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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 -

    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.

    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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