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Accuphase DP-70 Review (CD Player)

NTTY

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Hello Everyone,

This is a review and detailed measurements of the Accuphase DP-70 CD Player and Transport.

Accuphase DP-70_001.jpg



Accuphase DP-70 - Presentation

Released in 1987, this old CD Player was one of the most expensive at a time (3 times the price of the top of the line Sony CDP-557ESD!), sweating luxury from inside out, starting with a weight of 21kg, as a statement.

And I must say that, like all other Accuphase devices, it is of an incredible quality, really appart.

Nearly 40 years later, it is flawless, at least externally:

Accuphase DP-70_002.jpg


What makes the interest of that one is fact that Accuphase thought they could not find a DAC decent enough, on their perspective, so they designed their own discrete one! Of course, when I got to know that, I had to get one and test it!

The back of it is as full as it could be in 1987:

Accuphase DP-70_003.jpg


We get fixed XLR and RCA and variable RCA. SPDIF Coax and optical are also available. The connectors are superb. Bottom right corner was damaged in its long life, unfortunately.

Accuphase has been building roughly 7'000 devices per year, total, for the last 50 years, 70% of them being absorbed by the Japan Market. So that one is a challenge to source :cool:

The elements of interest are:
  • Discrete DAC based on 4x4-bit current switches (Intersil ICL8019ACPD) with specifically designed exterior film resistors of 0.0015% tolerance.
  • 4x oversampling filter, which was no so frequent at the time.
  • The crazy beautiful and marvelously fast drive Sony BU-1C, a legend alone!
  • The incredible overall quality.
The specifications given by Accuphase were the below:

1763137013172.png


And as all vendors should, Accuphase provided a nice set of measurements:

1763137068481.png


Count on me to go check what's left of that 40 years later ;)

I guess I might reach the max number of allowed pictures for one post, but allow me to take more time and space than usual to go deeper into this beast.


Accuphase DP-70 - Let's go inside

First, let's remove the top cover (1.5kg) to see the two power supplies (for Digital and Analog circuits), the superb servo board and the Sony drive:

Accuphase DP-70_005.jpg


That near-full metal drive is worth a book:
Accuphase DP-70_012.jpg


And now let's remove the bottom cover:

Accuphase DP-70_016.jpg


We get a nice view of the laser head on magnetic rails, and it's even better to see it in action than to look at it. On the left, we see the conversion board.
Below the metallic box is the oversampling filter. The attention to details is staggering.

The discrete DAC is made of 4 Intersil current switches that are 4 bits each, hence 4 of them to get to 16bits. They require high precision resistors as shown below:

1763137860426.png



Which translate to these beautiful blue resistors here:

Accuphase DP-70_033.jpg


The three white trimming pots are to adjust the linearity of the DAC. I played with them, of course, and in the absence of a manual, that was some fun. All of this means that the integration level was much lower than the usual Burr-Brown of Philips DACs ICs of the time, and that Accuphase did not want to use considering they were not linear enough.

Let's have a closer look at the conversion board (1 channel shown):

Accuphase DP-70_032.jpg


Find below details about the function of each block above:
  1. Analog Power Supply
  2. Optoisolator
  3. Serial to parallel digital converter (from the decoder to the DACs)
  4. The discrete DAC (4x4bits current switches and their external resistors)
  5. I/V converter and de-glitching
  6. Five-pole GIC Butterworth low-pass filter
  7. Balanced output
  8. Unbalanced output
  9. De-emphasis circuit
It is a pleasure to look at the details of this CD player, and I could continue to provide you with much more pictures, but I'll refrain and I’ll add only two more. The output plate of RCA connectors:

Accuphase DP-70_028.jpg


And that magnetic laser head again from the bottom:

Accuphase DP-70_027.jpg


Yeah, ok, one last, the power supply allows to change the voltage to match the one of the customer:

Accuphase DP-70_029.jpg


So, if you can get a Japanese version, it will be easy to adapt it to whatever local voltage you use.


User Experience

Do I need to talk about it? Yes of course!

What a delight! It does not do much, but everything it does, it does it so well, so smooth and so fast. The Sony BU-1C is faster than light. And it is stupidly fun to try being faster by pressing 20 times+ on the next button in an attempt to get at least 1 track before it, but no, fail, it wins every time. Besides that, this mech is totally silent.

I did not mention before, but there is a hidden panel on the front, at the bottom, to get access to other functions (eg keypad), including the variable output. But no phones out, that is big miss on my perspective.

Accuphase DP-70_035.jpg



Accuphase DP-70 - Measurements (XLR out)

All measurements performed with an E1DA Cosmos ADCiso (grade 0), and the Cosmos Scaler (100kohms from unbalanced input) for analog outputs, and a Motu UltraLite Mk5 for digital.

I am now consistent with my specific measurements for CD Players, as I described them in the post “More than we hear”, and as I reported them for the Onkyo C-733 review. Over time, this will help comparing the devices I reviewed.

The Accuphase outputs 2.5Vrms from the balanced and unbalanced outputs. The channel imbalanced was a low 0.04dB. Balanced output are non-inverting, unbalanced are.

Unless otherwise mentioned, all measurements below are from unbalanced outputs.

----

As usual, let's start with my standard 999.91Hz sine @0dBFS (without dither) from the Test CD (RCA out):

Accuphase DP-70_999.91Hz_@0dBFS_01.jpg


This is very good for 40 years discrete conversion! Only one channel is shown in the dashboard (the best one) because I adjusted it to be as linear as possible at low level. Fact is this is not an easy task because this CD player is very sensitive to the temperature. So when the bottom is open (to allow for adjustments) the final result varies a lot once closed. So that was a lot of fun and time to get there. I'll talk more about that later.

The SNR (97.4dB), with this max output level, is close to the theoretical 98dB max of the CDA. And that is 40 years later, from a not serviced CD Player....

Let's have a look at -6dBFS:

Accuphase DP-70_999.91Hz_@-6dBFS.jpg


As opposed to what I see usually with very old conversion, the distortion does not increase. There's less noise relative to the carrier, meaning this is a quiet conversion (the SNR increased to 97.6dB).

----

I usually have a look at any potential PS related leakage, and you saw it before, there is some, with my usual punishing 512k FFT length:

Accuphase DP-70_PS.jpg


But at -110dBr, it will be very difficult to hear that,

----

Next is the bandwidth:

Accuphase DP-70_BW.jpg


Not too bad but not flat. I think the roll off is due to the analog filter more than the oversampling one. Look at the below ultrasonic view of how it works:

Accuphase DP-70_OS.jpg


We get a sharp filter (as we should) that attenuates by -85dB minimum all artifacts of the conversion. This is a good result and a slap in the face of the slow filters that are so weak to attenuate aliases of the conversion. I like to see a filter with that efficiency.
By the way, the pink trace on that view is the IMD AES test (18kHz & 20kHz) and shows very little distortion (below -100dB). Even with modern CD Players I don't always get such good results.

----

Let's have a look at the multitone test that a lot of you like very much, and guess what:

Accuphase DP-70_MT.jpg


Wow, this is best is class results! Distortion is way below the CD Audio format. I don't recall why I used a 128kFTT length for that test, I usually go 512k - 32 averages (I suppose I was in a rush), but that is a very beautiful trace.

----

Oh yeah, the jitter test now, is the ancestor up to it?

Accuphase DP-70_JTest.jpg


Nailed!

The red trace is from the digital output (spoiler alert: which is perfect), and the blue one from the RCA. So, in 1987, Jitter was a solved problem.

----

Started with the Teac VRDS-20 review, and on your request + support to get it done (more here), I'm adding now an "intersample-overs" test which intends to identify the behavior of the digital filtering and DAC when it come to process near clipping signals. Because of the oversampling, there might be interpolated data that go above 0dBFS and would saturate (clip) the DAC and therefore the output. And this effect shows through distorsion (THD+N measurement up to 96kHz):

Intersample-overs tests
Bandwidth of the THD+N measurements is 20Hz - 96kHz
5512.5 Hz sine,
Peak = +0.69dBFS
7350 Hz sine,
Peak = +1.25dBFS
11025 Hz sine,
Peak = +3.0dBFS
Teac VRDS-20-30.7dB-26.6dB-17.6dB
Yamaha CD-1-84.6dB-84.9dB-78.1dB
Denon DCD-900NE-34.2dB-27.1dB-19.1dB
Denon DCD-SA1-33.6dB-27.6dB-18.3dB
Onkyo C-733-88.3dB-40.4dB-21.2dB
Denon DCD-3560-30.2dB-24.7dB-17.4dB
Myryad Z210-70.6dB (noise dominated)-71.1dB (noise dominated)-29.4dB (H3 dominated)
Sony CDP-X333ES-30.5dB-24.8dB-16.3dB
BARCO-EMT 982-32.7dB-24.5dB-16.3dB
TASCAM CD-200-73.5dB-36.3dB-19.7dB
Sony CDP-597-30.4dB-24.7dB-16.5dB
SMSL PL100-53.1dB-31dB-19.1dB
OPPO BDP-95-39dB-28.8dB-19.2dB
OPPO BDP-95 (vol -2dB)-95dB-97.5dB-32.7dB

You don't find the Accuphase? Really? Well yes, me stupid, please accept my apologies. I forgot to record the results. I'll update soon, but don't expect good resistance though. At the time, CD player engineers thought people in studios would respect the recommendation to keep a good headroom in digital domain...

----

Let's continue with the good old 3DC measurement that Stereophile was often using as a proof of low noise DAC. It is from an undithered 997Hz sine at -90.31dBFS. With 16bits, the signal should appear (on a scope) as the 3DC levels of the smallest symmetrical sign magnitude digital signal. This test is a killer of R2R conversion, let alone discrete conversion.

When I got the DP-70, it was showing the below disappointing view:

Accuphase DP-70_3DC.jpg


This asymmetry means the Accuphase was not linear at this low level. After playing with the trimming pots, I got here:

Accuphase DP-70_3DC_999.91Hz.jpg


This is much better, even if not satisfactory. I did not manage to do better than that, and the previous measurements were performed with the Accuphase's discrete conversion tuned as such. Note that if that view still shows lack of linearity, there is minimum noise, meaning the analog noise of that DP-70 is very low. I think with patience playing with the adjustment pots I can get better than that, but not sure.

----

Other measurements (not shown):
  • IMD AES-17 DFD "Analog" (18kHz & 20kHz 1:1) : -95.6dB
  • IMD AES-17 DFD "Digital" (17'987Hz & 19'997Hz 1:1) : -96.2dB
  • IMD AES-17 MD (41Hz & 7993Hz 4:1): -91.8dB
  • IMD DIN (250Hz & 8kHz 4:1) : -78dB
  • IMD CCIF (19kHz & 20kHz 1:1) : -95.9dB
  • IMD SMPTE (60Hz & 7kHz 1:4) : -108.6dB
  • IMD TDFD Bass (41Hz & 89Hz 1:1) : -78dB
  • IMD TDFD (13'58Hz & 19841Hz 1:1) : -108.9dB
  • Dynamic Range : 98.1dB (without dither @-60dBFS)
  • Crosstalk: 100Hz (-112dBr), 1kHz (-113dBr), 10kHz (-113dBr)
  • Pitch Error : 19'997.00Hz (19'997Hz requested) ie below 0.2ppm
  • Gapless playback : Yes
The IMD scores are very good and something that was not known before the CD was invented. Someone had to do it!
The Dynamic range is near the best that can be measured (unweighted) with the Audio CD. That was the marketing pitch of Accuphase at the time and they achieved!
Crosstalk is just below what Accuphase published at the time, they were not lying, and that well above everything we need.
Pitch error was surprisingly below what I can measure from a CD Player, not only at the time, but 4 decades later too! This means the internal clock was way beyond anything required. Did I hear overengineered? Exact!

----

Last and not least, I like to run a THD vs Frequency sweep at -12dBFS as it shows how the conversion has evolved over time. I am currently using the beta version of REW and I discovered that this sweep gives better and more reliable results than before.

I was nasty in the below test. Since Accuphase said a Philips TDA DAC of the time was not enough for them, I overlaid the below with a best in class Marantz CD-80 using the TDA1541A-S1, the crown (most linear) version of that range, released probably later, by the way. Let's have a look:

Accuphase DP-70_THDvsFreq.jpg


7dB less distortion! Eat this Philips! And well done Accuphase.

----

As I did with the Sony CDP-597, I add a "max DAC resolution" measurement test. It is performed from a 999.91Hz sine @-12dBFS with shape dither (from Audacity). I restrict the THD+N span to 20Hz - 6kHz in REW not to account for the noise of the shape dither beyond 6kHz. I take the calculated ENOB and simply add 2bits to it (due to the -12dB attenuation, as 1bits=6dB). The potential maximum, when calculated from the digital WAV file, is 18.7bits under this test. A "transparent" DAC should achieve 18.7bits, ie 100% in this test.

Here are the results compared to others:

CD Player model or DACCalculated ENOB (999.91Hz sine @-12dBFS with shape dither, THD+N span = 20Hz - 6kHz)Percentage of max resolution achieved (higher is better)
SMSL PL-20018.7bits100%
OPPO BDP-9518.7bits100%
SMSL PS-200 (from CD player)18.6bits99.47%
Denon DCD-900NE18.5bits98.93%
Onkyo C-73318bits96.26%
SMSL PL15018bits96.26%
SMSL PL10017.9bits95.72%
Sony CDP-59717.5bits93.58%
Onkyo DX-735517.3bits92.51%
Denon DCD-356017.2bits91.98%
Yamaha CD-S30316.8bits89.84%
Revox B-226S16.8bits89.94%
Accuphase DP-7016.6bits88.77%
Sony CDP-337ESD16.6bits88.77%
Teac VRDS-25x16.5bits88.24%
Marantz CD-8015.9bits85.3%
Marantz CD-7314.9bits79.68%

Yes, the Accuphase suffers on that test, but it behaves well for the time. By the way, it is so close to the very recent Yamaha CD-S303. Forty years of evolution does not bring much, sometimes... Ok, not the same price, I must agree.

----

Accuphase DP-70 - Testing the drive

What would be good measurements if the drive would not properly read a slightly scratched CD, or one that was created at the limits of the norm? The below tests reply to these questions.

Here are the results:
Test typeTechnical testResults
Variation of linear cutting velocityFrom 1.20m/s to 1.40m/sPass
Variation of track pitchFrom 1.5µm to 1.7µmPass
Combined variations of track pitch and velocityFrom 1.20m/s & 1.5µm to 1.40m/s & 1.7µmPass
HF detection (asymmetry pitch/flat ratio)Variation from 2% to 18%Pass
Dropouts resistanceFrom 0.05mm (0.038ms) to 4mm (3.080ms)1mm
Combined dropouts and smallest pitchFrom 1.5µm & 1mm to 1.5µm & 2.4mm1mm
Successive dropoutsFrom 2x0.1mm to 2x3mm1mm

The above are very good results for the Sony BU-1C, meaning the Servo control, with some ICs labelled Accuphase, obvioulsy did a good job. This is achieved with a drive that is still faster than light to skip one or ten tracks!


Accuphase DP-70 - Digital Output (from Audio CD)

Ok, so it's a cool conversion, for the time, but we can do better than that today, provided we get a "perfect" digitial output. So let's start testing with my standard 999.91Hz @0dBFS file...:

1763148270092.png


Nailed, perfect.

My ultimate proof of "perfect" digital output is when I reuse the intersample overs test at 5512.50Hz, with a phase shift of 67.5°, like I did for the TASCAM CD-200 review. This signal generates an overshoot of +0.69dB and so if the signal would be modified before being sent (by an ASRC for instance), it would show either a reduction of amplitude or we'd see some sort of saturation/increase noise/distorsion. So here we go:

1763148304648.png


Nailed again, so we get a "perfect" digital output to modernize the conversion, if one would hear a difference.

I also showed the absence of jitter, and that associated to a clock that is more precise than what I can measure, makes this CD Player the perfect (and fastest) CD Transport.


Conclusion

The Accuphase DP-70 gave me goose bumps.

The staggering build quality, the possibility to adjust linearity, the super fast legendary drive, and the more that decent results with the internal DAC, perfect as transport, are all to be appreciated.

I was not friendly with this old player, in the RAW measurements I show here. Yet, no fear, this Accuphase delivers per his Statement Of Work, and that 40 years later without being serviced. Proof? Accuphase says vs what I measured:

Accuphase DP-70_999.91Hz_@-60dBFS.jpg


This is a fab device.

Enjoy your weekend!
 
Last edited:
Sorry for the delay, I'm adding a few more measurements.

First, and since the trimming pots for fine adjustment of the distortion are on the conversion board which can only be accessed from the bottom, I had to do that with the Accuphase on its side:

Accuphase DP-70_031.jpg


The drive had no issue to play, but I had to insert the disc before putting it on the side, and to not open the tray, which of course I did, stupid me :)

With that, I got it linear down to -100dBFS (test with Shape Dither):

1763224604187.png


Beside the small leak from the PS, the trace is beautiful. I think I need to have a closer look at the source of the 100Hz and harmonics, it is probably an aging cap in the power supply section.

And I nearly got it to -110dBFS. I'm not sure I can be more patient and more precise than that with the trimming pot. At this level, I got the feeling that just looking at them made a difference in measurements :eek::facepalm::p

1763225197339.png


And last, an extended view up to 150kHz of the oversampling filter response and attenuation of ultrasonic noise. This is from a periodic white noise. The artifacts of the conversion are absent:

1763225632162.png


And like I already said, this is a sharp filter, therefore of symmetrical extended impulse response:

1763226160244.png


The ringing is due to the standard "sinc" based reconstruction filter.

Cheers
 
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Fact is this is not an easy task because this CD player is very sensible to the temperature.
You meant sensitive to temperature.

Got caught out by false friends there. Sensible [EN] = pratique, raisonnable [FR] = vernünftig, sinnvoll [DE]. A classic trap for young players, as Dave "EEVBLog" Jones would say.

Side note, any clue where the temperature sensitivity is coming from? Do things change after touching the resistors or switch ICs? Generally speaking, I'm not exactly surprised that adjusting a discrete R-2R DAC would be a fairly delicate affair.

This reminds me of the stereo separation adjustment in my Kenwood KT-1100 tuner. Drove me absolutely nuts. Close the lid and it's off again. Not so much thermal but rather stray capacitive coupling or mechanical stress in that case, I think. I guess this kind of stuff is why some people have had less than good things to say about Kenwood's construction practices at the time...

If you've been fiddling about with analog distortion compensation for a while (and trust me, I have - the collection includes both a KT-990SD and KT-1100D that I spent plenty of time on aligning), you will understand why people in the 1980s would have been most appreciative of the inherent linearity of 1-bit delta sigma conversion, despite substantial initial disadvantages in the noise department.
 
You meant sensitive to temperature.

Got caught out by false friends there. Sensible [EN] = pratique, raisonnable [FR] = vernünftig, sinnvoll [DE]. A classic trap for young players, as Dave "EEVBLog" Jones would say.
Shame on me, indeed, always the same mistake that I repeat. Thanks, I updated the text.
 
Wow to both this player and to this review! :oops:
 
Side note, any clue where the temperature sensitivity is coming from?
No, and that is an issue. I thought about using a hairdryer whilst adjusting the distortion when it is opened, so I could guarantee it once closed :facepalm:
Do things change after touching the resistors or switch ICs?
Yes :eek:
Generally speaking, I'm not exactly surprised that adjusting a discrete R-2R DAC would be a fairly delicate affair.
It is indeed.
This reminds me of the stereo separation adjustment in my Kenwood KT-1100 tuner. Drove me absolutely nuts. Close the lid and it's off again.
Same here :cool:
Not so much thermal but rather stray capacitive coupling or mechanical stress in that case, I think.
I think too. And it is fun to find the right adjustment, on my perspective.
I guess this kind of stuff is why some people have had less than good things to say about Kenwood's construction practices at the time...

If you've been fiddling about with analog distortion compensation for a while (and trust me, I have - the collection includes both a KT-990SD and KT-1100D that I spent plenty of time on aligning), you will understand why people in the 1980s would have been most appreciative of the inherent linearity of 1-bit delta sigma conversion, despite substantial initial disadvantages in the noise department.
Absolutely, what a relief this might have been for them! But so much less fun, no? :p
 
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Awesome review as always, love the detailed photos.

Interesting to observe that with all the claims of audiophile improvements over the years and deficiencies in early CD players etc., nearly-perfect CD players were already available in the late 80s - if you bought one in 1987 you'd have enjoyed 40 years of perfect playback.

Buy something good, be happy with it, stop thinking about the gear and just enjoy the music!
 
The build quality of this Accuphase CD player looks phenomenal and its finish is gorgeous.

By the way, is the maker of the RCA and XLR jacks identifiable ? They seem to be of very high quality.

The copper plate to form the common of the output RCA jacks is frequently seen in other Japanese disc players from Sony or Marantz.
 
Another wonderful review NTTY!

Though I could never afford it, as a second mortgage would really upset the bride, I’ve always loved beautiful design and uncompromising quality. With Accuphase it’s a passion.
40 yrs old and pretty much kicks derrière. Gotta love it.
 
By the way, is the maker of the RCA and XLR jacks identifiable ? They seem to be of very high quality.
The back, line blade of the RCA reminds the WBT or the ETI Research ones. Without the ground blade though.
Custom probably, they would have to be very long to pass though the chassis and the copper plate as well.
 
The build quality of this Accuphase CD player looks phenomenal and its finish is gorgeous.

By the way, is the maker of the RCA and XLR jacks identifiable ? They seem to be of very high quality.

The copper plate to form the common of the output RCA jacks is frequently seen in other Japanese disc players from Sony or Marantz.
Also, XLR by the looks and numbering reminds of Canon ones.
 
Just a gorgeous piece of gear. I have to imagine that the price in 1987 had to be eye watering. Probably $4k or more. But it is obviously a quality piece, and, for its intended purpose of rendering Red Book CDs, its performance holds up even today. Great review on a terrific vintage piece, NTTY. Now imagine having one of their incredibly beautiful and performant integrated amps to place in the equipment rack with it.
 
Thanks for this beautifull review :cool:

Comparatively, we should be able to see if an SMSL PS200 will still work in 40 years and if this is not the case, if it is repairable...
... this Accuphase DP-70, just like a REVOX B-226S have this 'ability' :)

I will avoid talking about 'SQ' so as not to start a controversy but from a purely aesthetic and manufacturing quality point of view, my heart leans towards these last two readers rather than a modern disposable plastic device. ;)
 
Thanks for this beautifull review :cool:

Comparatively, we should be able to see if an SMSL PS200 will still work in 40 years and if this is not the case, if it is repairable...
... this Accuphase DP-70, just like a REVOX B-226S have this 'ability' :)

I will avoid talking about 'SQ' so as not to start a controversy but from a purely aesthetic and manufacturing quality point of view, my heart leans towards these last two readers rather than a modern disposable plastic device. ;)
Ypu can buy 100s of SMSL, and if it breaks buy another brand which would be better than SMSL over the period with the money of Accuphase. Anyday I would choose something that has value over brand names.
 
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