The Class-A Amplifier Site - Constructors' Comments

The Class-A Amplifier Site

This page was last updated on 5 December 2001

Constructors’ Comments – Sound Quality

This page contains comments I have received from other constructors regarding the sound quality of the JLH Class-A amplifier. Though the quotes are extracts from emails, I hope that they can still be read in context. I have deliberately excluded my own comments since I am more than a little biased (I must be, otherwise I wouldn’t have spent the time needed to set up this site J).

From Rudy van Stratum, Holland – Modified JLH 1969 version (dual supply rails, no output capacitor)

Now the sound is to my taste, very good indeed, comparable with several good tube amplifiers I have at my disposal.

Sounds better, more open, more airy, tauter bass, etc than my old and trusted C-coupled version.

I've listened extensively to the differences between the Hiraga and the modified JLH 69. Of course this need not be a definitive judgement, so ..…

For a start: these two amps are very very good in transistor terms, indeed they are belonging to a remarkable class of all-time classics.

Differences between the two are very subtle. It's certainly not so that one of the two 'blows away' the other. If there are differences I should say that the JLH seems to flow somewhat more (vague terms, but alas). The general character of the sound is very similar (warm sounding, full bodied, airy).

Rudy has now tried different values (up to 1000uF) for the bootstrap (C1) and feedback (C3) capacitors and has sent the following additional comments:

I have settled on values of 470uF for both C's (bootstrap and feedback), they seem to work fine and are marginally better than both 220uF and 1000uF………. In comparison with my Hiraga the JLH now sounds very open and quick and with a fine texture in the highs. Very good indeed. But the Hiraga sounds 'fuller' and has more weight somewhere around 100-500 Hz I guess. My old JLH also had that full bodied 'tube' sound (but not the air and texture of the symmetrical version).

From Mike Jonasson, New Zealand – JLH 1996 version

I've compared my 1996 JLH Class A to some very costly valve amps - a single ended 300B project and a reworked Classic design from the 50's and I've listened critically to many commercial examples.

These have midrange charm which makes them attractive but valve devotees seem oblivious to shortcomings elsewhere - fairly obvious ones I find completely unacceptable. I have resolved that this probably has a lot to do with music choice - they listen to a lot of female cabaret stuff which is fairly light in musical texture, not too much outside the midrange and not a lot going on at the same time - avoiding intermodulation and bass problems that test equipment out on rock and classic.

It's not my cuppa tea and efficient speakers are mandatory for a lot of them.

The JLH Class A is also better than any SS amp I've built / heard. These include some Mosfet and Bipolar Class B designs with worldwide DIY popularity, as well as commercial products. The JLH simply has more finesse.

I believe the 1996 version betters the 1969 original as there is no capacitor to degrade the output signal.

From Nick Gibbs, England – JLH 1969 Version

I only expected the amp to be a stop gap until something more suitable came along. Well the amp has now been in use for 16 years (used on an almost daily basis) without a single fault or modification. During this time I have built and used the JLLH MOSFET design published in ETI, however, I always returned to the Class A amp after a few days.

Now I am using a pair of Quad ESL57 electrostatic speakers which present around 2 Ohms at 15KHz and about 30 Ohms at 80Hz, my Class A is running a 27V rail and 1.2A standing current, so I get a bit of clipping now and then. I am looking to build a version of the 1996 design with a substantially higher standing current to satisfy the Quad’s.

When I first got the Quad's I used a Quad 405 amp to drive them, however, this didn't prove very successful as apparently it can only deliver a few watts into 2 Ohms. Clipping occurred at low levels and was particularly awful. Next I tried the JLLH MOSFET expecting better results. This amp was audibly superior, however, it is capable of very limited current supply into low impedance loads, after a quick clip the PSU shuts down. I have done very limited listening with the MOSFET amp as the PSU shuts down very easily. Then I tried the little Class A not really expecting any surprises. Well, (and I don't read ANY hifi mags) the stereo image and ambience of a well recorded performance were unbelievable, clipping appears very gentle ?, it is surprising how much material falls within the bounds of 10W even on the Quads. This amp combined with the Quad's really is fantastic, even friends who consider my interest a little strange said "Wow". However, the combination appears utterly ruthless in its reproduction, bad recordings are bad.

From Jason Hubbard, England – JLH 1969 version

I have built the amp (I used it for about 6 months but gave up on it - I had inadequate heatsinking and the fan I needed to run in order to keep it all cool bugged me too much). Sounded great compared to anything I'd used before but I yearned for more power to drive woefully inefficient speakers in a large room.

From Asen Tutekov, Bulgaria – JLH 1969 (3 ohm) version

The sound is good. I was a bit disappointed at the very beginning - maybe because I expected a miracle to happen. That was because I hadn't listened to a SE power amp before that moment. After several hours of listening I found out that the amp is very detailed, doesn't tire out the ears and controls the bass better than my Quad 405-2 ..... In short - I'm content with it.

From Jason Wou, Australia – JLH1996 version

….. the amp sounds fantastic …..

For some CD's (like GRP's Rippington) the amp sounds just amazing. I can nod nod nod throughout the
CD. But for some other CD's I can hear distortion-like sound which I couldn't hear from my other amps.
Most MP3's sound terrible with this amp. It looks as if this amp + B&W Solid speakers seems to be somewhat "selective" to the type of music and brands, or it's just way too revealing. Any opinion?

(Yes, several people have commented that this amp shows up poor recordings and my findings are the same. I have a box of about 40 CDs that I can no longer listen to but that seemed alright when using other, well-reviewed, Class-AB amps – Geoff)

From Ian Mackenzie, Australia – JLH 1996 version

My feelings echo those other builders in the comments page. The amp sounds very liquid, subtle but very detailed and coherent on good recordings compared to any conventional A/AB amp.

There also appears to be a very even perspective and uniformity of the tonal balance in both timbre and dynamics. In short this amp is excellent and a boon for such a simple diy project.

From David Smith, England – JLH 1969 version

I have used Rod Elliot's pre-amp designed for the DoZ amplifier to feed the JLH amps and I am truly very pleased with the results; the sound is very smooth and easy on the ears, particularly noticeable is the absence of unpleasant sibilance with broadcast female voices. For the first time I can see why the amplifier is so highly rated.

From Tim Andrew, UK – JLH 1996 version

My version of the 1996 JLH design uses paper-in-oil capacitors on the input, Elna Silmic electrolytics elsewhere, with Vishay bulk foil and Tantalum film resistors in all signal carrying parts of the circuit. At the suggestion of Geoff Moss, I have also replaced the 2N3055s with MJ15003s. These modifications have been carried out individually so as to enable me to evaluate each in turn. Each one has produced a very noticeable improvement and, in particular, the capacitor and the MJ15003 transistor changes must be singled out as making a larger improvement than I had expected. The amplifier now sounds far more powerful than many 200 watt amplifiers that I have heard and owned but has a warmth, purity, delicacy and speed that has eluded them all.

From Chris Ma, Canada – JLH 1996 version

The JLH compares to the Rotel multi-channel (power section only) as follows:- The brightness/harsh high is gone. The vocal is a lot fuller. The four string bass has more emotion to the notes. The kick drum is easier to distinguish from the electric bass guitar. It has more depth in the sense of stage but narrower than the Rotel. The focus or image position is better with the JLH. It reviews the fine detail much, much more with ease. Certain tracks in some CDs I would not like to listen to before with the Rotel because they sounded really bad but now I can enjoy them with the JLH. The background noise is really quiet. I can enjoy heavy rock music again with the JLH because it can handle a lot of things going on musically without tiring me out with just noise. For such a simple design and inexpensive final product it is a very good amp. Now the JLH makes me really miss the Pink Triangle turntable.