Supposedly, Astell and Kern are using this in their latest AK-380 high-end/high-$ DAP:
I proto'd this DAC recently (along with AKM's new premium ADC)....what can I say ... I'm floored! This is the best digital I've ever heard to date.
Some hold-outs of antiquated multi-bit DAC religiosity may never be able to step outta their cognitive dissonance -- or warm-fuzzy nostalgia -- 'cause of their loss of virginity with their first loves (= classic R2R multi-bit) oh G A W D ... memories are so precious ... man -- I'm lookin' at my Philips CD650 and gettin' misty-eyed ....WAKE UP DUDE!!!
Folks, this is 2015 and technology does EVENTUALLY improve (tho', it takes time and is often 3 steps fwd, 2 back).
Unless Philips decides to revamp their TDA or SAA lines, AKM's your ticket ... or...
Posted 10th June 2015 at 01:10 PM byrjm (RJM Audio Blog)
Work stuff. I was writing Labview vis for an hp 4192A LF impedance analyzer and needed something to measure to check the data acquisition program. So I stuck some of my audio capacitors I happened to have into the 16047A test fixture "just to see".
I have no idea what these measurements are telling me other than yes, the 0.47 uF capacitors are indeed 0.47 uF ... up to about 0.5 MHz anyway. Maybe someone can do some technical analysis. I was struck though by just how quickly the inductance of these big film caps kicks in. As audio coupling caps they are fine, but if you are silly enough to use them as power supply bypass for example...
There are some reproducibility issues I'm still coming to grips with, but the differences shown in the plots is definitely from the capacitors themselves and not the leads or random variations. I've measured them several times over with similiar result.
Posted 8th June 2015 at 03:32 PM byMartinAndersen Updated 14th January 2016 at 04:56 PM byMartinAndersen(new link)
This is my collection of everything related to speaker measurements. Better to share it than hide it away in my bookmark collection
Understanding Cabinet Edge Diffraction
"One of the most misunderstood topics in audio is the subject of diffraction. Diffraction, acoustic phase, and how listening rooms impact our reproduction of sound, based on what I see posted in many discussions on the internet, are subjects of much confusion. In this article I will attempt to clear some of the fog on the topic of cabinet diffraction, and hopefully, present it in such a way as to make it much easier to understand."
Posted 8th June 2015 at 07:45 AM byrjm (RJM Audio Blog)
Updated 9th June 2015 at 12:09 AM byrjm
LTSpice copy (protection diodes removed) of the original JE-990 circuit. Even with BC327/337 subbed in for all the original transistors the simulation works without further modification.
C1 seems to be critical for stability. C2 and C3 damp overshoot seen on the simulated square wave response, hinted at by the high frequency rise in frequency response shown in the screen grab below.
My impression is that this circuit is of the heavily optimized, no-stone-left-untouched variety.
Thanks to the SMART feature of the hard disk and the utility which warned me the disk was dying. I was able to backup a WIN7 system image before things happening. Restoring the image on a new hard disk was done smoothly.
Posted 2nd June 2015 at 05:44 AM byabraxalito Updated 9th July 2015 at 09:43 AM byabraxalito
When I found this on Taobao a few days ago I could not believe the price wasn't a mistake, or that it was just for the case with nothing inside. But it turned out to be real, so I ordered one - it arrived just now so I'm taking it apart before having a listen. The case oozes quality and the volume control feels silky smooth.
When I've had a listen (gotta search for my 1/4" adapter) I'll get into modding.... Incidentally for those on 110V, it does have a mains voltage selector switch. Amazing.
I traced out the circuit (still haven't listened) and found its pretty much as shown on the Taobao page. 78/79 15V regulators feed BD139/140s and a TL072 sits between the volume pot and the discrete OPS. This stage resembles a diamond, but instead of the more familiar current sources to the rails, it has 1500ohm resistors. LTSpicing this arrangement (schematic shown) reveals its...
Posted 30th May 2015 at 06:23 AM bymlise Updated 30th May 2015 at 06:25 AM bymlise
I have new 2234/35 cones in the 2224H baskets making them into 2234H's. I bought some lead aquarium plant weights to load them up, but broke down and bought genuine JBL OEM mass rings for a mere $85 each. They appear to be zinc (pot metal) so I an be comforted I won't get lead poisoning listening to the speakers. Just have to glue the mass rings in and the dust caps on to make the drivers 2235H's.
The Eminence ASD1001 was my low budget plan for a mid, but I saw 2450J's were actually relatively cheap, so I now have the most modern neodymium magnet version of the 4" diaphragm tweeter JBL makes. The massive ferrite magnet versions cost twice as much.
In this far, I figured I might as well spring for a pair of 2405H's instead of the Beyma clones I already bought. Thanks to e-bay for refunding the first FUBAR pair of 2405H's, I found a second really nice pair.
I wound up air core inductors to make an N7000 dividing network (mid to tweeter x-over) and have the rest...
He's saying that diamond buffers sound better but that he has no idea why this would be.
Simulating the PSRR of the diamond vs a traditional EF2 reveals a significant difference - about 6dB better PSRR for the diamond. Could this explain the SQ improvement? Charles designs his amps without GNFB so you'd tend to think that his OPS PSRR is really rather critical.
Since making this discovery I've been on the look-out for opamps with diamond buffer OPSs - OP260 was one I found (courtesy of Esperado) but there are a few from Linear Technology which I've ordered up a few of. In particular, LT1886 and LT1723 look very interesting as potential amp/buffer stages in DACs. LT is fairly unique in that they publish a simplified internal schematic in all the DSs I've looked at...
Posted 21st May 2015 at 01:32 PM byrjm (RJM Audio Blog)
Updated 27th May 2015 at 01:54 AM byrjm
This post, about a push-pull MOSFET output stage for a headphone amp, got me thinking again about the Audio Technica AT-HA5000, which is something of a benchmark in its class. The "basic" signal circuit (not a complete schematic, it's clearly missing some ancillary details) is attached below. Probably out of MJ originally.
I think with any circuit like this, the differences are less about the MOSFETs and the operating points and more about the front end and what tricks you do with the power supply. That, and how you make sure it doesn't go up in a puff of vaporized silicon taking your headphones with it.
The Audio Technica schematic has nice old-school Zener regulators, a discrete JFET front end, a long tailed pair + current mirror for voltage gain and "proper" BJT Vbe multiplier and driver stage. Q7 is presumably in thermal contact with Q10,11 providing overtemp protection, and the output has a protection relay (not shown in detail) for...
Posted 20th May 2015 at 06:00 AM byrjm (RJM Audio Blog)
Updated 18th June 2015 at 11:26 PM byrjm(added schematic of original version)
The circuit was originally hosted on Headwize, but the site seems to have gone offline.
It was a single stage resistively-loaded MOSFET follower, a unity gain current buffer used to drive headphones.
Some updated versions provided below. As noted in the comments the "Reverso" version with the CCS on the V+ and a p-channel mosfet has better PSRR performance, especially with voltage divider network R6,R7,C4 on the collector of Q2.
So good in fact that I switched around the n-channel version to use a negative voltage rail to obtain the same result!