Fuzz with variable voltage
- Thread starter jhaneyzz
- Start date
BuddytheReow
Breadboard Baker
Like, a SAG or BIAS control?
Big Monk
Well-known member
Yeah definitely more info needed.
Feral Feline
Well-known member
You can always add your own starve circuit of choice to just about any fuzz (save digital).
What's in the Hephaestus?
What's in the Hephaestus?
Big Monk
Well-known member
Big Monk
Well-known member
I couldn’t tell either but a clearer picture meant putting the Reddit app on my phone, and ain’t nobody got time for that!
chris.knudson
Well-known member
Or you can starve the voltage at the source -- some power supplies will let you do this, or you can build one of these...
Robert
Reverse Engineer
Fuzz Foundry is the first one that comes to mind.
I JUST asked this exact question, and you can read the responses here: https://forum.pedalpcb.com/threads/...o-executive-a-la-hephaestus.19788/post-245441
I haven’t built the Executive (Bosstone) yet, but some fine folks here gave me great pointers. I’m very green still, so not sure if what they recommended is a Transistor Bias situation or overall Voltage Starve. I’m not sure which one the original Hephaestus has either! They might have similar effects on the Bosstone… Maybe?
I haven’t built the Executive (Bosstone) yet, but some fine folks here gave me great pointers. I’m very green still, so not sure if what they recommended is a Transistor Bias situation or overall Voltage Starve. I’m not sure which one the original Hephaestus has either! They might have similar effects on the Bosstone… Maybe?
CR0SSBL4DE
Active member
Just an idea I had reading the thread. You may even add a resistor for higher source impedance / SAG. Not sure, I'm not a fuzz guy.
I've never seen this used in a pedal, so maybe there's a better way of getting the same result.
I've never seen this used in a pedal, so maybe there's a better way of getting the same result.
Big Monk
Well-known member
here’s the problem I have with a global voltage starve control:
It changes the bias for all transistors. Especially for a two transistor circuit, that means slight changes to the global voltage will have big changes to the local Q2 voltage in addition to the changes the global voltage has on Q2.
Voltage Sag/Bias control is super overrated in my opinion. Everything is happening at the extremes so a bias switch is a better option.
It changes the bias for all transistors. Especially for a two transistor circuit, that means slight changes to the global voltage will have big changes to the local Q2 voltage in addition to the changes the global voltage has on Q2.
Voltage Sag/Bias control is super overrated in my opinion. Everything is happening at the extremes so a bias switch is a better option.
jhaneyzz
Well-known member
But that means I already have several pedals that do that and I won't have to make any new pedals. What a buzz kill.... or should I say fuzz kill...
Robert
Reverse Engineer
Well now just HANG ON. Let's not start talking crazy.....
I guess the question is- does the Hephaestus just have a straight-up transistor bias knob or an overall starve? If it’s the former (which sounds likely), I’m not sure how the Mythos is getting quite that much lower octave. I certainly get it on a Fuzzly Bear clone, but it‘s not quite as strong… Maybe the Mythos has a transistor bias knob with a different pot value than would normally be used for that..? If not, I don’t see how the Hephaestus is any different than the other “Bosstones With Bias” in that regard. Here’s the pic I posted in the other thread:
Big Monk
Well-known member
It’s clear as day they are simply varying the source voltage.
What does that entail? I have an Executive Fuzz to build and wanted to add the Heph’s volts control. It sounds like the advice in my original thread may be a transistor bias mod. I’m still new at this, please excuse my lack of knowledge. Would love some guidance!
Robert
Reverse Engineer
Yep, looks like a series resistance similar to the Stability control on the 'Foundry feeding the entire circuit through R5. The combination of R5 and the pot are probably the equivalent of R5 on the Executive Fuzz schematic.
The next resistor over is the LED CLR, then a filter cap.
Robert
Reverse Engineer
Omit R5 from the Executive Fuzz PCB.
Connect a wire from the top pad of R5 to lug 3 of your new Starve pot.
Connect a 10K resistor from lug 2 of the Starve pot to the lower pad of R5 on the PCB.
It just dawned on me that this is exactly what we're describing right here, so take a look at this schematic:
The Ermahgerd uses a 1K resistor and 100K pot.
Here's a bigger / higher res version of the pic above.
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