Thank you. Yeah... It took some thought in 3D to get everything shoehorned into the enclosure. I got the idea during Burning Amp and just could not let it go. To calm my brain down, I went home and drew up the CAD drawings. I concluded that it was possible to get the bits to fit, so I pressed on with the project.
To bridge the amp, you need to invert one channel. If you're building the amp with XLR inputs, all you need to do is to make a Y-cable where one of the branches in the Y is inverted (pins 2,3 swapped). If you're building the amp with RCA inputs, you'll need to configure one channel as the inverted channel (swap pins 2,3 on the input connector to the MOD286 board).
The non-inverted channel (+) output is then speaker(+) and the inverted channel (+) output is speaker(-).
C: None of them. I designed it for this kit and had it custom made. It will be included with the kit.
Tom
Upon closer look at the labelling and detailed interior photo, I see you’ve used 4 pole Speakons- am I correct in deducing that the L+R/M can be used for mono use, and for both channels in the case of bi-amping - such as with, say LX minis, etc?
For folks with older Mod86 kits awaiting assembly, might you consider offering the chassis, or at least rear panel, separately? I know that with my last scratch build before ACA kits - i.e. Hypex UCD- making a tidy job of hacking out the rear panel by hand was the most time consuming part, for which I’d have gladly paid extra over the cost of the stock HiFi2000 slimline chassis.
For folks with older Mod86 kits awaiting assembly, might you consider offering the chassis, or at least rear panel, separately? I know that with my last scratch build before ACA kits - i.e. Hypex UCD- making a tidy job of hacking out the rear panel by hand was the most time consuming part, for which I’d have gladly paid extra over the cost of the stock HiFi2000 slimline chassis.
this build looks PRETTY AWESOME, makes me want to build my 2x86 once and for all
Just do it!
Yep.
The Modulus-86 will not fit in the chassis I'm using for the Modulus-286 Kit. The MOD86 board is quite a bit larger than the MOD286.
You could certainly fit a Modulus-186 in the Modulus-286 Kit chassis. I did consider offering a MOD186 Kit, but it didn't make sense financially. The chassis is the main cost driver, so the MOD186 kit would only be about $100 less than the MOD286 kit. The Modulus-186 would not offer bridging, so I suspect most would spend the extra $100 to get higher output power and bridging capability.
Tom
Yeah! I'm narrowing down to 2 options for the DAC and 2 for speakers as well. Case will be last decision but yours got me excited.Just do it!
But if I'm not wrong it's also 3cm shorter or so (12x6 vs 9x7 approx?). What I don't find in the page is the height of the Mod86 though. So, in the end, they might fit. To get some extra room, thinking if I could use the same as yours but the 300mm depth instead of the 250mm version.
Sorry. I had the MOD186 dimensions in my head for comparing with the MOD86. Here are the dimensions:
MOD86 dimensions: 3.550 x 2.744 inches
MOD186 dimensions: 3.550 x 2.421 inches
MOD286 dimensions: 4.550 x 2.421 inches
The modules are all about the same height (~35 mm / ~1.4 inches).
25.4*2*2.744 = 139.40 mm -> 10.6 mm between MOD86 boards if mounted in the ModuShop 2U x 230 x 200 chassis. You may just be able to squeeze the input wires into the connectors. Then add the power supply on a mezzanine like I did in the Modulus-286 Kit shown above.
This thread is for the Modulus-286, however. I'm more than happy to discuss chassis options for the MOD86 in the Modulus-86 Build Thread.
Tom
MOD86 dimensions: 3.550 x 2.744 inches
MOD186 dimensions: 3.550 x 2.421 inches
MOD286 dimensions: 4.550 x 2.421 inches
The modules are all about the same height (~35 mm / ~1.4 inches).
25.4*2*2.744 = 139.40 mm -> 10.6 mm between MOD86 boards if mounted in the ModuShop 2U x 230 x 200 chassis. You may just be able to squeeze the input wires into the connectors. Then add the power supply on a mezzanine like I did in the Modulus-286 Kit shown above.
This thread is for the Modulus-286, however. I'm more than happy to discuss chassis options for the MOD86 in the Modulus-86 Build Thread.
Tom
Pretty clever using that mezzanine panel to nest the SMPS above the amp boards, but of course on the smaller chassis doesn’t leave room for any extra gadgets, such as Guardian or ISS. Frankly though, in over 45yrs I’ve never had an issue with speakers damaged by power amp failure - from other dumb shite, yes.
Maybe an assembly photo with either the front or rear panel off - before wiring is installed, of course - would show just how snugly it all fits.
Maybe an assembly photo with either the front or rear panel off - before wiring is installed, of course - would show just how snugly it all fits.
I’m guessing that both acts as a “spreader”, and simplifies assembly of the kit - requiring only three screws to attach the amp board modules to each heat sink?
I note that the earlier photo appears to show the “T” (metal tabbed) version of the chip, while the assembly photo shows the thicker plastic tabbed version.
Are my presbyoptic eyes betraying me, or is there a reason for that I’ve missed in the discussion?
Thermal impact: None that I can measure. I suspect the performance of the plastic version of the LM3886 (which is fine for the MOD286) will perform worse thermally than the LM3886T+Keratherm+aluminum I have going on.
Risk impact: Having the backplate allows me to control the most important thermal interface: That between the LM3886 and the backplate. Having the ability to torque those screws to spec makes me sleep better at night. The backplate also makes it easier for the casual DIYer to get the modules mounted to the heat sink as the tolerances on the hole placements are relaxed considerably compared to if I'd left the LM3886es for the end user to attach to the heat sink.
True. And thank you.
That's a good idea. I'll add that to the list of photos for the next photoshoot.
The reason is that I built the prototypes with what I had available. One board is with the LM3886T. The other with the LM3886TF. The production version uses the LM3886T (metal-back).
Tom
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As discussed at length in the “LM3886 Thermal experiment (with data)” thread, that interface between chip body and whatever dissipation methodology employed would be critical to the long term reliability of any product designed to squeeze as much juice from the peach as possible - I should think even more so for a kit such as this where the manufacturer has no QC over the final mechanical assembly process.
But there is a NHL pro team in Phoenix Arizona.
A hockey puck is 3 inches in diameter and 1 inch thick. (76mm by 25mm)
and weighs about 6 ounces.
I think it's more of a conductor as the heat should just flow through the thickness of the aluminum and go to the heat sink. The backplate might also help keeping the two LM3886es at the same temperature.
I did consider delivering the boards with the LM3886es populated and leaving it at that. You'd then have to purchase the brackets separately. Another forum member pointed out that the required tolerances for the mounting holes for the LM3886es would be tighter than what can be expected of a casual DIYer, so I added the back plate. The three mounting holes are 4.5 mm in diameter, so even with an M4x0.7 mm screw, there's plenty of slop. With Murican screw sizes, a #6 is 3.3 mm in diameter, so you'll have plenty of slop there. Use a flat washer with those. A #8 starts to get a bit tight (4.2 mm diameter), but should still be fine.
I'll use M4x0.7, 6 mm length in the MOD286 kit.
Tom