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Ebay audio kits - opinions

Discussion in 'd.i.y.' started by df_genius, Sep 12, 2015.

  1. df_genius

    df_genius Solder slinger

    The SOA chart for the MLJ3281/1302 looks similar to the 2SC5200/A1943, so I would stay under 50V rails and make sure the heatsinks are big.

    I fired one channel up today on 28V rails and it worked OK, the DC offset does drift alot at startup but the built-in protection circuit comes in at around +/-600mV.

    I've read on DIY Audio that it has low PSRR so a regulated supply might work well, I am thinking about using a low drop out LT1083
     
  2. PigletsDad

    PigletsDad pfm Member

    I would expect the main cause of the PSRR will be in the early stages, which only need low current, while teh output devices won't matter so much. So simply adding a second small rectifier bridge and pair of modest caps to power everything except the output pair may give many of the benefits of regulation at modest cost.
     
  3. df_genius

    df_genius Solder slinger

  4. Tony L

    Tony L Administrator

    Worth the price of admission just for the Chinese to English description!
     
  5. Tenson

    Tenson Trade: AudioSmile

    I know it may seem boring but if I were to buy an amp PCB from eBay I'd get something TDA7293 based. I believe a number of these ICs were used in parallel in a Mark Levinson power house and also in some Linn amps.

    This for example - http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=131605699788

    The trouble with eBay kits is that I doubt they refine the designs. They probably just make sure it produces sound with no horrible buzzing noises then ship. A good design will be measured and tweaked for ideal grounding and stability.
     
  6. df_genius

    df_genius Solder slinger

    I've bought the A1 kit just to see if it works.

    If you're building your first discrete amplifier I don't think you can wrong with these, I've not seen any dodgy parts in any of the LJM kits I've bought, they work fine and are reputed to sound very good. I have a pair and they work fine, they could drive my 5 ohm dummy load to 100W before clipping on 32V rails, I've not done extended listening yet as the FAST amplifier I am making with them isn't finished yet.

    http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=221357376090

    The designer LJM frequents DIYAudio and his designs seem to stack up to scrutiny reasonably well.
     
  7. firestorm

    firestorm pfm Member

    Any one with updates to their Ebay/aliexpress/banggood source amplifiers in the last 6 years?

    One thing I've seen that has caught my eye is the use of point-to-point wiring or "scaffolding" with chip amps, not sure what advantages it confers, but it looks different.
    I don't think it's a good idea to mount electrolytic capacitors onto a hot heatsink...

    [​IMG] [​IMG]
     
  8. slavedata

    slavedata pfm Member

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