DLM Ideas

[Littlewyan]

Hi Guys

I'm going to at some point build myself an amp for use at band practice and maybe small gigs. I've already got an Express but for practice it is way too loud and an attenuator just sucks the magic out of the tone. Anyway to make things interesting I've started looking at single ended amp designs and as I love Trainwreck Amps I've been scouring the forum for info on the DLM and come up with a couple of schematics which are based on what I've read.

Both have a fake PI and use 2 x 12AX7 with a 6V6 (will also try a 5881 once its built as I have a quad of those spare). One uses an Express Pre Amp and the other uses a Komet Pre Amp. I recall Mark Fowler suggesting the Komet Pre Amp may be what Ken used in the original DLM as it had a JCM800 voicing but with Trainwreck Clarity, so I reckon its the way forward. But I love the Express so made an Express version as well.

Let me know what you guys think of the schematics.

[10thTx]

Just to throw another idea of a lower volume Wreck into the mix, you could consider a 6BM8 version?

It would not sound totally like a Wreck, but then a single ended version probably won't either.

This would be about 7-9 watts push/pull. It is a DRAFT idea, I have not built it.

With respect, 10thtx

[Littlewyan]

Its a good idea but I've already got 6V6 and 5881 Valves spare. Plus I've never built a single ended before so should be interesting. Might use a GZ34 rectifier too.

[romberg]

My next project will be to graft an express preamp onto a gilmore jr. power amp (self split 6n1p). Should put out about 1 watt. I have no idea if this will work well or not . I suspect I will have to add a voltage divider to knock down the preamp output a bit.

Mike

[Littlewyan]

I don't know much about self split am afraid. I imagine you probably will have to do something about the pre amp gain, although as you haven't got a PI you might be alright. Start yourself a thread and ask. Or maybe take a look at the AX84 forum as I know for sure they've designed and used self split circuits over there.

[matt h]

(deleted)

[Littlewyan]

Trouble is I dont have any spare triodes. What do you think the sound difference would be between a proper LTPI and my single stage? As obviously for starters the NFB is only on the cathode whereas on a real LTPI its on the cathode and one of the grids.

P.S. This guy switches between PP and SE by grounding one side if the LTPI http://www.ampmaker.com/store/P1800-plexi-amp.html

[matt h]

(deleted)

[Littlewyan]

Fair enough. Might just have to add another 12AX7 then. Although I'm wondering how Ken made the original DLM. He wouldn't have used an LTPI as then he would have only been left with 2 triodes to play with. Sure you could have 2 gain stages then the phase inverter and you'd have nice distortion but once you turn the master volume down you'll lose the power amp distortion and wont be left with much. Thats why I think there is definitely 3 gain stages in this amp plus a fake PI or perhaps just a standard driver stage with NFB on the cathode.

One thing I can't get my head around is how on the front panel of the DLM the Master control comes before the Presence and the Slope control after the Presence. Surely the master would come after and surely the slope would be next to the Bass, Middle and Treble controls?

All I know is I definitely want to try and get a Komet sound. Those amps are great.

[M Fowler]

The pot labelled slope was a mid-control per wreckboy that owned the prototype DLM.

[Littlewyan]

What kind of mid control though? What pre amp did you use for your DLM Fowler?

[M Fowler]

What kind of mid control though? What pre amp did you use for your DLM Fowler?

From what I can gather it's just a normal 25k mid pot. Probably was something else in the prototyping since it is located away from the treble and bass. But you could put in a slope control pot, as that is considered a mid shift control (such as on mojotone 50w bass amp). They use a 250k pot for slope labelled mid shift.

I didn't really build the DLM I built the Allen's Amp Class Act schematic.

[statorvane]

One thing I see is your 6V6 has no grid leak. I think you need to swap C11 and R20 around. Have C11 coming right off the volume pot wiper, then join with the grid lead and grid stopper, R7.

[Littlewyan]

O yeah I'll swap them around.

How did the class act amp turn out? Did it have a lot of gain with good clarity?

[Colossal]

I remember a post about the Allen Class Act by Funkalicious Groove some years ago. He said it was a great amp and that he actually gigged with it. That post is in the Dumble Discussion archives.