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Noise modulation and subjective performance of DACs

Posted 25th December 2012 at 04:22 AM by abraxalito
Updated 20th September 2014 at 03:41 PM by abraxalito

I've recently come to the view that the best metric of SQ in DACs is noise modulation, however as yet I'm unclear how best to go about making the measurement. Stereophile tried, and here's what they did - Noise, Modulation, & Digital/Analog Conversion | Stereophile.com

Robert Harley reports no correlation with listening so I deduce from this that the test method isn't looking for the right thing. My own gut feel is we need a multitone test waveform rather than a single sinewave as a sinewave has a crest factor quite unlike music and if a sine provoked the condition we'd see it on the 'N' part of a THD+N vs level test.

Having said that, of course we do indeed see something weird going on - on Weiss Medea's implementation of the ESS Sabre. The THD+N plot versus level shows kinks which most certainly are not increased THD at various levels, so can only be noise floor modulation. See a critique I made on WBF here - http://www.whatsbestforum.com/showth...l=1#post133677...
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To boldly go where no audiophile, or, perhaps just me, has gone before ...

Posted 23rd December 2012 at 03:07 AM by fas42
Updated 23rd December 2012 at 03:11 AM by fas42

As 'threatened' in a comment in abraxalito's blog I'm going to kick off posting and linking to some samples of sound generated by myself, at the moment examples of replay on my system, recorded using a very basic technique.

I'll probably regret it, but I'm going to put up a rough and ready trial run, to give a smell of what I'm aiming at. It's full of problems, but it gives some good indicators of what I'm dealing with, and hopefully some feedback will help me for future runs.

The system is my 'dud' HT all-in-one setup, heavily tweaked, and the recording device is a Fujifilm S4000 camera, which does HD video rather nicely, with mono 44.1/16 audio thrown in - that's handy. To maximise sound quality and minimise card storage used, hopefully, the lens was covered while recording, yes, no pics! Unfortunately, signal to noise is poor and the automatic volume control keeps falling over its feet, but you can't get everything for that sort of money ...

...
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Rating: 2 votes, 5.00 average.

Rebuilding a Hafler DH200 Part 1

Posted 10th December 2012 at 11:42 PM by Stormrider

Doctor, Doctor

David Hafler (RIP) must have sold tons of these amps... There are always a wide selection of different models on ebay, but the DH200 and DH220 seem to be the most common. I have three of my own (2 P230's and a P125) that I cycle in and out of use. I've repaired and rebuilt several for other people, and yet I keep running into more of them. The most recent being Brokencrank's DH200, which I have documented below for reference, and to have a place to put my notes. I don't claim any of the info below to be gospel, just my experience. I also don't claim this to be a step by step guide to resuscitate your old Hafler. A basic understanding of electronics and amplifiers will be required. Know what you're doing before you do it, and you will make less mistakes. If you have questions, ask!*

Note: All of the component reference numbers (ie. R3, C14, Q10, etc...) I mention will be based on the schematics available in the manuals at Hafler.com. Because...
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Digital that sounds like analog

Posted 10th December 2012 at 03:18 AM by abraxalito
Updated 15th February 2013 at 05:11 AM by abraxalito

For those who missed Frank (fas42)'s link on a thread I started then here's where I'm continuing my minimal oversampling DAC developments for the time being : Digital that sounds like analog
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Google+ DIY Audio community.

Posted 7th December 2012 at 10:06 PM by rjm
Updated 14th April 2013 at 11:14 PM by rjm

There was no DIY Audio community on Google+.

So I made one.

Google+ has always been a "quiet room" where like-minded people got together to talk about things, away from the noise and chaos of facebook.

The problem was that it was difficult to find said like-minded people. They were there, but for the majority you had no way of knowing that.

Well, now Google has fixed that by introducing "communities". It's a user-created hub, a digital meeting room ~ salon ~ lounge ~ front porch, a designated gathering place associated with a certain hobby, interest, or topic.

This feature is brand new, so I have no idea whether it will work. It could, like facebook, devolve into noise and spam... or it might be useful and worthwhile. I think its worth a shot, anyway.

I created the group, but it is free and open. It's not mine in the sense I don't intend to use it as a platform. I have my own G+ page for...
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Amplificador SubZero-Dr Jacobid

Posted 2nd December 2012 at 09:17 PM by SERGIODS

SUBZERO

Hello fellow forum would like to know if anyone har Zero sub amplifier, is an amplifier that caught my Atencio.
It is the famous Dr Jacoid
> Output power (RMS) 180W into 8 ohms -------------
> Output power (RMS) 230W into 4 ohms -------------
> Output (music) --------- 220-230W into 8 ohms
> Output (music) --------- 270-300W into 4 ohms
> Check osetljivost/impedansa----0, 6V/47koma (by 200Wrms ohms /
> ----- 7 Hz 112KHz-/-3dB frequency response (to less than 0.01% distortion)
> ------------------- THD <0.003% (a 130WRMS into 8 ohms)
> ------------------- THD <0.005% (a 180WRMS into 4 ohms)
> S/N------------ noise> 95 dB (compared to 100Wrms)
> ------- Damping factor> 300 (in 150WRMS into 8 ohms)

Notice of Copyright. Everything on this website is copyrighted by Dr. cheekbones Borivoje. Reproduction or re-publication by any means, electronic,...
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6C33C OTL - Construction Journal Continues -Cutting the aluminum

Posted 1st December 2012 at 02:00 AM by wlowes

I am keeping this journal for my own record. There is no new engineering in this project. This is just my own journey while building my first tube amp.

Major milestone achieved today. I finally took the plunge and cut the aluminum. I am very happy with the results. Each and every part fits perfectly.

I planned this project around Front Panel Express. I used their tool designing and redesigning the lay out until I was confident in my layout and fit. Problem is FPE is expensive. Then I saw some comments from other builders that the edge FPE leaves is not really finished. I went searching for a more cost effective solution. I landed on cutting using WaterJet while searching for local CNC shops. There is a company in Toronto close to where I work www.pva-enterprises.com that has an advanced waterjet cutting machine. I exported my FPE file and sent it in for a quote. Given I need a left and a right panel for the 2 mono's I got them to cut both panels...
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