Burr-Brown PCM1702 A Really Interesting Audio DAC From the 90s
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| Burr-Brown PCM1702-L |
I've just acquired from eBay a CD player to complement another very old CD player, both with Burr-Brown Digital to Analog converters.
The photo shows the inside of the Denon CD-655 from the late 90s, a super low distortion and high signal to noise ratio CD player which uses 2 x PCM1702 DACs from Burr-Brown.
The BiCMOS process 20-Bit PCM1702 was a really interesting DAC which was an improved version of the PCM63P. Early R-2R ladder DACs suffered from some noise/glitches at low output levels (and degraded linearity) due to the Most Significant Bit current source turning on at the lowest volume output point. Multi-bit DACs had significantly higher performance than contemporary 1-bit and "MASH" DACs, but had this one flaw.
The PCM1702 was effectively two 19-bit DACs in a complementary design which negated the zero cross point issue. They had all the benefits of R-2R ladder DACs and now removed the other issue. Around this time Burr-Brown were also producing Delta-Sigma CMOS DACs, but they didn't have the same performance. Compared to the PCM63P, the PCM1702 improved Signal to Noise (SNR) by 4dB and had a better typical Total Harmonic Distortion (THD).
Denon must have persuaded Burr-Brown to test a higher grade spec than the datasheet. The datasheet has -J and -K options, but not -L. I remember many years ago, when I was in Burr-Brown, Linn asking us to create a higher grade audio DAC for them at final test. However they were only going to buy a small number so we said no. Denon would have had much more clout in the late 90s.
A few months back I decided to create a hi-fi system in a much bigger room in my house. I bought a new turntable (Pro-Ject Debut III SE) and a set a Tannoy floorstander speakers. Rather than spend another large bunch of money I decided to go for used equipment. I bought a Philips FA930 amplifier which came out in the 90s. Better specs than some decent amplifiers today, kind of equivalent to the Marantz 6006 UK Edition, but with a bunch of extra features for the time, and more power. Philips and Marantz were always one and the same anyway. I paid less than 1/10 of what a new price would be. (Update - I now have the higher output power and higher performance FA931).
Same with the Denon CD player, although DAC technology has moved on further than amplifier technology (Class-D amplifiers extant). The output buffer amps on the PCM1702-Ls are ultra wideband very low noise operational amplifiers from NEC, so you could argue that the noise performance on buffer amps has not yet been beaten. In effect I paid less than 1/10 again of what I would pay for new today with only negligible (if any) benefits. I also looked at the 900 series CD players from Philips from the same era as my FA930 amp, but the performance was terrible, due primarily to the fact Philips had used their own 1-bit sigma delta DAC, which gave really poor performance.
The photo shows the inside of the Denon CD-655 from the late 90s, a super low distortion and high signal to noise ratio CD player which uses 2 x PCM1702 DACs from Burr-Brown.
The BiCMOS process 20-Bit PCM1702 was a really interesting DAC which was an improved version of the PCM63P. Early R-2R ladder DACs suffered from some noise/glitches at low output levels (and degraded linearity) due to the Most Significant Bit current source turning on at the lowest volume output point. Multi-bit DACs had significantly higher performance than contemporary 1-bit and "MASH" DACs, but had this one flaw.
The PCM1702 was effectively two 19-bit DACs in a complementary design which negated the zero cross point issue. They had all the benefits of R-2R ladder DACs and now removed the other issue. Around this time Burr-Brown were also producing Delta-Sigma CMOS DACs, but they didn't have the same performance. Compared to the PCM63P, the PCM1702 improved Signal to Noise (SNR) by 4dB and had a better typical Total Harmonic Distortion (THD).
Denon must have persuaded Burr-Brown to test a higher grade spec than the datasheet. The datasheet has -J and -K options, but not -L. I remember many years ago, when I was in Burr-Brown, Linn asking us to create a higher grade audio DAC for them at final test. However they were only going to buy a small number so we said no. Denon would have had much more clout in the late 90s.
A few months back I decided to create a hi-fi system in a much bigger room in my house. I bought a new turntable (Pro-Ject Debut III SE) and a set a Tannoy floorstander speakers. Rather than spend another large bunch of money I decided to go for used equipment. I bought a Philips FA930 amplifier which came out in the 90s. Better specs than some decent amplifiers today, kind of equivalent to the Marantz 6006 UK Edition, but with a bunch of extra features for the time, and more power. Philips and Marantz were always one and the same anyway. I paid less than 1/10 of what a new price would be. (Update - I now have the higher output power and higher performance FA931).
Same with the Denon CD player, although DAC technology has moved on further than amplifier technology (Class-D amplifiers extant). The output buffer amps on the PCM1702-Ls are ultra wideband very low noise operational amplifiers from NEC, so you could argue that the noise performance on buffer amps has not yet been beaten. In effect I paid less than 1/10 again of what I would pay for new today with only negligible (if any) benefits. I also looked at the 900 series CD players from Philips from the same era as my FA930 amp, but the performance was terrible, due primarily to the fact Philips had used their own 1-bit sigma delta DAC, which gave really poor performance.
Update : SACD passed me by until now. Here's a new blog post which talks about a 2000s DVD player from Pioneer that can play SACDs, has a Philips Semiconductors SACD processor and three Burr-Brown DSD DACs.
Come across this page when I'm looking up more info on how to wire the bunch of PCM1702 modules that I've recently acquired. It is a PILE of stereo modules from broadcast/video processing equipment in late 90s by Pro-Bel They are all PCM1702P-K grade goodness.
ReplyDeleteThe circuit of the module is nearly identical to DEM-1702 board, including the SM5842AP digital filter, but starting at I/V stage, everything seems to be doubled for possibly balanced audio output. All the LPF and output stage are doubled as well, with LPF capacitor value idental to PCM1702's datasheet.
After a bit of digging, it appears Pro-Bel cares very little about parts cost, nearly every resistor is 0.1%, 15PPM good stuff, most caps are Wima boxes, and the rest and tant caps and a few ceramics for the digital circuit. With circuit at least 4 layers or more. Really really want to figure it out and jury rig it to see how it sounds in my system, might just give my Gustard DAC X-20 (dual ESS ES9018 DAC) a good run for the money.
Unfortunately, PCM1702P-L is not a high grade, it is low-end/-cost. Before i understood this, I bought a lot of old Denon CD players, to desolder the chips ...
ReplyDeleteESS I trust. For a while they were led and designed by the same audio IC design guru (whom I know) from Wolfson Microelectronics.
ReplyDeleteRemember this is a 90s product and listening experiences are subjective/personal taste driven.