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alexcp alexcp is offline

diyAudio Member

About Me

  • About alexcp
    United States


Total Posts
Blog - My DIY projects
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General Information
  • Last Activity: Yesterday 11:42 PM
  • Join Date: 9th June 2009


View alexcp's BlogRecent Entries
Latest Blog Entry

Posted 25th June 2015 at 09:05 PM by alexcp Comments 0
Posted in Uncategorized
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)

Posted 7th September 2013 at 10:51 AM by alexcp Comments 0
Posted in Instrumentation
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...

Posted 25th June 2013 at 07:17 PM by alexcp Comments 0
Posted in Uncategorized
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.

Posted 13th May 2013 at 10:08 PM by alexcp Comments 0
Posted in Instrumentation
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...

Posted 12th May 2013 at 08:51 PM by alexcp Comments 2
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.

Here is the result:
Recent Comments
I've now got a PCB Layout...
Posted 8th February 2015 at 12:06 PM by SNAPEFU SNAPEFU is offline
very good! :cheers:
Posted 1st March 2014 at 12:46 AM by sjh327 sjh327 is offline
That is the most difficult...
Posted 2nd November 2013 at 09:46 AM by alexcp alexcp is offline
How does it sound Alex?...
Posted 1st November 2013 at 03:41 PM by udailey udailey is offline
I got my kit from,...
Posted 18th March 2013 at 05:17 PM by alexcp alexcp is offline
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