Denon DA-500 Vintage R2R DAC Review

[PeteL]

FTDI (in)famously updated their USB serial driver to exploit a quirk in one of the fakes to disable them, the problem being that the fakes had infiltrated the supply chain to the extent that manufacturers who thought they were using the genuine article from a reputable supplier were caught out when they stopped working.
It's also an issue with STM32 micros which you might think were too cheap to bother with.

Thanks, I like to be wrong when I learn something from it.

 

[restorer-john]

PCM1702U-L
PCM1702U
PCM1702U-J
PCM1702U-K

BB also had a selection -S only ever seen in the Japanese flagship models of CD players and a few TOTL D/A converters.

 

[Lopsided]

Noob question here, is a multibit DAC an R2R DAC? Are 80s 14, 16, 18-bit DACs R2R? Are current ESS and AKM chips variations of 1-bit design? Thanks.

 

[infinitesymphony]

Noob question here, is a multibit DAC an R2R DAC?

Yes, I believe "multi-bit" / R-2R / ladder generally refers to the same type of DAC. Popular DAC types like delta-sigma are usually running at 16 to 32-bit so in the literal sense they are also multi-bit.

Are 80s 14, 16, 18-bit DACs R2R?

Some but not all. Here are some R-2R chips, not sure which ones were available in the '80s beyond the Philips.

Analog Devices AD1861 through AD1866
Burr-Brown PCM1702, PCM1704, PCM56, PCM61P, PCM63P
Philips TDA1541, TDA1543, TDA1545

Not necessarily. Are current ESS and AKM chips variations of 1-bit design? Thanks.

Most of the higher-end DACs from those manufacturers are 32-bit delta-sigma.

 

[ElNino]

Noob question here, is a multibit DAC an R2R DAC? Are 80s 14, 16, 18-bit DACs R2R? Are current ESS and AKM chips variations of 1-bit design? Thanks.

All R2R DACs are "multibit" by definition. Current ESS and AKM chips are sigma-delta designs with a multibit sigma-delta modulator (5-6 bits, typically). The era of 1-bit sigma-delta modulators in reasonably high-performance audio applications has largely been over for two decades.

 

[bolserst]

Any chance we can see a square wave? Denons Alpha processing was said to not show ringing when on square waves.

Yup, they definitely could reproduce square waves without ringing. I saw it demoed several times at local Denon dealer in the mid 90s; no ringing on impulse either. Stereophile published measurements showing this for the Denon DA-S1(full review attached). I always wondering how they did that…no ringing yet the dual HF tone IMD test not showing prominent aliasing artifacts from a slow roll-off filter.

I recently ran across an old Denon CD player with the ALPHA processing logo in a thrift store and decided to pick it up to investigate. Using ARTA to make test CDs, I quickly determined that with a noise signal, it had a standard brick wall filter. But, with a single bit impulse signal it had a very slow roll off filter. After playing around a bit more, as best I can tell the sharp and slow filters are both operating in parallel and the processor decides based on looking at the 3 previous samples of the LSB whether to pass along the output of the slow filter or the sharp(LSB not changed in last 3 samples = use slow filter). If there is a large change in amplitude, the processor continues to use the filter it had been using before the large change. So, you can force which filter is being used by dithering or toggling the LSB on and off when you want the brick wall filter, and not dithering when you want the slow roll-off filter.

Here are a few examples:
Example 1: Single bit impulse with or without LSB dithering illustrating the time and frequency domain responses of the two filters.

Example 2: Single bit impulse with dithering turned on/off during different parts of the signal.

Example 3: 1kHz square wave with dithering turned on/off during different parts of the signal.


See Section V. in the attached ALPHA Processor description article.
“…ALPHA processor includes an Automatic Low Pass Filter Harmonic Adjustment feature-the world's first of its kind-which is able to identify the type of incoming signal and automatically select the shut-out band. Because the filter automatically varies according to the incoming data, reproduction of musical data is remains flat very close to the super-high frequency of fs/2. And in the case of pulse data reproduction, the pass band is widened so that the impulse response can be reproduced as intended without ringing…”

So with music CDs, the brick wall filter would always be used. When playing Denon made test CDs the slow filter is used, giving “pretty” impulse and square wave pictures on oscilloscope displays in dealer demos to help sell CD players.

Pulling a page each from an English and Japanese brochure for their later AL24 version of the ALPHA processor. Looks like they moved on to having 3 filters that they switched between based on the abruptness in amplitude change of the signal.

 

[GXAlan]

The documents you attached are really helpful! It would be interesting to see how Ultra AL32 performs in the latest Denon products. I still think ALPHA adds a lot of benefits when playing older non-dithered CDs from the 80's and early 90's.

 

[gvl]

Nice summary. I did come across some ancient discussions in the depths of the Internet stating similar, but this is the best explanation I’ve seen.

 

[restorer-john]

I still think ALPHA adds a lot of benefits when playing older non-dithered CDs from the 80's and early 90's.

How many undithered discs do you acually have (apart from the Denon Alpha demo disc)?

 

[GXAlan]

How many undithered discs do you acually have (apart from the Denon Alpha demo disc)?

Probably two dozen? I assume that “Super Bit Mapping” was when Sony started dithering? So I assumed that everything DDD produced in the 80’s was probably undithered?

Some of the original stuff from DMP and Telarc is incredible and there are certainly 80’s classic pop as well.

 

[tcli]

See Section V. in the attached ALPHA Processor description article.
“…ALPHA processor includes an Automatic Low Pass Filter Harmonic Adjustment feature-the world's first of its kind-which is able to identify the type of incoming signal and automatically select the shut-out band. Because the filter automatically varies according to the incoming data, reproduction of musical data is remains flat very close to the super-high frequency of fs/2. And in the case of pulse data reproduction, the pass band is widened so that the impulse response can be reproduced as intended without ringing…”

The Pacific Microsonic ADC & HDCD encoder use the same trick : switching between two anti-alias filters depending of high frequency signal content. Then, it encodes the filter used in the HDCD hidden data stream.
It seems that the HDCD decoder (PMD100) don't do anything with this data.

About Denon alpha processing, I don't think that it was just a marketing trick for dealer demos. In AL24 they use 3 different filters so they really try something with variable filters.

I am surprised that, today, nobody try some deep learning adaptativ filter

 

[GXAlan]

The Pacific Microsonic ADC & HDCD encoder use the same trick : switching between two anti-alias filters depending of high frequency signal content. Then, it encodes the filter used in the HDCD hidden data stream.
It seems that the HDCD decoder (PMD100) don't do anything with this data.

About Denon alpha processing, I don't think that it was just a marketing trick for dealer demos. In AL24 they use 3 different filters so they really try something with variable filters.

I am surprised that, today, nobody try some deep learning adaptativ filter

People used to say that this digital filter was one of the reasons why HDCD enabled CD players sounded better even with non HDCD encoded discs.

In Ultra AL32, they are using a FPGA with the same power as an old Pentium CPU. They are really coy about what algorithms are used but in blog interviews do say that it’s built from databases of music in Denon (Nippon Columbia) music.

The obvious question is if a deep learning filter results in an audible improvement or not.

 

[ElNino]

I am surprised that, today, nobody try some deep learning adaptativ filter

There's a lot of active research work being done on applying deep learning to DSP. I haven't been following it closely enough to be able to comment on whether anyone's improved meaningfully on conventional low-pass filter design, but one very recent paper I can recommend showing how good deep learning can be at replacing a traditional filterbank for audio encoding/decoding is this one: https://arxiv.org/abs/2107.03312

 

[Gaspar74]

Thank you or this indeed. I actually have a sony professional cdp d500 as my main cd player and I love it. In the Sony this is the same chip, pcm 1702, but in dual mono configuration, I couldn’t know If it gives it a benefit to use 2. Probably because it makes it easier to have balance outputs would be the reason for this. Funny thing is, it is, subjectively a great sounding cd player, but obviously only used for 16 bits redbook cds. I had it hooked to a modern dac, but lately for kicks I went back to use the r2r one. there is definitely an audible difference, and knew full well that it’s not as accurate than modern delta sigma dacs, but somehow I like it. I don’t want to get into the reviewer senseless lingo here to describe the sound, but it’s pleasing to me... (being political here... I know what I like about it... ) I know, subjectivity... Way back I worked in radio broadcasting, so I´m very familiar with he sound of em and it might be this familiarity that makes me biased. On another note, it’s not relevent to this review, but it’s sound is not the main reason I like this cdp. It’s such a robust hyper reliable thing, with great tactile feedback, ultra fast loading, and any cuing functions you can think of, and obviously all kind of digital outs, including aes ebu. I wouldn’t want anything else for cd transport at any price. They sometime show up around 200$ in the used market and it’s a great score for anybody that uses cds.

Would you describe this as a nice sounding dac. Considering using one for streaming seeing most I listen to is 16/44 it seems.

 

[PeteL]

Would you describe this as a nice sounding dac. Considering using one for streaming seeing most I listen to is 16/44 it seems.

As I said, yes to me it's good sounding as a CD Player. But what do you mean exactly by using one for streaming? there is no digital input other than the CD Player. There are digital outs. It's to play CD either with the included R2R DAC or any external one.

 

[Gaspar74]

As I said, yes to me it's good sounding as a CD Player. But what do you mean exactly by using one for streaming? there is no digital input other than the CD Player. There are digital outs. It's to play CD either with the included R2R DAC or any external one.

I apolagize, I thought you were referring to the DA 500 dac.

 

[rocksteady]

Thank you or this indeed. I actually have a sony professional cdp d500 as my main cd player and I love it. In the Sony this is the same chip, pcm 1702, but in dual mono configuration, I couldn’t know If it gives it a benefit to use 2. Probably because it makes it easier to have balance outputs would be the reason for this. Funny thing is, it is, subjectively a great sounding cd player, but obviously only used for 16 bits redbook cds. I had it hooked to a modern dac, but lately for kicks I went back to use the r2r one. there is definitely an audible difference, and knew full well that it’s not as accurate than modern delta sigma dacs, but somehow I like it. I don’t want to get into the reviewer senseless lingo here to describe the sound, but it’s pleasing to me... (being political here... I know what I like about it... ) I know, subjectivity... Way back I worked in radio broadcasting, so I´m very familiar with he sound of em and it might be this familiarity that makes me biased. On another note, it’s not relevent to this review, but it’s sound is not the main reason I like this cdp. It’s such a robust hyper reliable thing, with great tactile feedback, ultra fast loading, and any cuing functions you can think of, and obviously all kind of digital outs, including aes ebu. I wouldn’t want anything else for cd transport at any price. They sometime show up around 200$ in the used market and it’s a great score for anybody that uses cds.

The PCM1702 is a monolithic Chip. It requires a minimum of Two for stereo operation. That Sony player used 2x PCM1702-J chips...

 

[rocksteady]

But the interface for the digital receiver is the Yamaha YM3623B which definitely only has a 16-bit word output.



View attachment 91177

Mind numbingly stupid to use such an ancient Digital Receiver, limited to 16 Bits, and poor Jitter Rejection performance, when employing Top of (then) line 20 Bit R2R chips. Even at the time, there were far better alternatives (Crystal, Burr Brown). Quite a nonsensical choice...