Search found 4004 matches

by guest
Wed Apr 08, 2020 1:00 am
Forum: Music Tech DIY
Topic: Buffer Follower and LED Driving on Percussive Noise
Replies: 8
Views: 77

Re: Buffer Follower and LED Driving on Percussive Noise

thats interesting. how would you describe the difference in sound? i could see it increasing the decay time by an order of magnitude or more, and the envelope shape might alter as well. you could always just use the buffer for the led, and run the transistor as it is.
by guest
Tue Apr 07, 2020 11:40 pm
Forum: Music Tech DIY
Topic: Buffer Follower and LED Driving on Percussive Noise
Replies: 8
Views: 77

Re: Buffer Follower and LED Driving on Percussive Noise

sounds like you have the output volume solved. the polarity shouldnt matter at all.

when you put an opamp after the envelope, was it a standard unity gain buffer configuration (signal to + pin, - pin shorted to output)?
by guest
Tue Apr 07, 2020 6:43 pm
Forum: Music Tech DIY
Topic: Advice needed on the necessary circuit for connecting an old phone as a mic
Replies: 3
Views: 64

Re: Advice needed on the necessary circuit for connecting an old phone as a mic

no, it should work with just a coupling capacitor. you can play around with the value of the resistor, but the largest signal will come when that resistor value matches the resistance of the microphone. so you can try to measure that first with your multimeter. just dont use too small of a resistor....
by guest
Tue Apr 07, 2020 3:23 pm
Forum: Music Tech DIY
Topic: Advice needed on the necessary circuit for connecting an old phone as a mic
Replies: 3
Views: 64

Re: Advice needed on the necessary circuit for connecting an old phone as a mic

a lot of old phone pickups are resistive, so you need to run a current through them to get a voltage. this can be accomplished with a resistor to +12V, and then you use a blocking capacitor to bring the signal back down to ground.
by guest
Tue Apr 07, 2020 3:16 pm
Forum: Music Tech DIY
Topic: TR-909 Handclap Modifications: Tune, Density, Intensity, and more
Replies: 3
Views: 56

Re: TR-909 Handclap Modifications: Tune, Density, Intensity, and more

i was wondering whether the crunch is due to the difference in noise sources, or perhaps some distortion in the VCA. im working on the rhythm wolf right now, and i find the crunch of the digital noise, when created through distortion, to be very unpleasant, but i liked the sound in your samples.
by guest
Tue Apr 07, 2020 1:31 pm
Forum: Music Tech DIY
Topic: TR-909 Handclap Modifications: Tune, Density, Intensity, and more
Replies: 3
Views: 56

Re: TR-909 Handclap Modifications: Tune, Density, Intensity, and more

sounds good, i like the crunch. is the analog noise source at a higher level than the digital? i know thats hard to compare, as noise doesnt have a fixed amplitude.
by guest
Tue Apr 07, 2020 1:11 pm
Forum: Music Tech DIY
Topic: Buffer Follower and LED Driving on Percussive Noise
Replies: 8
Views: 77

Re: Buffer Follower and LED Driving on Percussive Noise

try buffering the envelope with a transistor or opamp. that will allow you to drive the led, and will give longer decays. a lot of these circuits also have another 1nF - 2nF capacitor on the other side of the 1N4001 diode, going to ground. decreasing the 47k resistor on the noise transistor might in...
by guest
Tue Apr 07, 2020 12:43 pm
Forum: Music Tech DIY
Topic: Buffer Follower and LED Driving on Percussive Noise
Replies: 8
Views: 77

Re: Buffer Follower and LED Driving on Percussive Noise

what are the powersupply rails for your opamp? the LED drains the envelope capacitor quite qickly at the beginning, and then when it gets closer to the LED voltage, it has less of an impact, so i could see it having a large effect on the sound. you could just put it at the output of your opamp if ju...
by guest
Mon Apr 06, 2020 9:15 pm
Forum: Music Tech DIY
Topic: rhythm wolf teardown: any questions?
Replies: 176
Views: 4774

Re: rhythm wolf teardown: any questions?

thats an interesting question, how much is C-E veresus C-B flow. ill think on that for a bit. ill have to make some guesses as to what the reverse beta is.
by guest
Mon Apr 06, 2020 9:06 pm
Forum: Music Tech DIY
Topic: Application Note 299 VCO Issues
Replies: 4
Views: 89

Re: Application Note 299 VCO Issues

it just needs to increase by a small amount. try between 3k - 3.1k.
by guest
Mon Apr 06, 2020 8:09 pm
Forum: Music Tech DIY
Topic: Application Note 299 VCO Issues
Replies: 4
Views: 89

Re: Application Note 299 VCO Issues

increase the 3k resistor. the exact operating point of this circuit is not impilicitly defined, and it can vary with transistor type and temperature. are you using a transistor array (eg, LM3406)?
by guest
Mon Apr 06, 2020 10:54 am
Forum: Music Tech DIY
Topic: how to make cd40416 vco?
Replies: 13
Views: 257

Re: how to make cd40416 vco?

you could power both from +12V, but there are cases where the opamp wont work under those conditions (or the circuit would need to be redesigned to work). the 2 downsides to having a single rail are: 1. you need to AC couple your signals back down to ground, which means its only good for audio and n...
by guest
Mon Apr 06, 2020 10:48 am
Forum: Music Tech DIY
Topic: rhythm wolf teardown: any questions?
Replies: 176
Views: 4774

Re: rhythm wolf teardown: any questions?

just did a quick edit above. meant C-B and not C-E. its like the 606 bass drum mods you have up on your site, with the 2 back to back diodes, except its just one transistor. the odd thing i found, which originally had me thinking i was messing something up entirely, was that there wasnt any pitch sh...
by guest
Mon Apr 06, 2020 12:10 am
Forum: Music Tech DIY
Topic: rhythm wolf teardown: any questions?
Replies: 176
Views: 4774

Re: rhythm wolf teardown: any questions?

i built up a replica and i see voltage modulation on the base of my replica. again, not certain how closely this matches the real thing. this effect is largest at high accent and long decay time. for short decay and and accent, its only visible on the 1st or 2nd period. ive reached out to a friend w...
by guest
Sun Apr 05, 2020 8:58 pm
Forum: Music Tech DIY
Topic: Can't get rid of this hum in my Mackie
Replies: 4
Views: 118

Re: Can't get rid of this hum in my Mackie

if you have a scope, you can check the power supply rails to see if they have hum on them. that might help narrow it down. is it plugged into an outlet that youve used before when it didnt have hum?
by guest
Sun Apr 05, 2020 8:16 pm
Forum: Music Tech DIY
Topic: rhythm wolf teardown: any questions?
Replies: 176
Views: 4774

Re: rhythm wolf teardown: any questions?

ok, im very convinced of the reverse conduction theory now. the voltage on the base of Q43 almost identically matches the pitch shift plot in figure 11, which means that it must be the negative going peaks tha cause the shift. since this is out of phase by 90 degrees to the output, this means the ou...
by guest
Sun Apr 05, 2020 6:48 pm
Forum: Music Tech DIY
Topic: rhythm wolf teardown: any questions?
Replies: 176
Views: 4774

Re: rhythm wolf teardown: any questions?

i built up the circuit, and i dont see any pitch shifting after the first 10ms. i dont have the exact transistors, i used 3906 instead (i had to invert the whole circuit to allow for PNP), but these would have lower beta than the 945P used in the 808, and as such would be more likely to allow for "w...
by guest
Sun Apr 05, 2020 12:16 pm
Forum: Music Tech DIY
Topic: Trouble with my quarantine synth
Replies: 6
Views: 203

Re: Trouble with my quarantine synth

if moving that resistor over doesnt help, then its most likely a wire picking up a signal someplace. you can usually hunt around for these by touching the wires and seeing which one effcts the frequency the most. its always the wire with the highest impedance. for example, if you have a panel mount ...
by guest
Sat Apr 04, 2020 10:48 am
Forum: Music Tech DIY
Topic: Trouble with my quarantine synth
Replies: 6
Views: 203

Re: Trouble with my quarantine synth

the LM4040 needs a minimum current to operate. this is around 100uA, but its usually best to give it a bit more to be on the safe side. when calculating this current, you need to take into account the things that the LM4040 feeds current to. in this case, thats those 3 pots. so lets see if its enoug...
by guest
Sat Apr 04, 2020 10:25 am
Forum: Music Tech DIY
Topic: Problems with my DIY lm13700 VCA
Replies: 37
Views: 405

Re: Problems with my DIY lm13700 VCA

if it didnt work after you removed R16/24, but did work after you do the solder rework, then it sounds like it was a bad solder joint. the flakiness it is currently exhibiting sounds like a bad solder joint as well (or bad cable or connector).
by guest
Fri Apr 03, 2020 11:07 pm
Forum: Music Tech DIY
Topic: rhythm wolf teardown: any questions?
Replies: 176
Views: 4774

Re: rhythm wolf teardown: any questions?

i wish i had an 808, id like to poke around see what the voltages are. i suppose i can easily enough build up this section and test it. i suppose i could see Q43 being "weakly" off. ill give that some thought. something needs to account for the period based modulation, which means either Q42, Q43 or...
by guest
Fri Apr 03, 2020 8:29 pm
Forum: Music Tech DIY
Topic: rhythm wolf teardown: any questions?
Replies: 176
Views: 4774

Re: rhythm wolf teardown: any questions?

also, i finished the hihats rework. apologies for the wall of text, i just finished writing this up for the wiki and figured i would just copy and paste: i tried a number of different mods, and ended up using a small set of them. The ones i kept were as follows: 1. Minimum decay time - change R208 t...
by guest
Fri Apr 03, 2020 8:25 pm
Forum: Music Tech DIY
Topic: rhythm wolf teardown: any questions?
Replies: 176
Views: 4774

Re: rhythm wolf teardown: any questions?

are you the author of the paper? im a bit confused as you mentioned being referenced in it previously, but maybe that i misinterpreted that statement and you meant that the paper itself was being referenced in this thread. if so, its great work, but i just dont see how Q43 could possibly be in condu...
by guest
Fri Apr 03, 2020 7:09 pm
Forum: Music Tech DIY
Topic: rhythm wolf teardown: any questions?
Replies: 176
Views: 4774

Re: rhythm wolf teardown: any questions?

there is a pitch up at the beginning of the note, when Q43 is on, and that can be done on the RW, but i dont see how current can flow thorugh Q43 (as the author states) after this period is over, and create the "sigh" as he describes is. as best i can tell, the sigh is a result of current through R1...

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