Memory Lane Tap Tempo Analog Delay

[robotboy]

Has anybody seen this?

http://www.diamondpedals.com/products/memorylane.html

I was under the impression that tap tempo analog delays were almost impossible to make?

[Mark Hammer]

This is an interesting and thoughtful product line.  More than just a another clone-in-a-1590BB enterprise (well, I suppose the 1590BB part is true).  Never heard of them before.  Thanks for the link.

If delay time can be set by a single variable resistor, then it matters not whether the delay path itself is analog or digital.  Tap tempo IS possible with analog delays.  Just note that it isn't going to be simple and cheap.

[Vsat]

Tap tempo for analog delay somewhat restricted since a "long" analog delay typically provides well under one second of delay... maybe a tap-flanger?

A small microcontroller like a PIC or Atmel could be used to time the interval between taps, and either generate the clock directly (since we are talking about long delay rather than flanging the clock would be slow and easier for the uC to generate) or provide a simple D/A to send the appropriate control voltage to the delay clock oscillator, which could be just a simple CD4046.

Cheers, Mike

[cd]

If delay time can be set by a single variable resistor, then it matters not whether the delay path itself is analog or digital.  Tap tempo IS possible with analog delays.  Just note that it isn't going to be simple and cheap.

Cripes, $430US is a LOT to swallow for a mere 550ms of delay time.

As for tap tempo, personally, I can live without it, but what about a digital pot IC controlled by a PIC?

[Mark Hammer]

Tap tempo for analog delay somewhat restricted since a "long" analog delay typically provides well under one second of delay... maybe a tap-flanger?

A small microcontroller like a PIC or Atmel could be used to time the interval between taps, and either generate the clock directly (since we are talking about long delay rather than flanging the clock would be slow and easier for the uC to generate) or provide a simple D/A to send the appropriate control voltage to the delay clock oscillator, which could be just a simple CD4046.

Cheers, Mike

Hi Mike,
There are two aspects to tap tempo.  One is the actual feasibility of implementing foot control of speed/rate/tempo.  The other is what one might call the "coherence" of it.

The "coherence" would seem to be something that is easier to achieve when oscillation/repeat rates are in the middle low frequencies.  In other words, not much faster than 2hz, and not much slower than maybe 0.25hz.  That part would seem to be more a function of planning out human foot movements and capacity to convert subjective time estimates into coordinated movements.  When it comes to much longer intervals, one of the strategies is to use division or multiplication of foot movements in translating tapping into rate/time.  The Line 6 Echo Park pedal does this, and so does the T-Rex Replica delay pedal.

For VERY long sweeps, I have to say from some limited (and legally protected) experience, that tap tempo, for me anyways, gets much harder to plan and execute.  I suspect that optimum tap tempo control to modulate, say, a "deluxe" phaser sweep at 0.1hz would require some sort of visual or other aid, since it is hard to keep track of what the phaser might be actually doing while engaging the tap tempo switch (one usually does this off-line).  One approach, for example, might be to use a bi-color LED, with eah color corresponding to an opposite-phase peak during the sweep cycle.  I know you've used this in past to monitor sweep of a "normal" LFO in phasers, and I can see where it would be tremendously helpful to have a visual sense of where one is in the context of a particularly long sweep cycle.  

In general terms, the notion is that one would tap once for the "top" of a sweep, tap again for when you want the sweep to be at its lowest point, tap again, for the next peak, and once more for the next trough, with the resulting 4 datapoints yielding the assumed LFO rate.  Make sense?

[dr]

.....its not exactly tap tempo, but I rigged up a motorized pot to a DPDT momentary on, center return to off switch wired to swap the DC leads changing the direction of the pot; and adjust either way with my foot;it works for me, since its foot-operated, and you can usually get it tweaked pretty quick; maybe not enough to tweak something less than 500ms.......

[Melanhead]

Yup, these guys are just down the street from me ( well about 20 minute drive! ) ... they make great pedals. I've tried most of 'em at the local music store and even bought a J-Drive, that is before I knew how to mod and build my own ...

http://www.diamondpedals.com/products/jdrive.html

I haven't tried the delay but friends of mine have and say it's amazing.

I have tried the compressor though and it's exactly as described! Great! ... almost bought one as well ...

[Vsat]

Mark,
Yes, there is the human interface problem for very slow sweeps and very fast sweeps... division or multiplication with some sort of visual feedback  would be needed for it to be a convenience vs. a nuisance. Perhaps an indication of rate of change as well as absolute level. My bi-color LED scheme which you mention also provides a rate indication as the brightness is proportional to the sweep position.  


Basic configuration:
a) knob for sweep depth

Deluxe configuration:
a) knob for sweep depth
b) knob for sweep symmetry

Processor measures time between two claps,  calculates LFO rate so one LFO period occupies the measured time interval between claps, taking into account the LFO symmetry/duty cycle.  LFO waveform initialized to  "zero degrees" position at start of first cycle.

Designed a microcontroller-based commercial product in 1995 which used a hand-clap interface with built-in "learn" mode.  Much of the code was devoted to rejecting  extraneous noise, which gave it much improved noise immunity compared to the competition. By present standards the uC would be considered fairly slow... much fancier stuff could be done nowadays with inexpensive parts.
Cheers, Mike

[Melanhead]

just borrowed one ... will try it and report back ...

there's a sound bite up on the site now and it sounds great!

http://www.diamondpedals.com/products/memorylane.html

[Melanhead]

Cool! ... It's a great pedal, tap tempo works really well. I don't need a delay though  ... I wanna build one!