# Looking for DSP family for hobbyist audio signal processing

#### pleriche

Joined Oct 29, 2017
16
There are plenty of microcontroller families with low cost of entry - AVR/Arduino, MSP430, PIC etc - but what is there in the DSP world?

I was recently fitted with behind-the-ear hearing aids to correct for loss of sensitivity in the kHz range, but I can't get the benefit of them when using headphones. I would therefore like to build a headphone amplifier giving the same correction as my hearing aids and it seems to me that DSP might be a good way to go. (This must be what my hearing aids contain.) Specifically, I need a DSP family capable of implementing a stereo digital filter with a customisable response up to 10kHz, and with a free IDE and programmable with a PicKit 2, BusPirate or AVR as ISP. Is there such a thing? Preferably with not too steep a learning curve?

#### shteii01

Joined Feb 19, 2010
4,644
Read application notes. If they have audio dsp note, then put them on the list for consideration.

#### pleriche

Joined Oct 29, 2017
16
Read application notes. If they have audio dsp note, then put them on the list for consideration.
Once I know which manufacturers make DSPs with accessible cost of entry, of course, I can look at the application notes, but I think you're putting the cart before the horse!

#### BobTPH

Joined Jun 5, 2013
2,396
The dsPIC family of PICs are the same cpu as the 16 bit 24F series plus DSP features. I think they would be capable of audio filtering. They also have 12 bit DACs, which, with oversampling, could handle the audio in, and PWM capable of putting oit decent audio.

Check them pit at the Microchip site.

Bob

#### shteii01

Joined Feb 19, 2010
4,644
Once I know which manufacturers make DSPs with accessible cost of entry, of course, I can look at the application notes, but I think you're putting the cart before the horse!
You said avr/Arduino. Microchip bought atmel. If you look for atmel avr chips, you go to microchip website and start reading.

Msp430 is ti. You go to ti website and start reading.

Pic is microchip...

Microchip has parametric search or some such.

Ti has some kind of guided search to help visitors to find products that fit their needs.

#### KeithWalker

Joined Jul 10, 2017
911
There are plenty of microcontroller families with low cost of entry - AVR/Arduino, MSP430, PIC etc - but what is there in the DSP world?

I was recently fitted with behind-the-ear hearing aids to correct for loss of sensitivity in the kHz range, but I can't get the benefit of them when using headphones. I would therefore like to build a headphone amplifier giving the same correction as my hearing aids and it seems to me that DSP might be a good way to go. (This must be what my hearing aids contain.) Specifically, I need a DSP family capable of implementing a stereo digital filter with a customisable response up to 10kHz, and with a free IDE and programmable with a PicKit 2, BusPirate or AVR as ISP. Is there such a thing? Preferably with not too steep a learning curve?
I have the exact same problem and I love music. I solved it a different way which was fairly simple and inexpensive. I still use my old analog audio amplifier with real speakers for listening to the radio, TV, CDs and Vinyl. I use headphones for good music.
I purchased a ten channel stereo equalizer circuit board from AliExpress and mounted it in a small cabinet along with a power switch, fuse and a couple of 120VAC to 5VDC power modules. There are RCA audio connectors and a stereo headphone jack on the back. The whole project cost less than $30,00 Canadian and went together really easily. The equalizer has enough range to compensate for my hearing loss and has brought back to me the ability to enjoy music as it is supposed to sound. It also works very well to compensate the compressed sound tracks on Netflix movies. #### Attachments • 120.5 KB Views: 8 Last edited: Thread Starter #### pleriche Joined Oct 29, 2017 16 I have the exact same problem and I love music. I solved it a different way which was fairly simple and inexpensive. I still use my old analog audio amplifier with real speakers for listening to the radio, TV, CDs and Vinyl. I use headphones for good music. I purchased a ten channel stereo equalizer circuit board from AliExpress and mounted it in a small cabinet along with a power switch, fuse and a couple of 120VAC to 5VDC power modules. There are RCA audio connectors and a stereo headphone jack on the back. The whole project cost less than$30,00 Canadian and went together really easily.
The equalizer has enough range to compensate for my hearing loss and has brought back to me the ability to enjoy music as it is supposed to sound. It also works very well to compensate the compressed sound tracks on Netflix movies.
Hi Keith - That's really interesting, and cheap enough that I might get one just for the fun of trying it. Do you know how much current it takes? But what I'd really like is something I could make portable and hence battery powered.

#### KeithWalker

Joined Jul 10, 2017
911
Hi Keith - That's really interesting, and cheap enough that I might get one just for the fun of trying it. Do you know how much current it takes? But what I'd really like is something I could make portable and hence battery powered.
Hi, I didn't measure the current but I am sure it is not very much. It would be possible to power it with a single Li-po cell with a dual switching supply. It needs minimum of +5V_0_-5V supply.

#### jjw

Joined Dec 24, 2013
540
Once I know which manufacturers make DSPs with accessible cost of entry, of course, I can look at the application notes, but I think you're putting the cart before the horse!
ARM Cortex M4 general purpose MCU has also DSP instructions.
There are development boards from several manufacturers. Look at https://eu.mouser.com/Embedded-Solutions/Engineering-Tools/Embedded-Processor-Development-Kits/Development-Boards-Kits-ARM/_/N-cxd2t?keyword=Cortex-M&No=125

and Teensy: https://www.pjrc.com/store/teensy36_pins.html

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#### pleriche

Joined Oct 29, 2017
16
Thank you jjy - in fact I have a Teensy 3.2 which I used a while back for synthesising sounds such wind chimes and peals of bells in arbitrary tonalities, but since it ran out of steam with more than 2 or 3 simultaneous mono sounds at 8,000 samples/sec I'd discounted it. I also have the sound adapter, which didn't seem to be useful for that project as I was only doing 8 bit audio. But maybe I should look at it again, at least to familiarise myself with how you build a digital filter. I'll then be in a much better position to decide how much more power I might actually need.

#### jjw

Joined Dec 24, 2013
540
Thank you jjy - in fact I have a Teensy 3.2 which I used a while back for synthesising sounds such wind chimes and peals of bells in arbitrary tonalities, but since it ran out of steam with more than 2 or 3 simultaneous mono sounds at 8,000 samples/sec I'd discounted it. I also have the sound adapter, which didn't seem to be useful for that project as I was only doing 8 bit audio. But maybe I should look at it again, at least to familiarise myself with how you build a digital filter. I'll then be in a much better position to decide how much more power I might actually need.
Teensy audio adapter has a 5 band equalizer, need only setup with a mcu.

From the forum:
"You might also want to try the built-in-EQ of the codec hardware in the Teensy audio board:

https://www.pjrc.com/teensy/gui/?inf...ontrolSGTL5000

This gives you a five-band-EQ without additional load on the Teensy processor itself.
And its quite easy to use, see the GUI under the link above.
It performs quite well, although it seems not many people use it. My experience is good with that EQ.

Have fun with the Teensy,

Frank

P.S.: or you try the 7-band parametric equalizer which is basically the same as a cascade of 7 biquad IIRs, but there you would have to provide the filter coefficients by yourself. Probably best to use some program to calculate them, eg. Iowa Hills IIR Filter designer, very good"

#### pleriche

Joined Oct 29, 2017
16
Have fun with the Teensy,

Frank
Some great leads there to follow up in the coming weeks - thanks Frank!

#### pleriche

Joined Oct 29, 2017
16
Hi, I didn't measure the current but I am sure it is not very much. It would be possible to power it with a single Li-po cell with a dual switching supply. It needs minimum of +5V_0_-5V supply.
My 10 band equaliser has just arrived (less than a week from China, and with the AliExpress introductory bonus, laughably cheap!)

For the sake of anyone following this thread in years to come, in an initial lash-up it seems to do the job pretty well though I need to feed the output into a headphone amp (which I don't instantly have to hand) to test it properly. To answer my own question, running it off 2 9VNiMH batteries (discarded microphone batteries) it takes 23mA (from each), so that would be a viable power source for portable use, if a bit bulky for carrying in a pocket. An alternative power source would be a LiPo with 5V boost converter and MAX660 voltage inverter for the negative rail.

#### pleriche

Joined Oct 29, 2017
16
To follow-up and for KeithWalker I've now successfully built my own version on a 6x6cm PCB using 2 TL084 quad opamps and a LM4880 headphone amp. It has 3 equalisation centre frequencies and runs off a single 5V supply.

If anyone is interested in building their own or modifying the design for their own purposes, follow me at https://www.instructables.com/member/p_leriche/ where I will be publishing full details in due course (don't hold your breath though), including Eagle files and an Excel spreadsheet for selecting component values for specific band frequencies.

#### Attachments

• 1.8 MB Views: 5

Joined Mar 10, 2018
4,057
PSOC 5LP family. DSP component, component being an onchip resource. See
attached catalog of onchip resources. Filter can do IIR, FIR, BiQuad. Example -

IDE and Compiler free, board is $10 for average design. Notice very few of the available onchip resources used (right hand window). Configuration for the filter - Regards, Dana. #### Attachments • 178.5 KB Views: 1 #### JohnInTX Joined Jun 26, 2012 4,087 To follow-up and for KeithWalker I've now successfully built my own version on a 6x6cm PCB using 2 TL084 quad opamps and a LM4880 headphone amp. It has 3 equalisation centre frequencies and runs off a single 5V supply. If anyone is interested in building their own or modifying the design for their own purposes, follow me at https://www.instructables.com/member/p_leriche/ where I will be publishing full details in due course (don't hold your breath though), including Eagle files and an Excel spreadsheet for selecting component values for specific band frequencies. Nicely done! When you get the package together consider publishing it here in the Completed Projects section, too. We love that. Plus, I have old ears too Thread Starter #### pleriche Joined Oct 29, 2017 16 PSOC 5LP family. DSP component, component being an onchip resource. See attached catalog of onchip resources. Filter can do IIR, FIR, BiQuad. Example - View attachment 191277 IDE and Compiler free, board is$ 10 for average design.

Notice very few of the available onchip resources used (right hand window).

Configuration for the filter -

View attachment 191278

Regards, Dana.
Thanks Dana, that looks very interesting. Bookmarked for checking out later.