[sdiy] Tap Tempo LFO

[Tom Wiltshire]

Mike,

Thanks for the kind words.

There are two reasons why what you suggest isn't possible.

One is that the output sample rate simply isn't high enough. It's  
only 19.5KHz, which rules out any frequency above almost 10K even in  
theory. In practice, you wouldn't get much above 2 or 3KHz. The sort  
of output rates you're talking about are 100's of KHz.

Secondly, the part of this that is 'tap tempo' is the LFO frequency,  
e.g. the rate of change of some parameter. This is not the same as  
the delay time being tap tempo. For this, you need to do a different  
sum involving the clock rate of the delay and the length.

It's a damn pity that it isn't do-able though, because this is  
something I've wondered about enough times myself. If you could get a  
uP to generate a clock signal for a BBD directly, you be able to do  
tap-tempo delays, flangers, chorus and the like, and you'd only need  
the uP and the delay line. None of that messing about with clock  
chips or VCOs driven by LFOs.

Still, BBDs suck, so it doesn't matter, right? ;)

T.


On 8 Dec 2009, at 20:44, Mike Beauchamp wrote:

> Tom, First of all this is absolutely brilliant.
>
> Secondly, I'm wondering how easy it would be to reprogram it to have a
> 1:4096 tap:clock ratio? (if that makes any sense).
>
> The reason I ask is that I'd really like to use this to add a
> tap-tempo to an analog delay...
>
> The actual wave output could remain 1:1, just the clock output needs
> to be 1:4096. Then I could use the wave output to drive an indicator
> LED for example.
>
> -- 
> Mike Beauchamp
> mobile: +64 21 0 AS I BIKE (2742453)
> home: +64 4 801 8304
> work: +64 4 915 4068
> http://mikebeauchamp.com
> http://therevox.com
>
>
> On Wed, Dec 9, 2009 at 12:40 AM, Tom Wiltshire  
> <tom at electricdruid.net> wrote:
>> Hi All,
>>
>> I've mentioned my Tap Tempo LFO project here before. The  
>> difference this
>> time is that I've actually finished it!
>>
>> Details are online:
>>
>> http://www.electricdruid.com/index.php?page=projects.taplfo
>>
>> There are example circuit diagrams for a tap tempo LFO, tap tempo  
>> sequencer
>> clock, and tap tempo tremolo, plus, a datasheet, code, etc. Any  
>> questions,
>> please ask.
>>
>> If you're into PIC programming or know someone who is, you can get  
>> code from
>> the site. If not, I'll be trying to sort chips out soon, and if I can
>> persuade Steve Daniels that this is a good idea, you might be able  
>> to buy
>> programmed chips from Small Bear. He did show some interest, but  
>> we'll see
>> whether it's really worth his while. I hope so.
>>
>> Thanks,
>> Tom
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