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abraxalito abraxalito is online now

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    abraxalito posted a comment on page TDA1387 X8 NOS DAC 13th July 2015

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  • Last Activity: Today 03:38 AM
  • Join Date: 19th September 2007

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Posted 23rd May 2017 at 09:58 AM by abraxalito Comments 15
My Superlux HD668Bs are the best value purchase I've ever made in headphone kit, far and away the best bang for the buck at their very modest price-point. If any pair of cans is worth designing a specific amp for, they are most certainly on the short-list. The amp I designed specifically for my AT MSR-7s doesn't have enough ooomph for these as the impedance is appreciably higher and the efficiency lower.

So here is my attempt at a dedicated HD668B amp with no corners cut in SQ while still being cheaper to buy the parts for than the cans themselves. I've designed it to run from a single lithium ion cell - a Panasonic 18650 would work fine and give around 60hrs of listening time. Its a single-ended classA topology driven by a single current-source loaded MOSFET. And naturally enough it sounds like no amplifier at all - a straight wire without gain, seeing as its just a buffer.

In actual fact it certainly does have gain, but only current gain. And no shortage of...

Posted 1st May 2017 at 01:04 PM by abraxalito Comments 3
As avid readers of my blog over the years may well know, I've modded quite a few active speakers. Mainly Swan/Hivi D1010s and D1080s of various generations along with some 3Nods. The entry level Swans are super-cheap on Taobao nowadays with pairs of older generation D1010s going for about 375rmb.

As a result of all these mods and my learning by doing I haven't got a single pair of actives in working condition, primarily because the mods I currently want to do (including fitting transformers inside and swapping out the classAB chipamps on bass/mid to replace with classD) won't fit in the available space. All the amp and active XO parts have been hacked about almost beyond recognition and are of very dubious reliability. So I have come up with a plan - I've thrown all the electronics boards away and will convert the carcasses into passive speakers. Since I also prefer to feed speakers via step-down transformers for better dynamics, I wanted to explore the possibilities of using...

Posted 8th February 2017 at 12:30 PM by abraxalito Comments 4
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I've been looking for something like this on Taobao for a few years now. A cheap player which includes a digital output so I can pair it up with one of my DACs. There have been cheap players, and there have been FLAC players but never cheap FLAC players - the cheapest prior to this one being a media player around 500rmb. This one goes into the pocket change category as its just 88rmb. What's more it includes Bluetooth. Order placed - will update after I've played with it.

Just received this - the heart of the beast is the Actions Semi ATS2825, some information about its features is available here :
Whereas a connector for headphones (top right) is shown on the photo, this doesn't support any analog out (my board has no connector fitted there). Its purely digital output - a header for I2S and...

Posted 31st October 2016 at 08:42 AM by abraxalito Comments 6
The Intersil D2 chipset based amp arrived and while it sucked pretty badly on speakers I had a hunch that like the STA333BW boards I've been playing with recently, it would acquit itself admirably on headphones, given the much lower demands on the supply.

The mods I've done to this are fairly straightforward - changing the output filter to work more optimally with headphones (via a 7:1 step-down transformer) and tweaking up the power supply a bit.

To run with cans I went for an output load impedance of 1100ohms. This was determined primarily by the choice of inductor (MSS1210 8.2mH from Coilcraft) which in turn was chosen so that the carrier frequency would be below the SRF of the coil. This choice is fairly arbitrary in that the inductor would still work fine above its SRF just it's starting to look like a capacitor. However it turned out that with 8.2mH the cap value required was fairly simple, 5nF so I stuck two 10nF NP0s in series.

Mods in the...

Posted 28th October 2016 at 03:19 AM by abraxalito Comments 13
I've been mighty impressed with the STA333BW board (just 62rmb on Taobao, see an earlier post for the link) driving headphones via a transformer (ferrite cored step down 7:1, I've tried various sizes). So much so that I don't much feel the need to upgrade my headphones beyond my Superluxes (HD668B). The sound I'm getting is immensely satisfying - rich (which I got from my TDA1387-based DACs, but not from my phone with its ES9018K2M, that doesn't qualify as rich in tonality) and dynamic beyond anything I've so far heard. I noticed in a recent thread post by TNT (here - he says he doesn't much like listening on headphones due to the 'in-head' quality of the sound. Yeah I used to get that, transformers pretty much get rid of it giving an out-of-the-head-all-around-holographic kind of experience, along with stupendous dynamics. I like listening to classical piano and that's very demanding...
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Richard, today I have...
Posted 11th June 2017 at 12:55 AM by Alexandre Alexandre is online now
Having looked at the...
Posted 29th May 2017 at 01:21 AM by abraxalito abraxalito is online now
Ok thanks ! that's sounds...
Posted 28th May 2017 at 03:10 PM by kasey197 kasey197 is offline
My first four prototypes...
Posted 28th May 2017 at 01:50 PM by abraxalito abraxalito is online now
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