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Re: Toshiba MOSFETs with a twist
Posted: Wed Aug 16, 2017 9:28 am
by abraxalito
Just wait til you hook it up to one of these DACs....
Re: Toshiba MOSFETs with a twist
Posted: Wed Aug 16, 2017 10:06 pm
by nige2000
abraxalito wrote: ↑Wed Aug 16, 2017 9:28 am
Just wait til you hook it up to one of these DACs....
rough and ready "hot buff "
or warm buff its kinda cool this evening
ive little experience with headphones but it sounds excellent
Re: Toshiba MOSFETs with a twist
Posted: Thu Aug 17, 2017 12:41 am
by abraxalito
How about this case to build a DAC in? I'm asking Wendy to enquire what kinds of customization of the back and front panels are possible -
https://item.taobao.com/item.htm?spm=a2 ... =12#detail
Re: Toshiba MOSFETs with a twist
Posted: Thu Aug 17, 2017 7:39 am
by Georgi
Very nice and good stuff in that Taobao, but how you find the things inside, can't find how to change the language or maybe there is no change button. :)
Re: Toshiba MOSFETs with a twist
Posted: Thu Aug 17, 2017 1:30 pm
by abraxalito
As far as I know there's no language option other than Chinese. I use Google translate to create my search terms. Sometimes Aliexpress has a similar product and that's in English.
Re: Toshiba MOSFETs with a twist
Posted: Sun Aug 20, 2017 2:52 pm
by abraxalito
Here's the implementation of the digital part of this DAC, which I'm thinking I shall informally call the 'no DAC'. I'm experimenting with the equivalent of 'overclocking' it by upping the bias to pin7 to prize more mA out. Previously I've blown up one or two by over-driving pin7 so I'm doing this fairly gently. So far I'm up to 1.5mA output current without any apparent detriment to SQ.
- dac1387.jpg (75.05 KiB) Viewed 738 times
Here's the implementation of the filter whose plot I showed previously, with the >90dB stop-band rejection. The inductors are wound from litz wire (19 strands of 0.1mm) to achieve the highest possible Q @ 20kHz (above 140) - when wound with a single strand of thicker wire (around 0.5mm diam), proximity effect rears its head to increase the AC losses at the top of the audio band. Caps are in the main multiple paralleled NP0 100nFs (the highest affordable value) for extremely low loss.
- Neo_filter.jpg (71.36 KiB) Viewed 710 times
Re: Toshiba MOSFETs with a twist
Posted: Wed Aug 30, 2017 10:11 pm
by nige2000
heres the tk50j30d preliminary test with the gainstage
Re: Toshiba MOSFETs with a twist
Posted: Thu Sep 07, 2017 9:17 am
by abraxalito
How's it sounding? Have you gotten both channels fired up yet?
Here's the 2nd generation version of this DAC which I'm calling 'Neo' - its using balanced outputs from the same DAC board as before. The coils are the same ones as before, just twice as many. Output bal-SE conversion is handled with E25 10k core transformers. They have huge leakage inductance which is put to good use as another LPF. The headphone amp is the standard one (no paralleling of output transistors) running from a single 18650. The result is ...... music. Seriously addictive music.
- firstneoprotoA.jpg (94.07 KiB) Viewed 652 times
Re: Toshiba MOSFETs with a twist
Posted: Thu Sep 07, 2017 4:59 pm
by nige2000
two channels up and running last night, was experimenting with pcb etching,
hand drawn using a etch resistant marker for making the gain stages which worked fine although a bit rough and ready
time build wise is similar
sound wise it certainly shows promise but i haven tried in a critical listening setting as of yet
what sort of powersupply and capacitors should i be using for this?
Re: Toshiba MOSFETs with a twist
Posted: Fri Sep 08, 2017 2:09 am
by abraxalito
You got me there, I'm still only using a bench supply for mine. The gain stage is sensitive to power supply noise, needs a lot of care to get clean sound - suggest passive filtering with LC on any low noise regulator.