Walrus Audio 385 Overdrive MKII

[Smrtokvitek]

The previous version has been done as a projectile overdrive. MKII seems to be two of those circuits with a gain stage in front to push it even more. It seems bit more versatile. Definitely an interesting one and there shouldn't be anything exotic inside.

 

[Laundryroom David]

intriguing

 

[Feral Feline]

I upvoted this before watching the vid as I liked the 385 circuit as it was — then I saw Walrus included a BASS demo, sounds great!

I doubt the MKII has two of the 385-circuits inside; more likely, it has two sets of VOL and GAIN controls. I'd be happy if I was wrong, though.

I like that it has the extra gain switch. Again, I wonder if there's actually another gain stage, or if they've just swapped out a resistor value — perhaps R3 or R5 in the Projectile schematic.


EDIT: Yeah, from Walrus' yutoob description —

"The MKII adds an A/B switch to toggle between two sets of volume and gain knobs that can be used like a preset to change volume and/or gain for specific parts, as well as a 385+ switch that slams the front end of the circuit for added high-gain saturation."

 

[Smrtokvitek]

I upvoted this before watching the vid as I liked the 385 circuit as it was — then I saw Walrus included a BASS demo, sounds great!

I doubt the MKII has two of the 385-circuits inside; more likely, it has two sets of VOL and GAIN controls. I'd be happy if I was wrong, though.

I like that it has the extra gain switch. Again, I wonder if there's actually another gain stage, or if they've just swapped out a resistor value — perhaps R3 or R5 in the Projectile schematic.


EDIT: Yeah, from Walrus' yutoob description —

Yes, you are right. There are two sets of controls. I was not paying attention enough when writing my post. They actually say "adds additional gain stage at the front" so I would suggest there will be one Jfet stage added. Nevertheless a nice addition to an original circuit I would say.

 

[music6000]

The previous version has been done as a projectile overdrive. MKII seems to be two of those circuits with a gain stage in front to push it even more. It seems bit more versatile. Definitely an interesting one and there shouldn't be anything exotic inside.

I want something I can get my foot on!!! :

 

[Feral Feline]

Yes, you are right. There are two sets of controls. I was not paying attention enough when writing my post. They actually say "adds additional gain stage at the front" so I would suggest there will be one Jfet stage added. Nevertheless a nice addition to an original circuit I would say.

Indeed, they say an additional gain stage in this other vid:

I suspect you're spot on with an additional JFET stage.

I'm already thinking of taking my current Projectile PCB in this direction.
I can add an additional JFET stage on a scrap of perf or GPCB GBOF, but I'm wondering how to get two knobs to swap out with a 4PDT while adding the LED indication. Might have to work up a relay-board instead of 4PDT?

Like Music6000, I'm thinking 1590BB.

 

[Feral Feline]

Using a 4PDT to switch two pots

I think it can be done, but I’m struggling to wrap my head around it. I built a RAH clone from here and love it, I leave it on all the time. What I’d like to do is use a footswitch so that I can have a preset option. The switch would change from the stock volume and gain pots to a different...

forum.pedalpcb.com

Robert's diagram below from the thread above

What if you just wired the outputs (Lug 2) of the pots to the PCB's LUG2?



Only the pot receiving signal from the switch would make it to the PCB, and this would free up a pole for LED. However, the "inactive" pot's remaining resistance to ground would still be interacting with the active-pot's resistance to ground ... If you moved the inactive pot, you'd still be changing the active pot. If it weren't for that, you could do a 4knobjob with just a 3PDT.

 

[Feral Feline]

Found this thread:

Adding a second volume and gain control with 3pdt and LED

Adding a second volume and gain control with 3pdt and LED

www.diystompboxes.com

It had this schemagraphic:

Frequency Central (who makes and sells a lot of rack-synth gear) had this to say about the schem above he posted in the DIYSB thread above:

Each pair of pots are in parallel, therefore the resistance is halved, so you may want to double the stock pot values. Really, it's only the resistance at lug 2 of each pot that we are concerned with, as the resistance between the signal and ground remains constant regardless of how the pots are set. So we are just switching from one set of wipers to another set of wipers.

So maybe I wasn't so far off the mark after all...

 

[jwyles90]

they posted this on their IG the other day. It sounds freakin sweet