diyAudio - rjm
Go Back   Home > Forums > Blogs

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

B-board v2 line driver : development circuit

Posted 30th October 2015 at 01:49 PM by rjm
Updated 30th October 2015 at 01:56 PM by rjm

Original version is here.

I've been meaning to get around to updating this by folding in the improvements to the diamond buffer stage made during development of the Sapphire 3 headphone amplifier. Here is the first look of the bboard v2 under LTSpice.

I've gone back to simple emitter resistors on the input, running under much lower current to keep the input impedance high. The output is simplified to a basic Sziklai compound transistor pair with the bulk of the bias current running in the second transistor.

In terms of distortion, for line level output level, CCS loaded input has no advantage. I'll have to double-check PSRR and a few other things before signing off on this version though.

FYI only, not a production circuit.
Attached Thumbnails
Click image for larger version

Name:	bboard v2.png
Views:	106
Size:	69.6 KB
ID:	1754  
Attached Files
File Type: asc Sapphire3 bboard 10 mod.asc (4.5 KB, 34 views)
rjm's Avatar
diyAudio Member
Views 260 Comments 7 rjm is offline

ASUS Xonar Essence STX soundcard

Posted 9th October 2015 at 11:46 PM by rjm
Updated 7th November 2015 at 10:44 PM by rjm

I admit I did not give ASUS the benefit of the doubt and seriously consider their Essence STX soundcard as a replacement for my Onkyo SE200-PCI. ASUS make nice motherboards, but unlike Onkyo have no previous expertise in high end audio.

I am happy to report - a bit late in the game, the card came out in 2009 - that they've done a really good job with it and the drivers for Windows 10, technically still in beta, work just fine.


Asus updated the design recently to the STX II. The PCB has been redone, but the only visible change is the PCM1792A DAC has been moved towards the top of the card closer to the IV conversion op amps. An second LDO regulator IC, U34, empty on the STX, is now populated. A "TXCO" clock source is added next to the ASUS audio controller IC. The four film caps next to the output IC are replaced with WIMA brand. It's basically identical, so it...
Attached Thumbnails
Click image for larger version

Name:	controlpanel.jpg
Views:	47
Size:	104.2 KB
ID:	1737   Click image for larger version

Name:	DSC_8149bs.jpg
Views:	28
Size:	301.9 KB
ID:	1738   Click image for larger version

Name:	DSC_8136bs.jpg
Views:	51
Size:	318.0 KB
ID:	1739   Click image for larger version

Name:	DSC_8152bs.jpg
Views:	28
Size:	266.3 KB
ID:	1740   Click image for larger version

Name:	DSC_8136b.jpg
Views:	39
Size:	467.7 KB
ID:	1750  

Click image for larger version

Name:	DSC_0780 sm.jpg
Views:	25
Size:	151.5 KB
ID:	1751  
Attached Files
rjm's Avatar
diyAudio Member
Views 277 Comments 0 rjm is offline

Onkyo SE200-PCI sound card windows 10 driver issues / disable immezio 3D effects

Posted 8th October 2015 at 08:35 AM by rjm
Updated 24th November 2015 at 12:30 AM by rjm

Apologies for the Google-friendly title, I'm hoping people experiencing the same problem will find their way here.

Onkyo download page:

Current version is 5.60C, last update was 2012 to be compatible with Windows 8. Driver package 5.60C installs without issues on Windows 10 64 bit. The AudioDeck utility installs as well.

However, all is not well:

On installation, Immezio 3D effects are enabled. This locks the sample rate at 48 kHz. 44, 96, and 192 kHz cannot be selected. Deselecting the Immezio 3D effects prompts a reboot, but the Immezio 3D effects remain enabled after rebooting. The card is stuck at 48 kHz. 3D effects (which enables the DSP processing such as Qsounds, EAX, A3D) cannot be shut off.

I see three possible workarounds:

1. Find a command line switch, or edit the installation batch file to disable Immezio 3D on installation...
Attached Files
File Type: zip (159.9 KB, 39 views)
rjm's Avatar
diyAudio Member
Views 524 Comments 3 rjm is offline

Orb JADE-1 headphone amplifier and DAC : review

Posted 2nd October 2015 at 06:07 AM by rjm
Updated 9th November 2015 at 02:44 AM by rjm

This is a headphone amplifier with digital inputs, not a DAC with a headphone jack. Though technically given equal board space, the headphone amp, with hot-running single-ended class-A output stage, is surely the centerpiece of the design. (The Asahi Kasei DAC, with MUSES01 for the I-V, is no slouch mind you.)

First impressions. It is large, solid, and very nicely made, but - after seeing the inside - rather simple, spartan even. From the DAC output to the headphone jack is just two op amps and two transistors, the op amps being shared between channels. A third op amp most likely just buffers the analog line output. Apart from the headliner MUSES01 op amp none of the parts are especially expensive, though many were clearly carefully chosen for sound quality - the 2SC5196 for example. The TE7022 USB receiver is a disappointment, as is, to be honest, the single set of power rails and the use of dual op amps shared between channels.

On a positive note, the front...
Attached Thumbnails
Click image for larger version

Name:	DSC_7802s.jpg
Views:	93
Size:	299.9 KB
ID:	1731   Click image for larger version

Name:	DSC_7804s.jpg
Views:	60
Size:	333.1 KB
ID:	1732  
Attached Files
rjm's Avatar
diyAudio Member
Views 341 Comments 0 rjm is offline

Choosing a USB DAC

Posted 26th September 2015 at 12:49 PM by rjm
Updated 9th October 2015 at 05:24 AM by rjm

My Onkyo soundcard drivers stopped working when I upgraded to Windows 10. Onkyo says they have no plans to release a patch, so I'm left with no high quality audio solution for my computer. Since I already have a good headphone amplifier, what I'm mainly looking for is a high quality line level analog output.

One options is another soundcard, the ASUS Xonar STX being the obvious choice. I dunno, it doesn't grab me.
I was thinking with going with an external box this time, connected via USB. As this opens up about a zillion options, I'm going to limit things to,
  1. Respected audio brands with a solid reputation for digital audio.
  2. Small enough to be placed on top of my computer case.
  3. $500-ish, used or new.
My short list includes the following: Denon DA-300usb, TEAC UD-301, and Onkyo DA-1000. Teac also makes the 301's big brother, the UD-501. This is a much nicer unit, very substantial. A bit large. Rounding out the field is the LUXMAN DA-100 . These can be found deeply...
Attached Thumbnails
Click image for larger version

Name:	gb1.jpg
Views:	41
Size:	44.7 KB
ID:	1727   Click image for larger version

Name:	gb3.jpg
Views:	55
Size:	232.3 KB
ID:	1728   Click image for larger version

Name:	K0000429480.jpg
Views:	44
Size:	60.0 KB
ID:	1729   Click image for larger version

Name:	UD-501_m_chassis_l.jpg
Views:	62
Size:	213.4 KB
ID:	1730  
Attached Files
rjm's Avatar
diyAudio Member
Views 537 Comments 5 rjm is offline

Audio Op Amps

Posted 26th June 2015 at 03:59 AM by rjm
Updated 1st October 2015 at 08:04 AM by rjm

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...
Attached Thumbnails
Click image for larger version

Name:	bryston.png
Views:	494
Size:	141.7 KB
ID:	1669  
Attached Files
rjm's Avatar
diyAudio Member
Views 907 Comments 1 rjm is offline

capacitance measurements with the hp 4192A

Posted 10th June 2015 at 02:10 PM by rjm

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.
Attached Thumbnails
Click image for larger version

Name:	capacitance.png
Views:	122
Size:	30.1 KB
ID:	1665   Click image for larger version

Name:	conductance.png
Views:	117
Size:	29.9 KB
ID:	1666  
Attached Files
rjm's Avatar
diyAudio Member
Posted in The Lab
Views 482 Comments 0 rjm is offline

Jenson JE-990 discrete op amp

Posted 8th June 2015 at 08:45 AM by rjm
Updated 9th June 2015 at 01:09 AM by rjm

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.

Sourced from m.nats page and The John Hardy Company.
Attached Thumbnails
Click image for larger version

Name:	je990.png
Views:	253
Size:	76.8 KB
ID:	1660   Click image for larger version

Name:	jensen 990.png
Views:	671
Size:	98.7 KB
ID:	1661  
Attached Files
File Type: asc 990-2.asc (6.7 KB, 186 views)
File Type: pdf DIY.JE-990.DOA.V1A.pdf (77.7 KB, 129 views)
File Type: pdf 990.pdf (1.80 MB, 132 views)
rjm's Avatar
diyAudio Member
Views 690 Comments 2 rjm is offline


Posted 21st May 2015 at 02:32 PM by rjm
Updated 27th May 2015 at 02:54 AM by rjm

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...
Attached Thumbnails
Click image for larger version

Name:	AT-HA5000.png
Views:	448
Size:	98.0 KB
ID:	1636  
Attached Files
File Type: asc HA5000 mod 01.asc (6.0 KB, 186 views)
rjm's Avatar
diyAudio Member
Views 790 Comments 0 rjm is offline

Szekeres 2015

Posted 20th May 2015 at 07:00 AM by rjm
Updated 19th June 2015 at 12:26 AM by rjm (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!
Attached Thumbnails
Click image for larger version

Name:	szekeres 2015 reverso.png
Views:	266
Size:	51.2 KB
ID:	1651   Click image for larger version

Name:	szekeres 2015 negative.png
Views:	243
Size:	41.3 KB
ID:	1654   Click image for larger version

Name:	szeke2.gif
Views:	524
Size:	6.0 KB
ID:	1668  
Attached Files
File Type: asc szekeres 2015 reverse split CCS.asc (3.8 KB, 139 views)
File Type: asc szekeres 2015 negative.asc (3.3 KB, 135 views)
rjm's Avatar
diyAudio Member
Views 800 Comments 12 rjm is offline
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 12:26 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2