Mod-286 build thread

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Tom,


The output on the Mod286 is more than on the Mod186. On the mono retired version seemed to only have a higher output when run at higher than ~27V rails. Will that still be the case?


Since the new version is only going to be mono can you run it with ~27V rails and what would the output be?


Or is there not much to be gained and just go with the Mod186 instead of running the Mod286 on ~27 V rails?
 
I would have thought that part of the reason for the 286 would be performance into lower impedances rather than ultimate voltage output.

I am quite interested in a 286 build to use with my ESL63s, so it would also be good to know if there was any difference in stability into capacitive loads.
 
The output on the Mod286 is more than on the Mod186. On the mono retired version seemed to only have a higher output when run at higher than ~27V rails. Will that still be the case?

Yep. The underlying physics, ya know V2/R, hasn't changed. ;)

Since the new version is only going to be mono can you run it with ~27V rails and what would the output be?

I expect to hit the same or better specs as Rev. 1.1, so 60/120 W into 8/4 Ω on ±35-36 V rails. 40/80 W (8/4 Ω) on ±28-30 V rails.

A stereo MOD286 amp would be bridgeable for 100-120 W into 8 Ω (mono) on ±36 V. Bridged operation into 4 Ω is not recommended with ±36 V.

You could run a stereo MOD286 on ±28-30 V rails and get 40/80 W stereo and 70-80/140-160 W bridged mono into 8/4 Ω, respectively.

Or is there not much to be gained and just go with the Mod186 instead of running the Mod286 on ~27 V rails?

The MOD186 on ±28-30 V rails should provide 40/65 W (8/4 Ω). Operation into 4 Ω load on higher rail voltages is not recommended.

I would have thought that part of the reason for the 286 would be performance into lower impedances rather than ultimate voltage output.

A single LM3886 can't provide enough output current to drive a 4 Ω load well when operating on ±36 V. Two LM3886es in parallel can provide enough current, hence, offer better performance into low-impedance loads.

You can read more about that here: Taming the LM3886 - Output Power.

I am quite interested in a 286 build to use with my ESL63s, so it would also be good to know if there was any difference in stability into capacitive loads.

No difference. I test with 8 Ω || 1 nF -> 1 uF.

In other Modulus-286 related news:
I'm thinking to put together a Modulus-286 kit. 2 x MOD286 + Connex SMPS300RE (±36 V) in a ModuShop Mini Dissipante 2U (80 mm) x 230 x 200 mm (HxWxD) chassis with all the necessary holes cut and digital printed front and rear panels. I'm still getting quotes from vendors, so the pricing is subject to change. I'm hoping to be able to offer the full kit with everything included to build a complete amplifier for about $1200. I'm also toying with the idea of a pretty deep introductory discount for the early adopters. Maybe something like $899 for the first five amps sold, $999 for the next 15, and $1199 for the rest.
The chassis alone will set you back $350/each + shipping if you order it from ModuShop. That's actually quite reasonable considering that I'm modifying all panels of the enclosure except the top panel. :)

I'll need to build a prototype first. I expect to have that completed within about 4-5 weeks. Once I've verified that the kit design is good, I'll open up for pre-orders. I'll announce the opening of pre-orders here and in my newsletter (subscribe here: Sign Up to Stay Informed).

Tom
 
Well I was trying to determine for the future lx mini amp build if I was using a Mod686 for the woofers and a Mod186, Mod286 or Mod 86 for the full ranger. Due to the heat sink capacity I would run with the +/- 28V to 30 V for the Mod686, so I was just figuring which module to use on the opposite heat sink. So since the full ranger on the lx-mini is 4Ohm, with the Mod186/Mod86 at 65W peak and the Mod286 (bridged mono) at 140-160W (if I understand what you just posted correctly).
 
Tom - just subscribed to the stay informed mail list, and according to mailchimp/captcha, I'm still - or maybe only now just officially not a robot.

BTW, I think you know one or two names with which to populate your early adopters lists. I'm thinking that even a Mod86 / 186 might work well for my little upstairs background system. After over a decade of some rather nasty looking chassis bashing / repurposing, and the "fun" with drilling and tapping holes in the little Galaxy chassis used for another project (no fun when vendor supplies no mounting template or drawings), I'd be happy to pay the few extra bucks for something professionally machined. The HiFi2000 chassis work I saw on your 686 this summer was very tidy.
 
Well I was trying to determine for the future lx mini amp build if I was using a Mod686 for the woofers and a Mod186, Mod286 or Mod 86 for the full ranger. Due to the heat sink capacity I would run with the +/- 28V to 30 V for the Mod686, so I was just figuring which module to use on the opposite heat sink.

Ah. I understand your intent a bit better now. Thank you for the explanation.

Linkwitz and Pass arrived at 80 W being the recommended minimum power for the LXmini. So that's one data point. I used to recommend 4xMOD86 on ±28 V (40 W into 8 Ω) and have been running with such a setup since 2015. I did have some harshness when I really cranked it, but I attributed that to the room (and maybe that I'd usually had a few too many beers at that time anyway :)). That harshness went away when I used the MOD686 on the woofers and the whole system really shined with MOD686 on all drivers. This leads me to suspect the 6 dB bass boost in the woofer EQ causing the woofer amp to clip earlier than I thought. Now it would be nice with data (concept!!) to back this up, but so far all I have is the handwaving.

So what to do. If you want 80 W into 8 Ω from a ±28 V supply, you're looking at a bridged amp. That means the Modulus-686 (or 2xMOD286). I'd put a MOD686 on the woofer.
For the tweeter/full-range driver, I'd go with the Modulus-286. That'll get you to 80 W into 4 Ω.
If you want to, and you have enough heat sinking to support this, you can then bump the supply voltage up to ±32-36 V. That'll give you 160+ W into 8 Ω from the MOD686 and probably 90+ W into 4 Ω from the MOD286.

I think MOD686+MOD286 on ±32-36 V will be my recommended LXmini amp (or 2xMOD686 if you can). 2xMOD686 on ±27-28 V is really nice as well (been there, done that, loved it!) 2xMOD286 on ±36 V (as my MOD286 Kit will be) should be alright as well. MOD186+MOD286 on ±36 V would also work. The latter two configurations offer less power into 8 Ω than the MOD686 option (60 W vs 130 W), but that's the only drawback.

A perfectly reasonable thing to do would be to use 2xMOD286 to start. If you find the woofer amp to be clipping, add another 2xMOD286 so you can have two bridged amps for the woofers and one stereo amp for the two tweeters.

I've spent quite a bit of time massaging the numbers on the Modulus-186 and 286. I don't have all the quotes in yet, but with some reasonable guesses, I arrive at about $365ish per module for the MOD286 and just shy of $300 for the MOD186.
This cost is for the fully assembled module. The modules will be designed, manufactured, and assembled in Canada. All electronic components will come from Mouser/Digikey/et al. and the assembly will be done professionally in an ESD controlled environment, which is important for reliability.

I'll probably drop the "SMD pre-populated" option and just offer the fully built modules. It'll provide everybody with a higher quality product at a lower price. Just as important, it will hopefully free me up to focus more on growing my business.

This goes for the MOD686 as well. Once my current stack of pre-populated boards is gone, I'll move to the fully assembled version only.

Tom - just subscribed to the stay informed mail list, and according to mailchimp/captcha, I'm still - or maybe only now just officially not a robot.

Hey... I won't judge. :)

BTW, I think you know one or two names with which to populate your early adopters lists.

That'd be very cool. More is merrier.

I'm thinking that even a Mod86 / 186 might work well for my little upstairs background system.

I do have a secret plan for a Modulus-186 kit. ±30 V supply ... in a 2U 230 x 200 mm Mini Dissipante. :)

I'll have to stagger the kits, though. Otherwise I'll run out of money. Each of these kit projects require a >$10k upfront investment to get started.

I'd be happy to pay the few extra bucks for something professionally machined. The HiFi2000 chassis work I saw on your 686 this summer was very tidy.

And the MOD186/286 kit will be even tidier. You'll like it.

The kits will include everything, by the way. The whole idea is that you can complete the amp with everything that's included in the box. You'll need basic hand tools, solder, and a soldering iron (for the input connectors), but that's it.

Tom
 
Yeah. The hardcore DIYers will be a bit miffed. But then again, they were already disappointed with the SMD pre-populated boards. I can understand that. After all, the Y in 'DIY' is there for a reason. :)

Fact is that I can deliver a better product for a lower price by delivering the fully assembled modules. I also get to focus more on growing my business, which means I get to stick around for the long run.

Also, if you're in it for the challenge, nothing prevents you from buying my modules and going all out on the chassis design.

Tom
 
When I saw the board prototypes I sort of figured they may only be available fully assembled. The only items not SMD on the boards are the amp chips, terminal blocks, and the inductor coil. Less than $20 in parts. If the Mod-686's are only available fully assembled it will just take longer to acquire. Fully assembled seems the way to go to get higher fidelity. You are not the only one to go down that path.


I have 4 channels of Mod-86 to try out first. I will see how that goes. I was going to install 2xMod-86 for each speaker in a 2U miniDissapente chassis, but I decided to put 4xMod86 in one enclosure (since I already purchased it) to see how it works. It is a bit tight in the chassis based on preliminary layout, so if I decide to go with the Mod-686 and something else I will remove one of the Mod-86's from the enclosure and have a 3 channel amp for my surrounds and center channel (so I can add an ISS. Not enough room for it currently).
 
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When I saw the board prototypes I sort of figured they may only be available fully assembled. The only items not SMD on the boards are the amp chips, terminal blocks, and the inductor coil. Less than $20 in parts.

Yep. Plus about $30-35 in aluminum bits. I'll have a bracket at each end of the board holding a piece of aluminum that the LM3886 will mount to. It's an expensive solution, but it eliminates the mechanical stress on the LM3886 associated with misaligned holes and such. If every DIYer had access to a CNC milling machine, we wouldn't have these issues... :)

If the Mod-686's are only available fully assembled it will just take longer to acquire.

Fair enough.

Fully assembled seems the way to go to get higher fidelity. You are not the only one to go down that path.

True that. It's the reality in which we live. Some try to go cheap by using frying pan SMD reflow. That's not my idea of a good time. :)

I have 4 channels of Mod-86 to try out first. I will see how that goes. I was going to install 2xMod-86 for each speaker in a 2U miniDissapente chassis, but I decided to put 4xMod86 in one enclosure (since I already purchased it) to see how it works.

I hope you got one of the wider chassis options. I'm trying to shoehorn two channels of MOD286 and the power supply in to the smallest Mini Dissipante. That's a tight squeeze, but I think I can make it work.

Thanks for your support.

Tom
 
I got a 330mm wide by 300mm deep mini dissipante. 4xMod-86, 200VA Antek transformer, and a Power 86 fit in there. Wiring will be somewhat challenging. Will have to mount the amp boards higher so that the back panel jacks are mounted above and below the amp modules.
 
And just like that Rev. 2.0 is born: https://www.diyaudio.com/forums/ven...d-composite-amplifier-module.html#post5576031

I expect to open up for pre-orders over the weekend. I'm waiting for one quote to trickle in before I can lock in the pricing, but I'm thinking $350-375 is realistic. I'll offer these to the early adopters at a significant discount as a thank you for your patience as manufacturing will take a bit. I expect the modules to be in stock by the end of November. At that time the intro pricing will end.

Tom
 

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Hi again!

I'm sure a few of you are procrastinating as I had with completing a Modulus 286 build. Well, perhaps this post will serve as an impetus for you folk that need that encouraging boost ;)

Pretty self explanatory (you can click on each of the photos to enlarge them):



Over 170 SMD parts/board - loved the experience! :smash:







A lot going on here. 300VA transformer with electrostatic shielding and a steel enclosure. AMB Epsilon 24 board for momentary switches w/relay. 2 PS boards, a total of 88,000 uf of capacitance. 4 channel Modulus 286 build, hence the name Modulus 286^2.



Chassis ground - single most important part of the build; complete with a locknut for safety :sarge:



Closeup of the AMB Epsilon 24 board with relay.







When I first fired it up, DC offset on the speaker outputs initially measured about 0.13 mV for all the channels. Within about 30 seconds however, they all drifted down very close to 0mV on my Fluke 87. In late winter 2017, I built a precision 1khz oscillator (2ppm) from AKITIKA that has proven to be useful for my amp builds. It measures about 1.006 kHz and set to an output of 99 mV, I measured between 990 mV to 1010 mV on each of the Modulus 286 outputs confirming my gain setting of 10X (about 20dB to 20.17dB).

What can I say? Precision performance!

Can't wait to put it to the test in my HT setup, these will be powering my L/C/R mains with 1 channel to spare. They are 96dB efficient with an impedance minima of 4.8 ohms, so no worries there :D

If you have any questions or comments, please don't hesitate to ask. Thanks for reading!

Best,
Anand.

gorgeous build and meticulous. I've been trying to find those gold plated xlr connectors for one of my projects. how did you find them? everytime i searxh i find nothing.
 
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