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Upgrade an ageing REL plate amp?

Paddy

pfm Member
I have a pair of working Studio iii REL subs and am considering their amplifiers, both of which are working. I've had one for 20 years and did have a repair done, some years back, so have seen the amp which I had to remove rather than try to cart a near 100kg lump down three flights of stairs and back up again.

The amp is similar to the one in the picture below, but with larger caps



I've read of people swapping out the whole plate amp for one from Hypex or BK Electronics but, they don't then fit the recess left by the original amp so need external boxes.

From what I've read, the amp is the weak point of these subs and replacing it does offer a possible improvement in the sound. What I'm pondering is whether it is possible to simply replace the amplifier section alone with a hefty class D amp and keep the rest of the thing OEM. Any thoughts gratefully received folks
 
Consider getting a BK.

I have had great service long term from their monoblock 'slave' amps (used by auntie). No longer made...
indestructible!

I think their subs super.
Best,
eguth
 
Thanks for the thought eguth. My plan is to keep the REL's rather than replace them with new BK subs if that's what you're suggesting
 
That looks like the classic Hitachi copy lateral mosfet design.
Nothing wrong with it except a tendancy to cook the hot running bias setting resistor
 
Hi Dave, I read that it was a Hitachi clone somewhere else so I guess you're right.

What I'm wondering is if a Hypex type amp could be substituted ie plug in the transformer and the connections to the switches in some way. I'm guessing not as surely someone will have done it and shared already.
 
The hypex units includes psu, it's all in one, literally all you need to do is plug the driver into the sockets on the board.

Is the current amp board in a sealed compartment or sharing the main volume with the drive unit? Either way use a router template to make hole bigger, or square it off with glued in strip inserts then router it out to fit.

Easy job unless the hypex is too big for the panel size.

The benefit of the hypex is the PEQ and much finer control of FR beyond gross level, phase and xo point.
 
Hi Si,

It's sharing the main volume from memory. What I was hoping to do was keep the cutout the same but replace the amplifier board itself, retaining the existing crossover/volume etc controls. I'm using a Trinnov Amethyst for RC / PEQ and crossover now anyway so could just replace the plate amp completely, put in a metal plate with some speaker inputs and then use a suitable amp externally.
 
I'd leave it alone personally. It's a perfectly good amp already and there may be functionality built in to the standard unit that you need... EQ etc
 
Thank Jez, I'm happy to do that for the time being, although having had one amp fail already, there may come the day it happens again, so I'm trying to develop options
 
Thank Jez, I'm happy to do that for the time being, although having had one amp fail already, there may come the day it happens again, so I'm trying to develop options

Easily repaired but you may want to buy in some TO3 mosfets as they are going end of life right now unfortunately.
 
It's a simple circuit, nowt that can be fixed, as said above usually the boas resistor that goes.
 
Hi @Paddy, having a Strata.. managed to repair its (badly heated up) amp once which died unfortunately not long thereafter.. and I am considering that it is beyond repair now.. bodging with the idea to fixing it some day, using the Strata transformer, psu section and its four to-3 slots with an NCC200 module.. with a different speaker.. could be fun..
 
Good to know about the mosfets but, am not sure which I need to get hold of being uneducated. Am i on the right track? https://uk.rs-online.com/web/p/mosfets/1927849

What set me thinking was a quote from someone else on AVForums who used a Hypex FA501 plate amp.

"I feel the new power and clarity offered by this board is a substantial upgrade over the original amp and lifts the Studio III to a new level of performance whilst preserving its remarkable low-frequency extension and musical timing."

I like the idea of a substantial improvement but, this plate amp would need substantial surgery to the cabinet to allow it to fit and I'd rather avoid this, hence trying to see if the old could be combined with the new.
 


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