The Squarewave Parade - DOWNGRADE

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
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iloophao
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Post by iloophao »

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this is a sample rate reducer, which is the analog counterpart of the digital bitcrusher. this is achieved with a very tailored sample and hold circuit and the resulting effect is also often compared to ring modulation at certain settings

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miwanone
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Post by miwanone »

There is quite a bit of difference between a bitcrusher and a sample rate reducer. Also, a sample rate reducer can not be analog, since sample rate is a digital thing (when you convert sound from analog to digital, AD conversion, the sample rate is the rate at which the input is 'measured', CD quality is 44100 times per second, or 44.1 kHz). So it's either digital or not a sample rate reducer :roll:

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marshmellow
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Post by marshmellow »

Unfortunately you're wrong. A sampled signal is still analog, but at discrete points in time.

AD conversion, thus a digital signal, means time AND value discrete. That means you also have to quantize the voltage, that's where you get the bit resolution from.

A perfect example would be a bucket brigade device, where you sample time discrete but still have continuous, non-discrete values.

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rackham
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Post by rackham »

According to the guy who makes (made?) them, it's a Bugcrusher. The recipe is here:

http://www.getlofi.com/?p=626

Given that it's using one battery, I'm thinking one of those ICs is a charge pump.

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Whoismarykelly
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Post by Whoismarykelly »

rackham wrote:According to the guy who makes (made?) them, it's a Bugcrusher. The recipe is here:

http://www.getlofi.com/?p=626

Given that it's using one battery, I'm thinking one of those ICs is a charge pump.
The bottom-most IC in the photos is a Maxim chip.

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rackham
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Post by rackham »

Whoismarykelly wrote:
rackham wrote:According to the guy who makes (made?) them, it's a Bugcrusher. The recipe is here:

http://www.getlofi.com/?p=626

Given that it's using one battery, I'm thinking one of those ICs is a charge pump.
The bottom-most IC in the photos is a Maxim chip.
Go me! :D

So otherwise, there's some kind of buffer/booster stuff for the input, the schematic is on Tom Bugs' site for the Bugcrusher and the rest is some kind of LFO/Crazy Larry style envelope stuff?

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rackham
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Post by rackham »

Just had a listen to the sound sample - think I'm a bit wide of the mark with the envelope thing. Lowpass filter maybe?

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iloophao
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Post by iloophao »

rackham wrote:Just had a listen to the sound sample - think I'm a bit wide of the mark with the envelope thing. Lowpass filter maybe?
Lowpass filter ??????????????

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hazelwould
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Post by hazelwould »

So what are all the other knobs?

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Post by hazelwould »

So what are all the other knobs?

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deathofaparty
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Post by deathofaparty »

hazelwould wrote:So what are all the other knobs?
TSP added a lot of features from the original Bugcrusher idea. I think he might have redesigned the circuit to not even be based off of the same chip.
Has anyone built the bugcrusher though? I'm REALLY interested in a usable sample or bit rate reducer.
But anyways, as far as the "other knobs, this is from http://thesquarewaveparade.com/DOWNGRADEv2.html
I/: this is the input gain, which is in phase, has little or no frequency loss, and a ridiculous amount of gain ( over 200x ) so you can plug low level or passive devices directly into it with no need for an extra pre-amp. at its lowest setting it simply acts as a buffer, there is no input attenuation. like all of my devices its been designed to accept all synth, line level and instrument level inputs sources with no impedance issues so feel free to plug your synths and sound cards directly into it without the need for any stepdown. note: at the highest setting there will be some self oscillation and noise so if oddly pitched noise or cleanliness is a concern simply don't use the highest setting - i should point out that this is just a feature for the noise makers out there. normal use will never require you to run the pre that hard.

disrupt: this is the new distortion control, at high levels it will completely squarewave the input signal by itself. also at high settings the distortion is so strong the reducer will seem to have little or no effect so be careful. note: at the highest setting there will be some self oscillation and noise so if oddly pitched noise or cleanliness is a concern simply don't use the highest setting - i should point out that this is just a feature for the noise makers out there. normal use will never require you to run the distortion that hard.

downgrade: this gives you control over the rate reduction (clock). it controls the speed that the sample and hold is triggered. this is the heart of the pedal and setting it to the desired position will determine the max sweep range for the EXP pedal / CV input when its in use.

dissect: this is a new feature that you won't find anywhere else. but its hard to explain if you don't fully understand how reducers / sample and holds work. to put it simply, it gives you control over how long the sample of the sample and hold is. from the very short length used to make the reducer effect, to a wide squarewave used for a normal sample and hold. the samples and videos should explain further. what this does is allow you to use the downgrade in far more applications because you can now adjust the amount of the source sound that comes through the reduction process. also if you flip the descend switch and increase the range that the reducer can travel, what used to be rather worthless in the lower setting can now be slowly swept into a big chunky sample and hold similar a squarewave tremolo except that the sound that comes through is now a sample and its staggered in time. so if its hooked up in parallel with other effects you can achieve very interesting results. also being as how this can be put under voltage control you can use it as a modulating chopper/ stutter effect

\O: this the output volume control.

dialup: this allows you to switch on an internal feedback / self oscillation bend that lets you use the DG as a fucked up bass heavy synth. nearly every control has a different effect on the result so you will have to play around with it yourself. the CV input will give you control over the pitch but its not perfect. its really just intended more for special effects or noise making. when feeding the DG a source that is really loud, like a synth for example, you may need to turn it down at the source a little to not overpower the feedback or it may just work more like a 50/50 wetness control.

descend: this is a reduction range extender which allows you to choose between the higher range of the reducer giving you more precise control over the downgrade and dissect settings, or the full wide range that will allow you to achieve the slow blocky sample and hold / tremolo effects.

LEDs: this is a clock rate indicator used to tell you the speed you are running at. at higher speeds it will just seem to stay solid but when you flip the descend toggle and you start running at slower speeds it will pulse in time. i did this to help make it easier for you to sync up the rate with an outside tempo. for example to sync up the DG with a drum loop, which you will probably do quite often. it will also pulse along with an CV signal you send it. there is no real power indicator so you will have to pay attention to whether or not its on or you can waste batteries

bypass switch: this is a heavy duty true bypass / power stomp switch

9V wall jack: this is a 9 volt 2.1mm center negative power input so you can run it off of any standard 9v wall wart. the DG only consumes about 6ma at the most so just about any will work. there is reverse polarity and over voltage protection to keep you from destroying it. you can feed it anything up to about 15vDC and be fine

single 9v battery clip: the new DG now only requires one 9 volt battery and only 6ma at most. so it will run for approximately 100 hours or 4 days solid on a standard alkaline battery.

input jack: the mono input is on the right side and marked with a triangle pointing into the box. there is also over voltage protection here as well - the ring shunts to ground

expression / CV pedal input: there is now an expression pedal / control voltage input that gives you external control over the downgrade / rate reduction. upon plugging in an EXP pedal or control voltage the downgrade knob becomes the range limiter and turning it adjusts how much the sweep of the EXP pedal or CV will effect the reduction, but the range of the sweep is somewhat limited, only giving you about 50% of the normal knob range. there is a switch on the back to choose between CV and EXP pedal, when facing the front - left is EXP, right is CV

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