fohman
Posts: 14
Joined: Sun Feb 04, 2018 2:52 am

Re: Powered by XLR cable "Phantom Power" (+48V 14mA)?

Mon Feb 05, 2018 6:07 pm

I'm fine with dynamic mics only. The latency can be up to 5ms I suppose without being bothersome. The idea here would be to have a kind of small project box with an XLR in and XLR out, and three LEDs to indicated accurate pitch. You plug the SM58 into the box, then plug the box into the mixer, turn on the phantom power for that channel, put on your headphone and solo that channel on the mixer, and there you go. That is a marketable product. From the bit of research I've done (I'm no expert) it seems that having an external power supply or a battery or a rack-mount unit decreases the marketability... this is aimed for on-the-go musicians who want to do a bit of pitch practicing before they record their tracks or perform live.

What I feel that I really need is a way to find people who might want to help me complete this project for some negotiated amount of pay based on a finished product. How do I find such people? Sites like Upwork and Toptal are problematic because you have to pay up front for the time spent explaining the project to the would-be designer, and I don't want to do that. The reason I was digging around here in this forum was because I figured I might just have to do enough of my own research to present a more finalized solution to an hourly engineer on TopTal. Where do I find project-based designers and engineers?

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mline
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Location: Austria, Vienna

Re: Powered by XLR cable "Phantom Power" (+48V 14mA)?

Mon Feb 05, 2018 6:35 pm

fohman wrote:
Mon Feb 05, 2018 6:07 pm
The latency can be up to 5ms I suppose without being bothersome.
No way without DSP.
fohman wrote:
Mon Feb 05, 2018 6:07 pm
What I feel that I really need is a way to find people
I read your posts/threads and waiting for this phrase ;)
<~~>

Heater
Posts: 14278
Joined: Tue Jul 17, 2012 3:02 pm

Re: Powered by XLR cable "Phantom Power" (+48V 14mA)?

Mon Feb 05, 2018 6:45 pm

fohman,

Ah, I see, so you want us to advise on your scheme to make money. For free?

I'm inclined to tune out at this point but...
..this is aimed for on-the-go musicians who want to do a bit of pitch practicing before they record their tracks or perform live.
So basically the idea is like those guitar tuner boxes but for the human voice?

So how about forgetting the phantom power thing and just use batteries. In a stand alone box. Like those guitar tuners do?

Of course you will want to use a processor that uses a lot less power than a Pi. Perhaps an STM32 F4 or some such.
Memory in C++ is a leaky abstraction .

fohman
Posts: 14
Joined: Sun Feb 04, 2018 2:52 am

Re: Powered by XLR cable "Phantom Power" (+48V 14mA)?

Mon Feb 05, 2018 8:55 pm

Of course you will want to use a processor that uses a lot less power than a Pi. Perhaps an STM32 F4 or some such.
Would a STM32 F4 be able to do low latency audio DSP like EQ and pitch recognition and have analog read and write? About how much power would it consume?

fohman
Posts: 14
Joined: Sun Feb 04, 2018 2:52 am

Re: Powered by XLR cable "Phantom Power" (+48V 14mA)?

Mon Feb 05, 2018 9:01 pm

Heater wrote:
Mon Feb 05, 2018 6:45 pm
Ah, I see, so you want us to advise on your scheme to make money. For free?
I'll pay you to help me complete this project if you think you could do it. PM me if so...

Heater
Posts: 14278
Joined: Tue Jul 17, 2012 3:02 pm

Re: Powered by XLR cable "Phantom Power" (+48V 14mA)?

Mon Feb 05, 2018 9:04 pm

You could check the data sheets and find out:

http://www.st.com/en/microcontrollers/s ... tId=SS1577

Of course there are hundreds of other MCU/DSP chip about that might be more suitable.

I understand that companies are using the XMOS devices for audio processing to good effect:

http://www.xmos.com/products/voice
Memory in C++ is a leaky abstraction .

Heater
Posts: 14278
Joined: Tue Jul 17, 2012 3:02 pm

Re: Powered by XLR cable "Phantom Power" (+48V 14mA)?

Mon Feb 05, 2018 9:14 pm

fohman,
I'll pay you to help me complete this project if you think you could do it.
Thanks for the offer.

I doubt that I'm the guy for the job. I have done audio DSP before, using FPGAs, but it's not really my thing.

I'm too busy just now anyway.
Memory in C++ is a leaky abstraction .

PiGraham
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Joined: Fri Jun 07, 2013 12:37 pm
Location: Waterlooville

Re: Powered by XLR cable "Phantom Power" (+48V 14mA)?

Tue Feb 06, 2018 9:31 am

fohman wrote:
Mon Feb 05, 2018 6:07 pm

What I feel that I really need is a way to find people who might want to help me complete this project for some negotiated amount of pay based on a finished product. How do I find such people? Sites like Upwork and Toptal are problematic because you have to pay up front for the time spent explaining the project to the would-be designer, and I don't want to do that. The reason I was digging around here in this forum was because I figured I might just have to do enough of my own research to present a more finalized solution to an hourly engineer on TopTal. Where do I find project-based designers and engineers?
You want free consultancy. Well you have had some. The fact that the advice you got isn't what you hoped for might actually mean something.

PiGraham
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Joined: Fri Jun 07, 2013 12:37 pm
Location: Waterlooville

Re: Powered by XLR cable "Phantom Power" (+48V 14mA)?

Tue Feb 06, 2018 9:36 am

Heater wrote:
Mon Feb 05, 2018 6:45 pm
fohman,

Ah, I see, so you want us to advise on your scheme to make money. For free?

I'm inclined to tune out at this point but...
..this is aimed for on-the-go musicians who want to do a bit of pitch practicing before they record their tracks or perform live.
So basically the idea is like those guitar tuner boxes but for the human voice?

So how about forgetting the phantom power thing and just use batteries. In a stand alone box. Like those guitar tuners do?

Of course you will want to use a processor that uses a lot less power than a Pi. Perhaps an STM32 F4 or some such.
That is THE question.

And a tuning indicator doesn't need <5ms latency.

You would think that someone would make such a thing.

Roland VT-12 Vocal Trainer
Vocal Pitch Monitor App

As for a singer using their own mini effects in their mic lead won't that annoy most sound engineers and give very variable results?

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
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Re: Powered by XLR cable "Phantom Power" (+48V 14mA)?

Tue Feb 06, 2018 10:27 am

As I suggested earlier, T off the audio signal into your device and nick some phantom power. Do not convert to digital and back again to forward on to the desk. You'll save a bunch of power and remove all latency concerns. The function of measuring tuning accuracy can then be a much simpler job (analogue electronics possibly), and you may be looking at something like an Arduino instead of a full processor to do the final analysis and display.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
I'm not interested in doing contracts for bespoke functionality - please don't ask.

PiGraham
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Location: Waterlooville

Re: Powered by XLR cable "Phantom Power" (+48V 14mA)?

Tue Feb 06, 2018 11:09 am

6by9 wrote:
Tue Feb 06, 2018 10:27 am
As I suggested earlier, T off the audio signal into your device and nick some phantom power. Do not convert to digital and back again to forward on to the desk. You'll save a bunch of power and remove all latency concerns. The function of measuring tuning accuracy can then be a much simpler job (analogue electronics possibly), and you may be looking at something like an Arduino instead of a full processor to do the final analysis and display.
For some reason fohman wants to combine some audio processing with the vocal tuner, hence in-line AD-DA and low latency. It doesn't seem a good fit with the practice tuner aspect. Maybe there is an unstated desire to add auto-tune. There is a logic there to making it a personal mic add-on. The singer might be able to correct poor pitch without others realising they are using an auto tune (far fetched). That would have to discretely plug into the existing mic lead and run on phantom power. It would explain why it's not done in a rack mount processor.

I that's the real agenda why no go the whole hog and include an mp3 player to allow the bad singer to mime to top quality vocals?

CheatMike ®

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