1. Things you need to know about the new ‘Conversations’ PM system:

    a) DO NOT REPLY TO THE NOTIFICATION EMAIL! I get them, not the intended recipient. I get a lot of them and I do not want them! It is just a notification, log into the site and reply from there.

    b) To delete old conversations use the ‘Leave conversation’ option. This is just delete by another name.
    Dismiss Notice

Upgrade an ageing REL plate amp?

Discussion in 'd.i.y.' started by Paddy, Sep 16, 2022.

  1. Paddy

    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
  2. eguth

    eguth pfm Member

    Consider getting a BK.

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

    I think their subs super.
  3. Paddy

    Paddy pfm Member

    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
  4. eguth

    eguth pfm Member

    Good luck.
    Paddy likes this.
  5. davidsrsb

    davidsrsb pfm Member

    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
  6. Paddy

    Paddy pfm Member

    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.
  7. sq225917

    sq225917 Bit of this, bit of that

    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.
  8. Paddy

    Paddy pfm Member

    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.
  9. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    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
  10. Paddy

    Paddy pfm Member

    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
  11. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Easily repaired but you may want to buy in some TO3 mosfets as they are going end of life right now unfortunately.
    a.palfreyman likes this.
  12. a.palfreyman

    a.palfreyman pfm Member

    Good call...
  13. sq225917

    sq225917 Bit of this, bit of that

    It's a simple circuit, nowt that can be fixed, as said above usually the boas resistor that goes.
  14. geoturbo

    geoturbo tinkerer w/o highly evolved auditory stimulus cpu

    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..
  15. Paddy

    Paddy pfm Member

    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?

    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.

Share This Page


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice