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D1080 MkII 08 actives - under the hood

Posted 14th December 2010 at 12:46 PM by abraxalito
Updated 5th March 2012 at 03:55 AM by abraxalito

I've been spending my free time these past couple of days reverse engineering these speakers, as a prelude to devising the mods. The first stage in doing that is to photograph the PCBs both sides and have both images up on the screen at once, the underside is flipped horizontally so its as though I'm looking through the board. I then annotate the components by hand with the mouse drawing tool. Sometimes I'll write the values in this way too, other times just paste text for the value next to the component. Most of the time though I'm too lazy to add any annotation.

Here's the result for the volume/tone control PCB - one of two PCBs in the design. There are two quad opamps, TL084s - they're marked up in magenta. Interestingly there's no tone control circuitry as such, the bass and treble controls just act as volume to the woofer and tweeter respectively! I've never seen tone controls implemented in this way before...
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From W Mclean

Posted 12th December 2010 at 03:37 AM by wmclean

I have an old pair of MB Quartz 850S speakers that i gave to my daughter. One of the speakers has a blown tweeter. Where can i buy a replacement tweeter ? I believe there 1" titanium dome tweeters. Thank you for any help in advance.
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How low can you go in active speakers?

Posted 12th December 2010 at 12:54 AM by abraxalito
Updated 5th March 2012 at 03:57 AM by abraxalito

On one of my regular pilgrimages to the computer plaza a couple of days ago, I noticed these little puppies. The price apparently was a shade over $80 the pair so I was indeed very curious. A quick peek around the back showed they were not using a standard speaker cable, rather a custom 4-way umbilical between the two boxes. Whenever I see this, my heart misses a beat because what floats my boat is genuine active speakers, not just powered ones which still sport passive crossovers.

Click the image to open in full size.

Not wishing to ask to disassemble the powered unit on the spot (and doubtless be turned down) I went back home to do some online research. I was pleased to discover these were indeed true actives, and what's more they're powered by TDA8947 chip amps. I'd not come across this part before but its cool at least on paper because its 4 channels in one package - they're using two...
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Old

Subwoofers...

Posted 11th December 2010 at 08:53 PM by chris661

Well, here we are again (unless, of course, you're here by mistake).

After much contemplation, I've decided that my subwoofer needs upgrading. Currently, it's a pair of MCM DVC woofers (you will probably have seen me going on and on about them), which, while good for the price, aren't that good compared to my Fostexes (which, now fully broken in, are fantastic). They're given ~100w between them, with a Linkwitz Transform to get them down low. Good for normal listening levels, but quickly run out of displacement below 40Hz at anything about normal listening levels.

So, a new bass system is in order. I've always wanted to try a Tapped Horn, so I've chosen a design originally intended for an Exodus 6.5" midbass, that's shown to work pretty well with the Tang Band 6.5" subwoofer... All the way down to 25Hz. Those will be fed by an amp1-b from 41Hz, with a +/-34V supply. Should be more than 100w per side. Ca suffice, especially for a bedroom system ...
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First test post to blog - general audio gear

Posted 11th December 2010 at 02:48 AM by googlyone

Couple of projects of mine - not sure if the photos will load OK.

First is a pair of 25Hz horn subs I used to have - used 18inch p.audio drivers, placed facing one another along a wall to form part of the horn and achieve adequate mouth area for the 25Hz cutoff.

Efficiency was well over 100dB/w/m.

Second photo is one of my digital crossovers I built, 4 way AD1940 based audio DSP with an AD1939 CODEC as A/D and D/A. Works a treat, and makes setting speakers up a snip, as can program in delays, HPF / LPF, parametric etc.

Also included my subwoofer couch - I built this as a challenge from a colleague of mine. The carcass of the couch forms an 800 litre enclosure, the ports exit at the back of the headrest three of them, and I used four fifteen inch drivers. It is tuned to 19Hz, and achieves a -3dB point below 20Hz.
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krell

Posted 6th December 2010 at 04:10 AM by ihaveKRELLparts

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Software

Posted 29th November 2010 at 08:36 PM by klewis
Updated 5th January 2011 at 11:25 PM by klewis

Pcb software

Sprint-Layout

Audio analysis software;

Virtins MI http://www.virtins.com/
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Old

Opamps for dc servo

Posted 29th November 2010 at 03:57 PM by klewis

For servo duty, there are some newer TI offerings which look worthy. That is assuming that lowish noise and bias currents are desirable (they would be to me if I were seeking out a servo amp). OPAX141, OPAX376 and OPAX209. The latter is bipolar but has lower noise than any JFET I've seen coupled with commendably low input bias current for a bipolar.
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Squeezebox SB3 update 3

Posted 26th November 2010 at 10:54 AM by audi0

Hi guy's I haven't added to this blog for a couple of weeks as progress has been a little slow.

I have however had the front and back plates cnc milled and I have drilled and cut the connector holes in the back plate. The plates will now be cleaned up, acid etched and clear anodized.
The timber sides are cut and the threaded bushes are in, I still need to rabbet the top and bottom edges for the covers, but the enclosure is taking shape. I'm not sure about the perforated ally for a top? What do you guy's reckon?

A redesign has slowed the power supply board a little, I now have the board (thanks to Neville @ Sesame who etched and drilled it for me) all the components are ready to stuff, so the next blog will update how the power supply performs
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Teac TD-X250i Service Manual

Posted 25th November 2010 at 10:18 AM by Andrew Burn

Hello,
Please can anyone give information about where to obtain a service manual or schematic diagram for a Teac TD-X250i CD/iPod micro hifi. Information seems to be un-available as this model was apparently made solely for the Currys/Dixons retail chain.

Any help would be greatly appriciated.
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