rhing Posted December 26, 2019 Share Posted December 26, 2019 The Pass Labs and First Watt amplifiers are built with different design philosophies. Pass Labs amps are built to work with a wide range of high end audio speaker systems—some which represent very difficult loads, while most First Watt amplifiers are designed for high sensitivity speaker systems like horns and full range single driver systems with minimal crossovers. Not sure if meaningful apples-to-apples comparisons can be made since they are designed for different purposes. Having attended several Burning Amplifier Festivals in San Francisco including the last one a month ago, I can tell you that Nelson Pass’ passions are with the First Watt and Pass DIY crowds. 2 Quote Link to comment Share on other sites More sharing options...
rhing Posted October 26, 2020 Share Posted October 26, 2020 I recently completed a Pass DIY clone of the Aleph J amplifier. I’ve been comparing it to my Dynakit Stereo 35 with Enhanced Fixed Bias (EFB), Pass DIY Sony VFET, and rebuilt McIntosh MC240 amplifier. To my ears and one of my audio buddy’s ears, the Aleph J is a very special amp with my Klipsch Forte II speakers. It is most similar to the Pass DIY Sony VFET amp, but has something special that puts it in the running with my favorite, the McIntosh MC240 tube amp. The soundstage is huge like the Sony VFET and MC240 amp, but the level of detail, natural tonality, and excellent separation combined with the pace and timing are something to behold. I’ve only had the amp running for over a week now. We’ll see how I feel about this a month or two from now. I suspect I will continue to enjoy this amp. My friend who heard it wants me to build one for him with a dual mono configuration in a larger chassis with larger heat sinks to set the output bias even higher. This amp gets warm, but Fall weather is settling in now, so the heat radiating from the amp’s heat sinks is not a problem. 2 Quote Link to comment Share on other sites More sharing options...
OO1 Posted October 26, 2020 Share Posted October 26, 2020 8 minutes ago, rhing said: This amp gets warm, but Fall weather is settling in now, so the heat radiating from the amp’s heat sinks is not a problem. a perforated rear bezel could aid in cooling - Quote Link to comment Share on other sites More sharing options...
henry4841 Posted October 26, 2020 Share Posted October 26, 2020 8 hours ago, RandyH000 said: a perforated rear bezel could aid in cooling - I think he just means the amplifier is supposed to run hot and not that it is running too hot. Inside the amplifier is not what is getting hot, it is the heatsinks. Those Passlabs and Firstwatt amplifiers are class A and are supposed to run approximately 55 degrees celsius on the heatsinks all the time. Five seconds with your hand on the heatsink is a good judge of 55 degrees. Even at idle unlike a class A/B amplifier that only gets warm when it is run continuously at a high volume. Class A is most linear than any other class of amplification for this reason. Purist love the sound of class A, not that other forms do sound good as well when designed right. 1 Quote Link to comment Share on other sites More sharing options...
Full Range Posted October 26, 2020 Share Posted October 26, 2020 I am going to build a second M2 when I have time My first amp was mostly built by a friend and used the early release M2 boards This time I’m using the new M2X boards that have 4 types / designs of sister boards on the output stage one being the original and the others are different designs that give a different sound flavour I have the boards at home now and it took a couple of months to deliver during Covid 🤬 Im going to build the original Nelson Pass M2 version sister board, as I have the NOS hard to get parts 2 Quote Link to comment Share on other sites More sharing options...
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