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Tech note: Balanced lines-1

Posted 13th January 2010 at 06:54 PM by jan.didden
Updated 13th January 2010 at 06:57 PM by jan.didden

Why would one use balanced interconnects, and how can we make them work well?

Balanced lines came about at a time where very long signal lines were coming in use for telephone and later for large audio performance venues. If you use a single screened line for your signal, and the line is long, the ground current through the screen causes a voltage between the ground points of the cable ends. Since the signal send out (and received) is the difference between the voltage on the signal wire and the ground wire, the unwanted signal (noise, hum) is effectively added to the wanted (music) signal. We don’t want that.

The trick is to use TWO signal lines in parallel. You send the signal over the two lines in such a way that the signal you want to transmit is the difference between the signals on these two wires, and then at the receiving end you have an amp that reacts to the difference between the two lines, so your signal at the far end is the difference between...
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CSS bias

Posted 12th January 2010 at 04:32 PM by DougL
Updated 13th January 2010 at 09:52 PM by DougL

I found a great comment in post post #10.

Very few details were given, but it caught my imagination.
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Confessions of an audio DIYer

Posted 11th January 2010 at 01:58 AM by Damon Hill

Current projects:

P. Millett's Sound Card Interface

Long term projects


I'm a DIYer, and that means for me a lot of test equipment. I bought a lot of Heathkit gear in my day and still have most of it, supplemented with a Hewlett Packard oscilloscope and Tektronix audio distortion test set, but the Heathkit gear is still my mainstay.

Since an Audio Precision test set seems to be forever out of my reach, I'm taking a crack at a sound card based analyzer, as above.


My main amplifier is based on Marshall Leach's design, version 4.4, with a massive power supply (about 1/4 farad!) on a dual mono chassis. I've been building his amplifiers since the late 70's with excellent success, to the point that I've neglected making a serious effort to build anything else.

At the moment I'm considering Jan Didden's design using Hawksford error correction...
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Finaly did some DIYing again

Posted 10th January 2010 at 10:26 AM by wintermute (Wintermutes Rantings)

With the Silly season and general busier than normal work shedule (working a lot of weekend) I haven't made any progress on anything much at all lately.

Last week my Mother In Law put my 2 YO daughter in the bathroom basin. It was only attached with what looked like tile grout. It didn't hold... Today My Father in law assisted to glue it back in with some marine polyurethane adhesive/sealant . Hopefully it holds! This stuff was similar to the glue I had bought a while back to seal my 3 ways (see the leaks are stealing my bass blog entry) but hadn't got around to using yet. It seems perfect, it remains flexible, seals, sticks incredibly well apparently, and even claims to dampen sound and vibrations . As the tube was open, I pulled one of the Three ways out and basically sealed every interior joint. I then put a slight 45 degree chamfer on the back of the woofer cutout and glued in the front baffle (it has always only been screwed and didn't even have a gasket). ...
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A Decision

Posted 8th January 2010 at 08:40 PM by tomtt
Updated 14th October 2011 at 11:45 AM by tomtt


"The best way to control the opposition is to lead it ourselves."
- Vladimir Ilyich Lenin

"First they ignore you, then they laugh at you, then they fight you, then you win.
- Gandhi
in light of these quotes, from Famous Men,

I no longer care what my psychiatrist says.

I'm glad I'm a Jedi


Click the image to open in full size.



ImageShack Album - 36 images

Imageshack - dscn95063168587.jpg

ImageShack Album - 36 images

ImageShack Album - 36 images

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The white van is in Tucson

Posted 8th January 2010 at 05:27 PM by relder (Rob's active 3way with transconductance chipamps build blog)

I haven't been propositioned for white van speakers for several years (outside of a home depot.) But a guy I know was taken in this last week after leaving the ATM.

Why always a white van, why not mix it up with a red one or something?

They are a lot more sophisticated it seems now.

It might be fun to borrow his newly acquired $300 sound system and measure them, but I think I'd rather use my time on real audio projects.
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Tech note: voltage regulators-1

Posted 7th January 2010 at 06:10 PM by jan.didden
Updated 11th February 2010 at 04:31 AM by Jason

There are lots of types of voltage regulators, but in this installment I’ll talk about series regulators.

What’s a regulator? It’s all in the name: it REGULATES the voltage to the circuit to be powered to keep it constant and as free of noise and ripple as practical. The ‘regulation’ means that there is some circuitry that compares a reference voltage, like from a zener diode, to the regulated output voltage, and then uses the difference between the two to adjust another element to null that difference. The ‘compare-and-correct’ is crucial for a regulator, and is done by negative feedback….

Look at Fig 1: is there a regulator in there? No, they are all circuits that try to give a constant, ripple free voltage, but if you start to draw varying currents from them, the output will vary with that current and there is no mechanism that somehow tries to null out that variation. Fig 1c is better than 1b, because Q1 buffers the voltage from the zener reference, so...
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Old Style DCB1 information

Posted 1st January 2010 at 02:53 PM by Tea-Bag
Updated 13th October 2010 at 01:48 AM by Tea-Bag (updated some more timely info)

The basics on the boards....
The hypnotize is a 1 input/1 output Shunt regulated Direct Coupled Pass like B1 buffer. It has a relay delayed startup to avoid DC problems for the amps. This board (and even Mez) can be used just as a shunt power supply, and their is a thread for this also.

The Mesmerize can use up to 6 muting relay inputs, and is a larger board. All others matters being equal.

Here are some relevant threads.

Attached is a semi-built DCB1 mesmerize. Also the main schematics of the device, in case you need to troubleshoot. The below shot is a bare Hynotize PCB.
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File Type: pdf DCB1 BOM V4.2.pdf (44.6 KB, 4009 views)
File Type: pdf SalasDCB1shuntreg build guide v4.1.pdf (50.7 KB, 2070 views)
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Top plate finished...

Posted 1st January 2010 at 01:58 PM by Bas Horneman (Bas Horneman's blog)


Just a little sanding. And hopefully I will be able to put a layer of primer down.
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What I'm listening to

Posted 1st January 2010 at 12:37 AM by alazira
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