Digital audio

S/PDIF test generator
The generator is intended primarily for checking S/PDIF (Sony/Philips Digital Interface Format) receivers and any associated digital-to-analogue converters (DAC) and/or output filters. The externalclock – standard TTL level – enables 128 sample frequenciesto be generated. The clock may also be used for generating standardfrequencies with the remaining inverters serving as crystal oscillators(provided a […]

simple copybit killer
The Serial CopyManagementSystem (SCMS)prevents digitalcopying of audiomaterial from thesecond generationonwards.Unfortunately, thisprotection alsoworks on homerecordings and soprevents homerecordists fromdigitally copyingtheir ownmusical work more thanonce without degradationby the SCMS. This problemhas been highlightedbefore in this magazine,but it has not gone away– reason enough todescribe a simple andinexpensive circuit forpermanently removing thecopy-prohibit-bit from theS/PDIF* audio signal.

sampling rate converter
Although there arestill dyed-in-the-woolsound technicianswho swear by thegood old analoguerecording technology,most others, bitten bythe digital audiorecording bug, do notwant to revert to analoguerecording. Theyhave experienced thepleasures of loss-freeprocessing and copyingof recordings atdigital level. Thesepleasures turn to frustration,however,when they want toconvert a DAT recordingon to a CD. Thiscannot be done justlike that because thetwo […]

opto-to-coaxial audio converter
Most audio equipmentproduced in thepast five to ten yearshas digital inputs andoutputs. It is a pity,though, that there aretwo standards: opticaland coaxial, and notall equipment hasboth. Fortunately, theconnection difficultiesthat may ensue areeasily resolved by theuse of the adaptordescribed in this article.This enables anyoptical output to beconverted into acoaxial one or viceversa.

digital-audio-input selector
As the name indicates, the selector isintended to choose one of up toeight digital audio signal inputs,which it does with the aid of a multiplexer.The multiplexer, IC6 is controlledby preset up/down counter IC2. Thecounter is set with DIP switch S3(note that the MSB switch is notused in this application).The various inputs are selectedwith press-keys […]

COPYBIT INVERTER
The inverter can be included in theS/PDIF link between any digital a.f. signalsource (such as a DCC recorder, a CDplayer, a DSR receiver) and a (second) DCCrecorder without the need of opening ormodifying any of the equipment. Duringthe copying, any copybit is inverted and atthe same time the category code is altered.This means that […]

COPYBIT ELIMINATOR REVISITED
Our February 1994 issue carried anarticle describing an inexpensive andstraightforward circuit for eliminating thecopybit from a digital S/PDIF* audio signalto enable users to copy (digitally) their ownmusical work many times without degradationby the SCMS**. The present article describesan updated version of that circuit,which can be used with the latest DAT, DCCand MD players.

clipping indicator
A little while ago areader wrote to saythat he had foundoverdrive on some ofhis compact discs.This sort of newscomes of course likea thunderbolt since itis assumed by mostpeople that compactdiscs are examples ofthe quality of today’sdigital technology.The first reaction tosuch an allegation isone of outright disbeliefor at least scepticism.Moreover, it hasbeen alleged by otherreaders […]

This converter is intended primarily for use with the sample rate converter published in the October 1996 issue of this magazine. The conversion of a symmetrical signal to an asymmetrical one requires no more than a small transformer. Amplification is not required since the AES/EBU signal is strong enough to generate the S/PDIF signal (500 […]