EMUSIC-L Digest Volume 56, Issue 04 This issue's topics: 1-bit sampling?? (4 messages) Your EMUSIC-L Digest moderator is Joe McMahon . You may subscribe to EMUSIC-L by sending mail to listserv@american.edu with the line "SUB EMUSIC-L your name" as the text. The EMUSIC-L archive is a service of SunSite (sunsite.unc.edu) at the University of North Carolina. ------------------------------------------------------------------------ Date: Sun, 12 Sep 1993 10:24:25 U From: David Williams Subject: 1-bit sampling?? Can someone explain what 1-bit sampling is all about, please. I understand 8-, 12-, and 16-bit ADCs and DACs alright. But, I notice now devices that claim 1-bit ADCs and I don't understand how this works. Thanks for any help on this. Dave Williams Illinois State University ------------------------------ Date: Sun, 12 Sep 1993 11:12:03 -0700 From: Michael O'Hara Subject: Re: 1-bit sampling?? Picture a car jack. It can "notch" up, or down as needed. This is the basis of one-bit sampling. Obviously, in order to keep up with a fast moving signal, you must crank that sucker REAL fast. Now, unlike the car jack, we are always cranking in one direction or the other. This means, that an unchanging signal level is going to be represented as a sequence like up-down-up-down-up-down; exactly a 50% ratio. As the rate-of- -change increases, the sequence deviates from 50% as required. Advantages: Little or no filtering required. Comparitively simple circuitry. (sp) As an ADC, very good group delay characteristics. (overall an excellent performer) Disadvantages: Very fast components required; cutting corners in the comparater selection will compromise performance. As a DAC, requires especially long "digital filters" for good pulse response, but can give better performance with no analog filtering at all req'd. ------------------------------ Date: Mon, 13 Sep 1993 06:09:01 -0400 From: Andy Farnell Subject: Re: 1-bit sampling?? I believe that this type of 1 bit sampling is known as, amongst other names, delta modulation. As always I can recommend that fine text by K.Pohlman - Principles of Digital Audio - which I am sure deals with the subject. Andy Farnell Computing and Cognition ACE Bournemouth University England ------------------------------ Date: Mon, 13 Sep 1993 13:27:42 UT From: Hutzenbiler Leroy Subject: Re: 1-bit sampling?? Take, for example, a 4 bit sample. The bit values are 1, 2, 4, & 8. Instead of converting each bit to a voltage, convert each bit to a charge and integrate to a voltage. Look at the bits in any order at a clock rate of most significant bit value * the sampling rate ( e.g., 8 * 22,000). If the '1' bit is on, generate a constant voltage for one clock, If the '2' bit is on, generate a constant voltage for two clocks, if the '4' bit is on, generate a constant voltage for four clock cycles, and if the '8' bit is on, generate a constant voltage for eight cycles. The constant voltage generates a charge proportional to the bit value. Integrating converts to a voltage. The advantage of this is that one stable voltage and an accurate clock are easier to implement than a voltage adder. Oversampling is relatively easy, too. In the example, a clock rate of (4 * most significant bit value * the sampling rate) would give a 4x oversampling. LeRoy ------------------------------ End of the EMUSIC-L Digest ******************************