Tap, tap, tap...tap, tap, tap.....is this thing on?

[Mark Hammer]

I've mentioned this unit in past, and never stumbled on the schematic until today.

The Stereo Tapped Delay, made by A/DA in the early 80's was probably the most creative use of the Matsushita MN3011 that was ever produced.  The MN3011 is a 3328-stage bucket brigade chip (less potential delay than an MN3005 used in the Memory Man, et al, but more delay time than the 1024-stage chips commonly used in chorusses).  What distinguished the chip was the inclusion of 6 separate taps at different delay times.  So, one audio input, 6 audio outputs.  Although the chip seems to have originally been intended for mixing down all the taps into mono and use as a solid-state reverb (and the Gallien-Krueger amp Steve Giles linked to yesterday uses one in exactly that manner), that didn't mean it *had* to be used in such a fashion.  The most likely use was for karaoke machines...until cheap digital chips assumed that role.  Naturally, the chip faded from existence at that point, since I imagine it was a costly chip to produce relative to the potential market.

What A/DA did with it was to buffer each tap output, and use a toggle switch to make them all independently assignable to the left or right channel (or neither), where they would be mixed (or not) with the dry signal. One of the things this permitted was the production of an almost infinite variety of chorus sounds and ambiences.  A single common clock/LFO drove the whole thing.  Clock lines were nicely buffered by a bunch of paralleled invertor sections, but the actual clock rate and sweep width seems to have been left tame and optimized for chorus and doubling.  The flanging possibilities were never really fully explored as far as I know

Although the number of unused possible options frustrates a possessed modder like myself, the basic design is simply brilliant, and it is the sort of device you could move into and live there.  The only name artist I am familiar with who used one was Allan Holdsworth, but I have never knowingly heard one used, nor seen one other than in pictures.

The schematic (in a 2.5meg zipfile) and a host of other info about it can be found here: http://www.adadepot.com/adagear/gearpages/effects/ADA-STD-1.htm

Well worth a browse.

[Paul Marossy]

Figures Holdsworth would use one of those.  :wink:
I wonder if the come up for sale on ebay and how much they would go for...

I wonder if a DIY version of this is possible? I imagine that it would be fairly complicated, more so than the ADA Flanger, I guess.

[stm]

U N B E L I E V A B L E !

Gotta get a MN3011, but where?  I recommend reading the manual, it is full of info. Certainly a very versatile FX.

This kind of unit is well suited for a digital implementation (in replacement of the MN3011 only), the rest should be kept analog.  Perhaps a stereo A/D, six D/A's (I think there are sixtuple units), a 4kword memory and a fast microcontroller or DSP.  Some lowpass filtering at the outputs would help to "hide" the digital nature of the delay.  Also, this would have the added benefit of lower noise and improved dynamic range.

Thanks for sharing this info.    

[Mark Hammer]

I think the hardest part would be scoring a chip.  The MN3214, which has 1024 stages and 5 taps, and is also no longer in production would provide a great starting point for a DIY project of a similar type with an emphasis on distinctive flanging variations....if we could find some.

Of course, you just know that Jimbob will find an STD-1 with a missing knob for $5.95 next week. :lol:

Given that this unit was in production by A/DA around the time that A.I.D.S. first came to our collective attention and became associated with a transmissible virus, do you think having a product name like "STD" had an impact on sales? :roll:

[Paul Marossy]

Given that this unit was in production by A/DA around the time that A.I.D.S. first came to our collective attention and became associated with a transmissible virus, do you think having a product name like "STD" had an impact on sales?

Nah. I think most musicians probably couldn't appreciate it for what it was/is. But, then again...  :wink:

[Paul Perry (Frostwave)]

An alternative to a tapped BBD is a bunch of smaller BBDs in series. With independant clocks. The shrieking hetrodynes could only add to the general mayhem :lol:

[puretube]

you been thru that, Paul?

[Paul Perry (Frostwave)]

you been thru that, Paul?

No, but I have a vivid imagination :roll:

[puretube]

well, it`s all a question of neat layout, or having large space available...
("breadboarding prohibited"  :lol: )

[Paul Marossy]

I really have no idea of what kind of circuitry is involved in something like this, but I would imagine using perfboard would be pretty much impossible. Or at least it would make troubleshooting hell!

[Mark Hammer]

Some of the cleverer, more technically inclined folks here might be able to help me out on this.

Is the heterodyning mayhem a product of having multiple clock *products* or multiple *clocks*?

To clarify a bit, if one had a master HF clock and divided that down by prime numbers (e.g., f/3, f/7, f/11) to yield harmonically unrelated lower order clock frequencies, which in turn would step individual BBDs through their actions, would that be every bit as problematic as having several BBDs, each with their own individual MN3101 or other type of clock circuit?

It just seems to me that if one uses master clock division, that it would be guaranteed to have all leading edges of all clock pulses essentially synced.  It would be more like some of the BBDs simply "missing out" on some clock pulses.  My gut tells me that should be less problematic than the case where not all clocks are synced.....but then my gut tells me a lot of things that end up being foolish.

[christian]

to stm:
You wouldn´t need but one mono ADC (unless you´d really make a stereo unit with stereo inputs) and one(or two, in stereo) DAC(s). Stick 6 ROM´s in series clocking from the same clock-source and use digital mixing/switching circuitry. Alltough that makes a lot of AND/OR gates, you wouldn´t need to spend all that money to DACs.
You could of course use little "lo-fi" with discrete "weighted resistors" DAC. Very simple and cheap!

[puretube]

You`re not asking me, Mark?  

If you divide master=1MHz thru 3/5/7/9/11, you get
332/200/140/108/88kHz : no problem - the lowest diff is 20kHz;

but once you get just a little lower, e.g. to achieve longer delay,
you`re getting into the troublesome area;

will have a bench test soon;

the real trouble starts, when you feed back the "chopped" audio
@ frequency into another delay, that chops @ a frequency differing
only a few (kilo-)Hertz.....

more later...

[Mark Hammer]

Thanks, Ton.

So if I've understood you correctly, if the clock frequency difference is outside the boundaries of normal hearing one should be relatively safe?

Thinking it over, it occurred to me.  Most of us are accustomed to hearing time-based or phase-based pitch-bending using a single delay time or single cumulative amount of phase-shift.  I wonder what multi-tap vibrato sounds like?  What do you get when you hear several synchronized versions of the same signal under/oversampled at the same time?

Now that my mind has permission to wander, what do you get if you take the output of every second phase-shift stage from a phase shifter and feed it to the mixer stage?  JC Maillet pointed out earlier this year or late last year that amount of pitch-shift produced by phase-shift vibrato (i.e., a phase-shifter where there is only wet signal and the dry signal is lifted/cancelled) increases with number of stages.  So, if I have a 6-stager and I feed the outputs of the 2nd, 4th, and 6th stages to a mixer, yielding signals that can be 180, 360, and 520 degrees in their maxima, would I hear a slightly, more, and very pitch-distorted signal at the output?

[Mark Hammer]

Push to top. (Sheesh, move from the first page to the second and its like you don't exist!  :lol: )

I repeat, and expand, my query.

If one had a many-staged (more than eight) phaser, and took taps along the way from the phase-shift path, for routing to maybe a mixing stage, or maybe different paths, what would you get?

Let's say you have an MXR Phase 100 (see schem at GGG for reference).  The passive mixing stage here, after 6 variable and 4 fixed stages of phase-shift, occurs where R18 and R19 (both 6k2) meet.  But now suppose that, in parallel with R18, you have another 6k2 resistor.  Suppose on top of that you have a 6k2 resistor coming from pin 1 of IC3a, and those two 6k2 resistors form another passive mixing stage, with its own terminating cap and resistor forming another output.

In what ways would that output be different in its properties from the stock output?  Would it simply lack two notches that the stock output has?  In other words, would phase-shift taps behave in any way similar BBD taps?

Here's another possibility suggested by the STD-1.  One of the suggested configurations in the manual is to take the audio output signal for the wet part from an early tap, but the regen signal from a later tap.  They refer to this as "cloud flanging".

Okay, so now consider this.  That same R19 in the Phase 100.  Disconnect it from pin 1 of IC3b and reconnect it to pin 1 of IC5a.  You now have 4 stages of phase-shift in the wet signal, BUT the regen signal has an additional FIVE stages of phase shift.  I don't have anything right now that would let me do that experiment.

But I'm curious, perpetually curious.

[puretube]

Mark - I haven`t lost you....
just missing time to put into correct words...
have done dozens of these kind od of experiments quite a while ago - nothing to write home about, IIRC...


edit: nothing to write... = phase stages;
Real delay (BBD) = worth the strive!

[Yuan Han]

i suppose if it is multitapped, you don't have to feed back the combined output back into the source, but the individual outputs back into the indivual inputs. but that would mean...using seperate ICs instead oa one that is multitapped.

I have a bunch of 3208, 3207, and i might try using them with 1 clock to see how it sounds like..... perhaps about 20ms and 40ms of delay...

And I would think if its there's 2 clocks both out of audio range getting close to each other, there is possibility of generating something inside the audio range ? like resulting in a faster wave (approx f1 + f2) amplitude modulated by a slower wave (f1 - f2) [like how they use this in speed detection cameras...etc]

Han