Schiit's $2300 Yggdrasil D/A processor ...
link
...here's what Schiit claims on their product page:

To their credit, Schiit also uses the same AD DAC in their $600 "gungnir-multibit" D/A processor:
link

Just in terms of DigiKey pricing, the DAC chip is not cheap ($15...

Since acquiring and modding my Taobao headphone amp I've been enamoured of creating a much more portable headphone solution to deliver aural nirvana but on the move. Whereas transformers are a very practical solution for a desktop amp, steel and copper is not only bulky but also jolly heavy and hence a no-no for anything pocket-sized.

How else to get the dynamics I'm seeking though? For these amps I'm toying with different solutions to getting better PSRR, particularly in the all-important bass region which tends to suffer in commercial portable amps. The OPS (output stage) is what needs most attention in any classAB amp - the signal stages can all be classA but for efficiency (and hence battery life) the output stage can't be conducting all the time.

A fully discrete output stage where the output devices are cascoded looks to be one solution but initially I'm looking for a simpler, more cost-effective solution with lower overhead on the supplies if possible....

Over the years I have played with measuring - well - just about everything in audio.

distortion measurement has been one of these preoccupations, not the least because it is hard to do, and using commercial gear, expensive.

I have built analogue hear to do this, used mixes of analogue and digital and of late played with using modified commercial sound cards. My efforts on the Sound Blaster x-Fi were interesting but ultimately not rewarding enough for me to leave the mods in there.

I have also been playing with using the A/D and D/A converters from my DSP crossover for this purpose. These are modular and use a common I/O plug with power MLCK, SCLK, LRCLK and Data (alone with I2S for the CS4398 and sometimes a digital volume control).

--- notwithstanding the fact that in previous tests I have shown the digital volume control is the MAJOR source of distortion - I will plug ahead with this, and likely leave that out of the test...

I purchased a pair active speaker. This is manufactured by Fountek under the brand Rhyme Acoustic. The model number is A-100. It uses a 4" full-range driver with vented box. The electronic is contained in the right channel enclosure. The amplifier is LM4766 chipamp. The overall build quality is good. I just paid RMB 399.00 during its sales period. What a good deal!

Chinese product link is https://item.taobao.com/item.htm?spm..._u=od0rlto94d1 The frequency response shown in this product page does not match with that given the user's instruction of my pair. The curve shown in user's instruction does pretty much match with my initial listening impression: lack of treble.

I measured the speaker with my CLIO Pocket. Measurement shows left and right enclosure response are matched very well.

The last figure shows the left box (passive) driven by another amplifier. We can then see what filtering or EQ is...

When browsing Taobao I can't resist the temptation to try the very cheap stuff. This little TFcard player really takes the biscuit for the lowest price of a digital audio source - 9.9rmb. So I ordered up three, I might just order more soon.

First powering up I tried some FLAC files, these don't work but wav and mp3 work fine and it even finds files below the root directory. Power supply is nominally 12V but its using an EF fed by a zener diode, not an IC reg so almost anything from 6V will probably work. I haven't managed to find the technical blurb for the chip so far so a little reverse engineering was needed. It incorporates a 3.3V regulator to power the IR receiver and the TFcard - I have fitted an additional regulator for the first mod because I wondered if the low-level noise I was hearing was due to interference from the flash card's power draw. Turns out no as when playing .wav files this noise disappears.

Incidentally the 9.9rmb cost includes the remote...

I use DeskProto to generate toolpath for the CNC controlled by Mach3.

I am enjoying all the fun of building speaker enclosure. An inexpensive 2" full-range is employed. The cube is made by MDF. I have measured TS parameters of the driver and its response with a big baffle. I use Basta! and LEAP-5 to simulate the box's response and impedance. Once the box is built, I can compare actual and simulated data.

Two cubes will be built. One is sealed and the other is with passive radiator.

I am using a handheld force meter and caliper to measure compliance of passive radiators. The force meter is clamped to the caliper. Caliper is used to show the panel displacement whereas force meter displays the corresponding force. I can then obtain compliance C mm/N. I am planning to use an Arduino controlled Z-axis for automatic measurement. The force meter has a USB interface for data acquisition.

I should be able to measure BL vs displacement of a driver by adding a programmable DC supply.

I'm often asked "which op amp sounds better".

The reply is usually a scowl and muttered "does it look like I care!?" Which is something of a lie... I do care about getting op amps to sound good. It's the phrasing of the question I dislike.

Op amps do not come in "good, better, best" flavors. All it is - and this is pretty obvious I would have thought but apparently not - all this is about is matching an op amp to the job it's going to do; the circuit it's going to be sitting in.

The op amp you'd choose to use as a DAC IV converter is different from the one you'd choose to back a 100k volume potentiometer in a preamp is different from the one you'd choose for an MC phono preamp input stage...

Why do you think there are like a thousands of different op amps to choose from in the first place? It's because there are thousands of combinations of op amp characteristics and properties ... not because companies...

For every hobbyist-built amplifier in existence there are probably one thousand amplifiers which are planned on being built and maybe one hundred amplifiers that have all their parts collected in a box waiting to be built and ten amplifiers that are partially built and collecting dust in a closet.

(see full post here)