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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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S5 Electronics "L" series tube amps

Posted 12th August 2010 at 04:52 PM by alexcp
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
Views 2633 Comments 2
Main     Velleman K4040 »
Total Comments 2


  1. Old Comment
    It looks like a solid build. Very nice design. What do you think of the sound? If you don't mind ellaborating. The ls series seem to get quite mixes reviews but for the price nothing seems to compare. What transformers did you use specifically?

    Thank you
    Posted 25th March 2017 at 12:37 AM by bels bels is offline
  2. Old Comment
    alexcp's Avatar
    Thank you for the comment.

    The sound is sweet but in my opinion lacks clarity and resolution. It is pleasant on single vocal but ruins an orchestra.

    I used Edcor XPWR085 for power and two Edcor GXPP10-10K for outputs. The effect on the sound was minimal, although it does look better than with the stock transformers.

    After I posted, I found out that matching (preferably curve matching) output tubes helps. One can get them in matched pairs and quads from eBay; 6AQ5 or EL90 are other names for the 6005. Also, I am guessing that fine tuning the phase splitter and the screen grid voltage would improve the distortion a bit, although is requires at a minimum a good sound card and an appropriate software such as Arta or audioTester.
    Posted 10th May 2017 at 02:29 AM by alexcp alexcp is offline

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