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[EE] Audio Processing Project

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[EE] Audio Processing Project

Josh Koffman
Hi all,

I've been quiet for a while, so you know I must have been thinking
hard about a new project! Or...just really busy with work. While the
second might be most true, I have been thinking for quite a while
(nearly a year now) about a problem that I have, and I finally feel
like I'm starting to make some progress.

One of the jobs I do is in live entertainment. When I'm working, I am
often on a few different communication systems simultaneously. I'm at
the point where I now have more systems than ears, which is making
things tricky. Here are the three main ones I'm usually hooked up to
in some way:
1. Radio - two way radio (walkie talkie) - half duplex
2. Production Intercom - a partyline style full duplex intercom system
3. In-ear monitors - a wireless stereo feed from the sound system
(with some things added that the audience doesn't get to hear)
The way I currently deal with this is to wear an in-ear monitor in one
ear, my intercom headset over the other ear, and have the radio
speaker/mic clipped somewhere nearby in the hopes that it will bleed
through enough that I can hear it. For the record, that rarely works.

In the past, I've tried a small audio mixer to combine the radio
output and the in-ear feed into my ears. This was semi successful. It
did work, but impedance and signal levels were completely wrong, which
made it very touchy. In addition, I was getting audio from the radio
via an earphone output jack that is evidently just for show, as I
managed to go through 4 speaker/mics which would only last a week or
two before the jack stopped making reliable contact. Not fun.

I thought that making a custom mixer was going to be the ultimate
solution, but that still left the issue of multiple mics. I've been
doing some research towards that end, and what I've stumbled upon in
much closer to my ultimate goal. There is a market (mainly law
enforcement and military) that often use multiple radios and
intercoms, and so there are companies that now make devices to connect
these all together. As a matter of fact, Carey, a long time PICList
member makes these for base and mobile applications. Sadly I need
something a bit more portable. For a great example of what I'm talking
about, see the Invisio V60 here:
http://invisio.com/products/adv-hearing-protection/invisio-v60.aspx
and watch the video demo. It's pretty neat.

So now the question is, why not just buy a system like that? Not so
fast! First of all, I'd be willing to bet they are way out of my price
range. I don't have the backing of a major governmental department,
but I have sent them a few inquiries. We'll see if they get back to
me. Their system also does a lot more than I really need, including
"hear through" (their headsets have tiny microphones that can be
enabled to allow peripheral hearing), waterproofing (20 metres!), and
other fancy bits. It looks quite slick, but I'm starting with the
assumption that I can't get one for myself.

As a result, I'm starting to look at trying to build something
similar, but not quite as sophisticated. I envision a small box that I
can connect a headset (or other separate audio input and output
device) to, and be able to control where my voice routes to, and what
I'm hearing (ideally both volume and L-R panning). It would connect to
my radio, controlling its transmit functionality. It would connect to
my intercom, allowing me to talk and hear in full duplex. It would
also take my in-ear feed and mix it in with my other audio feeds.

In my mind there are two approaches to this, analog and digital.
Obviously both methods will require some analog interface circuitry. I
am already trying to compile the specifications of each device to be
able to determine interface specs. In the full analog solution, the
mixing will be done in the analog realm, perhaps with some digital
control over it (likely via PIC). The digital approach would digitize
the signals, and do all of the processing in a DSP of some sort.

In terms of my skill set, both of these are a stretch. I am not that
experienced in analog, and I've never touched a DSP before. I really
like the idea of using a DSP as it could be reconfigured without a
circuit redesign. In theory, if I was able to come up with some way to
send it commands (UI or computer front end, who knows), the routing
and processing could even be changed on the fly. Don't want the radio
in the left ear anymore? No problem, make it come out the right ear!
The other nice thing about a DSP is that things like compression and
limiting would just be a matter of writing the correct programs.

Sadly, that's probably out of my reach if I was to try this solo. So
I'm looking for help, on two fronts:

1. Can anyone recommend a good starting point to audio DSP? I'm
talking mainly about hardware. I've been doing some web searching, and
I've come up with a few that I'm already looking into, but I'm curious
what others recommend. Dev kits that aren't $2500 would be
appreciated.

2. Is anyone interested in teaming up on this? It would make a dandy
university project for a student, or a weekend project for someone
with more experience than I. And as I'm just doing this for me, there
aren't any ridiculous deadlines.

Anyway, please let me know what you think. I have been doing a lot of
thinking and research on this, but this post is long enough already!

Happy New Year :)

Josh
--
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completely foolproof is to underestimate the ingenuity of complete
fools.
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Re: [EE] Audio Processing Project

Carey Fisher - NCS
Josh,
Glad to see you're working on new projects that "stretch" you a bit. I'll
be glad to help you design your gadget since that's the type gadget I've
been working with for 10+ years.  The Left Ear/Right Ear thing is
implemented on one of our ham products and it's pretty easy to realize the
functionality and flexibility without going the DSP route.
Anyway, let me know how I can help.
Regards,
WB4HXE

On Sun, Jan 6, 2013 at 10:21 PM, Josh Koffman <[hidden email]> wrote:

> Hi all,
>
> I've been quiet for a while, so you know I must have been thinking
> hard about a new project! Or...just really busy with work. While the
> second might be most true, I have been thinking for quite a while
> (nearly a year now) about a problem that I have, and I finally feel
> like I'm starting to make some progress.
>
> One of the jobs I do is in live entertainment. When I'm working, I am
> often on a few different communication systems simultaneously. I'm at
> the point where I now have more systems than ears, which is making
> things tricky. Here are the three main ones I'm usually hooked up to
> in some way:
> 1. Radio - two way radio (walkie talkie) - half duplex
> 2. Production Intercom - a partyline style full duplex intercom system
> 3. In-ear monitors - a wireless stereo feed from the sound system
> (with some things added that the audience doesn't get to hear)
> The way I currently deal with this is to wear an in-ear monitor in one
> ear, my intercom headset over the other ear, and have the radio
> speaker/mic clipped somewhere nearby in the hopes that it will bleed
> through enough that I can hear it. For the record, that rarely works.
>
> In the past, I've tried a small audio mixer to combine the radio
> output and the in-ear feed into my ears. This was semi successful. It
> did work, but impedance and signal levels were completely wrong, which
> made it very touchy. In addition, I was getting audio from the radio
> via an earphone output jack that is evidently just for show, as I
> managed to go through 4 speaker/mics which would only last a week or
> two before the jack stopped making reliable contact. Not fun.
>
> I thought that making a custom mixer was going to be the ultimate
> solution, but that still left the issue of multiple mics. I've been
> doing some research towards that end, and what I've stumbled upon in
> much closer to my ultimate goal. There is a market (mainly law
> enforcement and military) that often use multiple radios and
> intercoms, and so there are companies that now make devices to connect
> these all together. As a matter of fact, Carey, a long time PICList
> member makes these for base and mobile applications. Sadly I need
> something a bit more portable. For a great example of what I'm talking
> about, see the Invisio V60 here:
> http://invisio.com/products/adv-hearing-protection/invisio-v60.aspx
> and watch the video demo. It's pretty neat.
>
> So now the question is, why not just buy a system like that? Not so
> fast! First of all, I'd be willing to bet they are way out of my price
> range. I don't have the backing of a major governmental department,
> but I have sent them a few inquiries. We'll see if they get back to
> me. Their system also does a lot more than I really need, including
> "hear through" (their headsets have tiny microphones that can be
> enabled to allow peripheral hearing), waterproofing (20 metres!), and
> other fancy bits. It looks quite slick, but I'm starting with the
> assumption that I can't get one for myself.
>
> As a result, I'm starting to look at trying to build something
> similar, but not quite as sophisticated. I envision a small box that I
> can connect a headset (or other separate audio input and output
> device) to, and be able to control where my voice routes to, and what
> I'm hearing (ideally both volume and L-R panning). It would connect to
> my radio, controlling its transmit functionality. It would connect to
> my intercom, allowing me to talk and hear in full duplex. It would
> also take my in-ear feed and mix it in with my other audio feeds.
>
> In my mind there are two approaches to this, analog and digital.
> Obviously both methods will require some analog interface circuitry. I
> am already trying to compile the specifications of each device to be
> able to determine interface specs. In the full analog solution, the
> mixing will be done in the analog realm, perhaps with some digital
> control over it (likely via PIC). The digital approach would digitize
> the signals, and do all of the processing in a DSP of some sort.
>
> In terms of my skill set, both of these are a stretch. I am not that
> experienced in analog, and I've never touched a DSP before. I really
> like the idea of using a DSP as it could be reconfigured without a
> circuit redesign. In theory, if I was able to come up with some way to
> send it commands (UI or computer front end, who knows), the routing
> and processing could even be changed on the fly. Don't want the radio
> in the left ear anymore? No problem, make it come out the right ear!
> The other nice thing about a DSP is that things like compression and
> limiting would just be a matter of writing the correct programs.
>
> Sadly, that's probably out of my reach if I was to try this solo. So
> I'm looking for help, on two fronts:
>
> 1. Can anyone recommend a good starting point to audio DSP? I'm
> talking mainly about hardware. I've been doing some web searching, and
> I've come up with a few that I'm already looking into, but I'm curious
> what others recommend. Dev kits that aren't $2500 would be
> appreciated.
>
> 2. Is anyone interested in teaming up on this? It would make a dandy
> university project for a student, or a weekend project for someone
> with more experience than I. And as I'm just doing this for me, there
> aren't any ridiculous deadlines.
>
> Anyway, please let me know what you think. I have been doing a lot of
> thinking and research on this, but this post is long enough already!
>
> Happy New Year :)
>
> Josh
> --
> A common mistake that people make when trying to design something
> completely foolproof is to underestimate the ingenuity of complete
> fools.
>         -Douglas Adams
> --
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>



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Chief Technical Officer
New Communications Solutions, LLC
678-999-3956
[hidden email]
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Re: [EE] Audio Processing Project

Mark Hanchey-2
In reply to this post by Josh Koffman
On 1/6/2013 10:21 PM, Josh Koffman wrote:
>
> As a result, I'm starting to look at trying to build something
> similar, but not quite as sophisticated. I envision a small box that I
> can connect a headset (or other separate audio input and output
> device) to, and be able to control where my voice routes to, and what
> I'm hearing (ideally both volume and L-R panning). It would connect to
> my radio, controlling its transmit functionality. It would connect to
> my intercom, allowing me to talk and hear in full duplex. It would
> also take my in-ear feed and mix it in with my other audio feeds.

I think you can do everything you want with just  opamps.  I don't think
bringing in DSP and microcontrollers are going to be of a benefit and
the low end stuff and digitizing, while giving you more control over the
output seems like it would be overkill for just mixing and switching
signals.

Mark


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Re: [EE] Audio Processing Project

Dwayne Reid
In reply to this post by Josh Koffman
At 08:21 PM 1/6/2013, Josh Koffman wrote:

>1. Radio - two way radio (walkie talkie) - half duplex
>2. Production Intercom - a partyline style full duplex intercom system
>3. In-ear monitors - a wireless stereo feed from the sound system
>(with some things added that the audience doesn't get to hear)
>The way I currently deal with this is to wear an in-ear monitor in one
>ear, my intercom headset over the other ear, and have the radio
>speaker/mic clipped somewhere nearby in the hopes that it will bleed
>through enough that I can hear it. For the record, that rarely works.

Hi there, Josh.

What you describe is something that I do regularly.  One of my hobby
jobs is doing live audio (at our local football stadium) as well as
doing RF (wireless mics & wireless intercom) *and* production
intercom for both live TV broadcasts and large live events.  For
example, the last large Intercom job that I did (late last summer)
was for the film crew doing a 3D movie with the rock band Metallica -
that was an RTS Adam digital-matrix system with just shy of 100 users
on wired and wireless headsets plus an additional 45-50 users on two
channels of half-duplex 2-way radio on something like 18 channels of comm.

Something that both myself and my users find very important is the
concept of spacial separation when monitoring multiple channels of
comm.  One of my buddies does audio for live broadcast TV - he often
sets up several small (Fostex) speakers above and in front of him
(top left and right corners of the room) as well as at his feet and
behind him.  This lets him identify which channel of comm
instructions are coming from - which lets him decide what to
ignore.  He can't wear a headset when he is mixing live audio, which
makes the little comm speakers vitally important for him to do a good job.

I regularly monitor 2 or 3 audio sources when I'm in front of my
intercom panel at the stadium - a walkie, the intercom headset and
program audio.  But I cheat - I wear an IFB earbud from my 2-way
radio in my left ear, then have the intercom headset over top of that
ear.  My right ear is either open (so that I can talk with people
coming into the audio booth) or has one side of Sony 7506 headphones
over it with program audio and/or monitor audio from the Wireless Mic
receiver racks.  Both headsets get tossed when I have to go run and
deal with a problem but the radio earbud stays in my left ear.

Can I suggest that you try using an IFB earbud in your ear for your
2-way radio?  You might be pleasantly surprised at how well it
works.  The earbuds that I use come from Audio Implements (USA) - 125
Ohm clarifiers with an air-tube to an accordion-style bud.  Audio
from the intercom headset speaker has no problem getting past the
earbud into my ear.  For what its worth, I'm using a Beyer-Dynamic
DT-108 single-muff headset when I'm sitting at that intercom panel.

For Motorola radios, at least, you can get speaker-mics that have a
3.5mm earphone jack.  That works well with the 125R Audio Implements
IFB earbuds.  I would assume that Kenwood and Icom (and other 2-way
portable radios) have similar speaker-mics available.  I mostly work
with Motorola HT-750 radios.

If you find the earbud to be too uncomfortable for long periods of
time, I've recently started using a small headset instead of the
earbud.  Unfortunately, I don't recall the names (manufacturer and
model) of the unit - but I can find out.  Its small enough that the
Beyer headset fits right over top of it.  This headset replaces both
the speaker-mic and IFB earpiece.  I used it for the first time last
season and quite like it so far.

You can try the mixer approach - I've got a small PCB that mixes 4
in-coming mono signals into a stereo output that I could send to you
(if I can find them - they were for Broadcast Talent boxes that I
built more than 20 years ago).  These cards have individual dip
controls as well as pan controls - the dip controls dim each incoming
audio channel by an adjustable amount when that channel's dim control
signal is active.  The card runs from a single +24V supply but will
probably work down to 12V.  It uses TL072 and TL074 op-amps, which
limits how low the supply voltage can be.

I hope this helps and I'd love to hear more about what you do.

dwayne



--
Dwayne Reid   <[hidden email]>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
www.trinity-electronics.com
Custom Electronics Design and Manufacturing

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RE: [EE] Audio Processing Project

alan.b.pearce
In reply to this post by Josh Koffman
> 1. Can anyone recommend a good starting point to audio DSP? I'm talking mainly about
> hardware. I've been doing some web searching, and I've come up with a few that I'm
> already looking into, but I'm curious what others recommend. Dev kits that aren't
> $2500 would be appreciated.

As it sounds like you would be building the hardware, I would suggest you look at one of Microchips DSP starter kits, probably a single simple PCB using a PIC33 series chip, rather than the explorer 16 with appropriate PIM. Microchip do have a library of DSP functions for doing auto-level control, echo cancel, etc. and I would suggest having a dig around in there for suitable code modules.

I haven't used any of their DSP stuff, so don't know how good it is, but for minimal $ it should give you a starting point.


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Re: [EE] Audio Processing Project

John Ferrell
In reply to this post by Josh Koffman
I have been studying DSP for quiet a while now with little success. I
need to do a little lab work if I am ever going to grasp the basics. In
my search for usable hardware I recently found a setup that allows
signal access to the interface between an AD and the DAC. It is intended
to be used with the Arduino Uno but should be adaptable to any
interface. It is available from ladyada.net as a kit for about $22.  I
have seen it called "audio Shield" and "wave Shield".  I have mine built
but not yet tested due to personal ADHD & other distractions. It would
be best for one to get the specs & info from LadyAda.

All of the other micro-DSP packages seem to make it difficult or
impossible to access/modify the digital data stream.
There are many high quality math lectures available on Youtube.com if
you can only pick out the ones you need!

I wear hearing aids which are expensive and not really as good as they
could be. I ordered Logitec earbuds for my laptop so I could watch the
Videos without disturbing others. I am amazed at how much better I hear
that way.  Quality Earbuds beat $4000.00 hearing aids.  It would be nice
to have a multichannel equalizer included but for now I am planning a
simple stereo amp in my shirt pocket. Mic's probably on glass frames.  
People don't really notice earbuds thanks to all the youth running
around using the...
BTW, hearing aids don't even try above 8 khz.

On 1/6/2013 10:21 PM, Josh Koffman wrote:
> Hi all,
>
> I've been quiet for a while, so you know I must have been thinking
> hard about a new project! Or...just really busy with work. While the
> second might be most true, I have been thinking for quite a while
> (nearly a year now) about a problem that I have, and I finally feel
> like I'm starting to make some progress.
>

--
John Ferrell W8CCW
That which can be destroyed by the truth should be.
P.C. HODGELL
   


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Re: [EE] Audio Processing Project

John Gardner
John -

Which Logitech earbuds are you using?

 thanks, Jack
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Re: [EE] Audio Processing Project

Roger Furer-2
In reply to this post by Josh Koffman
Josh,

Check out Cypress Semiconductor's Programmable System on a Chip: PSoC. These are similar to FPGA but have the devices already configured in blocks, such as op amps, filters, etc. There is also an ARM based processor on the chip as well. For the lowest cost ($40) development kit go to: http://www.cypress.com/?rID=2541

The next one up is $178 http://www.cypress.com/?rID=37815

For an over view of PSoC-! products go to: http://www.cypress.com/?id=1573&source=productshome

You'll need to download (free) PSoC Designer and PSoC Programmer.

I have only experimented with PSoC Designer,but it looks like you can build a mixer, have buttons that control Talk-Back, send signals to multiple outputs etc. All on one chip. Also the chips that are used on the $40 kit are 28-pin DIPs so checking them out on a solderless breadboard is also doable. (There is a small solderless bread board on each development kit plus an LCD.)


I plan to order one of these when I get settled into new digs. The price is better than any FPGA development/evaluation kit I've seen.and the PSoC Designer software is easy to start with. I'd be working on it now, but my workhorse computer is in storage awaiting my move.


Cheers,

Roger
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Re: [EE] Audio Processing Project

Josh Koffman
In reply to this post by Carey Fisher - NCS
On Sun, Jan 6, 2013 at 11:34 PM, Carey Fisher <[hidden email]> wrote:
> Josh,
> Glad to see you're working on new projects that "stretch" you a bit. I'll
> be glad to help you design your gadget since that's the type gadget I've
> been working with for 10+ years.  The Left Ear/Right Ear thing is
> implemented on one of our ham products and it's pretty easy to realize the
> functionality and flexibility without going the DSP route.
> Anyway, let me know how I can help.

Hi Carey,

I must admit, while I immediately connected what I was doing with what
you have done, it never even occurred to me to ask you for help!
Whoops!

Which product are you referring to? I'd love to check it out.

Thanks!

Josh
--
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Re: [EE] Audio Processing Project

Josh Koffman
In reply to this post by Mark Hanchey-2
On Mon, Jan 7, 2013 at 7:17 AM, Mark Hanchey <[hidden email]> wrote:
> I think you can do everything you want with just  opamps.  I don't think
> bringing in DSP and microcontrollers are going to be of a benefit and
> the low end stuff and digitizing, while giving you more control over the
> output seems like it would be overkill for just mixing and switching
> signals.

Hi Mark,

It does seem to be going that way. I liked the idea of a DSP because
it's reconfigurable via software only. However, I think it might be a
bit much to bite off on my first go. I'm going to keep looking into
it, but I might not end up going that way.

If anyone has any examples of projects that do mixing and switching
(even parallel applications, like home theatre, etc), I'd love to see
'em!

Thanks,

Josh
--
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Re: [EE] Audio Processing Project

Josh Koffman
In reply to this post by alan.b.pearce
On Mon, Jan 7, 2013 at 7:26 AM,  <[hidden email]> wrote:
> As it sounds like you would be building the hardware, I would suggest you look at one of Microchips DSP starter kits, probably a single simple PCB using a PIC33 series chip, rather than the explorer 16 with appropriate PIM. Microchip do have a library of DSP functions for doing auto-level control, echo cancel, etc. and I would suggest having a dig around in there for suitable code modules.
>
> I haven't used any of their DSP stuff, so don't know how good it is, but for minimal $ it should give you a starting point.

Hi Alan,

I will have a look. I'll need to check out their libraries, I'd
imagine most of them will be over my head off the starting block, but
maybe I can figure them out!

Josh
--
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completely foolproof is to underestimate the ingenuity of complete
fools.
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Re: [EE] Audio Processing Project

Josh Koffman
In reply to this post by John Ferrell
On Mon, Jan 7, 2013 at 11:47 AM, John Ferrell <[hidden email]> wrote:
> I have been studying DSP for quiet a while now with little success. I
> need to do a little lab work if I am ever going to grasp the basics. In
> my search for usable hardware I recently found a setup that allows
> signal access to the interface between an AD and the DAC. It is intended
> to be used with the Arduino Uno but should be adaptable to any
> interface. It is available from ladyada.net as a kit for about $22.  I
> have seen it called "audio Shield" and "wave Shield".  I have mine built
> but not yet tested due to personal ADHD & other distractions. It would
> be best for one to get the specs & info from LadyAda.

I found the Wave Shield. Seems interesting for audio output, but I'm
not sure it would be able to support what I'm looking for. I will keep
investigating though!

I have found a guitar stompbox project with a small DSP in it. It
seems interesting but it (and a few others like it) seems to be
limited to usually one in and one out.

> I wear hearing aids which are expensive and not really as good as they
> could be. I ordered Logitec earbuds for my laptop so I could watch the
> Videos without disturbing others. I am amazed at how much better I hear
> that way.  Quality Earbuds beat $4000.00 hearing aids.  It would be nice
> to have a multichannel equalizer included but for now I am planning a
> simple stereo amp in my shirt pocket. Mic's probably on glass frames.
> People don't really notice earbuds thanks to all the youth running
> around using the...
> BTW, hearing aids don't even try above 8 khz.

That doesn't surprise me too much. I read that one of the main things
we lose as our hearing diminishes is selectivity. Our ear/brain combo
is quite good at filtering out background noise and deciding to focus
on a specific source amidst other competing sounds. With hearing aids,
it doesn't work as well. I would be interested to hear about how it
goes when you do get your stereo amp -> earbuds working. If I was in
your shoes, I start by experimenting with some non portable, stock
equipment, just to see how it goes before you build something you can
carry yourself.

Josh
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Re: [EE] Audio Processing Project

RussellMc
In reply to this post by Roger Furer-2
> Check out Cypress Semiconductor's Programmable System on a Chip: PSoC. These are similar to FPGA but have the devices already configured in blocks, such as op amps, filters, etc. There is also an ARM based processor on the chip as well. For the lowest cost ($40) development kit go to:

             http://www.cypress.com/?rID=2541.

One could easily enough fall in love with a product like that.
The two included demo parts cost about $16 the pair at Digikey in 1's,
valuing  the balance of the kit  at $24.
Minimum voltage for the 8C29466 is 3V BUT it has an on board smps to
allow 1V operation.
$8/1 , $4.65/5000 for the SSOP28 part.
I have a "couldn't be done cheap enough" application that this may
address if one can persuade them to halve the volume price. (Can't be
done cheap ... :-) ).

The attraction is the ability to build in serious analog functionality:
The digital functionality does not hurt.



     R

As standard.

■ Advanced peripherals (PSoC® blocks)
❐ 12 rail-to-rail analog PSoC blocks provide:
• Up to 14-bit analog-to-digital converters (ADCs)
• Up to 9-bit digital-to-analog converters (DACs)
• Programmable gain amplifiers (PGAs)
• Programmable filters and comparators

❐ 16 digital PSoC blocks provide:
• 8- to 32-bit timers, counters, and pulse-width modulators
(PWMs)
• Cyclical redundancy check (CRC) and pseudo random
sequence (PRS) modules
• Up to four full-duplex universal asynchronous receiver
transmitters (UARTs)
• Multiple serial peripheral interface (SPI) masters or slaves
• Can connect to all general-purpose I/O (GPIO) pins
❐ Create complex peripherals by combining blocks

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Re: [EE] Audio Processing Project

Josh Koffman
In reply to this post by Roger Furer-2
On Mon, Jan 7, 2013 at 8:51 PM, Roger Furer <[hidden email]> wrote:

> Check out Cypress Semiconductor's Programmable System on a Chip: PSoC. These are similar to FPGA but have the devices already configured in blocks, such as op amps, filters, etc. There is also an ARM based processor on the chip as well. For the lowest cost ($40) development kit go to: http://www.cypress.com/?rID=2541.
>
> The next one up is $178 http://www.cypress.com/?rID=37815
>
> For an over view of PSoC-! products go to: http://www.cypress.com/?id=1573&source=productshome
>
> You'll need to download (free) PSoC Designer and PSoC Programmer.
>
> I have only experimented with PSoC Designer,but it looks like you can build a mixer, have buttons that control Talk-Back, send signals to multiple outputs etc. All on one chip. Also the chips that are used on the $40 kit are 28-pin DIPs so checking them out on a solderless breadboard is also doable. (There is a small solderless bread board on each development kit plus an LCD.)
>
>
> I plan to order one of these when I get settled into new digs. The price is better than any FPGA development/evaluation kit I've seen.and the PSoC Designer software is easy to start with. I'd be working on it now, but my workhorse computer is in storage awaiting my move.

Huh, I never even thought of the PSoC. I did a project once with one
about 8 years ago.

A quick search even brings up an app note with a mixer project:
http://www.cypress.com/?rID=2925

This might merit a bit more research...

Josh
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Re: [EE] Audio Processing Project

John Ferrell
In reply to this post by John Gardner
I am unable to answer that! I may still have the package, I will look. I
think they had a Staples price tag of $19.95 but I bought them from a
discounter for about half that. They came in a rounded case but
unfortunately it was too much of a hassle to stuff them back in on a
regular basis. They are definitely not the expensive variety!
On 1/7/2013 11:59 AM, John Gardner wrote:
> John -
>
> Which Logitech earbuds are you using?
>
>   thanks, Jack

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Re: [EE] Audio Processing Project

Josh Koffman
In reply to this post by Josh Koffman
On Mon, Jan 7, 2013 at 10:46 PM, Josh Koffman <[hidden email]> wrote:
> A quick search even brings up an app note with a mixer project:
> http://www.cypress.com/?rID=2925
>
> This might merit a bit more research...

I should add that after a few minutes of digging on their website, I'm
struck by how horribly it has been designed. If you try to drill down
far enough, it ends up searching itself, meaning that the results you
want are mixed in with other semi-relevant mentions. I'm trying to get
a list of all their development programmers and debuggers. I can't
seem to get the website to display that, only to do a search for them
all. Disappointing and very frustrating.

Josh
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Re: [EE] Audio Processing Project

Josh Koffman
In reply to this post by Dwayne Reid
Hi Dwayne,

Comments within!

On Mon, Jan 7, 2013 at 7:26 AM, Dwayne Reid <[hidden email]> wrote:
> What you describe is something that I do regularly.  One of my hobby
> jobs is doing live audio (at our local football stadium) as well as
> doing RF (wireless mics & wireless intercom) *and* production
> intercom for both live TV broadcasts and large live events.  For
> example, the last large Intercom job that I did (late last summer)
> was for the film crew doing a 3D movie with the rock band Metallica -
> that was an RTS Adam digital-matrix system with just shy of 100 users
> on wired and wireless headsets plus an additional 45-50 users on two
> channels of half-duplex 2-way radio on something like 18 channels of comm.

My intercom systems aren't usually that large, unless there's a film
crew (broadcast or DVD) present. I'm lucky in that it's usually only
one channel, simple Clearcom partyline.

> Something that both myself and my users find very important is the
> concept of spacial separation when monitoring multiple channels of
> comm.  One of my buddies does audio for live broadcast TV - he often
> sets up several small (Fostex) speakers above and in front of him
> (top left and right corners of the room) as well as at his feet and
> behind him.  This lets him identify which channel of comm
> instructions are coming from - which lets him decide what to
> ignore.  He can't wear a headset when he is mixing live audio, which
> makes the little comm speakers vitally important for him to do a good job.

I do something similar, but on a smaller scale. In my right ear is an
in-ear monitor. It's custom molded to my ear, so blocks external
sound. It's fed from the audio system. In my left ear I wear a
filtered earplug to drop the noise level down to something my ears can
handle safely, then my intercom headset over that. If I've got my work
kit with me, I use my Sennheiser headset. Radio is just a speaker mic
held close to my ear before the show, and I usually give up once we
start as I'm unlikely to hear it. I can tell when something said comes
from the intercom or through the in-ear system based on which ear it
appears in.

> I regularly monitor 2 or 3 audio sources when I'm in front of my
> intercom panel at the stadium - a walkie, the intercom headset and
> program audio.  But I cheat - I wear an IFB earbud from my 2-way
> radio in my left ear, then have the intercom headset over top of that
> ear.  My right ear is either open (so that I can talk with people
> coming into the audio booth) or has one side of Sony 7506 headphones
> over it with program audio and/or monitor audio from the Wireless Mic
> receiver racks.  Both headsets get tossed when I have to go run and
> deal with a problem but the radio earbud stays in my left ear.

Thankfully I don't often have to wander. When I do, my in-ears are
usually fed wirelessly. My intercom has to come off though. I'm
working on a short range wireless solution so that I'm not dragging
any wires, but that's on hold for the moment.

> Can I suggest that you try using an IFB earbud in your ear for your
> 2-way radio?  You might be pleasantly surprised at how well it
> works.  The earbuds that I use come from Audio Implements (USA) - 125
> Ohm clarifiers with an air-tube to an accordion-style bud.  Audio
> from the intercom headset speaker has no problem getting past the
> earbud into my ear.  For what its worth, I'm using a Beyer-Dynamic
> DT-108 single-muff headset when I'm sitting at that intercom panel.

I find that I have to keep a filtered ear plug in my ear, mainly to
knock down crowd noise, but also to keep the intercom from damaging my
ear. Often someone will key in at an inopportune moment and their mic
will pick up a lot of noise. I'd be hesitant to take that part of the
equation out.

> For Motorola radios, at least, you can get speaker-mics that have a
> 3.5mm earphone jack.  That works well with the 125R Audio Implements
> IFB earbuds.  I would assume that Kenwood and Icom (and other 2-way
> portable radios) have similar speaker-mics available.  I mostly work
> with Motorola HT-750 radios.

I usually use the same radios, and those are the speaker mics that I
went through rather quickly. It seems that the earphone jack went
intermittent rather quickly, which is a huge hassle. We only carry so
many spares, so I ran out of them quickly too.

> If you find the earbud to be too uncomfortable for long periods of
> time, I've recently started using a small headset instead of the
> earbud.  Unfortunately, I don't recall the names (manufacturer and
> model) of the unit - but I can find out.  Its small enough that the
> Beyer headset fits right over top of it.  This headset replaces both
> the speaker-mic and IFB earpiece.  I used it for the first time last
> season and quite like it so far.

I'd be interested to know more about what you're using, if you get the chance.

> You can try the mixer approach - I've got a small PCB that mixes 4
> in-coming mono signals into a stereo output that I could send to you
> (if I can find them - they were for Broadcast Talent boxes that I
> built more than 20 years ago).  These cards have individual dip
> controls as well as pan controls - the dip controls dim each incoming
> audio channel by an adjustable amount when that channel's dim control
> signal is active.  The card runs from a single +24V supply but will
> probably work down to 12V.  It uses TL072 and TL074 op-amps, which
> limits how low the supply voltage can be.

Interesting. What activated the dip circuit in its original application?

> I hope this helps and I'd love to hear more about what you do.

Everything helps! I tend to focus mainly on lighting, but I also do
video, and general design.

Josh
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Re: [EE] Audio Processing Project

John Ferrell
In reply to this post by Josh Koffman
I consider the Wave Shield to be a learning tool. I doubt that I will
find as serious use for it.
It takes a while to learn to use hearing aids. They are seldom
comfortable and a useless encumberence for a matter of days to weeks.
Fortunately if one persists, the brain will figure out what it can do
with them. People who don't wear them all the time never give their
brains a chance to adapt.  In my case the lows just turn everything to
mush. I can tune the church audio systems up to where us old folks can
hear pretty good but the fellow that takes care of the equipment on a
regular basis says it sounds terrible! Unfortunately, Neither Mackie or
Behrenger make miniature modules...
I think I have a couple of stereo audio chips in stock to try first. I
am undecided about mic's, I may need to wear a ball cap for testing.
When I passed my 70 th birthday I decided to abandon convention and
dress comfortably. Cargo pants/shorts are the rule, not the exception.
So much to do and so little time left to do it!

On 1/7/2013 10:37 PM, Josh Koffman wrote:

> On Mon, Jan 7, 2013 at 11:47 AM, John Ferrell <[hidden email]> wrote:
>> I have been studying DSP for quiet a while now with little success. I
>> need to do a little lab work if I am ever going to grasp the basics. In
>> my search for usable hardware I recently found a setup that allows
>> signal access to the interface between an AD and the DAC. It is intended
>> to be used with the Arduino Uno but should be adaptable to any
>> interface. It is available from ladyada.net as a kit for about $22.  I
>> have seen it called "audio Shield" and "wave Shield".  I have mine built
>> but not yet tested due to personal ADHD & other distractions. It would
>> be best for one to get the specs & info from LadyAda.
> I found the Wave Shield. Seems interesting for audio output, but I'm
> not sure it would be able to support what I'm looking for. I will keep
> investigating though!
>
> I have found a guitar stompbox project with a small DSP in it. It
> seems interesting but it (and a few others like it) seems to be
> limited to usually one in and one out.
>
>> I wear hearing aids which are expensive and not really as good as they
>> could be. I ordered Logitec earbuds for my laptop so I could watch the
>> Videos without disturbing others. I am amazed at how much better I hear
>> that way.  Quality Earbuds beat $4000.00 hearing aids.  It would be nice
>> to have a multichannel equalizer included but for now I am planning a
>> simple stereo amp in my shirt pocket. Mic's probably on glass frames.
>> People don't really notice earbuds thanks to all the youth running
>> around using the...
>> BTW, hearing aids don't even try above 8 khz.
> That doesn't surprise me too much. I read that one of the main things
> we lose as our hearing diminishes is selectivity. Our ear/brain combo
> is quite good at filtering out background noise and deciding to focus
> on a specific source amidst other competing sounds. With hearing aids,
> it doesn't work as well. I would be interested to hear about how it
> goes when you do get your stereo amp -> earbuds working. If I was in
> your shoes, I start by experimenting with some non portable, stock
> equipment, just to see how it goes before you build something you can
> carry yourself.
>
> Josh

--
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That which can be destroyed by the truth should be.
P.C. HODGELL
   


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Re: [EE] Audio Processing Project

Carey Fisher - NCS
In reply to this post by Josh Koffman
Josh,
The NCS-3230 Multi-Rx <http://www.ncsradio.com/m_rx.html> offers the
ability, not only to select left/right ear for any number of the 6 radios
(audio sources) but in the "spatial" mode, the two speakers are used to
spread out the audio from 6 radios from left to right giving apparent
spatial separation to the 6 radios for easy identification of which radio
the operator is hearing.  Diagram is
here.<http://www.ncsradio.com/images/m_rx/spatial.jpg>
The effect is really pronounced with a stereo headset.  All this is done
with opamp mixers and a few 4053 switches (and, of course, a PIC :-)

73, WB4HXE

On Mon, Jan 7, 2013 at 10:04 PM, Josh Koffman <[hidden email]> wrote:

> On Sun, Jan 6, 2013 at 11:34 PM, Carey Fisher <[hidden email]>
> wrote:
> > Josh,
> > Glad to see you're working on new projects that "stretch" you a bit. I'll
> > be glad to help you design your gadget since that's the type gadget I've
> > been working with for 10+ years.  The Left Ear/Right Ear thing is
> > implemented on one of our ham products and it's pretty easy to realize
> the
> > functionality and flexibility without going the DSP route.
> > Anyway, let me know how I can help.
>
> Hi Carey,
>
> I must admit, while I immediately connected what I was doing with what
> you have done, it never even occurred to me to ask you for help!
> Whoops!
>
> Which product are you referring to? I'd love to check it out.
>
> Thanks!
>
> Josh
> --
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> completely foolproof is to underestimate the ingenuity of complete
> fools.
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678-999-3956
[hidden email]
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Re: [EE] Audio Processing Project

Josh Koffman
On Tue, Jan 8, 2013 at 4:14 PM, Carey Fisher <[hidden email]> wrote:
> The NCS-3230 Multi-Rx <http://www.ncsradio.com/m_rx.html> offers the
> ability, not only to select left/right ear for any number of the 6 radios
> (audio sources) but in the "spatial" mode, the two speakers are used to
> spread out the audio from 6 radios from left to right giving apparent
> spatial separation to the 6 radios for easy identification of which radio
> the operator is hearing.  Diagram is
> here.<http://www.ncsradio.com/images/m_rx/spatial.jpg>
> The effect is really pronounced with a stereo headset.  All this is done
> with opamp mixers and a few 4053 switches (and, of course, a PIC :-)

Hi Carey,

Ah, I completely forgot to check the ham side of the NCS site! That's
a pretty neat system! The spatial mode is very cool.

I'm still doing a bunch of reading, but the PSoC idea is gaining some
steam. It will mean a bunch of re-learning for me, but that shouldn't
be too bad as ultimately the code is fairly simple, waiting for button
presses and affecting outputs. What I like about the system is that
even though the audio stays analog, all of the gains and routing are
under digital control. I'd love to do this via a PIC, but I'd have to
use a bunch of external op-amps and digital pots. With the PSoC it'll
all built into the chip. I still need to do more research to figure
out if the chips are capable of all the routing options I want, but so
far they are quite interesting.

Any pointers to similar PSoC audio routing/control projects would be
appreciated. I've already got the app note, and I found errata for a
Circuit Cellar article that seems to be extremely similar. I haven't
see the original article yet though.

Thanks!

Josh
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