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Digital Input Modules Power & Signal Schematic

Posted 8th May 2011 at 04:48 PM by dvb projekt

On request the section of my digital input modules

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Another Gain Clone

Posted 8th May 2011 at 02:07 AM by alexcp (My DIY projects)
Updated 7th July 2011 at 12:28 AM by alexcp (Added photos)

Unsatisfied with the sound of my gainclone amplifier, I re-used the enclosure and the power supply for a gainclone along the lines suggested by Bob Cordell, whose implementation of an LM3886 based amp was praised by at least one member on the NJ audio society.

I skipped both the Klever Klipper and the toroidal air core output inductor, and kept only 10,000 uF per rail in the PSU. The schematic can be found in Chapter 27 of Cordell's Designing Audio Power Amplifiers. The PCB was designed to re-use the existing mounting holes of the ChipAmp's PCB.

The result? Better than with a plain vanilla chip amp, but still not good enough for music. Perhaps I should not have limited myself to re-use of the PSU et al. but should have taken all the details of my implementation seriously.
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Velleman K4040 mods

Posted 8th May 2011 at 12:32 AM by alexcp (My DIY projects)
Updated 4th May 2014 at 12:59 AM by alexcp

I posted some time ago a note about my Velleman K4040 amplifier. The sound of the amp as built from the kit was unremarkable and definitely not in line with the price. Lacking experience with tubes, I was looking for some time for well documented mods to the kit.

I found two 2006 posts here and here and implemented them rather directly. The only difference is that I used IXCP10M45S instead of a pair of J508 current sources in each channel and replaced the 1N5408 rectifiers with UF5408 instead of adding noise suppressing capacitors in parallel to them.

The mods did not leave much of the original Velleman design in place; the result, however, is a remarkable improvement in sound!

However, two problems remain: (1) I got hum that wasn't present before the mods; and (2) a two-year old running around doesn't get along with eight hot, attractively glowing tubes. The project is shelved until a better time.

For future reference: The toroidal...
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Posted in Tube power amps
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Jumping back on board the digital train - part IV

Posted 6th May 2011 at 03:52 AM by abraxalito

Where is all this going I hear you ask? What's his point? Well to tell the truth I don't hear anyone asking this - the comments sections are remarkably empty save for jkeny egging me on

So here's my point, and its a single word: convergence. Convergence is coming to digital architectures - indeed its already here, just the majority of people have yet to notice.

The diverse marketplace for embedded processors is rather similar to the market for home computers in the early to mid-1980s. It was hard to make the choice - Acorn, Sinclair, Apple, Commodore, Atari, Amstrad, Dragon? Then convergence arrived in the shape of the IBM PC and those brands (with the exception of Apple) were relegated to the history books.

It took quite a while after the 1983 arrival of the PC for this to occur. I had an Acorn Atom which I built from a kit in the long summer vacation after I graduated, and I didn't make the jump into PC-land until the early 1990s. It wasn't...
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Posted in Digital
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External PSU finished

Posted 2nd May 2011 at 07:02 PM by dvb projekt

After a long weekend , i have finished the external PSU!

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Here are some internal view pictures.

On the upper side the two +/- Power Supply Modules,
in the lower left corner the 10H choke on amorphous cores from AE-Europe,
in the middle the 1st cap (3,9F Mundorf supreme silver in oil) of the HV-PSU line,
in the lower right corner the Power Switch Module with onboard solid state relays.

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And some close-up pictures

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Jumping back on board the digital train - part III

Posted 1st May 2011 at 02:11 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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Posted in Digital
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Jumping back on board the digital train - part II

Posted 30th April 2011 at 05:46 AM by abraxalito
Updated 30th April 2011 at 05:50 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
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Jumping back on board the digital train - part I

Posted 26th April 2011 at 04:53 AM by abraxalito
Updated 30th April 2011 at 05:51 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
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Wide-band RF filtering for mains - some interim conclusions

Posted 26th April 2011 at 04:12 AM by abraxalito
Updated 26th April 2011 at 04:16 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 10:26 AM by dvb projekt

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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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