track & hold and sample & hold...

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D/A A/D
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track & hold and sample & hold...

Post by D/A A/D » Tue Oct 28, 2008 1:12 am

So can someone explain the difference between track & hold and sample & hold?

It has never been clear to me, as I have only ever owned sample and hold kit.

Alex

Babaluma

Post by Babaluma » Tue Oct 28, 2008 1:32 am

i'm useless, i used to know this! it's explained very well in the synth bible (allen strange text), but i don't have a copy to hand at the mo. know the ms-20 has a track and hold.

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Post by The Alison Project » Tue Oct 28, 2008 1:54 am

The way the MOTM works.

With a very slow clock, the first half of the clock plays the input signal, The second half of clock samples a voltage from the input signal like a regular s&h.

Ex.
S&H Input - Pink Noise
S&H Output - First part of clock (Pink Noise)
S&H Output - Second part of clock (sampled voltage level from pink noise input)

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e-grad
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Post by e-grad » Tue Oct 28, 2008 3:55 am

S&H = samples the input signal. Every time the gate is high a new sample will be available at the output.

T&H = follows the input signal as long as the gate is high. If the gate is low the last signal is sampled and presented at the output.

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Post by wetterberg » Tue Oct 28, 2008 8:16 am

what e-grad said. In other words, it's like opening a gate where the last seen value "sticks"

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dkcg
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Post by dkcg » Wed Oct 29, 2008 1:19 pm

I'm not positive, but I think the PlanB ASR is more or less a track and hold device? I could be wrong, dead wrong. :eek:

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e-grad
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Post by e-grad » Wed Oct 29, 2008 1:28 pm

No, an ASR is made up from multiple S&H circuits. S&H 1 output is shifted to S&H 2 that output goes to the S&H 3... Thus every circuit gives out the same samples but delayed. There's no tracking of the incoming signal but "analogue sampling" (If that term makes any sense.).

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dkcg
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Post by dkcg » Wed Oct 29, 2008 4:34 pm

e-grad wrote:S&H = samples the input signal. Every time the gate is high a new sample will be available at the output.

T&H = follows the input signal as long as the gate is high. If the gate is low the last signal is sampled and presented at the output.
Ahhh, I didn't see that there. So T&H is more like a switching gate?

Personally I prefer the T&A over the S&H and the T&H. :hihi:

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Post by suitandtieguy » Thu Oct 30, 2008 4:30 am

fyi, the Ray Wilson sample & hold is actually a track & hold.

the clock oscillator that drives it is a pulse train with such an extreme duty cycle it gives the appearance of being a s/h when driven by its internal clock but when you clock it externally it becomes apparent this is not the case.

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Post by neandrewthal » Thu Oct 30, 2008 11:23 pm

suitandtieguy wrote:fyi, the Ray Wilson sample & hold is actually a track & hold.

the clock oscillator that drives it is a pulse train with such an extreme duty cycle it gives the appearance of being a s/h when driven by its internal clock but when you clock it externally it becomes apparent this is not the case.


I tried both of mine with all the square waves I have of any duty cycle and I can't confirm this :confused: What are you using to clock it?
Initiate the sequence, create catastrophe.

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Post by suitandtieguy » Fri Oct 31, 2008 1:06 am

neandrewthal wrote:I tried both of mine with all the square waves I have of any duty cycle and I can't confirm this :confused: What are you using to clock it?
i don't have one anymore, so if you're getting different results i defer to you.

i'm sorry if i mislead anyone, that is just the behaviour i remember it exhibiting.

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