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 Forum index » DIY Hardware and Software » Thomas Henry designs
SN-VOICE Noise Clock question
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goldenechos



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PostPosted: Tue Aug 28, 2007 10:40 am    Post subject: SN-VOICE Noise Clock question Reply with quote  Mark this post and the followings unread

What is the frequency range of the Thomas Henry SN-Voice 4046 based ext. noise clock?

I have not finished building mine yet, and I am considering re-designing my panel to allow for ext. clock in so that an LFO could be used as the noise clock. Seems like this could be cool if using the Noise source as a CV.

TR
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State Machine
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PostPosted: Tue Aug 28, 2007 1:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

I will assume you want to know the range of frequencies into the EXT NOISE CLOCK and not the range of the 4046.

The data sheet is rather sparse on the any min-max frequency specifications but says that it must not go above 10 volts peak so you nay want to protect to input with a diode so that it will not go negative. Looking at the block diagram though, the clock simply drives a PR counter (of which I use to remember the run length) so I would assume it can clock across the entire audio band. the limiting factor however would be the noise filter settings since the PR output from this counter passes throguh this filter before reaching the internal MIXER. The 3 dB frequency of the noise filter is:

Fc=1.28/(Rnf*Cnf) at Vreg=5VDC.

Rnf and Cnf are the noise figure components connected to pins 5 & 6 of the sound generator IC.

Hope this helps .... If you require, I can measure or calculate the range of the 4046 ......

Very Happy
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goldenechos



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PostPosted: Tue Aug 28, 2007 5:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey State Machine, thanx for your response... I was inquiring about the 4046 clock in Mr. Henry's design. Looking at both the schematic and the 4046 data sheet, I find myself guessing that the clock is operating above the audio range... but that is a guess as I have no idea what voltage range Mr. Henry is applying to pin 11 of the 4046.

If you, or anybody else has time, I would appreciate it if you could measure the frequency range of the 4046 based clock in the Sn-Voice.

As for your point about the Filter following the Noise output (and prior to the mixer), are you suggesting that the filter would remove much of the signal content when clocked at lower frequencies?

Thanx again for your insight,

Tony
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Thomas Henry



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PostPosted: Tue Aug 28, 2007 6:05 pm    Post subject: Re: SN-VOICE Noise Clock question Reply with quote  Mark this post and the followings unread

goldenechos wrote:
What is the frequency range of the Thomas Henry SN-Voice 4046 based ext. noise clock?


I glad someone finally noticed! That's been one of my favorite tricks that only Scott and I have been savvy to for the past couple of years.

Rather remarkably, I was able to get a whopping 100 Hz to 350 kHz sweep out of the thing.

It still blows me away (he said rather immodestly). Once again, the data sheet (and even Lancaster's Cookbook) gives no clue that a slightly different topology makes such a range possible.

So forget the control voltage input and go with a control current instead!

Thomas Henry
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goldenechos



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PostPosted: Tue Aug 28, 2007 6:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

Whoa, that is quite a sweep Thomas!

Tony
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