from TB-303 resources mailing list -------[ http://www.tb-303.org ] ---------------------- Hi Shaz,
It's the 303. The noise you hear is noise from the digital circuitry getting into the audio path within the TB303. The sequencer's microprocessor and associated circuitry causes a significant amount of electrical noise, which is what you're hearing. Specifically, most of the noise is being caused by the scanning signals going to the illuminated LEDs, which are actually switched on and off at a rate of several hundred Hz. It is the large voltage spikes from this switching that causes the interference. (LEDs take lots of current; switching this current causes voltage spikes, which means trouble). The rate of this 'siren' noise is related to tempo simply because the rate at which one of the LEDs is flashing is proportional to the tempo setting. My TB303 makes this noise. I must confess I haven't listened to your mp3 but I can imagine it's pretty much the same. But strangely enough, another TB-303 I have besides me which had been sent to me for repair appears to be much 'quieter', and everyone else I asked about this before didn't seem to notice this noise on their 303. I did try to eliminate the noise in my 303 by replacing various electrolytic capacitors that were cruical for power supply decoupling etc. but I didn't get anywhere. I just presumed it was either a 'feature' that was down to the board layout / general design, or because of a bad PCB ground plane in my 303 (the board got cracked in half by it's previous owner). Shaz, since you've encountered this noise yourself, I'm tempted to open my 303 up again sometime soon and make a bit more effort to eliminate it. Especially since I've got another one sitting here to compare with. So, anyone else notice this noise? Trev ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Friday, May 17, 2002 9:07 PM Subject: [TB-303.org] Does your 303 experience the same trait as mine? > from TB-303 resources mailing list > -------[ http://www.tb-303.org ] ---------------------- > > Hi all > > I've always noticed this problem on my on 303. > Well, to be honest... i'm not sure if it is a problem but a typical > trait of equipment of this nature and my lack of recording experience. > > Have a listen (file size 1.35mb) > > http://members.aol.com/stormstown/siren303.zip > > In this example I have my 303 connected to the line input of my pc with a > phono jack > from output of the 303. The leads I'm using are of average quality. > This "siren" sound that i'm hearing when the 303 is NOT playing any sound > seems related to the tempo and wether I use 9v adapter over battery power > source. The siren sound is in sync with the flashing red light on the "note > pad" of 303. > > At about 8 seconds into the mp3 I've increased the temp so you can hear what > I mean. And after 20seconds I have started a 303 pattern. > > It's sort of worrying as the 303 is very special and my long term plan is to > get an Akai MPC4000 sampler at a later stage when I afford it. It would seem > pointless if the quality of my samples are marred by faulty equipment. > > My 202,909,808,606 doesn't do this, so it makes me wonder!!! > > Pls advise, > Shaz > -------[ http://www.tb-303.org ] ---------------------- > Subscribe & unsubscribe there : > http://www.tb-303.org/ > > -------[ http://www.tb-303.org ] ---------------------- Subscribe & unsubscribe there : http://www.tb-303.org/
