I have finally got round to ripping open my 1978 Denon PMA 850 mk2 to remove the pre amp ( which had hundreds of irrelevant
bits ) and re house the remaining true dual mono power amp - which is terrific by the way.
I've changed all the caps to Rubycons and the main ps smoothing
caps to Aerovox models.
Tidied up the wiring, star earthed it all and put it in a 4 U Maplins case.
Looks OK and sounded good. Sort of a Meridian sound if you like that kind of thing.
However there was a buzzing which really irritated so I started
re wiring it again to get the 240v mains carrying wires away form the signal wires. Bit better but not gone.
I bought a 5 metre roll ( £5 including post ) of nickel plated fine mesh tubing from E Bay and started covering ALL wires with it and finished it off with a polyester braided sleeve to insulate and used heat shrink tube to secure.
GONE completely are the buzzes - it's a quiet hiss now !
There are very noticeable sonic gains otherwise I wouldn't be writing this.
I'm not a Hi Fi Anorac - I worked in HI Fi retail for a number of years so I imagine nothing and hear everything - if it's there !
I'm really happy with this power amp with it's BIG left / right channel independantly wound toroid and separate input and output stages - neat pure silver wiring and short signal paths.
It actually has no right to sound this good at all given it's age.
This is for info only - anyone wanting to have a go then I'll gladly
give you the contact details to buy the mesh - well worth it.
I'm going to experiment with all my external wires now as this
stuff is so cheap. Any elimination of RFI / EMI mush must be a good thing and confess to have underestimated these effects until now.
Andrew
bits ) and re house the remaining true dual mono power amp - which is terrific by the way.
I've changed all the caps to Rubycons and the main ps smoothing
caps to Aerovox models.
Tidied up the wiring, star earthed it all and put it in a 4 U Maplins case.
Looks OK and sounded good. Sort of a Meridian sound if you like that kind of thing.
However there was a buzzing which really irritated so I started
re wiring it again to get the 240v mains carrying wires away form the signal wires. Bit better but not gone.
I bought a 5 metre roll ( £5 including post ) of nickel plated fine mesh tubing from E Bay and started covering ALL wires with it and finished it off with a polyester braided sleeve to insulate and used heat shrink tube to secure.
GONE completely are the buzzes - it's a quiet hiss now !
There are very noticeable sonic gains otherwise I wouldn't be writing this.
I'm not a Hi Fi Anorac - I worked in HI Fi retail for a number of years so I imagine nothing and hear everything - if it's there !
I'm really happy with this power amp with it's BIG left / right channel independantly wound toroid and separate input and output stages - neat pure silver wiring and short signal paths.
It actually has no right to sound this good at all given it's age.
This is for info only - anyone wanting to have a go then I'll gladly
give you the contact details to buy the mesh - well worth it.
I'm going to experiment with all my external wires now as this
stuff is so cheap. Any elimination of RFI / EMI mush must be a good thing and confess to have underestimated these effects until now.
Andrew
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