Vampire Slayer DIY PCB?

iamjackslackof

Well-known member
I was researching the options out there for tube-based buffers, and I of course came across Sushi BoxFX again, as you do when you look for tube-based pedals. Mainly this is a question for @vigilante398, but I'm curious if there are any plans for releasing the Vampire Slayer as a DIY PCB? I'm also curious if there are any other pedals you have in the works as PCBs?

EDIT: Also curious on how a tube buffer works. I get the point of a buffer is to ensure a high input impedance and a low output impedance, and I know JFET/BJTs/opamps do this "naturally". But how does a tube do it? Is it truly all tube, or one of those pedals where the tube is added to the signal path for the sonic character it imparts, like a PT2399-based tube delay?

Thanks!
 
I've thought about it, I think one other person asked about Vampire Slayer so far. I don't currently have any other pedals in the works for PCBs right now, I'm not looking to expand my PCB lineup in a hurry. PCB design is hands-down my favorite part of building so I could just sit here all day and design new projects, but a) there are already people for whom PCB sales are their bread and butter and I don't want to steal anyone's thunder, b) my main focus and main source of pedal-related income continues to be selling finished pedals to end-users, so I want to keep that focus.

With regards to how it works, it's a lot like a FET buffer in that a tube has a naturally high input impedance and low output impedance, particularly when used as a cathode follower like Vampire Slayer. There are zero solid-state devices in the signal path, it's all tube. Not much to it, really. Just a couple triodes running in parallel as cathode followers. Input impedance is right around 1MΩ and output impedance is around 600Ω I think?

vampireSlayer.JPG
 
Thanks for the reply! Totally understand on not wanting to change your core business model.

I appreciate the schematic and the explanation though, probably wouldn't be too hard to build something based on this. Do you use high plate voltages for this, or does starved plate work fine, since it's not trying to overdrive the tube at all?
 
Oh, one more question. Can other circuits, like the Echo Foxtrot, work as a buffer if you turn them down to unity gain or so?
 
I appreciate the schematic and the explanation though, probably wouldn't be too hard to build something based on this. Do you use high plate voltages for this, or does starved plate work fine, since it's not trying to overdrive the tube at all?
I still use high plate voltage for this, I refuse to do starved plate designs. Just a promise I made to myself a while back.

Oh, one more question. Can other circuits, like the Echo Foxtrot, work as a buffer if you turn them down to unity gain or so?
Nope, a common-cathode gainstage has a much higher output impedance than a cathode follower. I don't have the numbers on Echo Foxtrot handy, but I know Space Heater and Particle Accelerator are both around 38kΩ output impedance, way too high to be a buffer.
 
We talked about it and decided to omit the footswitch. The original (Effectrode Glass A) doesn't have a footswitch, and neither of us could think of a reason to need to turn a buffer on and off while playing.
That's OK, I just modified it as I couldn't see any traces in the way??? :
Screenshot 2023-08-20 230724.jpg
 
Sooo... does that mean that the Vampire Slayer has the ''Ver. 1 Prototype'' label and going into a pre-production run ?
 
Sooo... does that mean that the Vampire Slayer has the ''Ver. 1 Prototype'' label and going into a pre-production run ?
Since the schematic had already been verified we decided it's a low-risk design and took a chance going straight for a larger first-batch order. It will still get built up to test before being available for sale, and if it doesn't work we'll spin a v1.1, but since it's low-risk I'm not worried about it.
 
This gives me an idea- what if the standalone power module came with a similar way of mounting a tube internally, but as a gain stage or as pinout board or something?
 
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