# resistor wattage/black ice

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two different subjects here. first, i want to start experimenting a bit with resistors and see that radio shack sells them in either 1/2 watt or 1/4 watt. what is the practical difference between the two in a guitar circuit and which is recommended?

second, i did a search here on stew mac's black ice assuming that they probably weren't too complicated inside and found what looked like it was going to be a tutorial but it was incomplete. it said that you just needed some diodes but didn't say what size or exactly how to wire them up. is there a better tutorial or link available?

thanks

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two different subjects here. first, i want to start experimenting a bit with resistors and see that radio shack sells them in either 1/2 watt or 1/4 watt. what is the practical difference between the two in a guitar circuit and which is recommended?

second, i did a search here on stew mac's black ice assuming that they probably weren't too complicated inside and found what looked like it was going to be a tutorial but it was incomplete. it said that you just needed some diodes but didn't say what size or exactly how to wire them up. is there a better tutorial or link available?

thanks

might as well buy the higher power resistors, better to be safe than sorry. the rating determines the total power dissipation before the resistor breaks down.

heres some formulas...

Power = voltage*current

Power = voltage^2/resistance

Power = current^2 * resistance

what kind of voltages and currents are we talking about here??

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hey gnome, thanks for the help. since they were fairly inexpensive i went ahead and purchased a pack of each. one is 100k ohms, 1/2 watt and the other is 100k ohms at 1/4 watt. i'm going to try them on a strat going for the hendrix sound.

i'm fairly knowledgeable of capacitors and how they effect tone just from practical experience but what do capacitors do and how do the higher and lower powers effect it?

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hey gnome, thanks for the help.  since they were fairly inexpensive i went ahead and purchased a pack of each.  one is 100k ohms, 1/2 watt and the other is 100k ohms at 1/4 watt.  i'm going to try them on a strat going for the hendrix sound.

i'm fairly knowledgeable of capacitors and how they effect tone just from practical experience but what do capacitors do and how do the higher and lower powers effect it?

Capacitors act like a filter, and the differences in sound you hear when using a capacitor is because some range of the sound spectrum is being attenuated, meaning that your 'knocking down' a particular frequencies range's amplitude. in a low-pass filter, for instance, your letting the original voltage of the lower (bass) frequencies through, and attenuating the higher (treble) frequencies.

you can search on the net and find all kinds of diagrams using capacitors and inductors in filter design for audio electronics.

if youre going to be designing anything in audio, it pays to buy the best parts possible as far as tolerances for resistors, caps , etc

as far as the power goes.... most of the barrell shaped caps should be fine for what your doing...

Edited by Gnome
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the black ice uses schotky diodes as they have an ultra low threshold to trigger them into clipping. in gutiar fx and guitars theres no reason to use any thing over 1/4watt. personally i use 1/8th watt on everything that isn't high voltage. preferably metal film 1 % tolerance resistors as it will cut down on any noise.

by placing the diodes back to back across the tone control pot you effectively have a volume control to the diodes only at a certain point .3mv i read on one package for schotkys will the diodes conduct and there fore square your waveform from your guitar signal its the same principle as a basic guitar clipper but this is passive. most of all your distortion stompboxes have this in their design but are driven harder via opamps and transistors.

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What I'd like to know is which schottky diodes you guys are using - I've seen the 1N5711 recommended, and somebody mentioned (not here) the 1N5817. Has anybody tried the BAT41? It looks like it would be ideal, since it has an incredibly low forward voltage at lower current levels. Ansil, javacody, what are you guys using?

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thanks for the question lovekraft. i was wondering the same thing. and since i know you'll be checking back in i've got another little question about farads. i found a good little tutorial explaining pico, nano and micro farads but looking in my trusty radio shack catalog i find pf and the u with the tail. is the uf larger or smaller than the pf?

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I asked the same question once. I'm almost positive they told me that uf was just a different name for mf. (that or uf was a different name for pf). Wait for someone smart to reaply though.

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thanks..if it's one of those it must be the same as mf because the catalog lists pf and uf. but i'm with you...i'll wait for one of the resident genii.

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thanks for the question lovekraft.  i was wondering the same thing.  and since i know you'll be checking back in i've got another little question about farads.  i found a good little tutorial explaining pico, nano and micro farads but looking in my trusty radio shack catalog i find pf and the u with the tail.  is the uf larger or smaller than the pf?

IT goes like this

so.. uf has a higher capacitance than pf

Edited by Gnome
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thank you sir. i just added that to my unclej gets smarter files. i appreciate it.

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Not to add to your confusion, but in the States for years microfarad has been abbreviated mfd. Since millifarad caps are both huge and very expensive, you can generally assume that any cap marked mf is microfarads, not millifarads, unless it's the physical size of a pickle bucket and really expensive.

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I still haven't built the black ice yet. I'm waiting to find a source for schottky diodes who will accept paypal.

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i got free ones from the free site from gringo's site where if you search the forum i did a topic on Free and legal diy stuff. in it links were given to gringo's site and it has all the free links in it. it was the same company i got some transistors from they sent them from maylasia for free. dont' know part no. though sorry. i think after looking at the ones lk was talking about i would try those as my recomendation. but i havent' fooleed with this thing since the last time i built one right after this was uploaded i thought it was ok but sounded about like the original black ice which didnt' do much for me either. however it is a good alternative to paying big money for little parts.

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That's too weird! I just ran across a place last week, completely by accident (I was hunting for germanium diodes for a fuzzbox). I haven't tried 'em, so I can't tell you how well they'd work... maybe Ansil will weigh in here with some more info, or somebody else who's built one. Here's that link:

<edit> Well, there's Ansil (thanks, man) - anybody else got any input?

Edited by lovekraft
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where are you guys located?

You could take a quick trip to the local university electrical engineering department. they usually have a good stock of parts for cheap for students. they probably wont even know youre not a student.

Also, back when i was a student I used to email semiconductor companies and request samples for 'student projects' even though I was using them for my own projects. i got TONS of free parts. It helps to have a .edu email address I would imagine.

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where are you guys located?

You could take a quick trip to the local university electrical engineering department. they usually have a good stock of parts for cheap for students. they probably wont even know youre not a student.

Also, back when i was a student I used to email semiconductor companies and request samples for 'student projects' even though I was using them for my own projects. i got TONS of free parts. It helps to have a .edu email address I would imagine.

other than asking the university i covered all the sites like national ti and others in the free thread

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While I appreciate the help, since small-signal schottkys generally run less than a quarter a piece, I really don't mind buying them - what I was hoping for was some info on which ones worked best. Oh well, guess I'll just have to buy a couple of dozen pair when I get sufficiently motivated, and decide what sounds best. If anybody else gets around to it before I do, update me if you don't mind.

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While I appreciate the help, since small-signal schottkys generally run less than a quarter a piece, I really don't mind buying them - what I was hoping for was some info on which ones worked best. Oh well, guess I'll just have to buy a couple of dozen pair when I get sufficiently motivated, and decide what sounds best. If anybody else gets around to it before I do, update me if you don't mind.

my message was more for javacody, than anyone else. he seemed to be ahving problems located them...

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Here we go! Some enterprising mad-scientist type has done the work for us, right down to crediting Ansil for the homebrew Black Ice idea:

Nice writeup, with photos and a soundclip.

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cool i am glad someone with a digital camera and more timeon their hands could help solve this dilema.i really must get a camera this year.

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