[PD] (OT) safely connect piezo transducer to soundcard as microphone
richard duckworth
richduckworth at yahoo.com
Sat Apr 21 02:14:19 CEST 2012
Piezo mics should go through a very high impedance buffer stage. When I say high impedance, I'm talking 10 megohms minimum. 1 Meg is too low, it basically will act as a high pass filter and your piezo will sound tinny. This page explains all and has a cute 1 stage FET buffer. I have built about 10 of these buffers and they work perfectly, sound great and do not clip:
http://www.muzique.com/news/piezo-pickups/
I bought generic 1 stage buffer PCBs from MusikDing and they keep the buffer circuitry tidy. The circuits, batteries and connectors were housed in guitar pedal/DI style boxes
If you want to tame piezo transients, you can use a small coil. This is what Roland do in those drums pads units - they stick a coil in series with the piezo to smooth out the peaks (a bit like a tiny compressor... ish)
For high-quality sound, don't use piezo - MEAS film contact mics are better. They are more expensive, but some outfit in Canada sent me a bunch for not much money so not too bad. They are finicky to solder - we're talkin' low wattage irons, lead solder (sorry ROHS) and heatsink clips.
You can also use an active DI box to interface your piezos - one that has a high impedence input. Normal Line level inputs are not high enough impedance for piezos, by the way. I've used BSS DI's on piezos and they sound great. I've also experimented with those cheapo Behringer active DIs - and they sound very good on piezos too. They come in a phantom/battery-powered stereo DI version for about 20 euro - 2 piezos to 2 channels on your desk per DI.
Rich Duckworth
Lecturer in Music Technology
Department of Music
House 5
Trinity College
Dublin 2
Ireland
Tel 353 1 896 1500
It's the most devastating moment in a young mans life, when he quite reasonably says to himself, "I shall never play The Dane!"
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Today's Topics:
1. Re: PhD Defense / Acknowledgement to the Pd-list
(Hans-Christoph Steiner)
2. Re: PhD Defense / Acknowledgement to the Pd-list (Jim Hickcox)
3. (OT) safely connect piezo transducer to soundcard as
microphone (Matteo Sisti Sette)
4. Re: (OT) safely connect piezo transducer to soundcard as
microphone (Martin Peach)
5. Re: (OT) safely connect piezo transducer to soundcard as
microphone (katja)
6. Re: Help with Jack and PD (Michal Seta)
----------------------------------------------------------------------
Message: 1
Date: Fri, 20 Apr 2012 09:55:55 -0400
From: Hans-Christoph Steiner <hans at at.or.at>
Subject: Re: [PD] PhD Defense / Acknowledgement to the Pd-list
To: Alexandre Torres Porres <porres at gmail.com>
Cc: pd-lista puredata <pd-list at iem.at>
Message-ID: <D7F486B1-8D83-405D-A68E-7C6A5C023646 at at.or.at>
Content-Type: text/plain; charset="us-ascii"
Congratulations on finishing it! Hope the defense went well.
.hc
On Apr 10, 2012, at 12:49 AM, Alexandre Torres Porres wrote:
> Hi Folks
>
> I defend my PhD thesis this friday here in Brazil. I'd like to share it with you because this list has always been very helpful, I actually made a remark about it in my acknowledgements. And I also put a special remark to all who were here for PdCon09, that was a great experience for me! :)
>
> My draft text, submitted to the board, is at the following link; https://docs.google.com/open?id=0B3AoiT0xk8fnZThjOWQ3YzUtOGUzYS00NGVjLTkwN2QtZjE1MmExZDY0Y2Ey I shall update it though after friday according to the feedback. Then I'll release an official one later one. Wish me luck.
>
> I know most of you can't read portuguese, sorry.
>
> I've used lots of Pd in the research as you might wonder, and there several figures on the text all made from patches. As soon as I get to clean them all along with the text, I'll spread it out over here.
>
> Thanks a lot people
>
> 'til next time
> Alex
>
> _______________________________________________
> Pd-list at iem.at mailing list
> UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
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Message: 2
Date: Fri, 20 Apr 2012 12:15:30 -0400
From: Jim Hickcox <tango.mceffrie at gmail.com>
Subject: Re: [PD] PhD Defense / Acknowledgement to the Pd-list
To: Hans-Christoph Steiner <hans at at.or.at>
Cc: pd-lista puredata <pd-list at iem.at>, Alexandre Torres Porres
<porres at gmail.com>
Message-ID:
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Content-Type: text/plain; charset=ISO-8859-1
Good luck with the defense!
On Fri, Apr 20, 2012 at 9:55 AM, Hans-Christoph Steiner <hans at at.or.at> wrote:
>
> Congratulations on finishing it! ?Hope the defense went well.
>
> .hc
>
> On Apr 10, 2012, at 12:49 AM, Alexandre Torres Porres wrote:
>
> Hi Folks
>
> I defend my PhD thesis this friday here in Brazil. I'd like to share it with
> you because this list has always been very helpful, I actually made a remark
> about it in my acknowledgements. And I also put a special remark to all who
> were here for PdCon09, that was a great experience for me! :)
>
> My draft text, submitted to the board, is at the following
> link;?https://docs.google.com/open?id=0B3AoiT0xk8fnZThjOWQ3YzUtOGUzYS00NGVjLTkwN2QtZjE1MmExZDY0Y2Ey?I
> shall update it though after friday according to the feedback. Then I'll
> release an official one later one. Wish me luck.
>
> I know most of you can't read portuguese, sorry.
>
> I've used lots of Pd in the research as you might wonder, and there several
> figures on the text all made from patches. As soon as I get to clean them
> all along with the text, I'll spread it out over here.
>
> Thanks a lot people
>
> 'til next time
> Alex
>
> _______________________________________________
> Pd-list at iem.at mailing list
> UNSUBSCRIBE and account-management ->
> http://lists.puredata.info/listinfo/pd-list
>
>
>
>
> ----------------------------------------------------------------------------
>
> "[W]e have invented the technology to eliminate scarcity, but we are
> deliberately throwing it away to benefit those who profit from scarcity."
> ? ??-John Gilmore
>
>
>
> _______________________________________________
> Pd-list at iem.at mailing list
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> http://lists.puredata.info/listinfo/pd-list
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------------------------------
Message: 3
Date: Sat, 21 Apr 2012 00:12:54 +0200
From: Matteo Sisti Sette <matteosistisette at gmail.com>
Subject: [PD] (OT) safely connect piezo transducer to soundcard as
microphone
To: PD-List <pd-list at iem.at>
Message-ID: <4F91DF66.6030708 at gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hi,
This is OT but I'm sure many of you have used piezo microphones sometimes.
I've often connected a piezo transducer to the microphone input of my
computer (and other computers) by simply soldering the two wires to the
T and S of a minijack plug, and it works just fine and my soundcard
hasn't suffered any damage (apparently at least).
However, I am concerned that a strong sound input (e.g. hitting the
piezo transducer with with fair strength) may actually generate a
voltage peak (thought only for a short time) capable of damaging the
soundcard, couldn't it?
Also, a friend of mine did the same with his Macbook and his headphones
output has stopped working (may be just a coincidence though).
Is there an easy way to make it safer? I seem to remember I had read
somewhere (can't find it) about connecting a 1MOhm resistor in
parallel... woudl that do the trick?
thanks
m.
------------------------------
Message: 4
Date: Fri, 20 Apr 2012 18:38:53 -0400
From: Martin Peach <martin.peach at sympatico.ca>
Subject: Re: [PD] (OT) safely connect piezo transducer to soundcard as
microphone
To: Matteo Sisti Sette <matteosistisette at gmail.com>
Cc: PD-List <pd-list at iem.at>
Message-ID: <BLU0-SMTP11C079BB820A3B32FFB2B5ED220 at phx.gbl>
Content-Type: text/plain; charset="ISO-8859-1"; format=flowed
You could put a resistor in series to limit the current or a pair of
diodes in parallel to clamp the voltage. Probably a pair of 1N4001s like
this would work:
IN---+------+-----OUT
| |
^ v
| |
GND--+------+-----
Martin
On 2012-04-20 18:12, Matteo Sisti Sette wrote:
> Hi,
>
> This is OT but I'm sure many of you have used piezo microphones sometimes.
>
> I've often connected a piezo transducer to the microphone input of my
> computer (and other computers) by simply soldering the two wires to the
> T and S of a minijack plug, and it works just fine and my soundcard
> hasn't suffered any damage (apparently at least).
>
> However, I am concerned that a strong sound input (e.g. hitting the
> piezo transducer with with fair strength) may actually generate a
> voltage peak (thought only for a short time) capable of damaging the
> soundcard, couldn't it?
>
> Also, a friend of mine did the same with his Macbook and his headphones
> output has stopped working (may be just a coincidence though).
>
> Is there an easy way to make it safer? I seem to remember I had read
> somewhere (can't find it) about connecting a 1MOhm resistor in
> parallel... woudl that do the trick?
>
> thanks
> m.
>
> _______________________________________________
> Pd-list at iem.at mailing list
> UNSUBSCRIBE and account-management ->
> http://lists.puredata.info/listinfo/pd-list
>
>
------------------------------
Message: 5
Date: Sat, 21 Apr 2012 00:42:42 +0200
From: katja <katjavetter at gmail.com>
Subject: Re: [PD] (OT) safely connect piezo transducer to soundcard as
microphone
To: pd-list at iem.at
Message-ID:
<CAFY0eaq1g1TY3ffVRRaYYRsR4_mKRwi4RQTK9VVJuyiR1LhhUw at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Hi,
A piezo transducer often produces a signal level somewhere inbetween
mic level and line level (it depends on size, and method of
excitation). Indeed it can be too loud when mic input is used.
Another point of concern is impedance, which influences the sound
character. If you mount a resistor (in series), the signal level is
reduced but the sound is altered as well. Mounting a capacitor (in
parallel or series) also works to reduce signal level and alter the
sound. Combinations of these (RC networks, effectively) are a great
way to tune the sound character to your liking, but it takes a lot of
experimentation. Also, the result may be different for each (mic)
preamp because input impedance is not fully standardized.
Katja
On Sat, Apr 21, 2012 at 12:12 AM, Matteo Sisti Sette
<matteosistisette at gmail.com> wrote:
> Hi,
>
> This is OT but I'm sure many of you have used piezo microphones sometimes.
>
> I've often connected a piezo transducer to the microphone input of my
> computer (and other computers) by simply soldering the two wires to the T
> and S of a minijack plug, and it works just fine and my soundcard hasn't
> suffered any damage (apparently at least).
>
> However, I am concerned that a strong sound input (e.g. hitting the piezo
> transducer with with fair strength) may actually generate a voltage peak
> (thought only for a short time) capable of damaging the soundcard, couldn't
> it?
>
> Also, a friend of mine did the same with his Macbook and his headphones
> output has stopped working (may be just a coincidence though).
>
> Is there an easy way to make it safer? I seem to remember I had read
> somewhere (can't find it) about connecting a 1MOhm resistor in parallel...
> woudl that do the trick?
>
> thanks
> m.
>
> _______________________________________________
> Pd-list at iem.at mailing list
> UNSUBSCRIBE and account-management ->
> http://lists.puredata.info/listinfo/pd-list
------------------------------
Message: 6
Date: Fri, 20 Apr 2012 19:16:37 -0400
From: Michal Seta <mis at artengine.ca>
Subject: Re: [PD] Help with Jack and PD
To: Rishabh Natarajan <rishabh.natarajan at gmail.com>
Cc: pd-list <pd-list at iem.at>
Message-ID:
<CABVh59=7KMxwa-ksQDD8GdNTapdRcHeU0icvWM8y8nXmNaAx+Q at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
On Thu, Apr 19, 2012 at 9:49 AM, Rishabh Natarajan <
rishabh.natarajan at gmail.com> wrote:
>
> 1. When starting pd with jack and 16 channels, does this mean that all 16
> channels have to go in and out of Jack itself?
>
no.
> 2. Do the number of input and output channels have to be the same (8 and 8
> in this case) or can they be different?
>
they can be different.
> When I tried starting pd with 18 channels and then assigned 16 to Jack
> incoming and 2 to built-in output for outgoing, terminal threw an error
> saying 'invalid number of channels'
>
I am not sure on this one but I think that if Pd does not find as many
physical (or jack) inputs or outputs it will warn you. When you do provide
enough IO you can reconfigure Pd for the new values and it should work (if
you cross your fingers).
3. I want to have 8 channels from one adc~ and another 8 from the other.
> This means all 16 channels are meant for input. How then do I route output
> from pd to the speakers?
>
you specify -audioindev 1,2 for example. You can specify -audiooutdev in
the same way and then you create the appropriate [dac~] objects. BTW, I
believe you can create aggregate devices on Mac (somewhere in the sound
preferences, I believe JackPilot manuals mentions that) to combine
different audio inputs and outputs. I vaguely recall doing something like
this in the past. Then you tell jack to use your aggregate, this may
simplify your setup routine...
> 4. If I am only inputting 16 channels through Jack can I use the dac~
> object to output sound from pd to the speakers?
>
if you run jack (and pd with -jack) then your [dac~] objects can be
connected to jack's outputs, i.e. Pd's inputs and outputs will appear in
JackPilot and you can route them any way you want to your system provided
I/O. Assuming that JackPilot uses the actual physical I/O, you should be
able to output sound from Pd to the speakers.
HTH,
./MiS
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