Work in progress….

It’s been a while since I have posted here, but real life is still getting in the way of my build time. At the moment this means I am mostly starting up new projects, because for some strange reason I can always find time to start new projects – even when time to finish the old ones is nowhere in sight 😀

I have been shopping a little at diyinhk.com recently and bought several DAC boards and power supplies, so one a few DACs are in the cards for sure 🙂 Also, one or two gainclones might make an appearance as well at some point. One reason for this is that I rediscovered some pictures of the Audiosector “Patek” amp a couple of weeks ago, so guess who has been scouring ebay etc. for reasonably-priced copper bars lately? 😉

Lastly, the Borbely and the Le Monstre front/rear panels have arrived and I am pretty happy with those, so now I am just waiting for my transformer order and a free weekend and then at least that should be sorted out.

However, I have to say that even with not much new going on there are still plenty of people that find their way here. The blog was at 15k page views in the beginning of January and it is now over 21k views total – I can’t complain about that, so thanks a lot for stopping by 😀

More monsters…

As mentioned in my previous post on the Hiraga “Le Monstre” design, I wanted to build my own version of this classic amplifier. I was pretty happy with my original board layout and it seemed to be working fine as well, but there was still some room for improvement so I could justify a version 1.1.

I received the PCBs of the new amp board layout around a week ago and put a couple together along with a couple of extra PSUs for a complete monoblock pair. The front and rear panels have been ordered and the transformer order should be ready to go within the next week or so, but here are some quick and dirty “work-in-progress” shots of one of the monoblocks 🙂

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.

Hiraga intro

After trying my hand at JLH and Pass, it is natural for me to move on to one of the other class A “design greats”, namely Jean Hiraga. Hiraga is probably most known for his “Le Monstre” design – a small 8W class A amplifier – and for his use of massive amounts of capacitance in the power supplies. This is then often taken to even more extreme levels by audiophiles of today that can get large capacitors relatively cheaply compared to the cost in the seventies when the designs were published.

I have already laid out my own PCB version of the “Monstre” design but it is not built yet, so for starters I have settled for a version of the Hiraga “Super 30W” amplifier based on PCBs from ebay seller jimsaudio. A spare Modushop 3U enclosure and a leftover 2x18V/500VA toroid from my Pass labs projects make up the main components otherwise. I am still missing a few parts but if I am lucky Santa might bring those within the next couple of weeks – and the Christmas break should bring some time off work for building as well 😀

There’s lots of info around the internet on the Hiraga designs, but TCAAS as usual is a good resource as it has the translated versions of the original Hiraga publications – go check it out! 🙂

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