8PAKAMP & 12PAKAMP KIT BUILD THREAD

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Joe Malone
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8PAKAMP & 12PAKAMP KIT BUILD THREAD

Postby Joe Malone » Tue Mar 20, 2012 6:02 pm

8PAKAMP kit is a 8 channel version of our popular 60W AMP kit. We originally designed the 8PAKAMP for a large Dolby Labs project we did a while ago.

    8 x 75Watts of power configurable for making active monitors or full surround sound amp setups in lots of combinations on 184mm x 81mm PCB
    (eg 4 x 140watt bridged, 2 x 280watt bridged, 1 x 560watt bridged, 1 x 280watt bridged + 1 x 140watt bridged + 2 x 75watt. etc)
    2 x 8000uF 50v capacitor power rail smoothing banks on board PCB. So only power transformer, Bridge rectifier and heatsink needed to complete full 8 channel amp.
    Fully balanced inputs to all amps (can be wired unbalanced in by shorting either +in or -in to 0v depending on amp phase needed)
    Amp level setting trims on all channels. Can be fitted under the PCB for external front panel trimming or on top of PCB for internal trimming.
    Inputs can be PCB XLR or TRS sockets or hard wire
    Amp IC's can be fitted flat under PCB or vertical standing on top of PCB for different heatsink setups.
    PCB can be run by 25 to 35Amp bridge rectifier and transformer of 300 to 500VA with 2 x 25vac to make +/-35vdc if no amps are bridged or 2 x 18vac to make +/-25vdc if any amps are bridged.
    Bridging is easily done by wiring two amp inputs together but with the second amp +in and -in are swapped to reverse its phase

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The LM3886 when mounted underneath should be placed flat on the bottom of PCB and 2 x flat 3mm washer or 3 x 3mm lock washer inserted in the gap between the PCB hole and mounting tab hole to pack the gap.
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8PAKAMP PCB measures 184mm x 81mm

JLM 8PAKAMP PCB PARTS KIT

1 x JLM 8PAKAMP PCB
8 x LM3886TF POWER AMP IC
16 x 1000uF 50v 105 degree caps (12.5 to 13mm diameter can only will fit PCB)
8 x 100uF 35v 105 degreee cap
16 x 10uF 25v Bi Polar cap
16 x 100nF Mono caps (100nF = 104)
88 x 10k
8 x 1k
8 x 10mm x 3mm bolt
8 x 3mm nut
8 x 3mm lock washer

8 x 10k trim pot 25turn screw on top type

Options

No Terminals

or

8 x TRS S4 PCB jacks
16 x fibre washer
8 x black plastic trim
8 x chrome nuts

or

8 x XLR Male
Joe :-)
JLM Audio
Capturing Audio without Injury

wizardofoz
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Re: 8PAKAMP kit BUILD THREAD

Postby wizardofoz » Tue Mar 20, 2012 7:29 pm

Joe...This is great news...I'll be getting my order in post haste.

I know you will busy updating this thread with details like transformer details and bridge specs needed.

Likewise the hook up notes for bridging and inputs etc.

I think the pricing is very reasonable, and from the looks of thing a lot of flexibility in the build too.

WELL DONE!!!

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Re: 8PAKAMP kit BUILD THREAD

Postby Joe Malone » Tue Mar 20, 2012 8:10 pm

wizardofoz wrote:Joe...This is great news...I'll be getting my order in post haste.

I know you will busy updating this thread with details like transformer details and bridge specs needed.

Likewise the hook up notes for bridging and inputs etc.

I think the pricing is very reasonable, and from the looks of thing a lot of flexibility in the build too.

WELL DONE!!!


Added this info to the top post. Will elaborate more as different setup configurations are asked for.
Joe :-)

JLM Audio

Capturing Audio without Injury

slb1959
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Re: 8PAKAMP KIT BUILD THREAD

Postby slb1959 » Wed Mar 21, 2012 10:46 pm

Hi,... you are my hero,...
Maybe now i wait and i dont need to by the other kits that i speak to you.
I nead a amp to conect the Assus Xonar.

http://www.asus.com/Multimedia/Audio_Ca ... 13_Deluxe/

Thanks, Luís

slb1959
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Re: 8PAKAMP KIT BUILD THREAD

Postby slb1959 » Thu Mar 22, 2012 9:02 am

Hi,...
Can we cut/transform the 8pakamp pcb to 2x4pcb´s to a different boxes, for example?

Thanks, Luís

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Re: 8PAKAMP KIT BUILD THREAD

Postby Joe Malone » Thu Mar 22, 2012 9:43 am

slb1959 wrote:Hi,...
Can we cut/transform the 8pakamp pcb to 2x4pcb´s to a different boxes, for example?

Thanks, Luís


If you are very careful you could use a sharp Stanley / utility / box cutter knife to V score the top and bottom of the PCB against a metal ruler several times until the copper is cut and a good V groove is left in the fiberglass board on both sides. Then bending the PCB up and down the PCB will clean break along the V score. You will lose either the +V or -V terminal on each PCB but that can be found either the top or bottom copper power rail strip and solder to after scrapping of the green solder mask.

If just trying to make the PCB smaller using 2 x 8PAKAMP PCB and cutting of one or two channels from either end of the PCB with a drop saw would be quicker and leave the power terminals intact on each PCB.
Joe :-)

JLM Audio

Capturing Audio without Injury

wizardofoz
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Re: 8PAKAMP KIT BUILD THREAD

Postby wizardofoz » Wed Apr 04, 2012 11:09 pm

Joe,

How would one go about doing 4 modules for one channel.. ie making a 2 channel amp from one of these boards or even a single channel setup using all 8 for a monoblock? Either balanced or unbal inputs.

I will be hopefully getting some parts counts in for this in a week or so, so I am looking at options.

***** EDIT *****

I am considering a demo setup at this stage to include the following

3 x 2 channels bridged with BAL and/or UNBAL inputs, plus 2 single channels with BAL and/or UNBAL inputs. How would one wire this?

Another option is to run miniDSP's for LCR on 6 of the amps for bi-amping and another miniDSP (or perhaps not if the delays are managable) for the remaining 2 channels for rear, this would work for 5.0 setups - again either BAL and/or UNBAL.

I am assuming that the UNBAL can be just connected to one or the other of the BAL inpouts depending on the need for inverting or non inverting configuration, with the remaining inputs grounded?

Thinking maybe connecting this up to an OPPO 95 and using the (variable oppo volume controlled option) BAL outputs for L/R and UNBAL for the remaining C/LS/RS to demo a very basic surround SACD setup at an upcoming DIY gathering here in SIngapore.

wizardofoz
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Re: 8PAKAMP KIT BUILD THREAD

Postby wizardofoz » Sun Apr 08, 2012 1:18 am

The finished project will be at NoiSING 2012 a Singapore based DIY group gathering.

I'm building a 5.0 version in a single case not much bigger than an Emotiva Mini-X.

It holds 3 x 140W bridged channels for LCR with 2 x 75W single channels for the LS/RS surround channels. 500VA toriodal with dual bridge supply :P

I actually have two to build up... I'm doing case works now and waiting on some mounting hardware - funnily enough its going to be using an Emotiva XPA-3 amp heatsink as I happen to have a dead module that's not going anywhere :D

Case is very rough right now and maybe replaced completely in time.
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Internals of the amp board look like this... output IC's have yet to be mounted. I couldnt get any smaller BP caps so had to mount them high and horizontal. Note that as component fit is quite tight getting the vertical resistors oriented is trial and error....do a dry fit of 2 channels before you commit to solder. Also the LM3886 chip leads take some thought too if you plan to mount underneath. I havent bothered with the 10K pots at this stage as control will be from an Oppo 983/95 transport.

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The cutting of the IC pins... shorter for the outer pins to avoid the Wima 0.1uF caps and trim off the redundant pins and thats about it. Sorry for the poor iPh macro focus
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and
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The power supply for the dual bridge part

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Re: 8PAKAMP KIT BUILD THREAD

Postby Joe Malone » Sun Apr 08, 2012 9:30 am

The 0.1uF should be multichip mono bead type ceramics for super low ESR. Cut the front long legs of LM3886 at there knee joint and drop the IC in from behind the PCB. Any legs not used will hit solder joints and bend up slightly so you can push them up 90degrees and back a couple of times and they will snap off at the LM3886 body cleanly. Doing this in place stops the chance of breaking the wrong leg off. Using the correct 0.1uF mono cap type and you will not have to the trim the outside legs at all.

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If using external 20000uF cap banks like above the 1000uF caps on the 8PAKAMP PCB can be made smaller like 220uF to 470uF 10mm diameter type to make more room. 35v types when using 2 x 18vac transformer or 50v type when using 2 x 25vac transformers.

The 2 x 10uF Bi polars and 1 x 100uF cap can be lowest voltage type you can get like 4v to keep them as small as possible.

To bridge a pair of amps it is as simple as wiring 2 amp inputs together with the second amp input phase swapped.
+input to amp1 +in and amp2 -in. -input to amp1 -in and amp2 +in. Amp1 will be the +amp and amp2 will be the -amp. (Unbalanced input wire -input side to 0v.)
Wire speaker + to amp1 output and speaker - to amp2 output.
Joe :-)

JLM Audio

Capturing Audio without Injury

wizardofoz
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Re: 8PAKAMP KIT BUILD THREAD

Postby wizardofoz » Sun Apr 08, 2012 6:08 pm

So the Wima 0.1uF is not ideal then? Will it be any issue if used? I'd hate to have to pull them all off.

I'm not using the extra 20,000uF caps in the dual bridge - just the dual bridge part.

Do the 10K pots need to be used at all as control will be from the source? Or is this more for balancing the channels with respect to one another?

Also no mute on this version of the PCB?

For Bridged unbalanced would one input be - to gnd and the other be + to gnd on the inputs? speakers both out signals. I assume the - in will be - out i.e. non inverted?

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Re: 8PAKAMP KIT BUILD THREAD

Postby Joe Malone » Sun Apr 08, 2012 9:06 pm

wizardofoz wrote:So the Wima 0.1uF is not ideal then? Will it be any issue if used? I'd hate to have to pull them all off.

They will be ok since the PCB has very low inductance heavy power rails in its design.

I'm not using the extra 20,000uF caps in the dual bridge - just the dual bridge part.

No point to dual bridge except to waste some voltages. Single 25 or 35Amp bridge is fine.

Do the 10K pots need to be used at all as control will be from the source? Or is this more for balancing the channels with respect to one another?

Trimpots can be left off if no level adjustment needed. Not needed for pair bridged or single amps unless you want to set different amp levels in active systems etc. To control a bridge amp with one trimpot use outside terminals of trim pot and wire to inverted channel trim pot outside terminals reversed. 10k trims useful for matching parallel amps as well.

Also no mute on this version of the PCB?

Each amp has the soft start mute parts so it will not thump on turn on or off but they are not bought out to a global terminal for switching mute on and off.

For Bridged unbalanced would one input be - to gnd and the other be + to gnd on the inputs? speakers both out signals. I assume the - in will be - out i.e. non inverted?

Yes as explained in my last post above.
Joe :-)

JLM Audio

Capturing Audio without Injury

wizardofoz
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Re: 8PAKAMP KIT BUILD THREAD

Postby wizardofoz » Mon Apr 09, 2012 7:16 pm

How many of the grnd connections should be made back to the power supply from the board? all of them or just one or a few maybe?

Not sure how much issue there will be with ground loops. The doesn't seem to be a single ground point on the board like there are for the power +/- rails.

Hope to finish this build in a few days. Then get this baby connected with some speakers and source material.

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Re: 8PAKAMP KIT BUILD THREAD

Postby Joe Malone » Mon Apr 09, 2012 7:50 pm

wizardofoz wrote:How many of the grnd connections should be made back to the power supply from the board? all of them or just one or a few maybe?

Not sure how much issue there will be with ground loops. The doesn't seem to be a single ground point on the board like there are for the power +/- rails.

Hope to finish this build in a few days. Then get this baby connected with some speakers and source material.


Just one ground from around the center of the PCB will do fine. But you can take all 8 back to one star point without ground loop issues if you like. They are all connected on the top and bottom ground planes of the PCB so are very low ohms between the 8 points.
Joe :-)

JLM Audio

Capturing Audio without Injury

wizardofoz
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Re: 8PAKAMP KIT BUILD THREAD

Postby wizardofoz » Tue Apr 10, 2012 10:24 pm

The latest on the build

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Decided to run all 8 GRND wires but will only use 6 for the power connections... the other 2 will go to the single channel speaker outputs as the balanced will not use GRND

Primary reason is so I dont have to solder them up again later if I redeploy the board for another project as they are hard to get the wires in the holes. Using 16AWG Silicone coated wire, nice and flexible and doesnt melt when soldering either.

UPDATE ....

Some more pics...

Needs some paint, chrome way too expensive - over $200 just to do the top cover (top/front and 2 sides)

Top view....Transformer cover is a PVC 6" pipe end cap...made in Japan also not cheap but should not be able to tell once its painted.
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Might tidy up the back panel with some Al plate if I can be bothered.
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8 Channels of LM3886TF GainClone amps in bridged-single-bridged-single-bridged config Power 140+75+140+75+140.
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The hammer paint finish on the case... maybe will do one more coat but scared I might ruin it...

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Now comes the fun part getting it all tested then put together and a finally into my system. Might have to run it as un-balanced until my XMC-1 becomes available.

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wizardofoz
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Re: 8PAKAMP KIT BUILD THREAD

Postby wizardofoz » Sat Apr 14, 2012 4:01 am

All done, fired it up and works as I knew it would with no faults...

Thanks Joe for a sweet board...

Once I get it on the big Yamaha speakers I'll push it a bit...no fuses in there now as the fuse holders broke, then I'll see how good it sounds.

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Now just have to put the right sex on the xlr's :oops:

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