D'Mars ODS with two cathode followers experiment

[10thTx]

Moderators feel free to move this to another forum if you want. I hoping it's OK to post it here? Wasn't sure where to post it?

I am posting this hoping it may be of interest or helpful to others who are experimenting with modifying their Dumble inspired builds.

I also thought that the info might be useful regarding the tone difference between the OD with and without a cathode follower given some of the mystery around " the Ripper" which supposedly has a CF in the OD (reportedly Carlton's amp)

Given this has a Marshall inspired clean and not a Dumble inspired clean, I realize this is somewhat apples to orange comparison to the Ripper. Having said that, this post will describe an apples to apples change in tone when adding the CF.

And given the interest in the recently discovered Dumble clones such as the ManZamp and Tweed D Deluxe, maybe someone is looking for new ideas.

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The D'Mars was originally an idea to use a Marshallish inspired preamp into a Dumblish inspired OD, FX and LTPI (but using cathode biasing).

The D'Mars has remained my favorite "clean" tone of any amp I've owned or played. However, the OD did not have quite the same "wow factor" to my ears.

I remember Talbany mentioning something to me about using the CF on the clean/preamp stage as the "send" section for an active FX. That ideas has stayed with me for about a yr and I ran across several Marshall FX ideas that simply had a return triode for the FX.

The experiment ................

So, I moved the send triode from the active FX to be a cathode follower on the OD stage. This is the results to my ear.

- I think the clean is somewhat more transparent/touch sensitive. And the
OD is significantly more transparent and touch sensitive.

- Adding the CF to the OD section seemed to add more harmonics,
compression, removed some slight high end hash and made the OD
sound more musical to my ears.

- However, adding the CF eliminated the "vowel" tone that the OD had
& it reduced the "blooming" feature where the notes seem to open up
and blossom. Ironically, the sustain is about the same but the notes
definitely don't swell and open like they did.

- I found the more original Dumblish OD sounded best to me with more
subtle picking and that aggressive picking lessened the sweetness to
the tone. In contrast, the added CF has a great musical sweetness
to my ears even (or maybe especially) when digging in and playing more
aggressively.

- The amp is now somewhat louder (& transparent) & I have to turn the
FX level pot down more.

The best I can describe is the tone is sort of Marshallish 75% & Dumblish 25% with the CF in the OD section.

It should be noted that the triode in the cathode follower is a 12AY7 and the return triode in the FX is the 12AY7 also.

I did try a 5751 which sounded good and more driven but not quite as musically sweet, to my ears. I also tried one of those reverse 12DW7's which I didn't care for too much.

Hopefully, there may be something in this post that may be useful to someone with a D-clone or D-inspired clone.

With respect, 10thtx

(the OD has a tone pot that was left out of the schematic on the 2CF)

[stiltamp]

Thanks a lot,
it is an highly interesting amplifier design to me.

With respect, Manfred