 12AY7 for the cathode follower tube as well as that extra gain stage.

The extra gain stage serves as far as a "Hot Rod" adjustment to the plexi but I wouldn't want too much of a good thing so the 12AY7 seems right... of course were not going to be able to stop some over the top shredder kid from putting a 12AX7 in there and scorching our ears with the thing... I don't know how many times you gotta tell'em, we all know all the notes and it's not a contest to see how many of them you can cram into one song - Listen to some Neal Young and see what you can do with just one note!

I've got the treble bleed feature like we read about for the DLM, but I have no idea if it's wired it up right.

I'll be curious what you actually build and if anybody builds this tell me how it works out... and what I need to change to make a good drawing.

rj

[mcrracer]

Hey RJ
This looks very interesting We may very well end up with several different workable takes on a DLM type amp. Without verification from an actual owner we just have to build until we are happy with the result.. B+1...should it really be before the standby switch? Exxcuse my question but I just don't understand this part. Also what do you think about it having a NFB control? If so should it come in on pin 8 of V1a? Do you have estimates of what you think the B+ voltages should be? I am sure your design skills far outpace mine so please excuse my noob type questions. Thanks for starting the ball rolling.

[El_Martin]

...just for your interest the schematic of the Allen Class Act:
https://tubeamparchive.com/viewtopic.php?t=2984&start=0

Brandon/Bludotone recommended this one as a starting point for a Dumble SE

Must be everything in those lil' tiny one cylinders...

Ciao
Martin

[sliberty]

Forgive my ignorance, but can you explain what C10 and VR6 are all about?

Thanks,
Steve

[Jana]

RJ,

If I might make some suggestions:

I don't think C10/VR6 will work as you intended with the values you have. Because it is across a 1 meg pot the value of 25K for VR6 will have little, if any, effect. I would change it to 250K to start with.

VR5, I would be concerned that the 1meg value is too high a resistance for the grid of a 6550/kt88 (when the master is turned up). I would change this to 250K at most.

V1a and V1b, V1a is the first gain stage and V1b is the final gain stage before the power tube. Given the higher gain of this pre-amp, I would be concerned about oscillations and other instability coming both from the internal close proximity of the tube and also the wiring to connect to this tube.

When I first read this thread and the mention of a "hotrodded JCM" amp, I thought about a JCM800 2204/2203 style pre-amp, not the 1987/1959 plexi style pre-amp. The 2204/2203 is a good starting point for a dirty amp and with some tweaking can yield a good rock tone. Maybe explore that too.

[Ron Worley]

FWIW, Allyn mentioned to me that Ken always used V1b as the first stage as it is typically the quieter of the two triodes in the tube...

I'm not smart enough to know why or how, but I know that Allyn is...

[Ron Worley]

Hey RJ
This looks very interesting We may very well end up with several different workable takes on a DLM type amp. Without verification from an actual owner we just have to build until we are happy with the result.. B+1...should it really be before the standby switch? Exxcuse my question but I just don't understand this part. Also what do you think about it having a NFB control? If so should it come in on pin 8 of V1a? Do you have estimates of what you think the B+ voltages should be? I am sure your design skills far outpace mine so please excuse my noob type questions. Thanks for starting the ball rolling.

Also, Ken put the B+1 before the Standby to minimize the "jolt" that the circuits see- if the filter caps were after the Standby, their charging would be quite noticeable... I think....

[mcrracer]

I was just wondering about putting B+ on the plate before it warmed up.

[dartanion]

Come on 2Tone! What's the harm in a little photo of the outside of the amp?

We all drool over this stuff, so make us salivate

[Zippy]

When I first read this thread and the mention of a "hotrodded JCM" amp, I thought about a JCM800 2204/2203 style pre-amp, not the 1987/1959 plexi style pre-amp. The 2204/2203 is a good starting point for a dirty amp and with some tweaking can yield a good rock tone. Maybe explore that too.

Jana, the earlier post mentioned both "He described it as a Killer Plexi with Trainwreck clarity and voicing with the master disengaged. Using the master gave it a more JCM 800 flare." Hence, my starting suggestion.

[M Fowler]

RJ, Jana, Ron, Zippy, Martin, and anyone else.

Now were cooking thanks for getting this going. I will study the data we are getting and I am not building anything yet but will.

Mark

[RJ Guitars]

RJ,

If I might make some suggestions:

I don't think C10/VR6 will work as you intended with the values you have. Because it is across a 1 meg pot the value of 25K for VR6 will have little, if any, effect. I would change it to 250K to start with.

VR5, I would be concerned that the 1meg value is too high a resistance for the grid of a 6550/kt88 (when the master is turned up). I would change this to 250K at most.

V1a and V1b, V1a is the first gain stage and V1b is the final gain stage before the power tube. Given the higher gain of this pre-amp, I would be concerned about oscillations and other instability coming both from the internal close proximity of the tube and also the wiring to connect to this tube.

When I first read this thread and the mention of a "hotrodded JCM" amp, I thought about a JCM800 2204/2203 style pre-amp, not the 1987/1959 plexi style pre-amp. The 2204/2203 is a good starting point for a dirty amp and with some tweaking can yield a good rock tone. Maybe explore that too.

Jana,

I am greatly appreciative of your input. I know that you mentioned before that you have a great sounding single ended amp.

I think you've made a good call on both the VR5 and VR6 values and I'll update my schematic to show those changes.

You also make a good point about gain stages and proximity effects. Let me see if we both understand what I have on that second preamp tube... I need to look at my own drawing and verify but I think it's: input - volume control - gain 1 - gain 2 - cathode follower - tonestack - gain 3 - master volume & treble bleed - output stage. So I assume the worry is that the cathode follower might cross talk to that final gain stage.

That makes a good case for going with the traditional three preamp tube Trainwreck standard layout. This would allow us to include that traditional Hi/Lo input section from the typical plexi or go with the cathode follower in a tube by itself like the Rocket amp does. Of course I know a few who will want to do some parallel triodes if there is a leftover section.

I thought of the 1959 Marshall because it is my own all time favorite... although maybe not every bodies idea of a hotrod plexi.

I'll try to get to the other comments and questions in short order.

rj

[RJ Guitars]

Forgive my ignorance, but can you explain what C10 and VR6 are all about?

Thanks,
Steve

Steve, from way back in some posts on the Blue guitar site as well as the posts made here on the AGF, we have a bit of a glimpse and some text about the front panel on the DLM as well as a little commentary on what the knobs do. There appear to be two inputs (I dunno what KF had in mind there) a typical tonestack, then a 5th and 6th knob. From what was said about those it seems one was a master volume knob and the other a treble bleed around it.

I've never seen a treble bleed circuit or built one before but I think of it as working like a bright switch around the master volume.

I'll be updating my schematic with the pot values that Jana suggested and then see what else we learn about this little monster before I start building...

rj