silicon chip magazine 15w class a amp

[jamesfeline]

Hello

My name is Nick from the UK and i have been making power amps for the last 20 years, this is my 1st response to this forum. Most of my amps have been designed by JLH. I was thinking of making the SC magazine 15w class a as described in this post. Any chance some of you could send me the CCT diagram and pics of your amps if you have constructed the amp in question ? also what are your views on this amp as regards sound quality ? would be helpfull before I start construction

best regards

Nick

[jamesfeline]

Hello again

Any body ?? surley some one must of construted this power amp ? or is it no good ?

best regards

Nick

[jamesfeline]

ok

what would you all go for ?

JLH 15w class A or the SC magazine 15w class A design ?

regards

Nick

[Netlist]

Nick,
I'm sure you will get more responce here in the Solid State forum.

/Hugo

[destroyer X]

Will be easier, and better for us, to watch it in advance, this may result in some comments from us.

20 years constructing is telling me that you may have a lot of things to comment too.

If you came from other forum section, chip amps or another...a transference (moved for good), post the schematic once more.

regards,

Carlos

[jamesfeline]

thanks for the feedback ... yes I am 42 these days a fully qualified electronics technician ,,, and I have had the audio bug since I was 14 years old. I have my own log cabin as a electronics workshop and dream of running my own company making audio gear ( all hand made ) at the highest quality possible ( well by me any way )
I will post some photos soon as I am still new new this site as I did not realise I was in the wrong section. I am a big fan of JLH as I have met the guy. I make highley modified JLH 80w mosfet power amps and a 250w bridged version .... you just need to see it also i have sold quite a few ... trying to get them CE approved

anyway

taking my wife out for a meal .... speak to you all when I get back

all the best

Nick

[destroyer X]

This forum is an enormous brotherhood..filled with knowledge till the top....bad folks are not more than 10 when we have thousands of nice educated folks.

I hope you enjoy and give us contributions telling things about your experience, and contributing in our threads too.

regards,

Carlos

[Greg Erskine]

hi jamesfeline,

I was just reading the May 2007 Silicon Chip magazine and guess what?.... they have just published an update to the old 15W ULD class-A amp.

Here's a quote from the front page, "All-new 20W Class-A Amp, the lowest distortion of any amplifier ever published...anywhere in the world!!"

Note 2 explanation marks.

regards

[sandyK]

I have been using this amplifier since shortly after publication.
The editor of Silicon Chip (as an engineer) was quite embarrassed about subjective quality of this amplifier when compared to a previous Class AB magazine project. He seemed to put most of the major audible improvements down to the superior channel separation of the Class A .
As good as the basic amplifier is, it is very accomodating of modifications to both the amplifier PCBs and Power Supply.
The output transistors , for example , may be replaced by 2SA1302/2SC3281 (or the latest Toshiba devices) for even better results. Using 2 regulator boards further improves the performance, as does replacing their series pass transistors with MJE15030/15031.Further benefit may be obtained by using a Harbuch PTT4639 transformer (dual secondaries) and 2 bridge rectifiers.
There are MANY other refinements also, that I won't go into at this stage.
sandyK

[smithy666]

I think you hit the nail on the head regarding Silicon Chip projects. Sure, the design may be good, but they could have gone just that bit further to make it really great. I find in virtually all their projects that component selection is lowest common denominator stuff, ie whatever cheap parts are available from Jaycar/Dick Smith will do. They rarely give consideration to capacitor types, even in the signal path, which I doubt even the biggest sceptics would argue over the benefits of film vs electro.

One example is Silicon Chip's Oct 2005 "the best preamplifier ever" project, which features 4 non polarised electros (2x47uF and 2x22uF) in the signal path of each channel!! Arrrgh! They also use the same relay to switch the left and right channel and the distance between tracks for the left and right channel is about 0.5mm (one channel's track actually runs through the relay terminals of the other channel). Don't get me started on the carbon volume pots running back to terminal blocks. I'm not attacking their design, just the fact they put these up as the "best ever" published (do they read Elektor?) and of "audiophile" quality. Oh, please.