Toshiba MOSFETs with a twist

[abraxalito]

Just wait til you hook it up to one of these DACs....

[nige2000]

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

[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

[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. :)

[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.

[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 756 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 728 times

[nige2000]

heres the tk50j30d preliminary test with the gainstage

[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 670 times

[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?

[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.