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More power from a 110?

Discussion in 'd.i.y.' started by PlattenFantast, May 6, 2009.

  1. PlattenFantast

    PlattenFantast TT pundit

    Since I have Sara 9:s, I'm looking for more power from my amp, a 110 (and a 140).
    Since these boards are common to the 110/140/250/135 et al, bar some component changes (mainly resistors & transistors I gather), I was pondering whether it would be very difficult or not, to beef a 110 up, all the way to the 250 standard (minus the front end regulation) or even 2x135? :cool:

    If this sounds just plain silly...?
  2. neiljadman

    neiljadman Senior Member

    Not silly at all - monoblock 110s are very fine amps, especially with improved recitifiers and caps banks (think A'dale Minicap type). Not sure that you get much more power out since the trafo voltage is still the same, but you do get oodles more control...
  3. PlattenFantast

    PlattenFantast TT pundit

    Wasn't thinking about monoblocking this amp, but rather rebuild it for more power - new bigger, larger voltage psu, higher rated output devices etc - simply "beefing it up" :D...what could possibly go wrong...

    ...and then try it with some DNM speaker cable he he...
  4. fursty-ferret

    fursty-ferret pfm Member

    well, indeed, the circuit boards, I have heard are all the same on all the naim amps, if the output transistors are the same, the only thing to worry about is heatsinking,

    but that means all you need to do is add a power transformer, caps and rectifier to take it up to a 250 level or whatever level can be tolerated by the design b4 going puff.

    so you can buy a 110 and make it into a 250 minus regs.

    I am surprised how few have cottoned onto that, less how many actually do it.

    It would be very interesting to hear from an amp designer, or even les wolstenholme how far the naim circuit can indeed be taken.

    its to do with the safe operating area range, or SOAR of the output transistors and what the input ones can stand, too.
  5. hacker

    hacker Delicious and nutritious

    If you're replacing the transformer then you'll need to watch the voltage - some of the transistors are 45V types that might not like 50VDC from a 35-0-35 transformer :eek: Replacing those with BC546 is a good way to mitigate any problems before they occur.
  6. PlattenFantast

    PlattenFantast TT pundit

    Been thinking about this for quite a while now.
    Another option would have been to use other, less power hungry speakers, but I don't want to go down that path - I like the Sara 9s enough to want to stick with them.
    My original idea was to try to recreate an 80's Flat Earth system sound anyway, so there you go.
    That leaves beefing the amp up .
    I have another 110 that has been upgraded to a 140, some time in the past.
    Funny thing is, that I hugely prefer the "stock" 110.
    I also remember back in the early 90's (I think...) how all the "fun" listening to the music system disappeared, when swapping from 32.5/Hicap/110&140/Kan to 32.5/Hicap/250/Kan.
    It wasn't long after that, that I sold all my Naim/Linn gear... :(
    So I'm not exactly lusting after that front end regulation in the 250.
    However; the "fun" factor is now back in the shape of 32&32.5/Hicap/110&140/Sara.
    But Sara:s being Sara:s - they do definitely require more power/control from the amp than what a 110 or 140 can muster.
  7. johnnym

    johnnym pfm Member

    Are you sure you’re not copying me?:D I’ve got a pair of Sara’s with a NAC32 & SNAPS and have just converted my NAP110 into a ZAP250 type of thing. The only thing I’ve changed on the boards where some of the caps and removed the SOA parts although I don’t think any of this was necessary.

    Basically just got a big HIFI 2000 case, a pair of 30-0-30 transformers, an upgraded pair of cap banks and rectifier bridges lashed it all together and sold the case to the old naim amp. The most fiddly bit was adjusting the boards so they didn’t get too hot but all is running well now.
  8. mudlark

    mudlark nearly half a clue

    There is a simple solution to get four times the power without messing with the amps. You do have to add a few bits and mess with the speakers.

    In brief, go active.
  9. PlattenFantast

    PlattenFantast TT pundit

    So you've done it then - GREAT!!! Did you manage to retain the Naim style presentation?
    I bet you did ;)
    What would I have to get ampwise please? I also reckon I'd be wanting a NAXO 2-4 or something like that too (any cheaper options around?)?

    I wouldn't mind messing with the speakers, even though some PFM members advice against it, due to Sara:s being almost "impossible" to take apart/open up, without causing permanent damage :eek:
  10. johnnym

    johnnym pfm Member

    Quite a few people have done it, I'm far from the first. I found it kept the name sound, but with more oomph which is what the Sara's like, not that there was anything wrong with them running on the old 110.
  11. mudlark

    mudlark nearly half a clue

    I made a DIY active filter from a circuit board made by ESPaudio. dead easy even for a dipstick like me. any two amps of naim sensitivity will do. I use a 140 and an avondale 260. You can use two 140s which would be rather cheap and good. I made my own speakers from a kit. The experiment I tried first was with a Behringer CX2510 active filter which is very cheap and gives reasonable results.

    If you don't like the results then sell second amp active filter and you will only be down about £50.00
  12. hacker

    hacker Delicious and nutritious

    This thread is of some interest to me because I've done some of the things mentioned, and am planning some of the things you guys have already done.

    I'm currently listening to a pair of monoblocks made from boards out of a NAP140. Each board is powered from a 500VA 35-0-35 Avel Lindstrom transformer. The rectifiers are hexfred diodes, the smoothing caps are NOS Chemicon 4600uF/100V cans in a cap8 style arrangement. There's a Rod Elliott soft start module on each monoblock to keep the inrush current under control.


    They're slightly different from that picture because I replaced the wires between the cap terminals with inductors. They have only a few windings just now, but will be 10uH in the final build:


    The boards are modified NAPs that incorporate some of the stuff from earlier posts. The first thing to go was the SOA components. After that, I replaced the LTP transistors with matched BC546C that are rated at 60-odd volts and can cope with the 50-0-50 DC supply:


    You can see the 22uF/16V Wima MKS2-XL feedback cap to the right. Critical resistors have been replaced with RC55Y 0.1% resistors. From left to right you can see the black RC55Y resistors 24k3, 3k01, 1k02, and 26k7:

    The 1k02 feedback resistor legs have been bent to accommodate the size of the Wima cap. The front end power supply is decoupled from the main supply Avondale-style with a 220R/330uF RC filter on the +ve and -ve rails. Here's the +ve one:


    The diode orientation on the -ve rail is reversed. The capacitor arrangement isn't ideal at the moment, following the Avondale 0V arrangement of returning the 0V points of the front-end decoupling caps directly to the signal input 0V:

    Junk in the power rails will show up at the signal 0V - hardly ideal. But it was an easy mod to make and is, on balance, worth it. In the final build I'll run the front-end 0V line directly back to the PSU 0V and remove it from the signal 0V.

    Both monoblocks will be incorporated into a single large Hifi2000 enclosure. Before that happens I'll be revising the PSU/amp/signal 0V scheme but haven't decided on the best approach yet. I think listening tests will be in order.

    In a parallel project I'm building another 4 amps (2 monoblocks in each enclosure) for a total of 6 amps to be used in an active 3-way system. The 4 new amps are based on the eBay clones:


    They've had quite a few component changes, but I haven't hooked them up to see how they sound yet. I still need to get the output transistors on and some testing done. The changes so far are based on the NCC200 list of parts, although some substitutions have been made. The resistors are a mix of Dale RN55 & RN60, Welwyn RC55Y for feedback and LTP, and generic metal films.

    The transistors small transistors are BC546, ZTX653, ZTX753, and 2N5551. The drivers are MJE15030G and MJE15031G. The legs on the ZTX and 2N transistors all had to be bent to accommodate the alternative pin assignments. For example here's the ZTX751 (Q4):


    The evil ceramic caps that come with the kit have all been replaced with polystyrenes, and there's a 47pF silver mica decoupling Q4. C5, the bybass of Q5, has been replaced with a 68uF BC128. The front-end decoupling caps are Panasonic NHG 100uF. Input and feedback caps are Wima MKS2-XL 10uF and 22uF, respectively.

    The zobel network is a 3W 8R2 + 220nF polyester cap. One thing that really needs to be done here is to separate the zobel 0V track from the signal 0V. Yuck. I'll be cutting the track and running a separate cable for that! The output of the boards has been replaced with an Avondale-style inductor//resistor combination.

    The 4 clone boards each have a dedicated 250VA 30-0-30 Avel Lindstrom transformer and will be used via a custom active crossover to drive the treble and midrange units of the 3-way speakers. The 500VA monoblocks will drive the bass units.

    It really is a labour of love to try and make all this stuff, so it's taking some time. I'll start a thread when I make some real progress.

    For you guys with the Hifi2000 cases: how did you go about drilling your casework?

  13. PlattenFantast

    PlattenFantast TT pundit

    WOW...I'm stunned - quite a lot to take in he he...this is extremely inspiring stuff!
  14. johnnym

    johnnym pfm Member

    The case was OK although the 10 mill front panel was a bit of a git. In fact I had to order a replacement as the first one didn't turn out too good (why are all my posts about me screwing things up). Second time around things went much better even drilling by hand.
  15. hacker

    hacker Delicious and nutritious

    Did you use a hand-held electric drill? I was thinking of using my drill press but it's good to know that it isn't too hard to make a nice job of the metal work using hand-held tools. The only problems I foresee are cutting rectangular holes for IEC inlets, and a large 30mm circular hole for a 19-way connector. Oh, and then there's cutting a rebated rectangular hole into the 10mm panel into which I want to place some smoked perspex to act as a window for the preamp's input selector/volume control readout. That one's going to have to be CNC milled.

    Can you use regular router bits on the thin metal panels?
  16. johnnym

    johnnym pfm Member

    Mine came with holes pre cut for IEC and a fuse holder. A 30mm hole should be no problem, it isn't that thick at other than the front panel. I managed to cut a circular 20mm hole in the 10mm think aluminum with only a 24v cordless drill with it clamped to by picnic table in the garden, no drill press used. I only used standard metal drill bits, but for a rectangular hole you'll need the CNC like you said.
  17. TOR

    TOR pfm Member

    When I did my rectangular holes I just drilled a pilot hole and inserted a coping saw and finished it off with a hand file. Not as cool as cnc milling but a lot cheaper!!! With a bit of care it'll look perfect.

    Cheers, Tim.
  18. hacker

    hacker Delicious and nutritious

    I just bought a solid carbide 1/8" cutter for my router. I'm going to build a jig and cut the rectangular holes using that. As part of the order I also bought a step drill bit that does 1/4" to 1 3/4" in 1/8" increments. Between them, that'll do all the holes I need :)
  19. PlattenFantast

    PlattenFantast TT pundit

    I know this is off-topic, but here goes; on Acoustica's Naim power amps mod page, one recommended mod is to replace the feedback caps with Evox MMK:s.
    For a 140 the recommendation is 47uF, for a 250 68-100uF etc.
    Now, since the 47uF, are very hard (difficult) to locate, would 68uF do in let's say my 110 or 140?
    Sorry if this is a dumb a_s question.
  20. martin clark

    martin clark pinko bodger

    Yup, just fine; in fact even 22uF is more than enough in the NAPs (-3dB at 7Hz). And 22uF MMKs can be a lot easier to find.

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