Adding SPDIF out to Synth w/only Analog Out

[electromusician]

Hi Fanatics,

I have an Ensonq SQ-1+ 32 voice synth circa 1995. Its digital but only has analog outs. If I didn't like and use this keyboard so much that wouldn't be a problem.

However its my main composition tool and nothing else can substitute for it. The trouble is running those analog outs to anything but the best A/D produces substandard results.

Can anyone here help me add a SPDIF digital out to this synth so I can go direct and skip another conversion??

I know a little about SPDIF driver chips- particularly AKM. There must be a point on the SQ-1 circut board where the 16 bit digital signal enters the D/A circut. Tapping into that with a proper SPDIF driver circut should do the job- unless I'm missing something- and I very well could be.

Someone out there must have done this with one digital keyboard or another. Its not something that seems radically difficult or theoretically impossible. From what I've read on these message boards I know there are people here who could not only tell me if this would work, but could probably do the whole thing during a typical commercial break! A very knowledgable group indeed!

In any case, thank you for any advice or help you can offer!!
smile

Electro

ps- I'm posting this in the music section also.

[rfbrw]

What D/A does it use?

[electromusician]

Hi

The only part that I found on the internet that Ensoniq used was the Analog Devices 7524 which is listed as an 8 bit DAC. This might be used on an older synth or sampler. I guess the only way to know for sure is to open it up and check. I'm going to ask one of the Ensoniq experts out there also as he might know.

What do you think of the idea- is it an easy project?

Thanks,
Electro

[rfbrw]

Originally posted by electromusician
Hi


- is it an easy project?

Thanks,
Electro

If they've stuck to using standard digital audio parts, yes.

[sync40]

I do not remember well (I open an Ensoniq SQ-1 almost five years ago), but what it is the main problem with the analog outs of your synth?

Noise? Dynamic range? Keep in mind that it is a 16-bit device and as I can recall it performs very well with that standards. If your problem are hiss, noise, etc. they may be not get rid when you do the SPDIF conversion.

I remember that the chips of the SQ-1 were custom marking, so you would need to figure out the PCB and try to identify the DAC of several chips of that time.

The project it is not difficult at all, but it seems pointless if you expect that your SPDIF output will be better than your actual sound -that will not happen.

[electromusician]

Hi guys,

Thanks for your input. The main reason I want to do this is not because of any noise in the analog out- they are actually very clean. The problem is whats lost in the conversion when those outputs go into a sound card or even a good stand-alone A/D converter. For some reason the SQ-1 loses some component of its sound that important- at least to me . Its my main composing instrument and whenever its sound is off, I am off. I've tried this keyboard with a number of sound cards and have even dragged it to a pro audio shop and run it through digidesign HD converters and it still seems to be missing something- though it is better than my M-Audio card.

So as I record more and more with this keyboard I'd like to go straight in with digital. I've been told not to be bothered by the conversion loss but it does throw me off. Thats the way musicians and composers (and audiophiles) are and why some will spend a fortune and expend a lot of effort just to make an minute improvement. In my case the amount of improvement is clearly audible and more importantly, its affecting my work so a small project to eliminate the problem is easily worth it for me.

Now, how should I start? Is there a standard SPDIF driver circut to use or do you need to know exactly what chip(s) do the D/A conversion? I'm going to open my keyboard tonight and start taking notes. I'll greatly appreciate any suggestions or directions you might have!

Thanks,
Electro

[Pulse-R]

The other thing you may find is that the DAC in the unit is what gives it 'the sound'
so taking a digital out may yield the same results as converting the A to D externally

[DragonMaster]

Maybe the loss is in the sound card DAC, not ADC(while the ADC is normally worse).

You will have to find the DACs, and their inputs, then to use some converter IC to get the signal.

In my(Kawai K5) synth, the job is not too difficult, when you open it, you look right before the easily visible output stage, and you find some BB PCM55 DACs (But the output stage of that synth produces -50dB noise, because it uses TL064 opamps, with crappy Mitsubishi M5222L VCAs running off a 7806 voltage regulator. Even more, the synth uses a NEC V40 cpu(The V20 was used in XT computers))