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Jumping back on board the digital train - part III

Posted 1st May 2011 at 03:11 PM by abraxalito

Apart from an architecture which is attractive to program in, I also have several other demands on the checklist for the digital toys I'm going to pin my colours to. Ease of entry into the game and low cost development tools are a must.

Arduino is a phenomenon I did a little research into. Its become jolly popular over the past six years or so since its inception and I wanted to understand some of the reasons for its acceptance. One of the reasons has to be its open source nature. Another is the well written materials to get you going - they've put quite a lot of thought into the practical issues, even inventing their own vocabulary for elements in the process - 'sketches' springs to mind. If there's a weakness in what they're doing its this - its tied to Atmel as they're the vendors of the chips used. There are no second sources of the parts to my knowledge. This vendor-specific approach doesn't sit at all well with the open-source side - Atmel's architecture is unique...
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Jumping back on board the digital train - part II

Posted 30th April 2011 at 06:46 AM by abraxalito
Updated 30th April 2011 at 06:50 AM by abraxalito

When I began writing real-time code for the 68k, the price of entry into the development game was rather high. My first project was a tachometer processor which my boss was applying on a patent for: US patent 4924420. In order to develop this we purchased a hardware emulator which became my pride and joy - it cost a sum equivalent to around two months of my salary at that time. This was a considerably more expensive solution than the other commonly used development technique in those days - EPROM emulators - it did though provide a much faster development path by virtue of providing a window into the interior of the CPU as well as a history in its trace buffer of everything it had done. During the course of this and subsequent projects which also used the 68k (later we added a 68020 too) I became a confirmed devotee of the architecture. One of my nicknames in the company was 'the cycle stealer' - if someone had some 68k code that wasn't running fast enough, I'd find some way to get it...
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Posted in Digital
Views 799 Comments 6 abraxalito is offline

Jumping back on board the digital train - part I

Posted 26th April 2011 at 05:53 AM by abraxalito
Updated 30th April 2011 at 06:51 AM by abraxalito

My first brush with a micro as programmer was as a schoolboy - my maths teacher had a National Semiconductor SC/MP board with LEDs and toggle switches. It could be programmed in binary. I was hooked.

About a year later Science of Cambridge came out with adverts for their Mk14, using the same SC/MP. This though had a real hex keyboard and calculator style 8 digit 7 segment display. I ordered one almost immediately I saw the ad. Trouble is, it seemed to take an age to come. Someone joked that Clive Sinclair's approach was to gather up the cheques and when he'd got a few thousand pay someone to do the design! I dialled SoC's number so many times chasing my order that its still engrained in my memory over 30 years later: 0223 311488.

When I got to uni, it was clear my room-mate was in a league above me - he'd designed a system with a Z80. That was a real man's processor, compared to my little boy SC/MP. I felt a tad threatened by his prowess. Science of Cambridge...
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Posted in Digital
Views 817 Comments 7 abraxalito is offline

Wide-band RF filtering for mains - some interim conclusions

Posted 26th April 2011 at 05:12 AM by abraxalito
Updated 26th April 2011 at 05:16 AM by abraxalito

The 1.8mm iron wire arrived and it did indeed have a 1.2mm internal diameter which is perfect for winding small chokes. I built a second box with steel chokes in but the third box I tried with the iron wire coils. Having insulated wire means the coils are smaller and I was able to fit the second tier filter into the same box.

I wound a couple of NiZn toroids with iron wire, but not as common mode chokes. When I did the sums I found that for the currents I'm running at (under 3A total draw) the toroidal core isn't close to saturation. Hence I decided on separate inductors to gain some differential mode filtering on top of the common mode.

The next stage of development has been trying to wind multilayer iron wire air-cored chokes. For this I've had trouble finding formers which allow more than 4 layers. The reason for wanting more layers is - this makes the chokes much more lossy. Proximity effect helps concentrate the higher frequency currents only in areas...
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Posted in Mains filtering
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The final parts for the Reference DAC Case

Posted 25th April 2011 at 11:26 AM by dvb projekt

Click the image to open in full size.

On the left side

USB-Isolator from Circuits@Home

Teralink X2 USB to I2S converter (with my modification)

TDA1541A Salas shunt reg. module

+5V Salas shunt reg. module
(downlink side of USB isolator incl. +5V line of Teralink X2/ Twisted Pear WM8804 / Ultra highspeed buffer module / I2S switch)

+3,3V Salas shunt reg. module (+3,3V line of Terlink X2)

In the middle

Twisted Pear WM8804 SPDIF to I2S converter

On top the Ultra High Speed Buffer module

I2S switch

2* TDA1541A DAC module with direct input shunt mod.

On the right side

2* SSHV-Shunt module (one for each channel)

Tube-I-zator V2.0
(the remaining parts of the onboard HV-PSU are not necessary,
because of the Tube-Rectifier
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YARPS, finally some progress!

Posted 23rd April 2011 at 01:34 PM by wintermute (Wintermutes Rantings)
Updated 24th April 2011 at 01:43 AM by wintermute

So I have almost all of the parts (yeah I know) for my YARPS power supply. As part of the order I got myself a prototyping breadboard.

I've knocked up one half of the yarps power supply, ie the positive side, and hooked it up to my old model railroad transformer which has a 15V output.

Parts still to be ordered are the dual secondary 15V transformer and some 50K trim pots. However I had enough to make one side of the dual rail supply.

It didn't smoke, and the CRCRC part of the PS works very nicely Pics attached at the end.

I need to do a further test with BC560c's with different HFE's to see whether this affects the output voltage (my suspicion is that it will). I put a 36K resistor (which I had at hand) in place of the 50K pot and only got 8.6V even though spice said I should get 9.13V with that value resistor so something isn't working as per the sim, the use of a pot certainly seems to be required to get the desired voltage...
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Posted in misc
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High Voltage schematic for the Reference DAC PSU

Posted 20th April 2011 at 09:21 AM by dvb projekt

Here you could see the final schematic for the HV lines.

The two 40mA current taps are the SSHV-Shunt´s,
one for each channel on the Tube-I-zator.

Click the image to open in full size.
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ads L810 may need caps?

Posted 20th April 2011 at 02:23 AM by neptune07

i remember ads L810 sounding better years ago, but alas my hearing in not what it used to be, how i check the cap in the crossovers, what value should it measure, what replacements would compliment the speakers?
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The PSU case

Posted 17th April 2011 at 12:45 PM by dvb projekt
Updated 4th May 2011 at 02:01 PM by dvb projekt

Finally the engraved top-, front- & backplate arrived.

Click the image to open in full size.

Surely you are asking yourself, why i made a 1mm deep square around the place for the transformer... here is the answer

Click the image to open in full size.

I´ve got a perfect aluminum transformer housing and now it sits perfect without an air gap.

Now it´s time to assemble the parts.

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Posted 16th April 2011 at 07:18 PM by tube dog

re: KENWOOD L-09 amp MODS :

Have interest in mods to improve these DC mono block amps. After 32 years of service, a RECAP job of electrolytics ( 2) is in order for my pair (electroylics caps dry-out and BURST/ FAIL - and will take-out 24 output transistors and probably your speakers also ) So while the IRON IS HOT ..... I noticed the following possible mods to improve these amps' performance :
MOD #1- Replace 6 foot # 16/2 ' zip cord ' AC power cord....with 2 foot of # 8/2 ( amp pulls 1200 watts @ full power each ) note; a # 10/4 stranded copper power cable can be wired in 2 pairs ( red+black / white+green ) which eliminates DRILLING chassis opening LARGER to accomadate # 8/2, but will NET #8/2 gauge AND provide added shielding with 4 conductor spiraling ! THIS IS A NO BRAINER AND SHOULD MAKE THIS AMP BREATH a bit easier
(note : factory issue AC cord has NO ground conductor-and I would suggest NOT adding a grounded conductor to new 15 amp plug either-...
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