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MOTM-101 clock range too low

2007-02-11 by Ben Stuyts

Hi,

I've finished my MOTM-101 noise/s&h, and the clock range seems a bit
too low. According to the specs it should be 0.1 - 20 Hz typical, but
I measure 0.4 .. 13.7 Hz. Which I think is a bit off, to be within
the 'typical' range. :-)

I checked and measured the the related parts, but they are allright.
(The cap is 34.7 uF which is quite good compared to the 33 uF it
should be.) The only difference I see is that the supplied 555 is
from ST (TS555CN), but I don't see any important differences from
e.g. a TI TLC555.

Anyway, If the values were wrong I'd expect a shifted range, not
really a smaller range. Also, this is one of the first modules I'm
building, so I don't know if the slightly limited range is of any
consequence in practice. Any ideas?

With kind regards,
Ben (Looking forward to receiving a couple of VCO's and an
MOTM-650! :-))

Re: [motm] MOTM-101 clock range too low

2007-02-11 by Scott Juskiw

>I've finished my MOTM-101 noise/s&h, and the clock range seems a bit
>too low. According to the specs it should be 0.1 - 20 Hz typical, but
>I measure 0.4 .. 13.7 Hz. Which I think is a bit off, to be within
>the 'typical' range. :-)

It's probably the pot (VR2) that is the problem. Most pots are only
good to within 20%. There's not much you can do to increase the pot's
maximum resistance (which affects the lowest frequency of the
internal clock), but you can change R23 to compensate. You can also
increase the highest frequency by lowering R22.

Re: [motm] MOTM-101 clock range too low

2007-02-11 by Richard Brewster

I find that I use the EXT CLK input of the MOTM-101 more than the
internal clock, typically driving it from a MOTM-390 LFO. Advantages:
1) larger range than the internal clock, 2) voltage control of the clock
rate, 3) with a multiple you can gate other modules, such as a MOTM-800,
in sync with each new sample. If external clocking is your typical S&H
usage, then the limited range of the internal clock isn't a big deal.

Richard Brewster
http://www.pugix.com

Scott Juskiw wrote:

Show quoted textHide quoted text

>> I've finished my MOTM-101 noise/s&h, and the clock range seems a bit
>> too low. According to the specs it should be 0.1 - 20 Hz typical, but
>> I measure 0.4 .. 13.7 Hz. Which I think is a bit off, to be within
>> the 'typical' range. :-)
>>
>
> It's probably the pot (VR2) that is the problem. Most pots are only
> good to within 20%. There's not much you can do to increase the pot's
> maximum resistance (which affects the lowest frequency of the
> internal clock), but you can change R23 to compensate. You can also
> increase the highest frequency by lowering R22.
>
>
>
>

Re: [motm] MOTM-101 clock range too low

2007-02-12 by Ben Stuyts

On 11 Feb 2007, at 23:44, Scott Juskiw wrote:

Show quoted textHide quoted text

>> I've finished my MOTM-101 noise/s&h, and the clock range seems a bit
>> too low. According to the specs it should be 0.1 - 20 Hz typical, but
>> I measure 0.4 .. 13.7 Hz. Which I think is a bit off, to be within
>> the 'typical' range. :-)
>
> It's probably the pot (VR2) that is the problem. Most pots are only
> good to within 20%. There's not much you can do to increase the pot's
> maximum resistance (which affects the lowest frequency of the
> internal clock), but you can change R23 to compensate. You can also
> increase the highest frequency by lowering R22.

The pot is 95 k, so it is not too far off. I've just calculated the
frequency range that I should get with the component values that are
in the kit, and my measured range is actually close to what I've
computed. (I did not see the trick with the diode across pin 2 and 7
before, nice!)

On the other hand, I just checked the latest MOTM catalog and in
there it says 0.2 .. 25 Hz. So that is yet another set of values.
Which is right???

In the end, the musical effect is what counts. So the real question
is, is 0.4 .. 13.7 Hz okay for that, or would it be a good idea to
tweak the values to some other range?

Ben

Re: [motm] MOTM-101 clock range too low

2007-02-12 by Ben Stuyts

On 12 Feb 2007, at 00:12, Richard Brewster wrote:

Show quoted textHide quoted text

> I find that I use the EXT CLK input of the MOTM-101 more than the
> internal clock, typically driving it from a MOTM-390 LFO. Advantages:
> 1) larger range than the internal clock, 2) voltage control of the
> clock
> rate, 3) with a multiple you can gate other modules, such as a
> MOTM-800,
> in sync with each new sample. If external clocking is your typical
> S&H
> usage, then the limited range of the internal clock isn't a big deal.

Good points, thanks! I haven't even received my 390 yet, so I'm sure
I'm going to use the internal clock for a while.

Come to think of it, I've ordered only one 390... Maybe I'll order
another one. :-)

Ben