Hardly lightweight 
They come in at about 25Kg per monoblock
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Pffffffffffft. Call that a monoblock…
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True, they are only 1.38Kg/W which is nothing compared to the SIT amps Pete has built
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I was lucky enough to snaffle some Tribute Iron from Pieter Treurniet (Tribute nl) for a couple of projects before they folded…such a pity
Measured that way my amps are 0.395 Kg/W…so they are relative lightweights
I had a very nice SUT made by Pieter.
I thought he had retired rather than the business folded?
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Pffffffffffft. Call that a monoblock…
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Everything is relative…
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Yes my bad… Wound up into a happy retirement would have served well.
Very droll 
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Next instalment from my vintage pile:
PYE HF25 mono amplifiers circa 1957.
The HF25 whilst virtually identical in build and design to its older brother PF91, PYE redesigned the winding topology of the output transformer
The newer circuit running a pair of KT66’s in U/L mode.
Power output: 25 watts into 8Ω (mono)
Frequency response: 2Hz to 160kHz
Total harmonic distortion: 0.1%
Speaker load impedance: 3.75Ω to 60Ω
Valve complement: 1 x ECC33, 1 x ECC35, 2 x KT66, 1 x GZ32.
Aluminium chassis.
As per the PF91 the circuit employed a combination of negative and positive feedback allowing for a damping factor from 5 to infinity.
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We love a pie man
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Spectacularly spec’d amps 
. Whoever owns the one showing its underside must be faced with a very tough call. It looks completely untouched, so just as original as it gets. Which means most of those Erie type 109 carbon comps will have gone over the hill and far, far away in terms of value (and probably noise, and possibly nonlinearity) and any/all of the TCC Metalpacks will either be leaking electrically or will start to as soon as his back’s turned. There’s even a dreaded Hunts Mouldseal in the top left corner !
These amps are so precious though that if it/they were mine I’d be tempted carefully to detach the turret board from the wiring loom and put it in a safe place. Then I’d make a brand new board, populated with top quality modern components. A shedload of work, but if the wound components are as good as the spec sheet says they must be then the work would be worth it.
VB
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Pleased that you like them…PYE knew a bit about winding transformers and circuit topology back then.
I have played around with several combinations of caps and resistors over the years in both the HF25’s and PF91’s.
For the most part I have settled on Riken Carbon comps / Amtranz Carbon films and Duelund film caps.
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My name is MooN and I am a Sansui addict…
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Just bought a pair of Quad II off Adam over on AOS and elsewhere.
Will get them on Sunday.
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Oh fuck, what are they? 
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This and the valve amp thread had made me want valve monoblocs. Of course, I couldn’t sell my Classe monoblocs so I’d have to keep both sets.
Sansui AU-111 integrated…I made a post about the amp further up the thread.
As Alfred said to Bruce Wayne about the 10,000 bat masks…at least we will have spares Arf…
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