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Tweeter DAC

Posted 22nd June 2014 at 04:24 AM by abraxalito
Updated 25th June 2014 at 05:49 AM by abraxalito

Hexacaps have their limitations - they provide a great low impedance for lower freqs but according to my LCR meter, turn inductive for frequencies in the mid-single digit kHz. Which is about the lower edge of the passband for a tweeter. So what to do to get a low impedance power supply to a DAC chip from 4kHz and up? Here's my first attempt - there are 7 TDA1387s each sandwiched between two low ESR 4700uF lytics. Sandwiching them together is an attempt to get the inductance as low as possible - the loop area can't practically get any smaller than this. Getting the wires in has tested my patience and that's even before powering the beast up....

Update - well I could have been knocked over with a feather - this worked first time I plugged it in. So now I'm thinking about how to build a markII version, considering if I can get more decoupling close in....
Oh I'm now not sure that my bandpass tweeter filter is really delivering the goods as per its simulation. Connecting...
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Old

DIY wooden_ rod_tonearm 17"

Posted 20th June 2014 at 08:14 PM by suwaned (tube audio friends suwaned)
Updated 21st July 2014 at 07:05 PM by suwaned

I have planning make a long wooden tonearm.

I have TA Technics as apart
I split apart and i put only Pivot.
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i made wooden rod for replace .

problem counter weight Technics light. and need more weight for balance.

Made counter weight from Bronze 220 mg.
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Distance Pivot to spindle new TA 17"
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try install to my TT not fixed and
Wooden TA on the track with cartridge MM Shure.
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outsite place, DIY wooden TA 17" wiht alum stand of pivot and arm base from wood.
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It's very Long TA extraordinary . and i think this have little error track than 9"

wacth " test DIY tonearm wooden rod !&" on the track. Test2 DIY Tonearm 17"_wooden rod - YouTube...
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Old

Just for fun - an ultra-low impedance AIF

Posted 18th June 2014 at 11:40 PM by abraxalito

DIYing high enough Q inductors for anti-imaging filters is a bit of a challenge so here's another way to approach this. I found its possible to build very high Q inductors by simply slipping ferrite beads over a fairly thick copper wire. The limitation though is that the beads I have offer about 1.2uH per bead. So making a ferrite bead version of a 660uH inductor will call for over 500 beads - rather impractical.

To make such a ferrite bead inductor filter a practical possibility its necessary to work at a much lower impedance. I've taken a 1ohm working impedance inititally to develop this filter. Now the largest inductor just needs 10 beads. Given this very low impedance the post-amplifier's noise performance becomes rather a challenge - but a transformer will probably do the trick nicely. I plan to try this with a 1:7 step up trafo and see how it goes.

This kind of filter is probably very suitable for DACs with higher output current - the communications type...
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Old

Tweeter line level passive XO

Posted 13th June 2014 at 04:47 AM by abraxalito
Updated 16th June 2014 at 04:51 AM by abraxalito

I'm really impressed with the bang for the buck with my 228rmb speakers, but have a theory they're rather being limited by their crossover. Especially the first order tweeter crossover which hasn't enough LF rejection.

In search of a steeper XO for the tweeter I've decided to go the whole hog and design a kick-*** filter that'll allow me to fully activate these puppies and see just how much they're limited by their electronics. kinku just pointed me to a filter design program called AADE which I've just finished using to design my first LC bandpass filter.

Its bandpass because I want to stick it straight after the DAC and it needs the anti-imaging function, meaning a steep low pass around 18kHz. The tweeter doesn't need this as they're fairly low on IMD, but the tweeter amp sure benefits from having no ultrasonics. Hence here is my first attempt at a tweeter bandpass filter, to go between the DAC and a dedicated tweeter amp.

For now I'll use the TDA1521...
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Old

How Beats Conquered The World (via The Verge)

Posted 13th June 2014 at 12:04 AM by rjm
Updated 13th June 2014 at 12:44 PM by rjm

Original article, by Ben Popper

~ my spin ~

There was the iPod. It was cool, and the distinctive while earbuds that came with it showed people you had an iPod, so they were cool, too. A few audiophiles invested in better IEMs, but they tended to be expensive and discreet and anyway were only ever a niche thing.

Meanwhile the Japanese headphone makers - JVC-Kenwood, Sony, Audio Technica - tried competing with the iPod, and they came up with a spectrum of earbuds and headphones of every shape, price, and color. They sold as commodities, but none developed any real kind of identity or reputation. Certainly there was little effort at building a brand.

On the other side, Grado, AKG, and Sennheiser continued doing pretty much what they always did, making nice, expensive headphones for home/studio/DJ use.

Neither group addressed the obvious hole in the market: non-audiophiles wanting "good" sounding over-ear...
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Old

EEVblog #626 - Ceramic Capacitor Voltage Dependency

Posted 8th June 2014 at 05:59 AM by hollowman

The popular YouTube channel hosted by Dave L. Jones (Sidney, Australia bloke) just released his latest episode:

EEVblog #626 - Ceramic Capacitor Voltage Dependency

https://www.youtube.com/watch?v=TDDoi70cxw0

Of course some of DIYA's know-it-all will claim that this is not new info at all ... well if all you do DIY-audio and tweak and breadboard (and you've gotta lab bench in the little engineer's room ... so you can defecate-n-DIY at the same time) ... well, I suppose you really must know it ALL.
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Old

DIY for Dummies?

Posted 5th June 2014 at 03:37 PM by hollowman
Updated 6th June 2014 at 06:07 AM by hollowman

For those of you not familiar with the USA book scene ... yellow-cover "...for Dummies" series has been one of the most successful (=popular/best-selling) book series in U.S. history.
Click the image to open in full size.

It was so popular that the style was copied by several other publishers' series including:
"...for Complete Idiots".
The term "idiot" or "Dummies" is used as hyperbole in claiming ensured comprehension. The approach relies on explaining a topic via very basic terminology.

But that is not subject of this Blog post ... so stay tuned for a bit... I've gotta take a dump...
Click the image to open in full size.
...and need a cup o' tea, love ...
Click the image to open in full size.

....OK,...
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Old

Linsley Hood amp on Taobao

Posted 4th June 2014 at 05:27 AM by abraxalito

Looks like a bargain, around $120. Sorely tempted to get one to play with - what do you think ?
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Old

A Better Audio Comparison Tool

Posted 2nd June 2014 at 07:25 AM by fas42
Updated 14th July 2014 at 02:01 AM by fas42

I've mentioned a few times the difficulty in using the software tool, DiffMaker - and others have experienced similar issues. So, I'm thinking seriously about attempting to put together a "better" utility, something that will be more intelligent in correlating between different versions of sampled waveforms, wherever they came from. And it will be specifically aimed at trying to ferret out the deep down differences, not the obvious stuff like frequency response, phase shifts and the like - but rather the low level, detail variations that seem to be so important in subjective quality evaluation.

To give an idea of the "challenge", consider taking 2 recordings from 2 vinyl plays of a particular record. Having already seen what results, this is impossible for the likes of DiffMaker to handle - the constant speed variation between the 2 captures completely defeats it. But this what I would aim to be able to deal with, to synchronise in meaningful ways between...
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Posted in Tweaking
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Old

Cubist Subwoofer to go with Ikea bowl Speakers - just looks wrong!

Posted 1st June 2014 at 12:20 PM by googlyone
Updated 1st June 2014 at 12:24 PM by googlyone

A while back I built some Ikea bowl speakers using Vifa bassmids and tweeters. The performance came out very good indeed, but when you are dealing with a 5 odd inch driver, there will never be masses of bass.

A subwoofer was always on the cards.

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Given the spherical speakers perched on the retro "rocket like" stands, I initially thought of doing a spherical subwoofer - but in the end concluded that while I could do this, I was looking at using fibreglass on a "fit-ball", placement in the room was looking to be a challenge.

So I chose to do the absolute opposite - and came up with an off the wall approach to a conventional sub.

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The idea was to move the implementation of a conventional sub well away from the "box with a driver stuck on the front".

I find it fascinating that...
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