Posted 7th March 2017 at 03:00 PM byalexcp (My DIY projects)
Updated 13th March 2017 at 09:20 PM byalexcp
I purchased an Aikido Cathode Follower 2 (ACF-2) All-in-One 9-Pin PCB from Glass-Ware.com. The PCB is designed by John Broskie, the editor of Tube Cad Journal (tubecad.com), and the flexibility that he designed in is quite remarkable. The PCB allows to test various configurations, which is often not a feature of a design committed to a PCB. The quality of the PCB is outstanding; it withstands multiple soldering and desoldering without complaint. It is an outstanding product IMHO.
The schematic seems to be simple, with a cathode follower loaded by a triode current source. JJ E88CC with 221ohm cathode resistors shows 0.003% THD with pure 2nd harmonic, and select 6N1P-VI achieve 0.005%. (My 6N1Ps are hit or miss; some of them have much higher 2nd harmonic, and some of them have a mix of 2nd and 3rd at Ia=6ma and Ua=140V).
As I tested my ACF, I noticed excessive hum at its outputs - audible buzz in the speakers and 0.15% THD+N, well above the THD.
Posted 9th April 2016 at 01:27 PM byalexcp (My DIY projects)
Updated 11th February 2017 at 02:20 PM byalexcp
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.
Posted 9th April 2016 at 01:20 PM byalexcp (My DIY projects)
Updated 11th February 2017 at 02:25 PM byalexcp
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.
Posted 9th April 2016 at 01:14 PM byalexcp (My DIY projects)
Updated 11th April 2016 at 08:21 PM byalexcp
In April 2013, Linear Audiopublished in Vol.5Bruno 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...
Posted 25th June 2015 at 08:05 PM byalexcp (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.
Posted 7th September 2013 at 09:51 AM byalexcp (My DIY projects)
Updated 17th February 2014 at 05:08 AM byalexcp
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.
Posted 12th May 2013 at 07:51 PM byalexcp (My DIY projects)
This is a project developed by Douglas Self and published in the Elektor in October and November 2010.
The idea is rather unusual: "An interesting power amplifier can be made by connecting enough 5532s in parallel, how about 32 for a start? This may sound like a radical course of action, but it actually works very well, making it possible to build a very simple amplifier that retains not only the excellent linearity but also the power-supply rejection and the inbuilt overload protection of the 5532, which reduces the external circuitry required to a minimum."
Elektor used to sell PCBs for this project, which I used. I modified the circuit slightly to incorporate an active volume control along the lines of Douglas Self's preamplifiers.