Lm60 Lateral Mosfet Power Amplifier

Posted by ATMAJA'Z


As promised here are my thoughts on building and listening to your LM60 amplifier kit. I was very impressed with the delivery time after ordering (12days) The kit was supplied with good quality components, a good PCB with heavy solder tracks and component marking and a CD containing schematics, component list, build and test instructions. I think the inclusion of a photo of a completed board would be helpful. You did supply me one when I ran into a minor problem of my own making. in fact you could not have been more helpful.

For anyone able to solder the kit is simple and straightforward if the instructions are carefully followed but care in soldering is critical. I had a dry joint on 1 of my 2 boards which caused biasing and overheating problems when tested. With good help from Michael Chua this was resolved.

With the 2 boards (Stereo format) case mounted I connected to a single power supply, twin power supplies are recommended and probably best, but I only had a single supply to hand. This consisted of a 350Va - 24-0-24V toroidal transformer and 2 x 10,000mF caps in each power line and a 35amp solid state rectifier, giving me +/- 38vdc unloaded. This would result in a very slight reduction in power from the 60wpc output of the recommended power supply. Testing and biasing is simple following the instructions. DC offset in my case was about 5Mv and biasing set at the recommended 22Mv.

I connected to my 2 way monitor speakers (Ribbon Tweeters) with a frequency response from 35Hz - 40Khz and ran a a CD for listening test. I was totally amazed. Here was a very budget amplifier kit that had pretensions to be a Krell. There was no trace of hum or any other extraneous noise to interfere with the music even at high listening levels. Instruments and performers were very firmly locked into their own piece of the soundstage. Bass was very firm and deep and the Treble was as clean and open as a whistle.

Altogether a very balanced, clean and open sound. Remember the amplifier is not yet run in. After running for about 6 hours the heatsink temperature had risen 12 degrees over ambient level so no heat problems here.

This kit must be the absolute bargain for anyone who can solder and follow simple build instructions. It is the best kit amp I have ever heard and outperforms many amplifiers costing 20 times more. I would recommend this amp to anyone and am so impressed I will in due course return to Ampslab for a different more powerfull kit. Do not assume this kit is underpowered, it most certainly is powerfull enough for most circumstances but I am an inveterate meddler.

My congratulations to Michael Chua and staff at Ampslab. Keep up the good work in producing affordable audio gear. You may use any or all of this E Mail for publicity purposes.

from : ampslab.com