diyAudio - Headphones and Headphone Amplifiers
Go Back   Home > Forums > Blogs > RJM Audio Blog
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
If I put my notes here, I might be able to find them again later!
Headphones and Headphone Amplifiers "Personal" audio. Most of my listening is through headphones these days.
Old

Sapphire 4 headphone amplifier [Rev. 4.1m]

Posted 24th April 2017 at 01:02 AM by rjm (RJM Audio Blog)
Updated 29th April 2017 at 11:54 PM by rjm

Development thread starts here.

While I consider this my best work to date, the documentation trail has become hopelessly scattered so let me try to regroup in this blog post and make some sort of gateway/portal to the project. [Update: web page write up now finished.]

The followup to the Sapphire 3 started out as a generic musing on stacked diamond buffers and current mirror amplification, coalesced for a bit as the ill-fated Project Unity before becoming part of the Sapphire line initially as a temporary measure as something I could drop in my existing chassis for testing. The first iteration kept the open loop buffer of previous Sapphire iterations, but now I'm running the 4.1m boards closed loop I realize I've ended up at just the classic, dictionary definition current feedback amplifier. Sigh. So much for originality. It sounds great though, so I'm not as upset about it as I might have been.

*****

I'm being loose with the...
Attached Thumbnails
Click image for larger version

Name:	pcb-sapphire-41m-brd.png
Views:	69
Size:	20.9 KB
ID:	2360   Click image for larger version

Name:	sapphire-41m.png
Views:	47
Size:	198.3 KB
ID:	2361   Click image for larger version

Name:	pcb-sapphire-41m-sch.png
Views:	145
Size:	20.4 KB
ID:	2362   Click image for larger version

Name:	DSC_1165s.jpg
Views:	99
Size:	203.3 KB
ID:	2363   Click image for larger version

Name:	DSC_1172s.jpg
Views:	83
Size:	386.5 KB
ID:	2364  

Click image for larger version

Name:	sapphire-41-ltspice R3X 15dB.png
Views:	60
Size:	83.5 KB
ID:	2376   Click image for larger version

Name:	summary.png
Views:	31
Size:	21.8 KB
ID:	2377  
Attached Files
File Type: zip pcb-sapphire-41m3-bom.zip (195.9 KB, 31 views)
File Type: asc Sapphire 41.asc (6.2 KB, 49 views)
rjm's Avatar
rjm
diyAudio Member
Views 272 Comments 3 rjm is offline
Old

Project Unity Board Layout

Posted 27th December 2016 at 12:33 AM by rjm (RJM Audio Blog)
Updated 27th December 2016 at 10:11 PM by rjm

Two boards, each board configurable for line and headphone variants. Powered by nominal +12 V -12 V split regulated supply, though 9-15 V rails can be used without modification.
Attached Thumbnails
Click image for larger version

Name:	pcb-unityB-10b-brd.png
Views:	235
Size:	11.0 KB
ID:	2176   Click image for larger version

Name:	pcb-unityB-10b-sch.png
Views:	298
Size:	16.5 KB
ID:	2177   Click image for larger version

Name:	unityb-10b.png
Views:	144
Size:	134.5 KB
ID:	2180   Click image for larger version

Name:	pcb-unity-10e-brd.png
Views:	143
Size:	15.8 KB
ID:	2184   Click image for larger version

Name:	pcb-unity-10e-sch.png
Views:	310
Size:	19.5 KB
ID:	2185  

Click image for larger version

Name:	unity-10e.png
Views:	138
Size:	175.0 KB
ID:	2186  
Attached Files
File Type: zip pcb-unity-10e1-bom.zip (150.2 KB, 71 views)
File Type: zip pcb-unityB-10b1-bom.zip (98.7 KB, 63 views)
rjm's Avatar
rjm
diyAudio Member
Views 432 Comments 0 rjm is offline
Old

Introducing Project Unity

Posted 23rd December 2016 at 05:02 AM by rjm (RJM Audio Blog)
Updated 27th December 2016 at 11:46 PM by rjm

Following on from this post and this post, we arrive in time for the holidays with Project Unity. Merry Christmas everyone.

Four circuits: Unity, Unity H, Unity B, Unity BH. line preamp, Headphone amp, line Buffer, Headphone Buffer respectively, all derived from a common base circuit called Unity Root. Unity Root is conceptual, it exists only as a reference so you can see more clearly how the four working variants relate to each other.

It's the "all for one, and one for all" approach to diyaudio, a single research and development line applied to a range of applications, feedback from any of the applications brought back to apply to the line in general.

This simplifies not just the circuit development, similar efficiency is also brought to the documentation, board layout design, and BOM... about which I'll have more to say in a bit.
Attached Thumbnails
Click image for larger version

Name:	unity root 11.png
Views:	316
Size:	45.5 KB
ID:	2164   Click image for larger version

Name:	unity 11 family.png
Views:	189
Size:	82.7 KB
ID:	2165  
Attached Files
File Type: zip Unity 10 LTSpice.zip (5.6 KB, 44 views)
rjm's Avatar
rjm
diyAudio Member
Views 342 Comments 0 rjm is offline
Old

Sapphire Line Preamplifier

Posted 24th July 2016 at 01:11 AM by rjm (RJM Audio Blog)
Updated 26th July 2016 at 11:45 PM by rjm

Although the original Sapphire headphone amp can be configured as a line stage, or use as-is as a line stage, I've gone ahead and made a new circuit variant with a new set of boards.

The Sapphire Line (in development) combines the shunt-series regulator, bboard 2.0 buffer and an op amp voltage gain stage. Same basic idea as the Sapphire of course, but with a much less beefy output stage so the low noise regulator can be added and everything still fits on the board.

rev 10e - now with support for 2520 op amp modules
Attached Thumbnails
Click image for larger version

Name:	Sapphire LIne 10d LTSpice.png
Views:	506
Size:	107.4 KB
ID:	2029   Click image for larger version

Name:	sapphire line 10e brd.png
Views:	342
Size:	21.9 KB
ID:	2033   Click image for larger version

Name:	sapphire line 10e.png
Views:	496
Size:	17.5 KB
ID:	2034  
Attached Files
File Type: asc Sapphire Line 10d.asc (10.1 KB, 194 views)
rjm's Avatar
rjm
diyAudio Member
Views 592 Comments 0 rjm is offline
Old

Headphone amplifier ground. Where to make the chassis connection?

Posted 2nd February 2016 at 07:11 AM by rjm (RJM Audio Blog)
Updated 24th February 2016 at 01:02 AM by rjm

The discussion thread at the headphone forum is here, but I wanted to throw out the problem to the general blog-reading community here at diyaudio to see if anyone can nail this.

The earthed chassis (light blue) must connect to the circuit common i.e. "ground" (pale green). I do not know where the best place on the circuit ground is to tie that connection.

Suggestions please!

(COM and GND are completely equivalent pads on the circuit board, while IN- and OUT- also pads on the board but physically further away on the ground plane.)

****

Answer: as long as it connects at one point only, or the same point of both channels, it doesn't seem to matter at all. I have it connected at the ground tab of the headphone jack and that seems to be as good as anywhere.

****

The noise was in fact magnetic interference emanating from the transformers. Grounding layout changes / electrostatic...
Attached Thumbnails
Click image for larger version

Name:	Sapphire ground.png
Views:	920
Size:	32.5 KB
ID:	1775   Click image for larger version

Name:	DSC_5322b sm.jpg
Views:	1984
Size:	846.7 KB
ID:	1777   Click image for larger version

Name:	DSC_5407 sm.jpg
Views:	1816
Size:	748.4 KB
ID:	1780   Click image for larger version

Name:	Z-reg sim.png
Views:	566
Size:	273.4 KB
ID:	1782   Click image for larger version

Name:	IMGP6318sm.jpg
Views:	807
Size:	301.3 KB
ID:	1783  

Click image for larger version

Name:	permalloy.png
Views:	265
Size:	51.1 KB
ID:	1809  
Attached Files
rjm's Avatar
rjm
diyAudio Member
Views 1347 Comments 7 rjm is offline
Old

ASUS Xonar Essence STX soundcard

Posted 9th October 2015 at 10:46 PM by rjm (RJM Audio Blog)
Updated 7th November 2015 at 09:44 PM by rjm

https://www.asus.com/Essence-Hi-Fi-A...r_Essence_STX/

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:	417
Size:	104.2 KB
ID:	1737   Click image for larger version

Name:	DSC_8149bs.jpg
Views:	337
Size:	301.9 KB
ID:	1738   Click image for larger version

Name:	DSC_8136bs.jpg
Views:	1223
Size:	318.0 KB
ID:	1739   Click image for larger version

Name:	DSC_8152bs.jpg
Views:	307
Size:	266.3 KB
ID:	1740   Click image for larger version

Name:	DSC_8136b.jpg
Views:	767
Size:	467.7 KB
ID:	1750  

Click image for larger version

Name:	DSC_0780 sm.jpg
Views:	336
Size:	151.5 KB
ID:	1751  
Attached Files
rjm's Avatar
rjm
diyAudio Member
Views 1466 Comments 0 rjm is offline
Old

Orb JADE-1 headphone amplifier and DAC : review

Posted 2nd October 2015 at 05:07 AM by rjm (RJM Audio Blog)
Updated 9th November 2015 at 01:44 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:	1962
Size:	299.9 KB
ID:	1731   Click image for larger version

Name:	DSC_7804s.jpg
Views:	1139
Size:	333.1 KB
ID:	1732  
Attached Files
rjm's Avatar
rjm
diyAudio Member
Views 1428 Comments 0 rjm is offline
Old

AT-HA5000

Posted 21st May 2015 at 01:32 PM by rjm (RJM Audio Blog)
Updated 27th May 2015 at 01:54 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:	2499
Size:	98.0 KB
ID:	1636  
Attached Files
File Type: asc HA5000 mod 01.asc (6.0 KB, 441 views)
rjm's Avatar
rjm
diyAudio Member
Views 2852 Comments 3 rjm is offline
Old

Szekeres 2015

Posted 20th May 2015 at 06:00 AM by rjm (RJM Audio Blog)
Updated 18th June 2015 at 11:26 PM 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:	1594
Size:	51.2 KB
ID:	1651   Click image for larger version

Name:	szekeres 2015 negative.png
Views:	1400
Size:	41.3 KB
ID:	1654   Click image for larger version

Name:	szeke2.gif
Views:	2734
Size:	6.0 KB
ID:	1668  
Attached Files
File Type: asc szekeres 2015 reverse split CCS.asc (3.8 KB, 862 views)
File Type: asc szekeres 2015 negative.asc (3.3 KB, 871 views)
rjm's Avatar
rjm
diyAudio Member
Views 1850 Comments 14 rjm is offline
Old

JLH-2005 headphone amplifier

Posted 18th May 2015 at 08:15 AM by rjm (RJM Audio Blog)
Updated 27th May 2015 at 01:52 AM by rjm

I was perusing this thread earlier today. Which led me to what I think is the original source, at least as a modern, relatively clean headphone amp version of the original original (by way of ESP).

Some comments from our own Nelson Pass are seemingly relevant.

AC coupled, and simplified to a single supply voltage, the circuit can be run at +5 V operation (USB, etc) with fairly decent performance.

The circuit is optimized for 16 ohm headphones.
Attached Thumbnails
Click image for larger version

Name:	JLH2005 LV 23.png
Views:	2872
Size:	44.3 KB
ID:	1644  
Attached Files
File Type: asc JLH redux LV 23.asc (5.8 KB, 259 views)
rjm's Avatar
rjm
diyAudio Member
Views 1440 Comments 1 rjm is offline
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 06:19 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki