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<title>The Class-A Amplifier Site - Constructors' Comments - Sound Quality</title>
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<link rel="StyleSheet" href="class-a.css" type="text/css" media="screen, print">
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<link rel="shortcut icon" type="image/ico" href="favicon.ico">
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<meta content="Geoff Moss" name=Author>
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</head>
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<body background="slate.jpg" bgcolor="#E8E8E8" lang=EN-GB link=blue vlink=blue>
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<div class=Section1>
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<p align=right style='text-align:right'><b>The Class-A Amplifier Site</b></p>
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<p align=right style='text-align:right'><span style='font-size:10.0pt'>This
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page was last updated on 5 December 2001</span></p>
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<p><b><span style='color:blue'><a href="index-1.htm" title=index-1.htm>[ Back
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to Index ]</a></span></b></p>
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<p> </p>
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<p align=center style='text-align:center'><b><span style='font-size:20.0pt'>Constructors’
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Comments – Sound Quality</span></b></p>
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<p align=center style='text-align:center'> </p>
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<p align=center style='text-align:center'> </p>
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<p>This page contains comments I have received from other constructors
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regarding the sound quality of the JLH Class-A amplifier. Though the quotes are
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extracts from emails, I hope that they can still be read in context. I have
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deliberately excluded my own comments since I am more than a little biased (I
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must be, otherwise I wouldn’t have spent the time needed to set up this
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site <span style='font-family:Wingdings'>J</span>). </p>
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<p> </p>
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</div>
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<p><b>From Rudy van Stratum, Holland</b> – Modified JLH 1969 version
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(dual supply rails, no output capacitor) </p>
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<p> </p>
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<p>Now the sound is to my taste, very good indeed, comparable with several good
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tube amplifiers I have at my disposal.</p>
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<p> </p>
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<p align=left style='text-align:left'>Sounds better, more open, more airy, tauter
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bass, etc than my old and trusted C-coupled version. </p>
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<p> </p>
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<p>I've listened extensively to the differences between the Hiraga and the
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modified JLH 69. Of course this need not be a definitive judgement, so
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..…</p>
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<p><br>
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For a start: these two amps are very very good in transistor terms, indeed they
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are belonging to a remarkable class of all-time classics.</p>
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<p><br>
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Differences between the two are very subtle. It's certainly not so that one of
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the two 'blows away' the other. If there are differences I should say that the
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JLH seems to flow somewhat more (vague terms, but alas). The general character
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of the sound is very similar (warm sounding, full bodied, airy). </p>
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<p> </p>
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<p><i>Rudy has now tried different values (up to 1000uF) for the bootstrap (C1)
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and feedback (C3) capacitors and has sent the following additional comments:</i></p>
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<p> </p>
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<p>I have settled on values of 470uF for both C's (bootstrap and feedback),
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they seem to work fine and are marginally better than both 220uF and
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1000uF………. In comparison with my Hiraga the JLH now sounds
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very open and quick and with a fine texture in the highs. Very good indeed. But
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the Hiraga sounds 'fuller' and has more weight somewhere around 100-500 Hz I
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guess. My old JLH also had that full bodied 'tube' sound (but not the air and
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texture of the symmetrical version).</p>
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<p><b> </b></p>
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<div style='margin-left:14.2pt;margin-right:14.2pt'>
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</div>
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<p><b>From Mike Jonasson, New Zealand</b> – JLH 1996 version</p>
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<p> </p>
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<p>I've compared my 1996 JLH Class A to some very costly valve amps - a single
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ended 300B project and a reworked Classic design from the 50's and I've
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listened critically to many commercial examples. </p>
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<p><br>
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These have midrange charm which makes them attractive but valve devotees seem
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oblivious to shortcomings elsewhere - fairly obvious ones I find completely
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unacceptable. I have resolved that this probably has a lot to do with music
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choice - they listen to a lot of female cabaret stuff which is fairly light in
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musical texture, not too much outside the midrange and not a lot going on at
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the same time - avoiding intermodulation and bass problems that test equipment
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out on rock and classic.</p>
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<p><br>
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It's not my cuppa tea and efficient speakers are mandatory for a lot of them.</p>
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<p><br>
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The JLH Class A is also better than any SS amp I've built / heard. These
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include some Mosfet and Bipolar Class B designs with worldwide DIY popularity,
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as well as commercial products. The JLH simply has more finesse.</p>
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<p><br>
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I believe the 1996 version betters the 1969 original as there is no capacitor
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to degrade the output signal.</p>
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<p><b> </b></p>
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</div>
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<p><b>From Nick Gibbs, England</b> – JLH 1969 Version</p>
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<p><b> </b></p>
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<p>I only expected the amp to be a stop gap until something more suitable came
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along. Well the amp has now been in use for 16 years (used on an
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almost daily basis) without a single fault or modification. During this
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time I have built and used the JLLH MOSFET design published in ETI,
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however, I always returned to the Class A amp after a few days.</p>
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<p> </p>
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<p>Now I am using a pair of Quad ESL57 electrostatic speakers which present
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around 2 Ohms at 15KHz and about 30 Ohms at 80Hz, my Class A is running a 27V
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rail and 1.2A standing current, so I get a bit of clipping now and then. I am
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looking to build a version of the 1996 design with a substantially higher
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standing current to satisfy the Quad’s. </p>
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<p> </p>
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<p>When I first got the Quad's I used a Quad 405 amp to drive them, however,
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this didn't prove very successful as apparently it can only deliver a few watts
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into 2 Ohms. Clipping occurred at low levels and was particularly awful. Next I
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tried the JLLH MOSFET expecting better results. This amp was audibly superior,
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however, it is capable of very limited current supply into low impedance loads,
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after a quick clip the PSU shuts down. I have done very limited listening
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with the MOSFET amp as the PSU shuts down very easily. Then I tried the little
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Class A not really expecting any surprises. Well, (and I don't read ANY hifi
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mags) the stereo image and ambience of a well recorded performance were
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unbelievable, clipping appears very gentle ?, it is surprising how much
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material falls within the bounds of 10W even on the Quads. This amp combined
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with the Quad's really is fantastic, even friends who consider my interest
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a little strange said "Wow". However, the combination
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appears utterly ruthless in its reproduction, bad recordings are bad.</p>
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<p><b> </b></p>
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</div>
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<p><b>From Jason Hubbard, England</b> – JLH 1969 version</p>
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<p> </p>
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<p>I have built the amp (I used it for about 6 months but gave up on it - I had
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inadequate heatsinking and the fan I needed to run in order to keep it all cool
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bugged me too much). Sounded great compared to anything I'd used before but I
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yearned for more power to drive woefully inefficient speakers in a large room.</p>
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<p><b> </b></p>
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</div>
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<p><b>From Asen Tutekov, Bulgaria</b> – JLH 1969 (3 ohm) version</p>
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<p> </p>
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<p>The sound is good. I was a bit disappointed at the very beginning - maybe
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because I expected a miracle to happen. That was because I hadn't listened
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to a SE power amp before that moment. After several hours of listening I found out
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that the amp is very detailed, doesn't tire out the ears and controls the bass
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better than my Quad 405-2 ..... In short - I'm content with it.</p>
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<p> </p>
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</div>
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<p><b>From Jason Wou, Australia</b> – JLH1996 version</p>
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<p> </p>
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<p>….. the amp sounds fantastic …..</p>
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<p> </p>
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<p>For some CD's (like GRP's Rippington) the amp sounds just amazing. I can nod
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nod nod throughout the<br>
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CD. But for some other CD's I can hear distortion-like sound which I couldn't
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hear from my other amps.<br>
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Most MP3's sound terrible with this amp. It looks as if this amp + B&W
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Solid speakers seems to be somewhat "selective" to the type of music
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and brands, or it's just way too revealing. Any opinion?</p>
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<p> </p>
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<p><span style='font-size:10.0pt'>(Yes, several people have commented that this
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amp shows up poor recordings and my findings are the same. I have a box of
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about 40 CDs that I can no longer listen to but that seemed alright when using
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other, well-reviewed, Class-AB amps – Geoff)</span></p>
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<p> </p>
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</div>
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<p><b>From Ian Mackenzie, Australia</b> – JLH 1996 version</p>
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<p> </p>
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<p>My feelings echo those other builders in the comments page. The amp sounds
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very liquid, subtle but very detailed and coherent on good recordings compared
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to any conventional A/AB amp.</p>
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<p> <br>
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There also appears to be a very even perspective and uniformity of the tonal
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balance in both timbre and dynamics. In short this amp is excellent and a boon
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for such a simple diy project.</p>
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<p> </p>
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</div>
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<p><b>From David Smith, England</b> – JLH 1969 version</p>
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<p> </p>
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<p>I have used Rod Elliot's pre-amp designed for the DoZ amplifier to feed the
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JLH amps and I am truly very pleased with the results; the sound is very smooth
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and easy on the ears, particularly noticeable is the absence of unpleasant
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sibilance with broadcast female voices. For the first time I can see why the
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amplifier is so highly rated.</p>
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<p> </p>
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</div>
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<p><b>From Tim Andrew, UK</b> – JLH 1996 version</p>
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<p> </p>
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<p><em><span style='font-family:Arial;font-style:normal'>My version of the 1996
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JLH design uses paper-in-oil capacitors on the input, Elna Silmic
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electrolytics elsewhere, with Vishay bulk foil and Tantalum film resistors
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in all signal carrying parts of the circuit. At the suggestion of Geoff
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Moss, I have also replaced the 2N3055s with MJ15003s. These
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modifications have been carried out individually so as to enable me to
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evaluate each in turn. Each one has produced a very noticeable improvement
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and, in particular, the capacitor and the MJ15003 transistor changes
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must be singled out as making a larger improvement than I had
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expected. The amplifier now </span></em><strong><span style='font-family:
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Arial'>sounds </span></strong><em><span style='font-family:Arial;font-style:
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normal'>far more powerful than many 200 watt amplifiers that I have heard and
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owned but has a warmth, purity, delicacy and speed that has eluded
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them all.</span></em></p>
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<p> </p>
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<p><a name=ma></a><b>From Chris Ma, Canada</b> – JLH 1996 version</p>
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<p> </p>
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<p>The JLH compares to the Rotel multi-channel (power section only) as
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follows:- The brightness/harsh high is gone. The vocal is a lot fuller. The
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four string bass has more emotion to the notes. The kick drum is easier to
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distinguish from the electric bass guitar. It has more depth in the sense of
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stage but narrower than the Rotel. The focus or image position is better with
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the JLH. It reviews the fine detail much, much more with ease. Certain tracks
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in some CDs I would not like to listen to before with the Rotel because they
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sounded really bad but now I can enjoy them with the JLH. The background noise
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is really quiet. I can enjoy heavy rock music again with the JLH because it can
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handle a lot of things going on musically without tiring me out with just
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noise. For such a simple design and inexpensive final product it is a very good
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amp. Now the JLH makes me really miss the Pink Triangle turntable. </p>
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<p> </p>
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<p><span style='font-size:10.0pt'>Chris’s full email giving some
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background to his comments can be found <a href="jlhma.htm" title=jlhma.htm>here.</a></span></p>
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<p> </p>
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<p> </p>
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<p> </p>
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<p><b><span style='color:blue'><a href="index-1.htm" title=index-1.htm>[ Back
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to Index ]</a></span></b></p>
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<p> </p>
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<p> </p>
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<p><b><span style='font-size:8.0pt'>HISTORY:</span></b><span style='font-size:
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8.0pt'> Page created 24/06/2001 </span></p>
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<p><span style='font-size:8.0pt'>08/07/2001 Ian Mckenzie’s comments added</span></p>
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<p><span style='font-size:8.0pt'>24/07/2001 David Smith’s comments added</span></p>
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<p><span style='font-size:8.0pt'>05/08/2001 Additional comments from Rudy van
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Stratum</span></p>
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<p><span style='font-size:8.0pt'>18/08/2001 Tim Andrew’s comments added</span></p>
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<p><span style='font-size:8.0pt'>14/09/2001 Chris Ma’s comments added</span></p>
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<p><span style='font-size:8.0pt'>05/12/2001 Tim Andrew’s comments updated</span></p>
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<p><span style='font-size:8.0pt'> </span></p>
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