bevis@EE.ECN.PURDUE.EDU (Jeffrey A Bevis) (05/05/89)
Subject: Audio digitizer woes Summary: Problem with interface to Amiga Perhaps someone out there can help me with this... Some time ago I constructed an audio digitizer (of my own design, not anything recently posted on the net). It is based on the ADC0802. An 74LS374 is used to latch the output from the ADC, the whole affair being externally clocked (by external, I mean external to the Amiga). The 374 then drives the parallel port inputs. It works fairly well, except for the most significant bit. Using Audiomaster (from Aegis) to sample the parallel port, I notice random dropouts of the top data bit. This causes particularly loud clicks to appear in the sampled audio, which are quite annoying. My question is, what could cause this? The ADC is not being overclocked (ie, clock freq. is to high), and there are no problems with the other 7 bits. I've achieved identical results with an A1000 and A2000. Are there any peculiarities of the msb of the parallel port I should know about? Methinks they should all behave similarly. Funny thing is, when I connected the same digitizer hardware to a C-64's user port and sampled that, there were no problems with the msb. The digitizer doesn't seem to be at fault. What's going on here? All suggestions would be GREATLY appreciated. Thanx! Jeff