#1
Evening GB&C

Today a friend linked me a thing called a "Black Ice Overdrive" on stewmac. I saw the price and immediately thought it must just be some simple diode kinda thing build into a little box.
A quick google search revealed it's a pair of Schottky Diode's that clip the signal.
I also read that you need to know the output voltage of your pickups to work out how much clipping you will get.
The Stewmac pages says you need to use pickups with at least 10k output for it to work, I take it this is for the output voltage to match well?

I read that the forward voltage needs to be roughly 10% less than what your pickups put out?

Can anyone help me with finding appropriate diodes for this and measuring the voltage?

thanks,
Steve
#3
Quote by j6off9
i think u shud pick a topic that people care about

Your a loser. No one cares about you most likely, well except your mother (maybe).


TS, 10K would be the output impedance most likely. I don't see how that is relevant here though. You need to figure out the actually signal strength in mV of your guitar. That way you can select a pair of diodes that will do the job.

That is a lot of work without a scope and some other finicky measuring tools. Tbh I'd buy a few different diodes (they are very cheap) and experiment, see what works. Most passive pickups are in the 100mV-400mV iirc, please someone correct me if I am wrong.
#4
Cheers kurt,
I know that 10k would be output impedance, what i meant was I'm guessing stewmac's page says pickups of at least 10k is to make sure they output a voltage in a range that would cause the clipping to take effect?
Dimarzio's site gives output Voltage in mV, could I just find a pickup of similar impedance to mine and use it's output Voltage or does it not work like that?
Also, I take it a multimeter isn't the kind of thing I could use for this then?
#5
Ya at 10K you probably get an ideal scenario and the clipping occurs as designed.

The impedance will vary with frequency though, I would say just about any pickup will work here.


Unfortunately you can't measure the signal strength with a DMM. The voltage is changing way too quick, you are also probably looking for the peak signal strength. A DMM can't read little AC signals like this.
#6
righto, that's that one out the window

what about the using Dimarzio's statistics based on a pickup as similar as possible to my Iron Gear Hot Slag?
#7
Quote by kurtlives91
Your a loser. No one cares about you most likely, well except your mother (maybe).


TS, 10K would be the output impedance most likely. I don't see how that is relevant here though. You need to figure out the actually signal strength in mV of your guitar. That way you can select a pair of diodes that will do the job.

That is a lot of work without a scope and some other finicky measuring tools. Tbh I'd buy a few different diodes (they are very cheap) and experiment, see what works. Most passive pickups are in the 100mV-400mV iirc, please someone correct me if I am wrong.

No, you're right, but some go above and beyond 400 or even 500 mV (Dimarzio X2N comes to mind, not sure about Cord's Beefbucker but that's a definite candidate).
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#8
Quote by kurtlives91
Your a loser. No one cares about you most likely, well except your mother (maybe).
Oh, you.

Normally I don't care for that sort of thing, but considering the post you're replying to...


Quote by kurtlives91
Most passive pickups are in the 100mV-400mV iirc, please someone correct me if I am wrong.
sounds like a reasonable estimate to me.

Steve, when it comes to passive pickups and diode clipping you almost can't select a schottky that has a forward voltage that's too low. but tbh, the results are mediocre at best. if you use a control to dial in the amount of distortion, the more distortion, the weaker the output. this is exactly opposite from what you normally want. having a louder signal when distorted is usually what's called for.

you would probably be MUCH happier with a distortion pedal. any distortion pedal.
but diodes are cheap, so you won't waste much, other than your time to try this out.
if you proceed, let us know how it works out for you. thanks.


Quote by j6off9
i think u shud pick a topic that people care about
This is the only thing i see in your UG posting history. It's spam. While I enjoy a bit of humour here and there, this one isn't even remotely funny. Let's ask Deputy Fife his opinon.



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#9
right, so the plan is to get myself on a suitable electronics website and order a couple of quids worth of these Schottky Diodes (I've seen that they only cost a few pence )

I've looked on Rapid and the lowest I could find was 450mv though
#10
Wow, I've asked for an estimated output of pickups in mV for a while, and never got a great answer, and you got it on your first try.

Oh well, because of it I decided to take matters into my own hands!

I found that with a listed output of 14k, but being $23 pickups, I don't know how the quality control is, and using the AC Voltage measurement on my DMM, which oddly enough I didn't know it had, was around 250mV.

And that was really strumming. Single notes came off at around 150-200mV and strumming chords hard, I could get to around 290-300mV. With the pickups in series, and strumming so hard I was worried about the strings breaking, I finally broke half a volt

Yeah, just thought I'd share that with you guys, obviously, the higher the voltage, the more would be clipped.



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#12
You know what I meant, but thanks for the correction anyway.

I'd still like to see some guitar waveforms, just for the sake of it. I've heard they look almost more like sawtooth functions, and that with the higher frequencies on ocilloscopes it just looks like white noise.

But I haven't really looked around for it, and one of my relatives say they have an old tube osilloscope kit that I may be able to obtain and put together.


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#13
They are kinda crazy looking, there is lots of "fluff" and what not going on, lots of different harmonic orders. The guitar is pretty complex harmonically.

It would only look like a sawtooth if there was some seriously hard clipping. Think really nasty bad sounding fuzz.
#14
So i should be looking for 200mv diodes?
where can I get these?
Rapid only has 450mv and up from what i can see
#16
I am also planning on doing this mod, to my bass. Allthough I have no practical experience, researching I found some people use two 1N5818 Schottky diodes.

eg: http://www.talkbass.com/forum/showthread.php?t=598605&page=3

I also read somewhere else, (probably on another guitar forum) that after experimenting another guy ended up using 1N5818 ones because they were the ones he could find with the lowest forward voltage drop; anything higher and the diodes wouldn't clip the signal. Allthough obviously it's going to be different for different guitars. You're best bet would be experimenting as kurtlives said, however I will probably end up just using 1N5818 because I am lazy.


as a side note on oscilloscopes, I was mucking about with my casio keyboard and audacity a while ago, you can zoom in on the "picture" of a track far enough to see the wave itself, providing it's a low enough note Pretty sh**ty I know but, you could see if you can download a specialized "oscilloscope" type program from somewhere or something?
Last edited by jimRH7 at Aug 8, 2010,
#17
Would it be possible, in theory, to put this is a simple, passive overdrive pedal? If so, what would adding more diodes do?
#18
yes you can use it as a simple overdrive pedal, I think adding more diodes would make it clip less.


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