Building Colin's SECA kit

This discussion was created from comments split from: For Sale: Colin Wonfor SECA Class A Power Amp.


  • PCB's are now a vailable.
  • edited June 2015
    The new SECA KIT for the DIY is sounding very nice, PCB's for the Amp and the Dynamic PSU are now available.

    I had Sam build them and he has now soldering or building experience.


  • Here is a photo of the 4 layer Bass Amp PCB, a tiny bit complex for DIY.

  • edited June 2015
    Thanks Uncle Dave. (me twit)  ^:)^
  • I couldn't possibly comment.

    Oh, all right, you twit!
  • Oi, leave my mate a lone. He's not a twit, he has just lost a few marbles  :P
  • edited June 2015
    Oh dear. The Colin Protection League has finally made it on to Chews. :-SS
  • Thank Uncle Dave. (me twit)  ^:)^
    Oi, leave my mate a lone. He's not a twit, he has just lost a few marbles  :P
    No ball bearing or was in conkers shit old age is crap, now were my coffee.
  • Probably where you left your glasses.
  • Cor, well done Sam!

    I suppose our Colin deserves some credit also.
  • Probably where you left your glasses.
    James you were right in the garden by the strawberries mm nice.  >:)
  • Cor, well done Sam!

    I suppose our Colin deserves some credit also.
    No it was all Sam I just waited with burn kit to fix black fingers, pooo another nurses uniform wasted.
  • image
    Amp PCB 
  • Those are mighty big capacitors!
  • Only 0.033 Farads each small is only 5A/SEC
  • edited June 2015
    Colin - have you come across any cases out there that can accommodate two amp packs and PSU's? I'm thinking one with built in heat sinks ala some of the First Watt designs.

    I've not checked how big the modules are so this case might be overkill, but it sure does look purdy:
  • Alan found some in Italy and they looked lovely.
    I will try and find them again. back soon.
  • There's these from Modushop in Italy:

    I have boughT 11 cases from Modu shop and found their service to be EXCELLENT !
  • Thank James
  • Yup, bought a couple and they are great.  Not sure if the pfm discount code still applies?
  • Any Photo's anybody?
  • Well the Modushop ones look fine. Thanks very much fro the heads-up on those.
    Which is the size to go for with regard to internal height size (to accomodate the PCBs) and the heatsink capacity...?
    I'm hoping the "3 unit" ones here would be OK, as the 4 unit ones are taller than I'd like.
    And what does the "unit" bit refer to...? Is it something to do with the overall heatsink capacity...? If so is "3 units" enough...?

  • I like this one lots of cooling thus more power.

    Parts here started build Ben
  • Woop woop!
    Thank you.
    Feeling excited about this Colin. 8->

    Should I treat your suggestion on the case as a formal instruction (ie follow it to the letter)...?
  • Like the case .
    Are you able to use these heatsinks that is part of the case, or do you need more heat sinkerage?
  • No idea.
    I can't see any specs for the heatsinks (other than dimensions) on the modushop website, for me to fail to understand.
  • If you look under Spare Parts on the Modushop site it lists the various cases and the bits for them - this includes the heatsinks. It lists the heat dissipation for each of them.

    From that info there are two heatsinks per side, together they are .38 degrees per watt, so TOGETHER they are suitable, you just need a method of spreading the heat across the pair. The heatsinks Sovereign is using in the Big Beast are suitable (they are what I am using in my mono blocks) as each one is rated at .4 degrees per watt
  • Thanks Sondale. =D>
    I hadn't discovered the spare parts bit.
    Will take a good look later.
  • Fantastico!
  • Righto.
    So the modushop option to go for would be this one...
    (ie 4U 400mm (with 2 heatsinks each side))...
    And the 190 euro order there includes everything (4x heatsinks, front and back & top and bottom panels...?

    And the 0.38 heatsink rating is definitely adequate for the boards...?
    With regard to spreading the heat load over two sinks, would this be as simple as including some sort of metal plate that spans both heatsinks inside the case, and on to which the board can be mounted, or is there some other way...?
    Or, is there a simpler case & heatsink option elsewhere...? I should probably go back and read this thead... :D

    I appreciate everyone's patience with this. This is the first time I've ever done anything like this...
  • Ben,

    It has 4 heatsinks all rated at 0.38C/W thus two a side is 0.38/2 = cool amps at 23W nice.approx.
    Now all you need to do is couple both heatsink together to share the energy from the PCB. Try a Ali strip I have some here will cut two bit for you. (My metal work is crap got banned at school and woodwork, and the girls changing room why?) 

    How big /tall are the feet?

    And can you get it in Green for Dave  
    >:) :D
  • Green is my personal territory. Get off my property!

    Ben can have another colour.
  • :)) =)) :D                                                                                                       :((  not fair
  • 'Tis fair.

    Ben can have puce :-)
  • Olive Green maybe????
  • I think there is still a discount code on PFM
    for the cases.
  • There's these from Modushop in Italy:

    If this case is suitable I'll also be buying one Ben. 6% discount if two are ordered. I'm away for a week from today but will be ordering on my return.

    It looks like the same case I bought for my DAC except this one has heat sinks. Everything we need to build the box is included - apart from feet which I think I had to order from somewhere else.

  • When ever I have ordered from modushop the feet have been included
  • edited August 2015
    Colin: Thanks for your offer of the Ali strip. Please add the cost of these to the invoice for the boards!  :)>-
    Do the feet need to be of a particular height? I've noticed that on both my (your!) TOCA and the ID25 the feet are taller than one normally expects to see...

    Paul: Thanks for the reminder about the PFM cases. This Modushop thing continues to tempt me as it's an all in one (cases and heatsinks) package, so I won't be anxious about making sure that parts match.

    Brumjam: I'm happy to team up for a discount, but won't the order need to be sent to the same address to qualify...? If not, or if you live close to Gloucester, then I'm up for it.

    Sov: That's good. I'll see how it arrives. I'm guessing feet are not a hassle to source if the case arrives without. And, what sort of feet? My intention has been to use something like these:
  • Ben 50mm should be the min distance from floor or carpet or further if in bathroom, I used door stops good to reject vibration also.
    The gap it to allow air flow over the amp it will shut down the current until the max temp is 50C that will reduce power out, so the freezer would be better so chuck out fish, brussels, but keep ice cream, chocolate and pizza for fat Col I hate the others.

  • edited August 2015
    I don't hate many things. But, carpeted bathrooms are one.

    My freezer needs defrosting, so I will sling the boards in there the moment they are wired up...

    Thanks for everyone's ongoing input on this.

  • Colin did I read correct that we can use this amp in the bathroom.
    I do love to sing in the shower
  • Preparing components.

    Bend the resistor wire ends this is the 1K5 3W.


    100mR or 0.1R 3W


    The smaller resistors.


    The resistors mounted.

    Capacitor mounted. C5


    The current control  preset near the AD820 op-amp.


    Fuse holder and 18-0, 0-18V power input for the transformer.


    Bending and mounting the 6Amp diodes in the bridge rectifier.


    Mounting the Green Led that is used to generate the ref voltage for the Current control. Note the long leg is near the hole it will be soldered into this is the Anode.

    Led with the two 10nF caps behind.

    One of the two 33,000uF bulk capacitors note the stripe in the case it is the Negative terminal alway check these or big bang will be louder than the music


    Mounting the Op-Amp AD820.


    The BC337 transistor and the DC offset preset.


    The drive transistors BD139 na BD140, see there orientation and the BD140 is on the right. Solder them closed as the PCB acts as a small heatsink. Also mount the BC337 close but not tight to the PCB. See above.


    Here is the PCB,sI did for Ben, (thanks for the order Ben could do with more)


    On set up insure the IQ preset is Anticlockwise and the DC offset is centre.

    PCB 1 , 5Hz - 100KHz Flat PCB 2, 5Hz - 100KHz Flat at full power  (15W) in this case.
    DC offset -3.2mV 0.3mV
    I/P Z 13.5K 13.5K
    Damping 1150 1128 with a 250VA transformer tag on.
    Phase angle 20Hz - 20KHz -,+ 3.0 deg both PCB,s

    Boxed ready to go Ben

    Also not the insulators under the MOS FETs a small amount of heatsink compound only OK "U" yes you now who. :))
  • That looks very useful Colin.
  • when I built my DAC I found following pictures was FAR more helpful than anything else. A picture and a thousand words and all that.
  • Thanks Colin!
    =D> ^:)^ 8->
    Lovely work. Lovely photos. (Even though this bit is done for me, I would agree with Sov that photos are the single most helpful instructions for me.)

    My second response is "thank crikey you've done that for me". Incredible value for money: Hand built by the best designer of Class A amps in the business. :)

    I'm looking forward to getting things started...!
    I suspect it will be a single step process with each step checked here first. (E.g. "OK I have unwrapped the PCBs...What do I do next...?" or more likely "OK I have snapped the PCB in half while unwrapping it... What do I do next...?") A slow, steady and cautious pace will be the way forward here...

    Couple of questions...
    I notice you seem to have attached the metal plates for coupling the heatsinks...? (Many thanks. :) )
    If so, do I still need the heatsink compound to fix between the plates and heatsinks?
    If so, is this it, and is that quantity enough or do I need more?

    Above all, thanks Again Mr. Wonfor.
  • I've just noticed that Colin is trusting me to fit the fuses.
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