Such systems evolved into relatively popular units such as the Sony PCM-F1, used with the corresponding SL-2000 VCR for many amateur and professional recordings, and Technics even introduced a PCM console recorder with built-in VHS transport. . Nowadays, however, with the spread of professional multitrack digital recorders, the VCR method has largely been replaced by linear tape recording. Digital multitrack recorders, however, are very Expensive and considerable room remains for the “adapter” type of PCM recorder, which exploits the high information storage density of established inexpensive video recording systems.
When a true national DAT system was proposed, two systems emerged. One was based on the use of a stationary multitrack head for which thin film technology was offered, with around 20 parallel digital tracks needed for data and error protection data of a stereo audio channel. . For commercial reasons, the Japanese industry wanted to bring DAT to the domestic market and apparently could not wait for thin film technology to mature. Rotary head designs could provide the required information storage performance, but conventional VTR mechanisms were found to be too big and too noisy for serious use in a home audio recorder.
The development of the compact 8mm video carrier provided the potential for very small cassettes and tape widths. From there it was only a short step to define a unique miniature “video” type cassette, specify the complementary rotary scan video type recording method, and dedicate it to large audio recording. public, resulting in the R-DAT format. The design includes a sync timecode to allow fairly quick access to any part of the tape and the modest 90 ° head winding angle allows the use of easy loading mechanisms, as well as high speeds. very fast wind, currently 200 times higher reading speed.
The business result is a line of first generation household machines, resembling large CD players, with a similar drawer loading tray and very similar control keypad and digital display. Automatic track programming is a standard feature of R-DAT designs: once a tape has been recorded, the play modes and track selection function like a CD player. Compared to an older PCM / VCR system, or even the professional PCM-1630 / U-matic combination, the R-DAT recorder is a pleasure to use, with fast-access fast feedback of 2.4 s / minute ( 50s for two hours), and the mechanism is also reasonably fast compared to national CD standards.
Potentially, R-DAT provides the consumer with a near-professional quality digital recorder, allowing, in theory at least, very high quality recordings – better than wide open reel sound but with cassette convenience.
For comparison, Sony’s professional two-track machine is the PCM-1630, a unit in the $ 23,000 category when purchased with a matching U-matic recorder. The 1630 is well established in the industry and is specified by Polygram for CD mastering. As the performance of his laboratory will show, it is in a way a benchmark machine. I was fortunate enough to have access to a 1630 for extensive lab testing, and the results give some idea of the advancements that have been made in PCM recording technology. Against this background, it was instructive to subject the national budget equivalent, in the form of Sony’s DTC-1000ES R-DAT recorder, to virtually the same battery of tests (footnote 1). How would the domestic equivalent compare to the professional model at more than 10 times the cost?
Sony PCM-1630
Taking the 1630 first, a glance at the manual gives an overview of its internal organization. As with many professional units, the design is based on a large rack mount enclosure incorporating an internal backplane (a set of multi-way vertical jacks). The electronics are carried on a number of printed circuit assemblies that slide into the enclosure from the front and plug into the sockets on the backplane. The enclosure is the main chassis, and the backplane cabling, which is often quite complex, carries signals and power from one card to another.
The two balanced input signals enter the back of the 1630 via XLR jacks and semi-preset level controls, and are routed to the A / D card via 20k ohm series resistors; the first stage is a low noise 5532 operational amplifier (a double 5534) with differential input clamp diodes. Up to 10 V RMS can be applied to this input as it is followed by subsidiary level control, with maximum attenuation limited to 36 dB. Another op amp follows, whose frequency response is determined by a switched FET capacitor, this is the recording pre-emphasis option. Two other biFET operational amplifiers drive the thick-film, brick-walled anti-alias filter, which cuts frequencies above 21 kHz; more operational amps add phase feedback / correction to the filter. The filter stage for each channel is buffered by another 5534 op-amp, followed by the 16-bit linear A / D converter, a Sony CX-20018, driven by three peripheral op-amplifiers IC; in this case, 356s. The digital data from both channels is then conditioned and processed on the modulator board to form a standard NTSC video signal ready for recording.
The 16-bit linear DAC is stereo and has a considerable amount of circuitry, with Sony CX 20152 chips used for D / A conversion. Industry standard IC regulators – types 7815 and 7915 rather than types 317 / 337 low impedance – feed operational amplifier rails ± 15V, one set per channel. Many small L / C filters are present in power supplies and lines in order to filter and isolate stages from each other, removing digital pulses and their harmonics.
The interesting part of the 1630, compared to earlier professional PCM machines, is the D / A section, which uses 2x oversampling with digital filtering. It seems to owe a lot to the design technology of Sony’s DAS-702es home CD decoder (see Stereophile Vol.9 No.8 for the ‘702 and Vol.10 No.4 for the same decoder’ 703). A lot happens to the two stereo channels after digital oversampling / filtering and D / A conversion. The output goes through the LF356 operational amplifiers, through the logic switch deglitcher, to a “2525” filter stage IC, using feedback inductance and capacitor methods. This buffer drives the main thick film technology, AF LI / 201, low pass filter, labeled identically to the recording input filter. Four additional ICs are present, mostly 5534s, for additional filtering, phase compensation, and de-emphasis. The final op amp drives two discrete Class A / B output stages per channel, one for the “hot” halves and one for the “cold” halves of the balanced differential output.
I have included this circuit description because I think it might give some insight into the sound quality of this processor. It should be noted that the recording and replay level strings are essentially DC coupled, so the quality issues of the coupling capacitors do not arise. However, since each active stage plays a role in the sound quality chain, it is worrying to find 13 of them in the record / replay path, excluding A / D and D / A converters. knows that under critical home listening conditions we can hear the loss imposed by a single 5534 op amp in a preamp line stage. Considering the recording chain as a whole, if the audio went through a mixing console, it may at best have encountered another dozen 5532/4 stages, or, worse yet, stages with circuitry. less well thought out integrated, as well as by a number of coupling transformers. It seems to me that a lot needs to be done to improve the design practices of recording systems.
Sony DTC-1000ES
I couldn’t do an accurate head count on this R-DAT machine, but from a quick glance at the maps, I would estimate the number of active stages to be a third of that of the 1630. , while the physical signal path length is probably a quarter, and without the need for a backplane or balanced I / O. Assuming similar digital section performance, the DTC-1000 can be expected to sound more transparent only because of its relative simplicity.
As befits its “ES” suffix, the DTC is carefully crafted in Sony Esprit tradition. The chassis is copper-plated to combat induced currents flowing through the metal frame, and the case, like that of the PCM-F1, is damped to reduce acoustic vibrations. The analog and digital power supplies are separate – a clear change from the first generation Sony CD players – and it is clear that considerable care has been taken in the choice of components: ELNA Cerafine capacitors, for example, are used in applications reservoir and decoupling.
As with the 1630, the recording section is dual channel, using two of the same Sony CX-20018 ADC chips, not oversampled. There is an input op amp leading to the good quality Soshin anti-alias filter, a thick film encapsulated model. Two more stages of operational amplification lead to A / D. Once in digital form, the encoded audio is multiplexed and routed to the main digital processor, the two R-DAT chips, CXD-1008Q and CXD-1009Q. These, in conjunction with two 64k memory blocks, handle error-protected data transfer to the rotary head recorder section and vice versa.
Footnote 1: J. Gordon Holt reviewed Sony’s DTC-2000ES DAT recorder in November 1994. ??John atkinson
Such systems evolved into relatively popular units such as the Sony PCM-F1, used with the corresponding SL-2000 VCR for many amateur and professional recordings, and Technics even introduced a PCM console recorder with built-in VHS transport. . Nowadays, however, with the spread of professional multitrack digital recorders, the VCR method has largely been replaced by linear tape recording. Digital multitrack recorders, however, are very Expensive and considerable room remains for the “adapter” type of PCM recorder, which exploits the high information storage density of established inexpensive video recording systems.
When a true national DAT system was proposed, two systems emerged. One was based on the use of a stationary multitrack head for which thin film technology was offered, with around 20 parallel digital tracks needed for data and error protection data of a stereo audio channel. . For commercial reasons, the Japanese industry wanted to bring DAT to the domestic market and apparently could not wait for thin film technology to mature. Rotary head designs could provide the required information storage performance, but conventional VTR mechanisms were found to be too big and too noisy for serious use in a home audio recorder.
The development of the compact 8mm video carrier provided the potential for very small cassettes and tape widths. From there it was only a short step to define a unique miniature “video” type cassette, specify the complementary rotary scan video type recording method, and dedicate it to large audio recording. public, resulting in the R-DAT format. The design includes a sync timecode to allow fairly quick access to any part of the tape and the modest 90 ° head winding angle allows the use of easy loading mechanisms, as well as high speeds. very fast wind, currently 200 times higher reading speed.
The business result is a line of first generation household machines, resembling large CD players, with a similar drawer loading tray and very similar control keypad and digital display. Automatic track programming is a standard feature of R-DAT designs: once a tape has been recorded, the play modes and track selection function like a CD player. Compared to an older PCM / VCR system, or even the professional PCM-1630 / U-matic combination, the R-DAT recorder is a pleasure to use, with fast-access fast feedback of 2.4 s / minute ( 50s for two hours), and the mechanism is also reasonably fast compared to national CD standards.
Potentially, R-DAT provides the consumer with a near-professional quality digital recorder, allowing, in theory at least, very high quality recordings – better than wide open reel sound but with cassette convenience.
For comparison, Sony’s professional two-track machine is the PCM-1630, a unit in the $ 23,000 category when purchased with a matching U-matic recorder. The 1630 is well established in the industry and is specified by Polygram for CD mastering. As the performance of his laboratory will show, it is in a way a benchmark machine. I was fortunate enough to have access to a 1630 for extensive lab testing, and the results give some idea of the advancements that have been made in PCM recording technology. Against this background, it was instructive to subject the national budget equivalent, in the form of Sony’s DTC-1000ES R-DAT recorder, to virtually the same battery of tests (footnote 1). How would the domestic equivalent compare to the professional model at more than 10 times the cost?
Sony PCM-1630
Taking the 1630 first, a glance at the manual gives an overview of its internal organization. As with many professional units, the design is based on a large rack mount enclosure incorporating an internal backplane (a set of multi-way vertical jacks). The electronics are carried on a number of printed circuit assemblies that slide into the enclosure from the front and plug into the sockets on the backplane. The enclosure is the main chassis, and the backplane cabling, which is often quite complex, carries signals and power from one card to another.
The two balanced input signals enter the back of the 1630 via XLR jacks and semi-preset level controls, and are routed to the A / D card via 20k ohm series resistors; the first stage is a low noise 5532 operational amplifier (a double 5534) with differential input clamp diodes. Up to 10 V RMS can be applied to this input as it is followed by subsidiary level control, with maximum attenuation limited to 36 dB. Another op amp follows, whose frequency response is determined by a switched FET capacitor, this is the recording pre-emphasis option. Two other biFET operational amplifiers drive the thick-film, brick-walled anti-alias filter, which cuts frequencies above 21 kHz; more operational amps add phase feedback / correction to the filter. The filter stage for each channel is buffered by another 5534 op-amp, followed by the 16-bit linear A / D converter, a Sony CX-20018, driven by three peripheral op-amplifiers IC; in this case, 356s. The digital data from both channels is then conditioned and processed on the modulator board to form a standard NTSC video signal ready for recording.
The 16-bit linear DAC is stereo and has a considerable amount of circuitry, with Sony CX 20152 chips used for D / A conversion. Industry standard IC regulators – types 7815 and 7915 rather than types 317 / 337 low impedance – feed operational amplifier rails ± 15V, one set per channel. Many small L / C filters are present in power supplies and lines in order to filter and isolate stages from each other, removing digital pulses and their harmonics.
The interesting part of the 1630, compared to earlier professional PCM machines, is the D / A section, which uses 2x oversampling with digital filtering. It seems to owe a lot to the design technology of Sony’s DAS-702es home CD decoder (see Stereophile Vol.9 No.8 for the ‘702 and Vol.10 No.4 for the same decoder’ 703). A lot happens to the two stereo channels after digital oversampling / filtering and D / A conversion. The output goes through the LF356 operational amplifiers, through the logic switch deglitcher, to a “2525” filter stage IC, using feedback inductance and capacitor methods. This buffer drives the main thick film technology, AF LI / 201, low pass filter, labeled identically to the recording input filter. Four additional ICs are present, mostly 5534s, for additional filtering, phase compensation, and de-emphasis. The final op amp drives two discrete Class A / B output stages per channel, one for the “hot” halves and one for the “cold” halves of the balanced differential output.
I have included this circuit description because I think it might give some insight into the sound quality of this processor. It should be noted that the recording and replay level strings are essentially DC coupled, so the quality issues of the coupling capacitors do not arise. However, since each active stage plays a role in the sound quality chain, it is worrying to find 13 of them in the record / replay path, excluding A / D and D / A converters. knows that under critical home listening conditions we can hear the loss imposed by a single 5534 op amp in a preamp line stage. Considering the recording chain as a whole, if the audio went through a mixing console, it may at best have encountered another dozen 5532/4 stages, or, worse yet, stages with circuitry. less well thought out integrated, as well as by a number of coupling transformers. It seems to me that a lot needs to be done to improve the design practices of recording systems.
Sony DTC-1000ES
I couldn’t do an accurate head count on this R-DAT machine, but from a quick glance at the maps, I would estimate the number of active stages to be a third of that of the 1630. , while the physical signal path length is probably a quarter, and without the need for a backplane or balanced I / O. Assuming similar digital section performance, the DTC-1000 can be expected to sound more transparent only because of its relative simplicity.
As befits its “ES” suffix, the DTC is carefully crafted in Sony Esprit tradition. The chassis is copper-plated to combat induced currents flowing through the metal frame, and the case, like that of the PCM-F1, is damped to reduce acoustic vibrations. The analog and digital power supplies are separate – a clear change from the first generation Sony CD players – and it is clear that considerable care has been taken in the choice of components: ELNA Cerafine capacitors, for example, are used in applications reservoir and decoupling.
As with the 1630, the recording section is dual channel, using two of the same Sony CX-20018 ADC chips, not oversampled. There is an input op amp leading to the good quality Soshin anti-alias filter, a thick film encapsulated model. Two more stages of operational amplification lead to A / D. Once in digital form, the encoded audio is multiplexed and routed to the main digital processor, the two R-DAT chips, CXD-1008Q and CXD-1009Q. These, in conjunction with two 64k memory blocks, handle error-protected data transfer to the rotary head recorder section and vice versa.
Footnote 1: J. Gordon Holt reviewed Sony’s DTC-2000ES DAT recorder in November 1994. ??John atkinson