Ian Mackenzie(ax-p1)

Miscellaneous Projects

About me
My name is Ian Mackenzie, I live in Melbourne Australia. Having built the A2 and Bosoz I was is inspired to take the next step in my Passdiy journey and here is my X Amplifier.

As this is a relatively low powered version of the X Amplifier so I have termed this amplifier the Baby X Amplifier. The Baby X Amplifier is rated at appoximately 36 watts (8ohms) by design and the intention is to let the baby grow up to a 100 watt or so full size adult by adding more resources at a later stage. I also wanted to maintain a distinct diy theme and flavour rather than a cloned re engineered outcome. I think a diy mentality is a more relaxed way of approaching the home built task. The driver board is centrally mounted on a perspex platform for several reasons. To enable easy adjustment, access for assemble / re assemble via the screw in terminal blocks and is central to the box for future heatsinks. The output stage is point to point for similar reasons, so I can easily mix and match and scale the amplifier at a later stage. In fact I rebuilt the output with 2 pairs of IRF 240's per side recently for best practice, minimising wattage per device @ 14 watts each so there are now 8 output output fets per channel. But it is delicate and I will improve on this with terminal strips to provide strain relief for the wiring. To dissipate heat effectively the Baby X Amplifier is constructed around mono blocks measuring 350 x 420mm with the heatsink at the back. The heatsinks are Conrad 300 mm x150mm with 2 flanges and are rated at 0.25/per watt. The power supply is driven by a 300va transformer and underneath the driver platform are 8 x 15000 63 volt Nichion filter capacitors. The ripple is only about 500mv and the amp is totally silent even at point blank range. Technically, the supply rails are approximately 14 volts Dc and the bias reads about 0.5 volts across the 0.22 ohms resisters for a total DC bias of 4.5 amps per side. The offset, both absolute and Dc are only a few millivolts after 1/2 hour warm up. Matching of the negative drive side and the input pair seem to cure any offset ills without issue here. Credits This project would not have been possible without the technical assistance and expertise of Grey Rollins, John Inlow who kindly provided the pcbs and Mr Pass for supporting the development of the project. Subjectively Using the recently modified X Bosoz and wonderful Pearl phono stage by Wayne Coburn, the sound would appear to be from the works of Mr Pass in the AX Pdf. There is no point beating around the bush, its that good. The real surprise is an marked improvement in spatial imaging and staging of instruments and soloist vocals to the point where they can be quite visible. The drive, snap transparency appears to replace the warm & romantic engagement of the Amplifier, and creates a new kind of excitement (of being there) that is still quite sweet. And I can see the peanut butter & chocolate from here. Where do I go from here...my oh my. Thankyou Mr Pass. Ian Mackenzie .(JavaScript must be enabled to view this email address)

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