Sweet...

[Bennypapa]

I have never even seen any of these amps. I just go b y the schems that float around the 'net.

What I have seen is a schematic for a "Skyliner" that shows

330pf/250k for the treble
.022uf/1Meglinear for the bass
.022uf/20k for the mid.

following the output of the second stage of the overdrive section.

These pots are labeled as trimmers so I assume they are on the circuit board vs the front panel.

As we all know, tone stacks are infinitely "tuneable" to ones own tastes.
Not to mention that a lot of schematics on the net are someones best guess as to what is in a particular amp.
AND Dumbles have changed over the years.

For me, I am just gonna pick a best guess schematic and build it. If it doesn't suit me, I'll change it from there. That's half the fun for me.


I am so excited about the build. It will be great to be back inside an amp again and even better to get the thing finished and have some new sounds to explore.

Bennypapa

[mlp-mx6]

shall we get into the Robben Ford Mod..... my lips are sealed.....

Say what? Then why bring it up? (kidding, sort of)

Of ALL the tones I've ever heard, the RF&TBL tone is THE one I'd like to be able to build...

[pedro]

me too - its why I keep building amps and learning dimished runs for the I to the IV chord !!!!

Gary - get it off your chest - you'll feel a whole lot better ( and so will I )

cheers
Pete C

[Icetech]

Share the tricks:) And put them in a big layout that a guy like me can decipher:)

[glasman]

The RF mod is simply replacing the choke with a fixed resistor. Makes the amp a little looser. Check the files section, there is a picture of a Dumble that I think has this mod.

Gary

[mlp-mx6]

The RF mod is simply replacing the choke with a fixed resistor. Makes the amp a little looser. Check the files section, there is a picture of a Dumble that I think has this mod.Gary

That's cool - I already have that one in my plan. Thanks!

[Funkalicousgroove]

I stand corrected!! Per Dogears suggestion I changed my amp to 5uf on all cathodes, and a .01uf/250KA mid control and ditched the feedback loop on v1B and all I can say is WOW! It was AMAZING before, now I can't even find words to describe it!! I'll post some clips soon.

[Icetech]

Funka when you get it all tweaked make a layout:)

[Funkalicousgroove]

I've been playing it as it was for a good 6 months without a thought of modding it. I probably won't mod it again. The mid cap is definitely a personal taste issue, try .047,.022, and .01. I do like the 250KA mid control overall.

[glasman]

I stand corrected!! Per Dogears suggestion I changed my amp to 5uf on all cathodes, and a .01uf/250KA mid control and ditched the feedback loop on v1B and all I can say is WOW! It was AMAZING before, now I can't even find words to describe it!! I'll post some clips soon.

Adds a lot of touch to the amp when you dump the FB. When I built my first amp I did not include the FB. Later I added it on a switch so I could judge for myself and i just never warmed up to it. I leave the switch in the off position.

Gary

[pedro]

Gary - thanks for confirming the resistor instead of the choke.

I have both - 500ohm and choke - switchable so thats good to know as my amp isnt finished yet.

I think Bob I has this set up in his last build - Bob - does it work for you ?

Interesting to think that this "sag resistor" gets a lot of stick in other builds and classic tube approaches for deregulating the power supply, and turns out to be key ingredient in the RF tone.

The opposite of RF suppression !!!!!

Cheers
Pete C

[Funkalicousgroove]

I've built 3 so far, the first one was for a friend and had 400V on the plates with 4 6L6's, I used the 220K/2k2, 150K/2k2 5uf,1uf,5uf,5uf with the .047uf/100K mid and the local FB 22M/.047/22M and the amp sounds AMAZING!! I did the second one(My amp that I play) as basically a clone of that one but with 475V on the plates, and the 3rd amp was an EL34 HRM, but that was for someone so I didn't spend a ton of time with it. I really like the mods to my amp, and will pro'lly build myself a 6L6 HRM someday soon.

[dobbhill]

Have you tried different values for the resistor at the "tail" end of the bass control? The older amps have 1.8k and newer (Skyliner?) have 10k. I liked the small resistance when I first tried it, but it's been a few years. Just curious as to your (all of you) opinions.
D

[Funkalicousgroove]

yeah, I use that pre straight into a Fender style reverb and a PPI Master and I ended up with a 3.6K, smaller resistor= less bass.

[tonelab2]

What would be the value/wattage of the resistor for the RF mod?

thanks