KoT - A Low Gain Side and a High Gain Side

[nation]

Dear All

I'm putting together a KoT from a Rullywow PCB and would like to a nice difference between the two sides - one side a bit raunchier but with smooth clipping and the other side less gain and more glassier sounding (harder clipping!!??).  I will be using a 250k drive pot on one side, a 100k drive pot on the other and the stock 1s1588 diodes. I'll be subbing the MA856 diodes and don't want to use LEDs as clippers.

What MA856 replacements and which drive pot should I pair them up with to achieve this? I'll be experimenting with this but if a can get a ball park to jump into before I buy that would be great.

Thanks

[Mark Hammer]

Use the same value drive/gain pots for each.  If you want a "smoother" and glassier sound from one side, consider dropping the 220k feedback resistor in op-amp 2 to 150k or 120k.  Stage 2 multiplies the gain of Stage 1 by a factor of 22x at max gain.  Dropping that resistor to the suggested values reduces the multiplication factor down to 15x or 12x.  Combined with the Stage 1 gain, that's still enough to provide clipping if pushed, but can also yield cleaner sounds with just a bit of hair.  You won't have chaged all that much about the circuit, apart from making cleaner sounds a bit more dialable.

[GGBB]

The MA856 diodes are for the soft clipping in the second stage whereas the 1S1588 diodes are used for hard clipping after the second stage. Having just those two differences between the two sides will provide different characters. Add in different gain and tone knob settings for each side and you may already have what you need as far as raunchy and glassy are concerned. So start there trying to get those sounds. If you can't dial in what you want with the stock soft and hard configurations, tweak gain (as Mark recommended) and maybe the high pass caps.

The Rullywow/KoT version is what I call the "low gain" version of the BluesBreaker - it uses the 27k 33k resistor setup in the HP filter of the first stage's feedback section. The "high-gain" version (e.g. Morning Glory) uses the 4k7 3k3 setup - this is notably different - definitely brighter and maybe what some might call raunchy - you may want to try that for one side. This is kind of doing the same as what Mark recommended but from the other end - it raises the gain of the first stage vs. lowering the gain of the second stage. But because it also raises first stage high-pass it changes the tonal imprint at the same time which Mark's technique doesn't do (I think - at least not as much). While the low-gain setup might work well with a 250k gain pot, the high-gain version doesn't need it at all - 100k is plenty.

I also find that increasing the 10n cap to ground in the first stage can beef up the sound considerably - especially with the high-gain version. My go-to setup has been high-gain, soft-clip, with 150n to ground (and the other 10n changed to 15n) - I find this makes a really nice full sounding overdrive - smooth but with some bite. I wouldn't call it raunchy though - I guess it could be called glassy if you dial the gain in just so. For glassy - the presence control becomes useful along with dialed-back tone (what I think of as glassy at least).

[nation]

Thanks Mark and Gord. Except for the diodes I'm looking to keep the circuit in stock form, just try to get as much variation between the two sides by looking at different diode options.

[Slowpoke101]

I built a King of Tone a few month ago. I used BA282 diodes in place of MA856 diodes. Seems to sound pretty good so give them a go and see if you like them - at least they are somewhat easier to obtain than the MA856 type. Very similar specifications too. Just used a 100K linear pot for the drive controls.

[GGBB]

I used BA282 diodes in place of MA856 diodes.

Ditto. I have no comparison against MA856 or anything else, but I think my BluesBreaker sounds great.

[Joncaster]

Good thread timing.

I have a BBM with the KOT mods (GGG) on my breadboard now.
I'm pretty happy with it as is. I just have some 914 diodes in there. Can't find any fancy diodes locally, but whatever.

I like the 'clip 2' diodes to pin 5 more than the traditional BBM diode stack, though.
To the point where I might just leave clip 1 out entirely. Just have clean and OD on a switch.

Maybe I should twiddle a bit more, but man, what a great sounding circuit.
Really inspiring to play. Funny, that just a bit of light drive and clean transients is so cool.

Last night I got a bit carried away, Tele into this, into a Big Muff, into a flashback delay EP3 setting...yes please.