Some of the early LaserDisc players did not have digital audio circuitry, but did have a port through which the raw EFM signal could be led to an outboard decoder.

For Pioneer, this port was a 5-pin DIN, & it remained present on industrial players for a long time. The decoder was the Pioneer DA-1, and the same function was also implemented on a CD player called the PD-X707L. The DA-1 had a set of analog audio input jacks, and a switch to select between analog passthrough only and auto-switching to digital when present. This avoided using up two audio inputs on your receiver or whatever. The PD-X707L did not have this feature, so you would switch audio inputs to listen to LD analog audio, or LD or CD digital audio.

For Sony, the port was a simple RCA connector. I consider it very likely that this could be used with the "adaptor" output from the VP-1000 to obtain digital audio. The main feature difference between the Pioneer DA-1 & the Sony DSP-501 is that the latter has a headphone jack.

I currently have both units on the way from Japan, & a service manual for the DA-1 coming also. I have some hope of modifying both units with SPDIF output, probably via an add-on board with a transmitter IC, as I am planning on using with the Yamaha CDV-S100. Photos will follow when I have the units in hand.

Depending on how they handle the voltages, the Sony would probably work with any AC3 RF port.

The only schematics I have at hand for an AC-3 equipped player suggest there's a substantial bandpass filter (or, if you prefer to think of it that way, a frequency-selective buffer amplifier) ahead of the tap for the RF output, because the same signal goes directly to the audio FM demodulator, which couldn't be expected to cope properly with the video FM & EFM signals. So I wouldn't expect that to work. But I haven't actually hung a spectrum analyzer on a factory-equipment AC-3 output. Of course some retrofits may pass a good deal more.

The DA-1 service manual has arrived. The DA-1 itself is still weeks away by slow boat.

There are some intriguing features which I had not anticipated. In addition to EFM signal & signal ground, the 5-pin DIN connector carries two other signals from the player, 1/L & 2/R audio squelch. The function isn't explained in detail, but presumably it will allow you to select the digital audio channels by selecting the corresponding analog audio channel on the player (or via its remote control). There is also a "lock" signal fed back from the DA-1 to the player, to instruct the player to send the EFM signal. According to the manual, this is "not used" with player models LD-V15 or LD-7100, but presumably it is used with the LD-707, as this is the only other player model mentioned (in the brief section on adjustment procedure).

Unsurprisingly, the EFM decoding is handled by a CD player IC, CX23035, & the system clock is provided by a voltage-controlled oscillator which tracks the incoming bitstream, since (unlike in a CD player) the disc cannot be sped up or slowed down to adjust the data rate. As the manual points out, that would be unnecessary anyway because the synchronization of the videodisc is far more exact. The DAC circuit itself is a non-oversampled, two-channel type, CX20152, with the "brick wall" reconstruction filters one would expect.

Now to scan the manual for Julien.

The DA-V1000 LD-ROM adapter can also provide the same Digital Audio output (along with the SCSI interface). Have you ever tried to find one of these?

Running across any of these things is such a chance occurrence that I wouldn't know where to begin. I'm shocked that I managed to get both a DSP-501 & a DA-1 on Yahoo Japan within a month.

Any chance you can take a picture of the filtering from the input to the CD decoding chip? Thanks!

I
Hey I just ran across an LD-707 for sale. Heavy bugger. I could grab it for $15, but maybe next month blue tags will be 1/2 off, lol. If there's anything it could help you learn I could grab it now?
...or if they're sturdy & reliable I'd just tuck one away. Know if ac3 decoder can work with this?

You mean a PD-X707L?

Julien

There's at least three on buyee right now so I guess at least the DA-1 isn't too uncommon.

Is it possible to mod one to bypass the internal DAC and simply output the digital audio via coax?

The DA-1 is common, the DSP-501 much less so.
The one that sold recently was in really poor shape.

We're also talking sourcing these back in 2017, the landscape was very different from 2025 with few efficient proxy buying services available.

Julien

Was there never a US version of the DA-1? With the US industrial players like the LD-V6010A for example having the output, it seems strange that there would have been nothing available to plug into it?

I think the USA had the equivalent Pioneer DA-V1000.

Julien

I was looking for a picture of that, but all I could come up with was a black splodge on this (last page) - is that the only image that's known to exist, or are there others?

That doesn't sound like the same thing at all...

Found a picture of the front page of the service manual on Worthpoint

By zooming into the lo-res line drawing, it appears to have a power button, an "LD ROM START/STOP" button, and three LEDs, which might say "BUSY", "DIGITAL AUDIO", and "LD ROM MODE". Or might not.

Incidentally one of the paid-for manual sites, "manual universe" will do you a PDF of "Correction for Service (repair) Manual" for it for $1.50. Of course it might just be a page saying "capacitor C123 on page 25 should read 47uF" or something, which would be a bit of a waste of the $1.50...