I got it fully built which obviously meant full SMD but I did remove some of the thru hole parts (connectors). It also came fixated to the brackets and thin aluminum sheet.
FWIW, I tested this amp extensively this afternoon, and actually let it cook at 100 watts RMS/8 ohms for a good 15 minutes. Some parts of the heatsinks happily rose to 60 degrees C, but nothing blasphemous happened. Of course a 4U/400 chassis helps.
Given the crest factor of music, I went ahead with Tom’s method of using the brackets with the thin panel of aluminum, even though I could have disassembled it and mounted it direct. I realize now that I don’t listen to sine waves.
With typical music use, the heatsinks sit at a balmy 28 degrees C. Note that with a supply voltage of +/- 35V @ 365mA of quiescent current, we are talking about ~26 watts of dissipation which is a mere pittance for a 4U/400.
Best,
Anand.
FWIW, I tested this amp extensively this afternoon, and actually let it cook at 100 watts RMS/8 ohms for a good 15 minutes. Some parts of the heatsinks happily rose to 60 degrees C, but nothing blasphemous happened. Of course a 4U/400 chassis helps.
Given the crest factor of music, I went ahead with Tom’s method of using the brackets with the thin panel of aluminum, even though I could have disassembled it and mounted it direct. I realize now that I don’t listen to sine waves.
With typical music use, the heatsinks sit at a balmy 28 degrees C. Note that with a supply voltage of +/- 35V @ 365mA of quiescent current, we are talking about ~26 watts of dissipation which is a mere pittance for a 4U/400.
Best,
Anand.
Superlative build Anand!Poseidon‘s Voice Neurochrome Modulus 686 build
Well I guess it’s high time I join the Modulus 686 club as well. In all honesty, I’ve had these boards for roughly three years and had it all hooked up to a pair of spare heatsinks with test leads and a generic PS. Listened to it for a few days…and to my surprise I had a hard time pulling away, it literally sucked the mojo out of my amp building passion hence…I shut it off and postponed the build…until now.
Ingredients
The build itself was somewhat underwhelming to be honest as Tom’s detailed instructions as well as prebuilt Modulus 686 boards made it a breeze. I decided to challenge myself slightly by hoisting the Toroidy and placing the ISS underneath as well as adding in a Ground Lift board and T-Ground board, both of which are wholly unnecessary mind you. Moreover, I’m one of those fellas that likes center mounting my toroid both from a visual but mechanical/handling standpoint as well. And lately, my preference is to mount the power supply boards onto the front panel, which doubles as a small heat spreader. I’m a stickler for an easily visualized chassis ground point, easily visualized mains fuse as well as being tightly adherent to keeping the mains as well as the stepdown wiring from the secondaries as close to dead center as possible. It’s one of the reasons I stick with single toroids (and if a monoblock design is required, I just build separate enclosures or if pressed, vertically mount each toroid on top of one another).
- Customized Modushop 4U/400 Dissipante Chassis
- Customized Toroidy Audio Supreme v2 800VA transformer with quad 25VAC secondaries and a single 120V primary
- Neurochrome ISS v1.1 board (customized for the capacitive switch)
- Schurter capacitive multicolor touch switch
- Pair of Neurochrome Power 686 boards each with (4) 22mF Mundorf 63VDC capacitors
- Pair of Neurochrome Modulus 686 boards
- Pair of Neurochrome Guardian 686 boards
- Ground Lift & T-GND boards
- Furutech XLR, Furutech binding posts, and Furutech IEC
- Wires of various gauges from Neotech and generic mil-spec wire
What I’m basically saying (to the newbies reading this thread) is that my method of building is somewhat overdone and downright silly when you look at the prowess of the 686 as a design. It has a PSRR that is beyond reproach and is a balanced composite design with a differential input so all these ‘extras’ are really just that…gilding the lilly.
One can pretty much get superlative performance with Tom’s recommendation of using a well designed MeanWell switcher supply and not worry about power supply boards, ISS, etc…because the Modulus 686 as a design doesn’t care. It’s power supply agnostic. If you feel threatened by the switcher supply, then do this. Load the top with pretty looking granite (away from the vent holes) and voila, your switcher amp is ‘heavy’ and therefore…’mo betta.
Perusing this thread, I am humbled by the builds of @pinnocchio, @sledwards12375, and @stretchneck. My build is very much average with little innovation to be honest. The only part that really tickled my fancy was the implementation of the capacitive touch switch!
On it’s maiden voyage the amp fired up to +/- 35V and dc offset on the binding posts was <1mV all within a few seconds. This is a no brainer design.
Alright, y’all have read enough, it’s time to throw in some pics. As always, I‘ll rotate back with some initial sonic observations and comparisons in the near future. Kudos and thanks to @tomchr for all he has taught and all he will teach me. And yeah, a reference in Class AB designs.
Pics
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It's good to see some Rev. 1.0 material being put to good use. Thanks for sharing. I'm glad it came together nicely for you. Thanks for sharing.
Modulus-686 Rev. 1.0 was originally offered in an SMD-only option and a fully assembled option. I assembled the fully assembled option by hand which was a royal pain. Imagining yourself soldering 300 LM3886es... That's a job that's best outsourced, which is why the current version is only available fully assembled. I also changed the mounting such that the circuit board now mounts onto an angle bracket instead of mounting to a piece of flat bar with the two powder coated angle brackets. This lowered assembly cost such that I could keep my prices constant while delivering more value.
Also note the ISS Rev. 1.0 and Guardian-686 Rev. 1.0 in this build. The newer ISS is smaller and offers more functionality. The Guardian-686 has been discontinued. I changed the Guardian-86 such that it will work with balanced outputs as well as single-ended outputs. So those contemplating adding speaker protection to their Modulus-686 today should go for the Guardian-86.
Anyway. I like that the insides look as good as the outsides. I bet that amp performs very well.
Tom
Modulus-686 Rev. 1.0 was originally offered in an SMD-only option and a fully assembled option. I assembled the fully assembled option by hand which was a royal pain. Imagining yourself soldering 300 LM3886es... That's a job that's best outsourced, which is why the current version is only available fully assembled. I also changed the mounting such that the circuit board now mounts onto an angle bracket instead of mounting to a piece of flat bar with the two powder coated angle brackets. This lowered assembly cost such that I could keep my prices constant while delivering more value.
Also note the ISS Rev. 1.0 and Guardian-686 Rev. 1.0 in this build. The newer ISS is smaller and offers more functionality. The Guardian-686 has been discontinued. I changed the Guardian-86 such that it will work with balanced outputs as well as single-ended outputs. So those contemplating adding speaker protection to their Modulus-686 today should go for the Guardian-86.
Anyway. I like that the insides look as good as the outsides. I bet that amp performs very well.
It'll creep up a bit if you let it run for an hour. I specify the 4Ux400mm chassis for a reason. It'll get even hotter with 180 W into 4 Ω (worst case operating point).
You don't say...
Tom
^ Definitely. If the switch itself made that sound... I'd wonder ... 
I didn't mean thunk in a bad way. I like it. It sounds a bit beefier than your 'typical' click from a relay that might be used in relay-stepped attenuation / input switching etc. Could just be my computer speakers.
I didn't mean thunk in a bad way. I like it. It sounds a bit beefier than your 'typical' click from a relay that might be used in relay-stepped attenuation / input switching etc. Could just be my computer speakers.
Nah. It's a pretty authoritative click. The ISS uses a power relay rated for 16 A so it does emit sound when it engages and disengages.
The small-signal relays used in attenuators, input selectors, etc. are much quieter by comparison.
Tom
Another superbly build Modulus 686!!! Amazing workmanship Anand!!!
I like that you flipped the modules to keep wire symmetry, great for same distance cabling! Again, that beautiful encapsulated Toroidy transformer takes the center stage, all shiny and beautiful! You should add a Lexan top so anyone can see the build. Love those Mundorf MLGO caps in the PSU as well!
Nice backplate design. Is it FPE or somewhere else it was CNC'd?
Quick question about the touch switch... Where did you buy it and what circuit driver are you using for it?
Great work!
Do
I like that you flipped the modules to keep wire symmetry, great for same distance cabling! Again, that beautiful encapsulated Toroidy transformer takes the center stage, all shiny and beautiful! You should add a Lexan top so anyone can see the build. Love those Mundorf MLGO caps in the PSU as well!
Nice backplate design. Is it FPE or somewhere else it was CNC'd?
Quick question about the touch switch... Where did you buy it and what circuit driver are you using for it?
Great work!
Do
I must have missed this build. That's another really nice build. Thanks for sharing. Interesting with the addition of a LAN connection for home automation. Does this allow you to yell at your digital assistant and have the music come on even if the amps are off to start with?
Tom
He used the Intelligent Soft Start (ISS). You can see it poking out from under the transformer in the last image of Post 1539.
Anand used the Rev. 1.x of the ISS. The current revision is smaller and offers more features (thanks to a micro controller). It is now also only available as a fully assembled module: https://neurochrome.com/products/intelligent-soft-start
Tom
Do,
Thanks for the comments.
Since the design was just hanging around for 3 years, it ended up being a conglomeration of both FPE work as well as GianLuca’s Modushop customization service. Had I realized that GianLuca can do nearly everything FPE can I would‘ve just used him as I did with my FH9HVX build. So yes, the rear panel is FPE.
The capacitive touch switch is from Schurter and it is the large 22 mm model. I believe this is the Digikey link. You’ll notice it is RGB, so you can use any color you really want for your ‘ON’ color. I used an ISS v1.1 which is the thru hole version of the ISS and there is a small modification that one needs to make to the circuitry to allow for 3.3V to make the switch operate. I believe the ISS v2.0 workaround is even easier and involves just a 1N4148 diode or similar. I recommend consulting with Tom for your specific application and he’ll be happy to help.
Best,
Anand.
Thanks for the comments.
Since the design was just hanging around for 3 years, it ended up being a conglomeration of both FPE work as well as GianLuca’s Modushop customization service. Had I realized that GianLuca can do nearly everything FPE can I would‘ve just used him as I did with my FH9HVX build. So yes, the rear panel is FPE.
The capacitive touch switch is from Schurter and it is the large 22 mm model. I believe this is the Digikey link. You’ll notice it is RGB, so you can use any color you really want for your ‘ON’ color. I used an ISS v1.1 which is the thru hole version of the ISS and there is a small modification that one needs to make to the circuitry to allow for 3.3V to make the switch operate. I believe the ISS v2.0 workaround is even easier and involves just a 1N4148 diode or similar. I recommend consulting with Tom for your specific application and he’ll be happy to help.
Best,
Anand.
It depends on how purely obsessive your OCD is...
There's no technical reason to remove the mounting plate, but it does obviously add another thermal interface, thereby, the ICs will run a micro-degree hotter than they would without the plate. I will never design a circuit that operates that close to the edge. In fact, I have run the Modulus-686 with both "music" (32-tone AP test signal) at clipping levels and with sine waves at 1/2 the rated output power (worst case thermal operating point for a Class AB output stage) with a 4 Ω load for hours - hours! - on the recommended heat sinks with no issues. The heat sinks will get hot under those conditions. 60-65 ºC after an hour for music signal! The ICs will be hotter but still well below 100 ºC. They're rated for operation at 150 ºC die temperature! Some may argue about reliability. Higher temperature -> greater chance of failure. That's very true. But that function is highly non-linear and it doesn't really start to take off until the operating temperature approaches 150 ºC.
The most common comment regarding the heat sinks is that they run cool. "I ran my amp for hours and the heat sinks barely got warm. Is this OK?" Yes. This is OK. This is exactly what you want. I could probably attract more business if I recommended smaller heat sinks, but that's not how I operate.
Tom
The reason I went with the mounting plate is to ensure that all the LM3886es are flat against the mounting plate, thereby, flat against the heat sink. For a while I sold the mounting brackets separately so people could DIY the thermal interface. My instructions clearly said, "mount the board to the heat sink, then mount and solder the LM3886es", but some soldered the LM3886es first. It turns out it's very hard to get them flat against the heat sink once they're all soldered to the board. This will result in one or more of the LM3886es to run hot due to a crappy connection to the heat sink. That's way, way worse than any mounting plate. That's not the high-end experience I aim to offer.
The current revision of the Modulus-686 comes on a mounting bracket. There's nothing that prevents you from popping the board off from the bracket and mounting it directly to the heat sink if you really want to geek out. You can just make your own mounting bracket that goes on the bottom side of the board. Since the LM3886es were mounted to the bracket before they were soldered they will all be in the same plane so they'll lie flat against the heat sink.
That said, there's still no technical reason for removing the bracket.
Tom
The current revision of the Modulus-686 comes on a mounting bracket. There's nothing that prevents you from popping the board off from the bracket and mounting it directly to the heat sink if you really want to geek out. You can just make your own mounting bracket that goes on the bottom side of the board. Since the LM3886es were mounted to the bracket before they were soldered they will all be in the same plane so they'll lie flat against the heat sink.
That said, there's still no technical reason for removing the bracket.
Tom
Tom, I completely agree with you and I use heat spreaders in my builds too,
my question was more for Anand/poseidonsvoice.
With his skill level, somehow, I expected that heat spreader not to be used anymore.
my question was more for Anand/poseidonsvoice.
With his skill level, somehow, I expected that heat spreader not to be used anymore.
I’m sorry I disappointed you. And at this point I think we are beating a dead horse.
Best,
Anand.