Big Muff Diodes, Forward Voltage and the Big Monk SWAG

[Big Monk]

I have been entertaining and researching some specific Vf ranges for diodes in a Ram's Head project I am working on.

At the outset: I am trained as an Electrical Engineer, i.e. my degree is in Electrical Engineering. With that said, I'm a "Big Wires"/Utility Guy/Volts and Amps Man. IT usually takes 4-5 seconds of talking with @Chuck D. Bones for me to realize I'm not REALLY an EE....

As a guy whose works often involves field testing and troubleshooting, I DO consider my self and Applied Scientist, so I am always looking for reasonable SWAGs for things I need.

In this case, I'm looking for diodes with a Vf range of ~580-630 mV.

So what I did first was looking into my stash of 1N914 and 1N4148, which I have tested on my TC1 and catalogued in my Diode and Transistor binder.

The pattern I saw after engaging the datasheets was that for an If of 10 mA per the datasheet, my units were consistently testing around 670-700 mV for Vf. After consulting the I/V curves for the devices, it would seem that the TC1 is using ~2 mA as the test current.

So I felt I could reasonably infer 2 mA as my test current and consult some datasheets for prospective devices to give myself a general idea on how the devices I procur will spec out on my TC1.

This is not an exact science, but since I know that the units I have on hand provide the performance in the circuit, I can use this as a guidepost.

So I am going to order some units from Mouser using this methodology:

Vishay 1N4154



Vishay SD101

 

[fig]

Good stuff! I’m continually learning things I don’t know that I don’t know…I just one day hope to get to that next level of actually just learning things I don’t know.

So, why that range if I may sir?

 

[Big Monk]

Good stuff! I’m continually learning things I don’t know that I don’t know…I just one day hope to get to that next level of actually just learning things I don’t know.

So, why that range if I may sir?

I'm a nerd first and foremost. I like David Gilmour second. Obviously, I'm not the type of person who thinks you procur/build the gear your heroes have and you can play like them.

With that said, Kit Rae has a couple of nuggets buried in his epochal correlating on contents (any Lovecraft nerds out there... ) in the BMP universe around Transistor gains and diodes Vf:





I've made these changes to my own Muffin and result was lower gain at lower settings and an overall smoother distortion that blends well with the Vick Audio Overdriver and light compression.

Cranking the Sustain and bumping the volume up also gets me the more characteristic higher gain tones but there is more musical range lower on the dial with these changes.

 

[fig]

Gotcha….that’s the dragon.

 

[Big Monk]

Gotcha….that’s the dragon.

I wouldn't be chasing it if my tests with those ranges hadn't showed promise.

Frankly, I think cap values and Vf have WAY more effect than the transistors but there was definitely a more than subtle difference once I went below 200 hFE on the transistors.

 

[fig]

I agree it has both merit and validity

 

[Big Monk]

Update: Received a Mouser order and while I was pretty close in my SWAG, the diodes measured closer to 700 mV than 600 mV. So I went with another few choices. The Diotec BC547A also measured a touch higher than expected but I had read the datasheet wrong on that one. No bother either way, as the Diotec transistors, in all three gain ranges (A,B,C) are incredible consistent and have great hFE numbers, so they are keepers.

Here is the dat for the Nexperia BAV21 I ordered:



Curve 2 at 10 mA If seems to indicate these should measure just over 600 mV.

To have a few other choices to play with fopr transistors, I ordered the following:

OnSemi - KSC1008YBU

​

Taiwan Semiconductor - BC337

 

[Big Monk]

Some in progress pictures of the inaugural Big Monk Pi:

 

[Coda]

When is the contest for this one?…

 

[Big Monk]

When is the contest for this one?…

If my Fuzz Giveaway is any indication, sometime in 2024……

All jokes aside, I’ve got giveaway fuzzes being built next week and as soon as ALL of them are out, I’ll dream up a Big Muff contest for sure.

 

[Big Monk]

And she’s finished: