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Hiraga Le Monstre

Hmmm... thought that may well be the case. Casework isn't an issue - I'd probably build the PSU into a standard metal box and hide it away somewhere, and build the boards onto my huge heatsinks, and stand them on the floor behind the Quads. I've built plenty of PSUs so could work from a circuit and specification, some big caps, resistors, bridges and transformers.

If a few PFMers were interested could you be persuaded to build a few working and tested amp boards, or is it too labour intensive to be viable? I quite like the idea of 8WPC as it won't stress my ESL57s too much!
 
Hmmm... thought that may well be the case. Casework isn't an issue - I'd probably build the PSU into a standard metal box and hide it away somewhere, and build the boards onto my huge heatsinks, and stand them on the floor behind the Quads. I've built plenty of PSUs so could work from a circuit and specification, some big caps, resistors, bridges and transformers.

If a few PFMers were interested could you be persuaded to build a few working and tested amp boards, or is it too labour intensive to be viable? I quite like the idea of 8WPC as it won't stress my ESL57s too much!

It depends what you call viable... it is very labour intensive to match the devices and needs lots of them. Test jigs would need building. I would be willing to do it as a paying job but fear that as people will probably not appreciate just how much is involved I would be told "at that price you know where you can shove 'em". The FET's are silly money like £7 each for the P channel LSJ74 from Linear Systems and about say £3 each for the N channel as compared to say 80P each when they used to be readily available from Toshiba. There is one N and one P in each channel but probably 10 per channel would need buying in order to find decent matches. It may be possible to buy them pre matched but that would attract a large premium. Original 2SK170 and 2SJ74 are sometimes available on e bay etc but there are so many fakes about it is not a good idea...

I guess we would be talking say £100 per board and I'd want it organising by the group buy people such that say £700 of FET's arrive at my door for me to match and use.... I don't want to be doing the purchasing and chasing up FET or transistor orders that should have arrived last week etc etc as I have enough to do already...
 
+1 to the 'known-good, and matched' JFET problem; it's not that substitutes can't be found - if you want it enough - but it will be expensive, in parts and time.
 
I may have a modest stash of bl grade 2sk170 and j74. Enough for one and half channels, lol.
 
Nah I've done class A. Besides, sounds like I'd need more than my modest digital scope and bag of luck to do it justice.
 
Best power amps I've heard. Smack bang between the vice like grip of good class d and the sweetness of class a.
 
So it's a DIY design that needs a pro to build it. Doesn't sound like much of a DIY project at all this. Certainly sounds interesting though with high praise indeed!

How many would you need from a group buy to make it viable Jez?
 
So it's a DIY design that needs a pro to build it. Doesn't sound like much of a DIY project at all this. Certainly sounds interesting though with high praise indeed!

How many would you need from a group buy to make it viable Jez?

It was in the French magazine "l'Audiophile". It was never intended to be anything other than a high end design and the original article in fact calls for a pair of 70AH lorry batteries and up to a Farad of capacitance in the power supply!!!!

How many to make it viable? I've no idea. All depends on how much people will pay individually. If folks think they are going to get some giant killing super amp for just a few hundred quid then forget it! The only involvement I'm willing to have is in the technical side of things. If this is to become a pfm DIY group buy and project then I ain't the guy running it!
 
Maybe we could look at what J-fets people have left over in the bits boxes for swaps or for sale .
I have 17x 2sk170b 16x J74 all from pfm members
and 10x lsk170
All are genuine :)
i have bought from big company's to ebay traders which all turned out to be fakes.
the 10x lsk170 are free samples which have an IDSS of around 3- 4 mA so no good for a B1 buffer .
i will measure the idss of what i have and post back
would this test jig be ok or would paralleling the j fets effect each other ?
20190616_140101 (1) by glenn jarrett, on Flickr
 
Maybe we could look at what J-fets people have left over in the bits boxes for swaps or for sale .
I have 17x 2sk170b 16x J74 all from pfm members
and 10x lsk170
All are genuine :)
i have bought from big company's to ebay traders which all turned out to be fakes.
the 10x lsk170 are free samples which have an IDSS of around 3- 4 mA so no good for a B1 buffer .
i will measure the idss of what i have and post back
would this test jig be ok or would paralleling the j fets effect each other ?
20190616_140101 (1) by glenn jarrett, on Flickr

That should work fine but the big problem is we need to match N and P channel devices...
 
just how close a match would be needed for a N & P channel my dmm resolution is 0.000v and using 10v dc power supply
i have just got hold of a mached quad 170s but the readings are 7.42 7.43 7.39 7.52 are these tight enough for the Mesmeriser buffer ?
 
just how close a match would be needed for a N & P channel my dmm resolution is 0.000v and using 10v dc power supply
i have just got hold of a mached quad 170s but the readings are 7.42 7.43 7.39 7.52 are these tight enough for the Mesmeriser buffer ?

The closer the better but no we're not needing several decimal places!

I've never heard of a Mesmeriser buffer but those look fairly well matched.
 
just finished testing all mine
i have had a look on diy audio and even when the store sold matched lsk170 quads only matched to 1.0mA
i was under the impression they had to be 0.1mA:confused:
this is what i have
20190616_170008 by glenn jarrett, on Flickr

Quite a few good matches there on the Toshiba parts:) All rather high Idss for a Le Monstre though... many other nice uses for them though!
I wonder how the LSJ74's match up to the LSK170's???

Edit: I think I could work around the high Idss of those in a Le Monstre by a "cheat" though;)
 


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