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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.
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Zen V4

Posted 12th August 2010 at 05:16 PM by alexcp (My DIY projects)
Updated 11th April 2016 at 07:49 PM by alexcp (Amp reworked)

Nelson Pass' Penultimate Zen (aka Zen V4) proved trickier to build than the simple schematic suggested. I used a chassis from designbuildlisten and PCBs made with the gerbers posted on passdiy.com. Initially I used some Chinese electrolytic capacitors that were easily available, but the sound was not good at all. I replaced them with ELNA for Audio, and things improved greatly. I found that the apparent simplicity of the schematic belies the difficulty of making it right.
Update: I replaced the gain stage MOSFET with a SemiSouth SiC JFET and got a noticeable improvent in both the sound and the measured performance, see a separate post.
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Attached Files
File Type: pdf Zen-v4.pdf (907.9 KB, 136 views)
File Type: zip Zen-v4-gerbers.zip (26.8 KB, 54 views)
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Fostex BK-20

Posted 12th August 2010 at 05:06 PM by alexcp (My DIY projects)
Updated 15th August 2010 at 04:18 PM by alexcp

Having built a few amplifiers, I wanted to build a pair of speakers and settled on Fostex BK-20 kits from Madisound with Fostex FE-206E 8" full range drivers. I've always considered carpentry not my cup of tea, so gluing, sanding, and painting the speakers took longer than expected. However, I am very satisfied with the sound.
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Posted in Speakers
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Velleman K4040

Posted 12th August 2010 at 04:53 PM by alexcp (My DIY projects)
Updated 11th April 2016 at 07:45 PM by alexcp

Then was the K4040 from Velleman. Contrary to some reviews, I found this amp sounding rather nice, particularly after I replaced the EL34 tubes in the output stage with separately purchased matched quads. However, the sound does not quite match the price, and I keep this amp mostly for its looks.

Update: I modified this amplifier, leaving little of the original design. See a later post with the details.
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Attached Files
File Type: pdf K4040.pdf (1.32 MB, 119 views)
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Posted in Tube power amps
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Old

S5 Electronics "L" series tube amps

Posted 12th August 2010 at 04:52 PM by alexcp (My DIY projects)
Updated 5th May 2015 at 12:38 PM by alexcp

I started with a Model 8LS stereo amp from S5 electronics. Later I put it into a Hammond enclosure and replaced the tranformers with Edcors.

Separately, I built a Model 16LS, which is the same thing with a doubled output stage, giving a very similar sound. Both use a 5670 double triode in the voltage amplifier and phase splitter, and 2x6005 (4x for the 16LS) in the PP output stage.

Both versions are very easy to build, nice with vocals, but not quite HiFi - see the FFT charts. Matching tubes and the resistors in the split-load phase splitter circuit helps to reduce distortion.
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Posted in Tube power amps
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