| Title: | * * Computer Music, MIDI, and Related Topics * * |
| Notice: | Conference has been write-locked. Use new version. |
| Moderator: | DYPSS1::SCHAFER |
| Created: | Thu Feb 20 1986 |
| Last Modified: | Mon Aug 29 1994 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 2852 |
| Total number of notes: | 33157 |
Ok guyz, its technical time. I would like to build a mono noise gate from
scratch, and would like some input on my current design attempt. (havn't
tried implementing it yet.) I'm sorry to say that the design I have in
mind utilizes a relay (a relic, you say?), so if anyone wants to come up
with a transistor-going-from-the-active-region-to-the-cutoff-region type
of concoction, I'd certainly be willing to hear it. The design I currently
have in mind looks like this:
RELAY |
V
,'
INPUT ->-----+----------o' o----------> OUTPUT
SIGNAL | | SIGNAL
| |
| ^
| |
| +----------+
| | |
| | THRESHOLD|
+------>| DETECTOR |
| CIRCUIT |
| |
+----------+
The threshold detector circuit monitors the input signal level, tripping
the relay when the input signal exceeds a presetable level.
I already have a threshold detector circuit. It was made back in my Ham
Radio days, when I needed a circuit that would toggle my tranciever over
into transmit mode when I talked into a mic (VOX circuit). Any comments
regarding noise immunity through the relay, or anything else for that matter?
Oh yea, I should probably ground the output signal when the relay is open.
Todd.
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 389.2 | BARNUM::RHODES | Fri Jun 13 1986 10:08 | 8 | ||
Sounds like the operational transconductance amp is the magic device.
I will look into this. What is the cutoff freq/rolloff of the LP
filter? It seems that if the cutoff freq is too low and the filter
exhibits sharp rolloff, high frequency signals will not trigger
it properly.
Todd.
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| 389.3 | Delay | DSSDEV::SAUTER | John Sauter | Fri Jun 13 1986 10:21 | 4 |
If you insist on using a relay, consider putting a few milliseconds
in the audio path in front of it. That will give the threshold
detector time to switch the relay before the relavent sound arrives.
John Sauter
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| 389.4 | EVER11::WAKE | Fri Jun 13 1986 10:58 | 5 | ||
You might want to look at the one in Craig Anderton's
"Home Recording for Musicians". I think he used an
optoisolator instead of a relay along with a 555 timer/741
opamp combination for the detection part of the circuit.
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| 389.5 | It's a CLM6000 opto-isolator | MAX::MCPHERSON | It's my life and it's my wife. | Fri Jun 13 1986 12:25 | 10 |
Re -.1
Yep. Anderton's kits are pretty neat. I've got his Electronic
Projects for Musicians and it's a really good book for "low-budget
gizmo manufacturing at home."
i highly recommend it.
/doug
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| 389.7 | Sure, no problem | KRYPTN::JASNIEWSKI | Fri Jun 13 1986 15:26 | 10 | |
You can make it as simple or as complex as you'd like. I have
a scheme for a rather simple one, based on a CD4016. If you'd like,
send me mail and I'll try to dig it up for you. there's a book
"electronic circuits referance manual" that probably has 25 different
ways to do this, if a library is nearby. Its by markus.
Joe Jas
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| 389.8 | In case you were wondering... | BARNUM::RHODES | Thu Jul 17 1986 18:00 | 15 | |
Thanks for all the responses. I looked for but couldn't find my
'VOX' circuit so I guess I'm back to square one.
I haven't had much time lately as I have been busily renovating
parts of my house and thus using the music room for storage, ironing,
and various other non-midi things [where the heck are my priorities?
I should be using the living room for storage and ironing dammit!]
I have also been spending some tidbits of time on the FM program,
discussed elsewhere.
Soooooo, the noisegate is officially on the back burner for an
undeterminable amount of time.
Todd.
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