2266 series mod idea?

[Cascadem]

Far from done but getting closer.

Maybe not far but there are a couple things left to address before test time.

[Cascadem]

Ok, so, I tested the amp today. Its got lots and lots of distortion especially when you engage the oldmid boost sw. and use the v2a grid leak of 1 meg. It has a different flavor to it. The amp really sounds nice. I didnt get the chance to push it much past 5 on the master due the family being home but I will get there. I think I have to relearn the amp now as far as settings go but I am very satisfied so far, the amp has all brand new carbon comp resistors, tone caps, sino output tubes, and jj preamp tubes so things need alittle time to break in and I might roll some other preamp tubes and see where that takes the tone. But, minus the el34s as we are using kt66 tubes the amps gain level and overall feel really nails the Appetite For Destruction G&R sound. I cant wait to break this baby in and plug it into my rack of effects. Certainly needs to have a noise gain in the loop though with all the added thrash.

[Cascadem]

So I have decided after playing the amp more that it has a touch too much distortion. I am considering changing my grid stopper from 470k to 1 meg between v2b and v2a also the amp seems to have a quality that is almost too thick at times so I am considering changing my coupling cap between v2b and v2a from .022 to .01 first, then if that doesnt satisfy maybe even .002

On another note, I am also considering changing my cathode resistor on v2a which is my cold clipper stage from 10k to 4.7k. The flavor of the distortion is just a tad too modern for me so I thought this might be a decent idea while adding gain to that stage it would decrease distortion (clipping).

Not entirely sure if this series of changes will get me closer to my preferred sound but experimenting is the only way to voice an amp. What makes sense on paper or with a calculator doesnt always make sense to the ears.

The series mod saga continues....

[Cascadem]

So, I decided to change c2 ad c3, c2 is now .022 and c3 is now .0022, I moved my 470k grid stopper to after the grid leaks as opposed to before it was before the leak. I also changed the coupling cap between v2b and v2a to .0022 instead of the previously .022, I also changed the treble cap in the tone stack from 470pf to 250pf and the mid slope resistor from 33k to 56k. The cold clipper triode (v2a which actually comes after v2b) cathode resistor was 10k and (I decided to place another 10k resistor in parallel with it because I didnt have any 4.7k resistors on hand) is now 5.2k.

So lets see how the amp sounds now. It didnt sound bad before but, it did seem to have a tad bit too much high end in the tone stack while it had too much low end in the first few stages. So hopefully this thinned out but warmed up tye first few stages while shedding some of the high end from the tone stack area. I gotta admit this amps fine tuning has been kinda of tough as I have never fine tunesd an amp with this much flexiblity in the circuit for eq/character changes. But hopefully we have nailed it now after much thought before I have even warmed up my iron.

[Cascadem]

Ok so this might seem alittle crazy but I decided to pull the reverb from the amp (sort of) and repurpose the verb knob to use as a varible negative feedback control. On 0 its stock 30k and all the way up its 50k. I find that I like the tone when the knob is at about 10-11 oclock which is somewhere between 39 to 44k and I also dropped the .1uf cathode bypass cap on v2b as it yeilded too much gain...what I will say is I am closest to afd album tone as I have ever been with this amp. But I will say that the detail and body controls are no where near full at this point, currently they are at detail 6 and body at 8. Being as I swapped the coupling caps that feed detail and body it totally changed the temper of the preamp so all you folks whom are sayin that too much body is a bad thing well, this doesnt apply anymore on my amp.

[Cascadem]

Here is a shot of my current schematic with circuit changes, connector 8 is entirely removed to use my old verb pot in series with the original nf resistor. If I end up getting back into the amp soon I will photo that too...(not a mod for the faint of heart)
Whats really cool about the mod, even cooler than having reverb is you can adjust how loose the amp feels, I felt the stock value was good but at times wanted the amp to have alittle looser feel (47k) and it certainly does...I dont feel that I went to high in resistance here infact could have probably went higher but I wanted to stick at least somewhere not far from home and thats what I feel I have done. Nothing drastic.

[Cascadem]

Here is a shot of my amp settings that I used just a few minutes ago to test, I cant turn the amp up much as everyone except myself are asleep but I certainly will turn her up more tomorrow!

[Cascadem]

Well, as this is turning into more of my blog than a topic of discussion, I most recently feel that while my.amp sounds great at lower volumes, I tried it today at 5, 7, and 10 on the master....I do believe I still need to drop some gain as I am very certain at this point that it is overloading the preamp circuit...while I still really like the neg fb mod and tone stack mod I think the preamp has some more tweaking to be done. Understand that this isnt a project I need to finish right away, I have plenty of other amps to play at the moment, but more of a "can it be done and how much can I learn about making idea sound like a rippin plexi with a good cascade mod". I have always thought the marshall vm was one of the best (and coolest) layouts since the jmp/jcm 800/jubilee era. So the saga goes on, stay tuned.

[Anitoli]

Keep plugging away at it, you have gone this far already.