diyAudio - My DIY projects
Go Back   Home > Forums > Blogs
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
I returned to DIY electronics in 2009 after a 20 year pause by building a few kits to get in shape. This blog is for me to keep track of my progress.
Old

Aikido headphone amplifier

Posted 11th June 2017 at 04:16 AM by alexcp (My DIY projects)

I built a headphone amplifier using John Broskie's Aikido All-in-One PCB with Tube Rectifier. The PCB is well made and easy to build, and I am satisfied with how it sounds.

One comment is that R9, R10, and R13 (see the attached schematic) affect the distortion introduced by the circuit. By changing R13, I was able to cut the distortion by as much as 90%, from 0.2% @1kHz 1Vrms output down to 0.02%. My optimum was R13=90ohm with B+ at 310V (using the recommended Hammond 270EX power transformer) and all other values as in the attached schematic.
Attached Thumbnails
Click image for larger version

Name:	Aikido%20Noval%20Configured%20as%20Headphone%20Amplifier.png
Views:	9
Size:	22.2 KB
ID:	2403   Click image for larger version

Name:	Aikido%20Push-Pull%20Headphone%20Amplifier%20for%20300-ohm%20Cans.png
Views:	13
Size:	29.8 KB
ID:	2404  
alexcp's Avatar
diyAudio Member
Posted in Uncategorized
Views 73 Comments 0 alexcp is offline
Old

Removing hum from Aikido Cathode Follower (ACF-2 9-Pin)

Posted 7th March 2017 at 03:00 PM by alexcp (My DIY projects)
Updated 7th June 2017 at 09:41 PM by alexcp (Edited for brevity and, hopefully, clarity)

I purchased from Glass-Ware.com an Aikido Cathode Follower 2 (ACF-2) All-in-One 9-Pin PCB, designed by John Broskie, the editor of Tube Cad Journal (tubecad.com).

The PCB holds a pair of cathode followers, each loaded by a triode current source, and a respective power supply. In my build, a JJ E88CC with 220ohm cathode resistors shows 0.003% THD @1kHz 1Vrms with pure 2nd harmonic distortion.

As I tested my ACF, I noticed audible buzz at its outputs @0.15% THD+N - that's 1.5mVrms(!), well above the THD, and it was not a grounding problem.

A careful look at the schematic (attached), confirmed by some Spice simulation (an LTSpice model is also attached) revealed that the "Aikido" in the ACF-2 relies on the exact match of the voltages across the capacitors C18 and C19, including the hum component. These capacitors are in series for the rectifier (e.g. hum) current and, together with R4/R7, are in parallel for the signal current. In the ideal...
Attached Files
File Type: asc acf-2.asc (8.0 KB, 22 views)
File Type: pdf acf-2.pdf (51.1 KB, 12 views)
File Type: pdf acf-2 one solution.pdf (51.8 KB, 13 views)
alexcp's Avatar
diyAudio Member
Posted in Preamps
Views 555 Comments 0 alexcp is offline
Old

Restored and modded Cambridge Audio A3i

Posted 9th April 2016 at 01:51 PM by alexcp (My DIY projects)
Updated 13th April 2016 at 03:17 PM by alexcp

The designer of Cambridge Audio A3i had talked about the amp in this forum and suggested some changes to the components that bring the performance of the amp to a new level.

When I saw a cheap A3i on eBay, I decided to try it out. One channel was DOA, but it did not matter as I was about to mod it anyway.

Here is what I've done:
  1. Replaced all rectifiers (D201-D206 on the schematic) with soft recovery diodes and removed the capacitors in paralell with the diodes;
  2. Changed the grounding scheme so that the protection circuit and the relay driver are connected directly to the star ground;
  3. Added a 30ohm resistor in series with the rectifiers of the protection circuit;
  4. Replaced the electrolytic capacitors in the amplifier (but not the protection circuit) with Nichicon KA and replaced the two large power supply capacitors with Nichicon LLS;
  5. Replaced all film capacitors with Kemet PHE426 or, where PHE426 wouldn't fit, with Kemet SMR;
  6. Replaced the rectifiers
...
Attached Thumbnails
Click image for larger version

Name:	diyaudio_blog - 13.jpg
Views:	1421
Size:	858.8 KB
ID:	1906   Click image for larger version

Name:	diyaudio_blog - 15.jpg
Views:	614
Size:	870.3 KB
ID:	1907   Click image for larger version

Name:	diyaudio_blog - 16.jpg
Views:	642
Size:	900.8 KB
ID:	1908   Click image for larger version

Name:	diyaudio_blog - 17.jpg
Views:	598
Size:	781.5 KB
ID:	1909  
Attached Files
File Type: pdf A3I schematic.pdf (1,011.2 KB, 281 views)
alexcp's Avatar
diyAudio Member
Views 1330 Comments 0 alexcp is offline
Old

Krell KSA-5 clone

Posted 9th April 2016 at 01:27 PM by alexcp (My DIY projects)
Updated 11th February 2017 at 02:20 PM by alexcp

When I saw the discussions of KSA-5 headphone amplifier on head-case.org and on this forum, I thought it may be a nice use for the bag of 1000uF capacitors I had at the time. This was the main motivation for putting this Krell KSA-5 clone together.

The main challenge was to drill the front panel. The 10mm aluminum panel that came with the enclosure is easy to work with, but I wanted it to be pretty and asked the people at Modushop to CNC it for me.

Although it works ok, I think it is not a very good power amplifier for loudspeakers. As a headphone amplifier, it is no match for my Musical Fidelity X-CANv8.
Attached Thumbnails
Click image for larger version

Name:	diyaudio_blog - 10.jpg
Views:	2380
Size:	954.1 KB
ID:	1904   Click image for larger version

Name:	diyaudio_blog - 11.jpg
Views:	1591
Size:	908.3 KB
ID:	1905   Click image for larger version

Name:	ksa5.jpg
Views:	1108
Size:	656.2 KB
ID:	1924  
Attached Files
File Type: pdf ksa5.pdf (129.1 KB, 835 views)
File Type: pdf ksa5psschem.pdf (54.7 KB, 763 views)
File Type: zip ksa5ampfinal.zip (2.80 MB, 76 views)
File Type: zip ksa5psg.zip (631.6 KB, 48 views)
File Type: zip ksa5psorig.zip (791.3 KB, 56 views)
alexcp's Avatar
diyAudio Member
Views 1253 Comments 2 alexcp is offline
Old

NCore based power amplifier

Posted 9th April 2016 at 01:20 PM by alexcp (My DIY projects)
Updated 11th February 2017 at 02:25 PM by alexcp

Ever since I heard about the Hypex NCore technology, I have wanted to build a power amplifier based on Hypex NC400 modules. Here is what I got. It works very well with the preamplifier from the previous post.

I used a spare Arduino to control the SMPSes. For now, it simply allows to use a momentary push button on the front panel. I may add remote control (12V trigger or similar) later.
Attached Thumbnails
Click image for larger version

Name:	diyaudio_blog - 9.jpg
Views:	2410
Size:	460.3 KB
ID:	1903  
Attached Files
File Type: pdf NC400_04xx.pdf (2.97 MB, 79 views)
File Type: pdf SMPS600_DIY_R5.pdf (1.42 MB, 55 views)
alexcp's Avatar
diyAudio Member
Views 614 Comments 0 alexcp is offline
Old

Bruno Putzeys' MicroPre

Posted 9th April 2016 at 01:14 PM by alexcp (My DIY projects)
Updated 11th April 2016 at 08:21 PM by alexcp

In April 2013, Linear Audio published in Vol.5 Bruno Putzeys' article "The G Word, or How to Get Your Audio off the Ground". Linear Audio included a free PCB for the demo project from the article: a balanced volume controller, or rather a minimalist balanced preamp with two pairs of balanced inputs.

I have been looking at balanced interconnects for some time and decided to use the free PCB and build the preamp. Here is what I built.

The enclosure used is Galaxy GX247 with front and back panels custom made by Front Panel Express. It was difficult to place a C14 power inlet on the back panel, as the space is quite limited due to the central placement of the six XLR connectors. An easy solution would be to fix the power cord permanently to the preamp, but I found a compact snap-in connector that fits the 3mm back panel of the enclosure.

I understand the article is available for download at the Hypex web site, and the PCB gerbers and a...
Attached Thumbnails
Click image for larger version

Name:	diyaudio_blog - 1.jpg
Views:	619
Size:	594.8 KB
ID:	1899   Click image for larger version

Name:	diyaudio_blog - 2.jpg
Views:	301
Size:	190.8 KB
ID:	1900   Click image for larger version

Name:	diyaudio_blog - 3.jpg
Views:	529
Size:	203.6 KB
ID:	1901   Click image for larger version

Name:	diyaudio_blog - 7.jpg
Views:	613
Size:	320.6 KB
ID:	1902   Click image for larger version

Name:	bp v5 f28a component_placement.png
Views:	237
Size:	397.0 KB
ID:	1928  

Click image for larger version

Name:	bp v5 f28b top.png
Views:	194
Size:	417.4 KB
ID:	1929   Click image for larger version

Name:	bp v5 f28c bottom.png
Views:	204
Size:	159.6 KB
ID:	1930  
Attached Files
File Type: pdf The G Word.pdf (731.5 KB, 173 views)
File Type: zip MicroPre_gerbers.zip (53.9 KB, 73 views)
alexcp's Avatar
diyAudio Member
Posted in Preamps
Views 1220 Comments 0 alexcp is offline
Old

From Tube CAD Journal by JRB

Posted 25th June 2015 at 08:05 PM by alexcp (My DIY projects)

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)
alexcp's Avatar
diyAudio Member
Posted in Uncategorized
Views 989 Comments 0 alexcp is offline
Old

Soundcard measurements with ASIO

Posted 7th September 2013 at 09:51 AM by alexcp (My DIY projects)
Updated 17th February 2014 at 05:08 AM by alexcp

I talked earlier about soundcard measurements, and here is some news: Pioneer Hill Software updated SpectraPLUS 5 so that it can now use ASIO.

ASIO (Audio Stream Input-Output) replaces Windows' own MME (MultiMedia Extensions) or DirectSound. As far as I understand, the beauty of ASIO is that it bypasses Windows Mixer and thus doesn't bring any issues associated with sample rate conversion or level adjustment.

The ASIO drivers that came with my E-MU 0204 crash every time (on Windows 7 and WIndows 8). Thankfully, there is ASIO4ALL, which works well for me.

First picture shows two spectra taken with SpectraPLUS: red is the E-MU 0204 output fed directly into E-MU's input; and blue is the output of the E-MU fed into Pete Millett's interface, output of the interface fed to the input of the interface, and then back to the sound card. THD+N is 0.000781% is the first case and 0.001272% in the second.

Next two screenshots are THD+N vs frequency...
Attached Thumbnails
Click image for larger version

Name:	EMU0204+ASIO4ALL.png
Views:	769
Size:	136.6 KB
ID:	1123   Click image for larger version

Name:	EMU0204+ASIO vs freq.png
Views:	440
Size:	74.9 KB
ID:	1126   Click image for larger version

Name:	IF+ASIO vs freq.png
Views:	294
Size:	74.7 KB
ID:	1127   Click image for larger version

Name:	MyRefC.png
Views:	406
Size:	119.5 KB
ID:	1128   Click image for larger version

Name:	MyRefC vs freq.png
Views:	281
Size:	74.3 KB
ID:	1129  

Attached Files
alexcp's Avatar
diyAudio Member
Posted in Instrumentation
Views 1768 Comments 0 alexcp is offline
Old

Better than a box of chocolates

Posted 25th June 2013 at 06:17 PM by alexcp (My DIY projects)
Updated 25th June 2013 at 08:27 PM by alexcp

Got this today on the cheap - a box of 6N1P-VI, made in 1988, all new in authentic factory packaging. It is likely to keep me entertained for quite some time

Note: the PDF attachment is a scan of the factory three page insert from the box. It is in Russian and contains the pinout and electrical and limiting parameters of the tube but NO CURVES.
Attached Thumbnails
Click image for larger version

Name:	IMG_0242.jpg
Views:	345
Size:	45.3 KB
ID:	1099   Click image for larger version

Name:	IMG_0243.jpg
Views:	306
Size:	43.0 KB
ID:	1100   Click image for larger version

Name:	IMG_0237.jpg
Views:	286
Size:	60.0 KB
ID:	1102   Click image for larger version

Name:	IMG_0238.jpg
Views:	265
Size:	54.5 KB
ID:	1103   Click image for larger version

Name:	IMG_0239.jpg
Views:	229
Size:	41.5 KB
ID:	1104  

Click image for larger version

Name:	IMG_0240.jpg
Views:	231
Size:	40.0 KB
ID:	1105   Click image for larger version

Name:	IMG_0241.jpg
Views:	218
Size:	88.7 KB
ID:	1106   Click image for larger version

Name:	IMG_0234.jpg
Views:	224
Size:	88.9 KB
ID:	1107  
Attached Files
File Type: pdf 6N1P.pdf (6.03 MB, 216 views)
alexcp's Avatar
diyAudio Member
Posted in Uncategorized
Views 1043 Comments 0 alexcp is offline
Old

Measurements with a sound card

Posted 13th May 2013 at 09:08 PM by alexcp (My DIY projects)
Updated 7th September 2013 at 09:36 AM by alexcp (Updated for ASIO4ALL)

I am using a USB sound card for measurements. It's a pain, but I have nothing better yet.

The sound card is the E-MU 0204. I've chosen it for the specs:
  • Dynamic Range (A-weighted, 1kHz, min gain): 113dB
  • Signal-to-Noise Ratio (A-weighted, min gain): 113dB
  • THD+N (1kHz at - 1dBFS, min gain): -101.9dB (.0008%)

The sound card is intefaced to the real world by Pete Millett's sound card interface.

The software is SpectraPLUS 5.0 by Pioneer Hill Software (PHS). (No link because my antivirus says their web site is infected.) The software runs on an old MacBook running Windows 7 in Boot Camp.

The results do not seem to be affected by nearby computers, flurescent lights, switching power supplies, etc.

The results are affected by:
  • Windows Mixer settings (levels and sampling rates)
  • Software settings (levels and sample rate)
  • Grounding of the sound card, the interface, and the device under test

The greatest source of pain is...
Attached Thumbnails
Click image for larger version

Name:	E-MU 0204 loopback spectrum.png
Views:	1330
Size:	37.4 KB
ID:	1055   Click image for larger version

Name:	E-MU 0204 loopback THD+N vs Freq.png
Views:	899
Size:	37.5 KB
ID:	1056   Click image for larger version

Name:	E-MU 0204 ATEST spectrum.png
Views:	871
Size:	37.1 KB
ID:	1057   Click image for larger version

Name:	E-MU 0204 ATEST THD+N vs Freq.png
Views:	956
Size:	37.5 KB
ID:	1058   Click image for larger version

Name:	NE5532 power amp spectrum.png
Views:	564
Size:	32.4 KB
ID:	1059  

Click image for larger version

Name:	NE5532 power amp THD+N vs Freq.png
Views:	826
Size:	31.9 KB
ID:	1060  
Attached Files
alexcp's Avatar
diyAudio Member
Posted in Instrumentation
Views 1610 Comments 0 alexcp is offline
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 07:09 PM.


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