A modified theme. For the Hitachi/Maplin power amp

edited July 3 in DIY
This is based on the Maplin/Hitachi theme these board are stereo and use much better and rugged FETS.
The PCB is stereo and you build it,
It gives 100W RMS into 8R

Each PCB blank will cost £40 it is double sided 2oZ Cu with silk screen.

http://seca.freeforums.net/thread/222/modified-theme-hitachi-maplin-power

Comments

  • How's  that retirement going...?
  • It is not I got bored silly and started up again in a small but fun way,

  • I'm lost.

    What's 'the Maplin/Hitachi theme'?
  • In the late 1970s and early 1980s Maplin did a kit for MOS Amps, all were based on the Hitachi design and now obsolete MOS FETs. The Claymore was also based on the Hitachi design with some heavy mods to improve the sound. Now with new FETS the sound has been improved further and the amps are more efficient thus running cooler. And the damping factor has gone up because the Old FETS were 1.5-1.8 Ohm at 8Amps these are 0.06Ohms at 30+Amps little monsters. 
  • Ok, that's the Hitachi thing sorted but now we have damping factor.
    Never really got to grips with this!
    I've just come back from refreshing my confusion on wiki, psaudio and eaw sites where all the talk is related to the entire amplifiers damping factor in conjunction with connecting wires and speakers. All these articles seem to finish that unless in extreme circumstances the DF has negligible impact.

    Here Colin is talking about the DF just for the devices in question, you wot like mate?
    Totally nonplussed, can anyone explain this in Ladybird-book terms?
  • The higher the damping factor the lower the output impedance of the amp thus it ability to deliver high currents and drive odd impedance. So a 10 ohm load on a amp with a DP of 1000 give us 10/1000 = 10mR so at 20VRMS out in theory you could take 20V/10mR = 2000Amp pk if caps and psu and wiring was big enough and the output device could handle it without going bang.

    Most amps are low DP 50 so  this rarely happens.

    Confused you will be soon he he
  • AntiCrap said:
    In the late 1970s and early 1980s Maplin did a kit for MOS Amps, all were based on the Hitachi design and now obsolete MOS FETs. The Claymore was also based on the Hitachi design with some heavy mods to improve the sound. Now with new FETS the sound has been improved further and the amps are more efficient thus running cooler. And the damping factor has gone up because the Old FETS were 1.5-1.8 Ohm at 8Amps these are 0.06Ohms at 30+Amps little monsters. 
    Thanks Col
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