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'Arbitrary Waveform Generator'
1999\12\14@181405 by Mike Miller

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Hi All,

I've a need to build an AWG to impersonate a church bell. I think I can
do it with a PIC, some memory and a decent DAC. I don't want to use a
PWM because the quality I want would make the back-end filter painful.

Any thoughts, URLs I should know about?

TIA,
Mike.

1999\12\14@222505 by Russell McMahon

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>I've a need to build an AWG to impersonate a church bell. I think I can
>do it with a PIC, some memory and a decent DAC. I don't want to use a
>PWM because the quality I want would make the back-end filter painful.


Consider using a sound recorder IC - can be quite cheap
ISD1016 (AFAIR) is a 16 second IC which would allow a longish bell sequence.
Cost is probably a few dollars US by now.

If you do use an AWG then I suspect a simple R2R DAC on 8 port bits will be
adequate.


regards



     Russell McMahon
_____________________________

>From other worlds - http://www.easttimor.com
                               http://www.sudan.com

What can one man* do?
Help the hungry at no cost to yourself!
at  http://www.thehungersite.com/

(* - or woman, child or internet enabled intelligent entity :-))


{Original Message removed}

1999\12\14@224604 by Bill Bennett

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try this site might be of some help
http://www.qudravox.com

Bill

----- Original Message -----
From: Russell McMahon <spam_OUTapptechTakeThisOuTspamCLEAR.NET.NZ>
To: <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>
Sent: Tuesday, December 14, 1999 7:28 PM
Subject: Re: Arbitrary Waveform Generator


> >I've a need to build an AWG to impersonate a church bell. I think I
can
> >do it with a PIC, some memory and a decent DAC. I don't want to use
a
> >PWM because the quality I want would make the back-end filter
painful.
>
>
> Consider using a sound recorder IC - can be quite cheap
> ISD1016 (AFAIR) is a 16 second IC which would allow a longish bell
sequence.
> Cost is probably a few dollars US by now.
>
> If you do use an AWG then I suspect a simple R2R DAC on 8 port bits
will be
{Quote hidden}

> {Original Message removed}

1999\12\14@231327 by Bill Bennett

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sorry misspelled link
http://www.quadravox.com

Bill

----- Original Message -----
From: Russell McMahon <apptechspamKILLspamCLEAR.NET.NZ>
To: <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
Sent: Tuesday, December 14, 1999 7:28 PM
Subject: Re: Arbitrary Waveform Generator


> >I've a need to build an AWG to impersonate a church bell. I think I
can
> >do it with a PIC, some memory and a decent DAC. I don't want to use
a
> >PWM because the quality I want would make the back-end filter
painful.
>
>
> Consider using a sound recorder IC - can be quite cheap
> ISD1016 (AFAIR) is a 16 second IC which would allow a longish bell
sequence.
> Cost is probably a few dollars US by now.
>
> If you do use an AWG then I suspect a simple R2R DAC on 8 port bits
will be
{Quote hidden}

> {Original Message removed}

1999\12\15@020129 by Jinx

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A bell is two or more sine waves combined in a ring modulator, usually
modulating a high frequency with a low. Even simple addition of only
two will give a good bell sound. The CA3080 amp (and others) can be
used as an RM mixer for two sine waves from DACs. An ISD sound
recorder would be OK, but the HF response of these is not good. Might
just do for a big bell but not anything tinkly.

Jinx

1999\12\15@021021 by Sean Breheny

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I have often heard of RMs but I don't know what one is. Is it just a
slightly non-linear amplifier? What is the difference from a regular
modulator (not only balanced, but simple unbalanced)? Also, when you just
linearly combine two sine waves, you will of course get the effect of
hearing beat tones which aren't really present as actual frequency content,
just a modulated envelope of the total wafeform that your brain perceives
as additional tones. Is this what you are talking about? If so, I don't see
why any modulator is needed.

Sean

At 07:58 PM 12/15/99 +1300, you wrote:
>A bell is two or more sine waves combined in a ring modulator, usually
>modulating a high frequency with a low. Even simple addition of only
>two will give a good bell sound. The CA3080 amp (and others) can be
>used as an RM mixer for two sine waves from DACs. An ISD sound
>recorder would be OK, but the HF response of these is not good. Might
>just do for a big bell but not anything tinkly.
>
>Jinx
>
|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
EraseMEshb7spam_OUTspamTakeThisOuTcornell.edu ICQ #: 3329174

1999\12\15@052031 by Jinx

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From: Sean Breheny

{Quote hidden}

Perhaps the explanation I gave was a little quick and simple. "Addition"
didn't come out in perhaps the way I meant it to.

An extract from http://www.dacs-audio.co.uk/dataringmod.htm, describing a
commercial synthesiser module.

*******************************

The Effect

The effect can range from rich bell like sounds to a simpler "beefing up"
of a voice played in octaves. The module has two signal inputs and one
ring modulated output. The output contains frequencies given by the sum
of, and the difference between, the frequencies of the two inputs. For
example two sine wave inputs of 100Hz would give an output containing
only a sine wave at 200Hz (100 + 100 = 200, 100 - 100 = 0). Inputs of
100Hz and 50Hz would give an output containing 150Hz and 50Hz. As
the relationship between the input frequencies becomes more complex,
so the output becomes increasingly inharmonic, unstable and musically
interesting and useful.

*******************************

So you see the process of RM is not as simple as a plain "addition". You
do need a circuit or amp which is designed as an RM, not just a mixer. I
mentioned the CA3080 just as one I know off the top of my head.

As far as this relates to the PIC you'd need to be able to easily adjust
the outputted frequencies to get just the right mix. Atonal RM sounds
quite harsh and metallic, not what you'd want for a bell. The amplitude
of at least one of them should be adjustable too, so as to alter the depth
of the effect.

A little vibrato (or tremolo) would add extra life to the sound as well,
but you'd have to see if the DACs are up to rapid repetitive frequency
changes.

Jinx

1999\12\15@083516 by Leo Timmer

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A ring-modulator is nothing more or less than a analog-multiplier, with balanced outputs.
But the advantage over a 'normal' modulator is, that it suppresses the input signals.
So if you put 1Khz and 3Khz on the inputs, then 2Khz and 4KHz will appear on
the outputs, but not the 1Khz and the 3Khz signals. With an ordinary modulator
all signals will appear at the output.

Leo.

{Original Message removed}

1999\12\15@110924 by Sean Breheny

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Ok, thanks to Jinx and Leo,

The term I have always heard given to such a device is just a "balanced
modulator", and it is often used in RF communications circuits to produce
frequency shifting. I wonder why it has a different name in the audio
world? (Perhaps RM is used in other contexts,but I have only heard of it in
audio discussions).

Does the word "ring" in it refer to the structure of the modulator? In RF
work they are often made using a bridge of hot carrier diodes, so it could
conceiveably be referrered to as a "ring".

Thanks,

Sean


At 11:17 PM 12/15/99 +1300, you wrote:
{Quote hidden}

| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
shb7spamspam_OUTcornell.edu ICQ #: 3329174

1999\12\16@061628 by paulb

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Sean Breheny wrote:

> Does the word "ring" in it refer to the structure of the modulator?

 Indeed it does.

> In RF work they are often made using a bridge of hot carrier diodes,
> so it could conceiveably be referrered to as a "ring".

 Quite so.  I think if you use hot-carrier diodes, you require
resistors in series, as they (IIRC) have a very low threshold voltage.

 The ring modulator will not work *without* either a significant
threshold voltage or significant intrinsic resistance as it relies on
non-linearity of the diode.
--
 Cheers,
       Paul B.

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