SIT down and shut up

Inspired in part by coco and his SIT amps, and puresound and his Monster, it appears I am about to break a 25 year embargo on sand based amplifiers:scream:

when I say “about”, one must interpret that in a very loose way :grinning:



Circuit boards: check

Plastic bags: check

Turkey baster: check

Oh yeah - I’m all about the electrics.

That would be true if he adopted that class D shite a basis, with some £30 chip amp base and a fancy case and then sold it for £9K.

I’m rumbled :anguished:

need another plan now

What’s the amp, Simon?

Nice. Is there a link to the particular schematic this kit uses? (without me having to sift through too many multi hundred page threads on DIYAudio).

First Watt Article

and endless thread…

15W VFET amp, probably build it as 2 monoblocks as I want a big R-core mains tranny and LCLC psu

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what devices did you use for your SIT amps?

Sony 2SK82

do you think 2SK180 would be a suitable alternative?

2SK180 is a much larger device, but physically and electrically. Not really a viable substitute without reworking the circuit.

Is this using Sony VFETS or some that Nelson has commissioned?

Edit: and are they easily available?

This looks like it could be very interesting! Will be following this:-D

The amp uses original Sony VFETs from Nelson Pass’ personal stash. He designed the circuit and laid out the pcb

The DiyAudio kits include matched pairs based upon NP going through them all… across the 3 batches of kits it looks like there will be about 400 sets available in total. The first 2 batches are sold out and shipped, the last batch has a sign-up page to express interest and is due to ship in a few months.

You can buy the PCBs on their own, and source everything yourself, but good luck getting the VFETs, the last large stash of them at CircuitDiy appears to have been cleared out some months ago, and most of the VFETs on the bay appear to be fakes

Most of the amps are being built with a standard SS amp type psu, so toroidal mains tx and CRC filter, but I have a thing about toroids, and don’t like CRC supplies in valve amps, so why should this be any different? :grinning:
Hence the plan for an R-core and LCLC supply. I have some Llundahl filament chokes for a 300B amp which will never happen, so they will be used for this, and mono-blocks because I want dual supplies but would like to be able to lift it. :open_mouth:

The kit comes with Dale metal film resistors, but I don’t like them either… so I expect I will be changing them for something more in line with my personal set of prejudices.

I need to finalise the psu design, source the casework, psu parts, and that most rare of items, time. Expect them to be ready just ahead of rabski :grin:


I figured as much, need to keep looking…

never happen, so they will be used for this, and mono-blocks because I want dual supplies but would like to be able to lift it. :open_mouth:

If only Pete had thought of this :sweat_smile:


I did 4 rails of LCRC in a recent Monstre build. 1H @ 1A chokes. That was a lump.

mains tx dwarfed by chokes, generally a good sign :+1: