Yamaha AD-10 Analog Delay Schematic?

[trovador]

Hi Folks,
I've searched but can't find a schematic for this pretty cool, but old 1980s Yamaha AD-10 Analog Delay. It's a rare one so that's probably why it's hard to find it...



This is how it looks inside:

[Mark Hammer]

I'm having a hard time understanding why there are TWO MN3101 clock chips in there. There is only one BBD.

[dmeek]

In this alternate photo the number KLM-269B looks more like a Korg PC board. Can you post a photo of the foil side and a few of the component side with the metal bracket removed?

[trovador]

I'm having a hard time understanding why there are TWO MN3101 clock chips in there. There is only one BBD.

I know, right?

[trovador]

In this alternate photo the number KLM-269B looks more like a Korg PC board. Can you post a photo of the foil side and a few of the component side with the metal bracket removed?

I'm pretty sure these are manufactured (or at least designed) by Korg. These are not my pics, but when I open it again I'll try to post some that are better quality.

[Enzo]

The two clock chips are daisy chained. There is a simple NAND gate oscillator for a clock, that is fed to one 3101, and one of its outputs clocks the second 3101. That second one sends CP1 and CP2 to the BBD chip. SO the extra clock IC is there as a freq divider.

[Mark Hammer]

Any speculation as to what possible advantage this strategy might have?

[Enzo]

Um... no...

[ddt]

It just went through my shop.

Another thing catching my eye is that there is some kind of serious witchcraft going on after the signal leaves the BBD chip and before it hits the output buffer op-amp. Other analog delay pedals I've seen didn't have this.

Apart from the regular passive signal filtering on the BBD's output, the signal passes through two 4066 where all the clock driven switches are daisy chained. The common clock source is the 4011 NAND chip and frequency is 10kHz if I remember well.

Does anybody have an idea what is the purpose of having these 4066 analog switches in series? Is this to achieve additional signal 'smoothing'?

[ddt]

Did a little of a research and found very similar architecture in ROSS STEREO DELAY (FEB 1979), see attached.

[ddt]

I couldn't resist and did more research on the topic, this technique is called "tracking filter" and you can adjust the low pass filter cut-off frequency by changing the clock frequency.

[J M Fahey]

Yes, very high frequency chopping (relative to Audio signal present) works like a "variable resistor"

Advantage is you can cascade as many as you wish, they will all perfectly match and track, (try that with LDRs or Fets), itīs CHEAP, only disadvantage is added complexity.

[Frederick]

Hello, I have one of this fantastic pedal. But recently, the peak light stay on and the sound is not modified when the effect is on. I’m not really good in electronic, but maybe it is the first condensers (1000uf, 35V).
if someone can help me, it will be very fine.
and sorry for my English, maybe it’s cause I’m French !