EHX: Analog Delay w/ Tap Tempo

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toryjames
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EHX: Analog Delay w/ Tap Tempo

Post by toryjames » Sun Mar 07, 2010 4:26 pm

I have heard requests for tap tempo on the 104z and saw this the other day:

http://www.ehx.com/products/deluxe-memory-boy

I don't really care about tap tempo on an analog delay but I am wondering how they did it.

It seems to be a very versatile analog delay. I have the EHX Memory Boy and though it's a bit flimsier and doesn't sound quite as good as my Deluxe Memory Man, I do like it (especially considering the price). I just found out last night that the expression pedal jack can accept CVs!

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latigid on
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Post by latigid on » Mon Mar 08, 2010 12:43 am

Digital clocks can use tap tempo quite easily.

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Post by toryjames » Mon Mar 08, 2010 1:37 am

"Digital clock" but it's an analog delay.

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Klopfgeist
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Post by Klopfgeist » Mon Mar 08, 2010 2:04 am

toryjames wrote:"Digital clock" but it's an analog delay.

It has analog circuitry that is controlled by digital circuitry. Like the Voyager and the Little Phatty, there is no A/D or D/A conversion, the signal path is all analog, but it is still controlled digitally.
So this thing only plays one note?

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Post by UCAudio » Thu Mar 11, 2010 3:28 pm

Man I wish they would do this with all of the foogers. I love the fact that I can sync my midi murf to my project tempos using a midi clock. If the other foogers had this built in I would buy them in a second. I know you can rig it up if you buy the mp-201 and cp-251... and a bunch of cables, but it would be so nice to have tempo sync'd lfos or delay speeds built right in.

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Post by toryjames » Thu Mar 11, 2010 11:23 pm

Klopfgeist wrote:
toryjames wrote:"Digital clock" but it's an analog delay.

It has analog circuitry that is controlled by digital circuitry. Like the Voyager and the Little Phatty, there is no A/D or D/A conversion, the signal path is all analog, but it is still controlled digitally.

What I meant was, how can a bucket brigade analog delay be controlled digitally?
I guess it was a rhetorical question because I wasn't expecting anyone to actually understand the technology well enough to explain it.

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latigid on
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Post by latigid on » Fri Mar 12, 2010 2:42 am

The way I understand it is the clock pulse shifts the "bucket" being sampled/addressed. This clock can be digital or analog.

Analog clocks have the advantage of voltage control, but for tap tempo require a digital timing circuit (to sense the taps) then a D/A converter to drive the analog domain frequency (in the MHz). The charged cap pulse would then have to be sync'd/reset to follow the digital clock.

Digital clocks remain in the digital realm; after all a clock is just a 1 then a 0. Thus digital clocks are trivial to reset and so sync easily to other digital timers (tap, MIDI). This is probably why the MIDI MuRF came about, the sequencer was digital in nature to start with and so only required a few mods to be played over MIDI.

This isn't my day job, so please correct if I'm mistaken.

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Post by moremagic » Sat Mar 13, 2010 7:31 pm

I'd say it probably doesnt need a DAC since it'd just be easier to go ahead and use a DCO instead of a VCO to generate the clock signal, but otherwise yeah, that seems about right, latigid

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latigid on
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Post by latigid on » Sat Mar 13, 2010 9:01 pm

Wouldn't some sort of converter be required to have the oscillator respond to voltage control?

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Post by EMwhite » Sat Mar 13, 2010 10:43 pm

latigid on wrote:Wouldn't some sort of converter be required to have the oscillator respond to voltage control?


No, these pedals use optical couplers which allow digitally controlled clock to pulse the bbd clock.

Have a look at Diamond Tremolo (there's a NAMM 2010 clip of a demo); point is that the signal path remains absolutely analog but they have all sorts of tricks done digitally (ie. adaptive slide between single and double speed trem).

Give a call to Diamond just to ask for info. If you've taken any elementary digital electronics classes, have a look for some of the Panasonic bbd spec sheets. It's a very simple circuit.

Moog isn't using the Panasonic to the best of my knowledge but likely a similar chip.

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Post by latigid on » Sun Mar 14, 2010 12:47 am

The 104s use NOS MN3008s, IIRC the SD has three of them.

What I meant about voltage control is: if the clock is digital, then how would it be possible to use the 0-5V control input on the delay time? Being fussy people, we would want our delays both sync'able to tap tempo and MIDI, but also controllable by CV LFOs, Voyager touchscreens/wheels/envelopes....

Does the DCO design allow for analog control input?

I guess if people were seriously going to consider modding the 104s they might have a switchable clock: one for digital sync and the internal clock for analog mayhem. :P

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Post by Klopfgeist » Sun Mar 14, 2010 2:33 am

I think some one should build a delay made for crazy noisy sounds, that has a built in LFO to modify the rate, and some crazy feedback loop action. And have it be able to be synced to MIDI and CV.
So this thing only plays one note?

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Post by MarbledMoog » Mon Mar 29, 2010 11:18 am

well you know the only true analog delays are tape echos. The BBD-based analog units are digital/analog hybrids if I remember...I forget exactly because its too early in the morning for this, something about the time domain/sampling being a digital function while the thing being sampled and repeated is analog
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Post by Klopfgeist » Mon Mar 29, 2010 1:29 pm

Has anyone here ever used a Zvex lofi loop junky? It basically a really crappy (but cool) sounding analog looper. I bet it could easily be modified for cv control.
So this thing only plays one note?

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latigid on
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Post by latigid on » Mon Mar 29, 2010 5:22 pm

MarbledMoog wrote:well you know the only true analog delays are tape echos. The BBD-based analog units are digital/analog hybrids if I remember...I forget exactly because its too early in the morning for this, something about the time domain/sampling being a digital function while the thing being sampled and repeated is analog


BBDs are sample-based, and so have a limited bandwidth. But perhaps the difference is the quantization: are the "steps" between the samples continuous?

Same for tape, you get a higher "sample rate" = more bandwidth when you spin your tape faster. But the Gauss lines just move closer together the higher the recorded frequency is. So are the steps also quantized? Smooth between steps?

And if you go down further to a quantum scale, the energy levels in an atom/molecule are discrete anyhow, so at _some_ point things have to become "digital" :lol:

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