ilovefuzz.com

AC128 wrote:I could scale the pic differently, the question is: is this type of graph useful or not?

Meh.. I don't think so... I mean we already have the output waveform and the frequency response... That would kinda be slight overkill...

Absolutely yes. This graph is very usefull. You should check each pedal for the octave down harmonic. If it contains a subharmonic you should include it in the graph, if not, make the 444 hz the starting point for the graph.

I'd like to see a test that shows sub-harmonics. Could we add a short 100 Hz pulse to the test signal.

eatyourguitar wrote:Absolutely yes. This graph is very usefull. You should check each pedal for the octave down harmonic. If it contains a subharmonic you should include it in the graph, if not, make the 444 hz the starting point for the graph.

good point about the sub harmonic, thanks!

FullCustom wrote:I'd like to see a test that shows sub-harmonics. Could we add a short 100 Hz pulse to the test signal.

I can do that, but wouldn't sub harmonics show up with a 444Hz tone just the same? also, with the higher frequency the 1st and 2nd sub harmonic would stay in a relatively 'safe' area, while they would be 50 and 25Hz obvioulsy for the 100Hz tone, and most pedals have some weird looking stuff going on in the 1-30Hz range. I don't know if it's low frequency noise or DC offset showing up as a really low frequency, but there's quite a bit of it.

AC128 wrote:

eatyourguitar wrote:Absolutely yes. This graph is very usefull. You should check each pedal for the octave down harmonic. If it contains a subharmonic you should include it in the graph, if not, make the 444 hz the starting point for the graph.

good point about the sub harmonic, thanks!

FullCustom wrote:I'd like to see a test that shows sub-harmonics. Could we add a short 100 Hz pulse to the test signal.

I can do that, but wouldn't sub harmonics show up with a 444Hz tone just the same? also, with the higher frequency the 1st and 2nd sub harmonic would stay in a relatively 'safe' area, while they would be 50 and 25Hz obvioulsy for the 100Hz tone, and most pedals have some weird looking stuff going on in the 1-30Hz range. I don't know if it's low frequency noise or DC offset showing up as a really low frequency, but there's quite a bit of it.

Fair enough. But I think the tone should be a pulse that fades in and out followed but a pulse with a sharp attack and decay. The idea behind that being you are looking for hysteresis like you get in a Schmitt Trigger.

I haven't heard the H word since I looked at a neve console. still over my head.

eatyourguitar wrote:I haven't heard the H word since I looked at a neve console. still over my head.

Science and audio shake hands like a solid business deal.

FullCustom wrote:Fair enough. But I think the tone should be a pulse that fades in and out followed but a pulse with a sharp attack and decay. The idea behind that being you are looking for hysteresis like you get in a Schmitt Trigger.

good stuff!

response files from this are on their way to me



Studer 2" tape recorder

not exactly a fuzz, but it should be cool nonetheless!

Sweet Studer. Next week I'll be working on a pile to tube amps. I was already planning on recording test files with them.

FullCustom wrote:Sweet Studer. Next week I'll be working on a pile to tube amps. I was already planning on recording test files with them.

YES!

I sent you a hysteresis induced octave test

AC128 wrote:I could scale the pic differently, the question is: is this type of graph useful or not?

yes this is the graph i was trying to describe earlier. as eats said, log the x axis scale and its a beuty.

FullCustom wrote:Fair enough. But I think the tone should be a pulse that fades in and out followed but a pulse with a sharp attack and decay. The idea behind that being you are looking for hysteresis like you get in a Schmitt Trigger.

you should maybe consider instead, to do the graph multiple times for various input levels and layer it on the same plot in different colors. otherwise how will you differentiate which frequencies occurred at which input amplitude? there is no 'time' per se on the type of spectral plot presented.

Also i don't quite understand what the difference in response would be for something with hysteresis to a slow envelope (fade) on the signal vs a fast one (pulse). If you had a schmidt trigger that say sets at 1 volt input (rising) but doesn't reset till say .5 volts falling), you wont see any output unless the signal is over 1 volt, regardless of what the general envelope is. Could you explain more what you are looking for exactly?

If you run an audio signal in short bursts through a schmitt trigger you'll see on the decay you'll only get hysteresis on every other cycle. This divides the frequency by two. But it only lasts for a brief moment. The same thing can happen in some fuzz pedals. If you want to hear this effect taken to its extreme listen to a clip of the Wolf Computer Fuzz.

FullCustom wrote:If you run an audio signal in short bursts through a schmitt trigger you'll see on the decay you'll only get hysteresis on every other cycle. This divides the frequency by two. But it only lasts for a brief moment. The same thing can happen in some fuzz pedals. If you want to hear this effect taken to its extreme listen to a clip of the Wolf Computer Fuzz.

crazy i will have to check when i get back to a bench. i checked out some clips but found it quite hard to tell. Im probably wrong but I cant imagine a schmidtt gate making an octave down below the fundamental of the input. If you have super high gain often the first few harmonics can trigger these square type logic gate fuzzaz so the result is not a square version of the fundamental, but a sqaure version of the fundamental and the first few harmonics. Typically in string instruments the harmonics decay much faster than the fundamental so you do hear a pitch change but its actually just changing down to strictly the fundamental since the rich harmonics have called it a day and cease to trigger the gate. (Well thats my theory and experience from farting around with logic based fuzz but i will try just a schmidtt and see what happens for sure).

To get octave down these circuits usually go with a flip flop as a frequency divider, although harmonics triggering the gate screw things up which is why the blue box is so far from perfect although probably works amazing on a pure sine input or something lacking any real harmonic content.