A pair of monsters…

As mentioned in my short Hiraga-post a while ago, I have also been trying my hand at Hiraga’s “Le Monstre” design. The Monstre is a simple 8W class A amplifier that originally ran off a huge 12V battery supply.

The red monstre is built on a set of PCBs from ebay seller jimsaudio. This uses the original transistors (except the output transistors which are newer MJL/MJW-types) but the supply rails are raised to 18V for an expected 15W output. The power supply is a CRC-design also from jimsaudio and I am using 35A bridges and 22mF capacitors (because I already had them).

The green monstre is my own PCB layout. This is built on the original circuit but with never transistors based on the modified schematic by Kristian Kluric and deliberately made to be as compact as possible, just under 5×5 cm. The power supply is a compact CRC-type as well, but because of the lower supply rails the capacitors could be a bit bigger (47mF) even if the board is just 8×10 cm.

The amplifier board seems to work fine as it is, but I haven’t tested it in a way where I could check that it is thermally stable over a longer period of time, only that I am able to zero the output offset and play music through it. I made some small revisions to the amp layout and once those new boards arrive I’ll start building a complete dual-mono amplifier on the new boards. The output transistors in this version are TIP2955/TIP3055 but I will probably try to replace them with faster NJW/MJW-types later on.

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14 Responses to A pair of monsters…

  1. Pingback: More monsters… | theslowdiyer

  2. Hi,
    Very nice work.I would like to know the output transistors NJW/MJW-types ? We are designing PCBs for Le Monstre for GB here in India.Your help will be much appreciated. My email is sachu888@gmail.com

    Regards,
    Sachin

    • theslowdiyer says:

      Hi Sachin,

      The transistors I used were NJW1382/3281 types. The MJW-types would be better thermally because of the bigger package, but my PCB is so small that they don’t fit side-by-side.

      BR,

  3. I am thinking of using NJW0302G / NJW0281G and 2sk170bl/2sj74Bl as they are widely available. What do you think of this? I will post you our layout,once done.

    Regards,
    Sachin

  4. diyhifiaudio says:

    Thank you,I have desided to buy matched pair of 2sk170bl/2sj74bl from Spencer.I will keep you update.

    Regards,
    Sachin

  5. Sachin says:

    We have built this amp, sounding good but little thin in vocals and less bass. I have used cap multiplier with 33000uf per rail input caps, transistors used MJL21193G/94G, Jfets are 2sk170BL/2SJ74BL, transformer is 12-0-12 X2, 360VA. Will try to add more 33k uf caps per rail after multiplier if it improves the sound, build pics here http://www.diyaudio.com/forums/solid-state/5462-hiraga-le-monstre-132.html

    Regards
    Sachin

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