Hey.

Preparing for a few gigs and the very late album release, i've noticed that even though i'm down with a 4 button pedal i've built (distortion, gain boost, delay and volume boost), there's just too much stomping. I would like to mod my pedal to be programmable with presets instead. using an mcu, display and momentary switches instead to switch on/off multiple effects, but also change tone, delay and volume.

I can get the digital part off easily, and i already got the analog part. Now interfacing them in a convenient way is where i've hit the brick wall.

I know about digital pots, but i've also heard lots of arguments against them. i dont really need insane resolution, but it wouldnt hurt to get atleast a few possible variations, which kinda rules out the string resistor solution i experimented with, as i need 1 resistor per setting. i also found a forum thread about using LDR's, the way mesa boogie does in the triaxis amp.

But i'm really not sure what route to go here, something that wont enlarge the casing by a factor of 10 would be nice.

i did connect a jfet shunt to GND with a R2R ladder to set the level for the gain and volume, and well, it seems to work. But not tested enough yet. The tone stack though is where i'm entirely lost. Any suggestions are welcome

Hello, i have decided to create a thread where i will post the progress of the designing and building of this.

Hopefully other beginners will find this interesting, and that it will also give me the chance to get some help along the way with some of the mistakes i will probably make.

Now this is quite an ambitious project, probably bigger than recommended for someone with my limited experience and knowledge, nevertheless i'm going for it. There will be quite alot of experiments along the way. The project status right now is in the preparation for design stage.

So what's the Stormbringer Preamp supposed to become?

I'm playing in a Rock/Metal-band with female vocals, we get compared alot to Evanescense, nightwish, within temptation (mostly due to the female vocals), although i would say we got our own style, but that's really not important when it comes to this.

I use a quite limited array of sounds right now:
1. Clean with or without slight delay
2. Heavy driven distorsion for rhytm part
3. Distorsion with slight delay for leads/solos.

What i lack in my current setup, is a reliable volume boost with lifted mid for solos, currently using an analog pedal, i want this built in, inside the preamp itself, also, instead of the standard reverb, i would rather use a delay module, as it is way more useful to me when we're playing live, as i cant really use reverb directly on the amp when the rig is miked anyway.

Features:
Channel 1: clean channel with gain, bass, mid, treble and Level
Channel 2: Distorsion channel with gain, bass, mid, treble, presence and level, also switchable in to boost mode which has a Tone control + Level control, more or less a solo function.
Channel 3: Same as channel 2, but will try to color the sound a little differently between them.
Master volume, and delay, i haven't really figured out how many control knobs i'm giving it yet. Initially i was thinking about a single "blend"-control only, and lock it to 300 ms or so. But think that maybe a repeat+length control may be required anyway. Gonna have to get back to that later.

The footswitch and buttons:

• Channel 1
• Channel 2
• Channel 3
• Ch2 Boost
• Ch3 Boost
• Delay

I know that the amount of buttons could be lowered by making the first button toggle between 1 and 2/3 while a second button switch 2/3, and a single boost. But there's just too much stomping. on my randall RH100 this drives me nuts sometimes and makes me wanna take a riverdance class just to not get stressed when switching.

So that means i will use momentary buttons for channel 1/2/3 in the footswitch, the other could be latching.

Outputs:
Preamp Out, this goes to power amp input, i want to include a switch on the back that switches between 0.75, 1.0 and 1.25 v in order to match different input sensitivity in various power amps.
Line out with level control. A balanced line is always nice to have. Will build some rudimentary cab sim circuit here to avoid the satanic chainsaw-sound when connecting a very distorted guitar to a line.

I did some mockups on the front + back panel to get a better view of what i'm doing here. See attachments.

Power supply
i don't know yet how high voltages i need, this will require some more designing and experimenting. Will start at 12 and increase when needed.

Switching
Been looking at LDR, Relays and JFET, feeling that JFet seems to suit me best,

The Guts
JFET gain stages, i like the sound from the various j201 pedals i have built, but will try out some different JFets aswell.
the amount of stages is not yet defined, will also take some more designing.

Hopefully i got most of the information listed here, I will post whenever i got something interesting (well, that's subjective, isn't it? )

If you read all the way here, then thank you for your interest!

Hello.

I'm currently experimenting with a channel switching circuit. I got a working part using jfets to 1. with 0 voltage on gate let signals pass, 2. with -12 block the signal.

i have also made a circuit from 3 momentary buttons that sets a 74hc74 Flip flop to on/off for each channelwith the help of a 74hc08 quad AND Gate, while disabling the other "channels" latches. This one running on +5, output goes to a bc337 which lights a led for the currently selected channel.

But, now i need to merge the 2 circuits somehow, getting 0v when output is high on the bc337, and -12 when low, so that i can actually switch the jfet the way i want. anyone that can help me achieve this? Been googling forever...

Edit:

Just tried setting up an lm358 as a comparator, which atleast gave me +10.5 and -12 out depending on the on/off state of the bc337. But i really need to get that +10.5 down to 0, to keep the circuit from oscillating like mad.