Lateral Mosfet Power Amplifier

by Kostas Lentas ( UK )

Hi Mike,

Today is a bank holiday in the UK and found some time to do some further work on the amp. I totally agree with you, the speaker itself can dramatically change the final result along the source-preamp-power amp-speaker line.

My speakers are 3-way, closed cabinets, tuned roughly at 40Hz and go down to 30Hz (~ -3db), so yes, the change is not so noticeable but maybe slightly better. However, since I used my Mundorf aluminum/oil capacitors, I think that the midrange sounds a bit clearer now, but maybe all these changes are a bit subjective and due to the fact that we expect better sound clarity by using better components. Anyway, enough with rumbling, here's my review on the amp:

After listening to the amp for over a week now, I can say that it is definitely a very good amp, with pleasant sound, wide frequency band, punchy bass, realistic mids and crisp highs. I am using it in a full diy, flat response, system and have no response issues whatsoever. The build is simple enough, the components are of very good quality, and once you follow the instructions carefully no problems should arise. The bias which can cause anxiety to many who have seen caps exploding or resistors catching fire due to dodgy pots, should not worry at all with the use of a multi-turn pot. The circuit is very stable and once you bias it as suggested, the amp will happily deliver clear, detailed and pleasant sound.

I have attached a few new pics of the final build, where you can clearly see the dual mono configuration, with a 300VA toroidal transformer, two 35A rectifier bridges, a total of 27200uF capacitor bank and 100nF mkp bypass capacitors for each channel. The dc protection circuit has separate grounds even though the two channels are built on the same pcb. As a result the two channels do not share ground along the line from the input to the output, and the elimination of the crosstalk is remarkable. The only changes I did are the spade connectors that made the assembling a bit easier and the use of a better quality input capacitor, notably, I have used a 4.7uF Mundorf aluminum/oil capacitor which in my opinion offers slightly clearer mids, and in theory, lowers the cut-off frequency of the high-pass filter in the input stage.

With many cheap but questionable in terms of reliability kits that have over flooded e-bay, I think that these modules worth every penny and are a very serious option for somebody who wishes to build an amp that can keep and enjoy for many years. Of course with your help Mike, and your response is too much appreciated.

Many thanks,

60 Downes Street | Calais | ME 04619 | USA