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PIC Microcontroller as a potential DSP / DDS Element

Posted 3rd November 2013 at 02:29 AM by googlyone
Updated 3rd November 2013 at 02:31 AM by googlyone

I noted that the new PIC32 series micro controllers include I2S along with the SPI interface. Well at least a few in the range do. This got me to thinking:
- A 32 bit micro using a fairly efficient RISC architecture
- With I2S in and out
- That runs at 80MHz.

I chose the PIC32MX450F256H.

Surely to god I can do something fun with this. But what?

Ultimately I will try chucking some IIR filters in here to see how they go (there is heaps of processing time available). But in the first instance I want to do a DDS. Reason being that I have more active crossovers than I have speakers (and that is saying something! - ask my long suffering wife!).

One thing that I have been on the look out for is a decent DDS synthesister for audio band that has really low distortion. My current Audio synthesiser uses the AD9952 DDS chip. OK, this runs at 400MHz, but it does use a 14bit DAC, and can be run right down into the...
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Old

Ironamp Project Video Posted

Posted 1st November 2013 at 12:56 AM by Michael Rothacher
Updated 2nd November 2013 at 05:52 PM by Michael Rothacher

Ironamp project video posted here:

https://www.youtube.com/watch?v=FZymAeaVsAg

I hope you enjoy it.

I updated the captions if you want to try Youtube's translation option - should be funny
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Old

Jig to help soldering SMD components

Posted 31st October 2013 at 10:12 PM by tauro0221

Hi,
I was searching for a jig that to help me soldering SMD components to the board but unsuccessfully was unable to find one. Specially when your are an older person with checking hands like me. So I decided if you do not find it built it. Checking my junk box found some parts that allowed me to came out with this SMD holding down jig. It worked so good for me that I decided to share it with the diyAudio members.

To fabricate it I used a 1 x 8 inches aluminum strip and bent it like a square with one leg side cut out. Drilled a hole at the end of one of the leg and installed a 2 inches screw thru the hole and used one spring and holding it with a nut to applied pressure from the tip of the screw to the other side leg of the square. I think that a picture it is better than words specially when you are not a technical writer like me.
Attached it is a picture showing the final SMD soldering holding jig.
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Old

TI marches steadily down the road to oblivion

Posted 23rd October 2013 at 12:20 AM by abraxalito

But hey, its stock is 30% up on the year!

http://www.testosteronepit.com/home/...verpriced.html

Wolf is a little bit too polite in his analysis of TI's woes - #1 is crappy strategic thinking.
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Old

Prototype stereo balanced passive filter for Ozone

Posted 14th October 2013 at 06:57 AM by abraxalito
Updated 27th November 2013 at 01:42 AM by abraxalito

Here's my first stab at an affordable yet screened passive filter using off-the-shelf inductors. Its a 17th order quasi-Chebyshev using 8 equal valued series L and 9 shunt caps achieving slightly better than 50dB rejection at 24.1kHz.

Update - this might be the first and last filter I build with these Coilcraft inductors. (If anyone's interested, the part no. is LPS6235-335). Reason being - on trying to order more, the price got hiked more than 100%. Originally these were attractive because on Taobao there was a source selling well below the manufacturer's list, but that seems to have dried up. At the list price in USD, there are other alternatives potentially better value. However none with the same inductance (3.3mH). The key feature is the Q - the Coilcrafts have a Q around 40 at 20kHz - this is very hard to beat in such a small package. As a reference, my pot-core hand-wound inductors have a Q about 160 but they're huge in comparison, so these tiny inductors are actually...
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Old

Wharfedale Dovedale cone rubber repair

Posted 10th October 2013 at 11:28 PM by hbc

After the Magisters went I started missing them. Much irrational thought later I decided that I needed some Dovedales. It may be some left over residual memory of some super 8s I had when I was young, they were very nice despite the lack of tweeter (retrospective young thought). The big Dovedale woofers look similar with the green felt, bit nervous of those strange pink domes though... Anyway, eventually "won" some with mint drivers slightly tatty boxes. Long story short the rubber had got stiff, but not yet brittle.

Sulk, got the Magnums... (must have bass now). After much research and thought, the Dovedales don't seem to be a standard size for foam, and I had got to the point of contemplating cutting away some of the cone to fit a flat foam. I was tidying up the garden when I found a 700 inner tube I had changed recently.
At this point I thought what have I got to loose, so gave it a good wash, (lots of washing up liquid applied neat), chopped out the valve...
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Old

Introducing the Ozone DAC platform

Posted 9th October 2013 at 11:51 AM by abraxalito

The time has come to talk about the overall aim of my DAC developments - a modular DAC platform for DIYers and audio systems integrators. By this word 'platform' I mean this isn't going to be presented as a single end-to-end design that you can order up from a friendly reseller. Nor is this an 'open source' design, although it is open to anyone to use or adapt with no restrictions. Rather this is a DIYer's DAC architecture a series of interconnected modules that are subsystems from which an audiophile grade DAC can be assembled.

When I say 'audiophile grade' what I mean is this is a design optimized for aural satisfaction, not for the numbers. To be even more specific, its been optimized to give the highest perceived dynamics (within the limitations of the chosen DAC chip) rather than the lowest THD+N and flattest FR. If you're looking for ODAC-type measurements, feel free to move along now That's not to say measurements have been ignored, rather they're very much in the...
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Old

Passive line level filters.

Posted 6th October 2013 at 02:27 AM by MITsound (Dedicated satellite/sub combo)

Tried out fmod high and low pass filters to feed inputs on a 300B integrated and Nait 5 , used to drive mid&treble horns, and 15" trace Elliot woofers , respectively. All mounted on large(ish) open baffle. 6db highpass @ 900hz leaves out enough bass and eq's a "hump" in the mid's response. Instead of a series cap for the highpass leg of this "filtered rca splitter", would I parallel another cap from hot to neutral to create a low pass? This is being done with 3 rca sockets in a project box per channel as I don't wish to mod the original amps and to ease cap swapping which past speaker level crossovers have proven irresistible for me to avoid revising. I do wish to maintain 1st order filtering, for the sake of fixing a couple of minor "humps" and "knees" in these drivers' responses. Bear in mind I'm very new to the electrical side of audio. Any help welcome.
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Old

Goodmans Magnum and the Valve sound...

Posted 30th September 2013 at 11:07 PM by hbc

To try to recreate the Magister experience I hooked up the Magnums to the little ECL86 amp mentioned previously. I was greeted again with enormous deep bass, but not as happy over all, a rather lumpy frequency response, and a big question, what's going on... So I hooked up my Hybrid amp and the Magnums sounded a bit more normal, but the bass was considerably reigned in, disappointingly.

I think the Magnums like being back against the wall, they seem happy there and the in room response is now quite civilised with a nice boom free sound and bass is only there when it should be.

Still confused, had the ECL86 on the bench to measure to try and find out what's up. The frequency response looks a bit rolled off to the bottom, so no help there, but the treble peak is looking quite promising, explaining the "prominent" treble. After some wriggling the little amp surrendered its output impedance, all be it with significant 50Hz artefacts.

The output...
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