MOD686 Build
I built up at MOD686 a few months ago, now it has proved itself to be a reliable setup (my build not tom's boards) I thought I would post some photos and information.
I used the SMD pre-populated boards and the metal backed LM3886's. In hindsight I would have made my life a lot easier by using the plastic insulated ones
Power supplies are Chinese SMPS's that I bought directly from the manufacturer and ordered at +/- 32 V, I chose that voltage as they are slightly unusual in that they "stiffen up" as more load is applied, so I played it safe with the voltage. I have used them before and found the quality of construction to be good and the important parts seem to be of good quality. At 328 Yuan they are also very cheap.
I already had a 5U Dissipante case sitting around doing nothing from another project that I abandoned so it made it easy to pull the trigger on the MOD686.
I would like to have used tom's mains controller but with the horrible US/AUD rate the bare boards were already comparatively expensive for me so I cheaped out and found some good looking boards from Taobao that would work with a momentary switch.
I've been putting my power switches underneath instead of on the front panel for a while now, keeps the front looking clean and the LED doesn't burn a hole in my head
I bought keratherm insulators to use but had to abandon them them due to getting continuity from the heatsink to the modules. They do not like alcohol anywhere near them it seems. I wasn't prepared to risk it so I used some ceramic ones I had, no continuity with them, but they were sensitive to splitting torquing the LM3886's down so there was an amount of trial and error to get it right.
I have been using the amp in my system and I am pleased with it. I was using and still have a First One 1.4. They both sound good, there is a difference between them. I haven't made any attempt to compare them more fully as I have had trouble with DC protection tripping the First One with certain tracks. I haven't included any DC protection on this build, no tripping on any track no matter how much low Hz is in the track If I fix that at some point I might try and do a longer comparison.
The pictures are fairly large so I've left them as attachments below.
I built up at MOD686 a few months ago, now it has proved itself to be a reliable setup (my build not tom's boards) I thought I would post some photos and information.
I used the SMD pre-populated boards and the metal backed LM3886's. In hindsight I would have made my life a lot easier by using the plastic insulated ones
Power supplies are Chinese SMPS's that I bought directly from the manufacturer and ordered at +/- 32 V, I chose that voltage as they are slightly unusual in that they "stiffen up" as more load is applied, so I played it safe with the voltage. I have used them before and found the quality of construction to be good and the important parts seem to be of good quality. At 328 Yuan they are also very cheap.
I already had a 5U Dissipante case sitting around doing nothing from another project that I abandoned so it made it easy to pull the trigger on the MOD686.
I would like to have used tom's mains controller but with the horrible US/AUD rate the bare boards were already comparatively expensive for me so I cheaped out and found some good looking boards from Taobao that would work with a momentary switch.
I've been putting my power switches underneath instead of on the front panel for a while now, keeps the front looking clean and the LED doesn't burn a hole in my head
I bought keratherm insulators to use but had to abandon them them due to getting continuity from the heatsink to the modules. They do not like alcohol anywhere near them it seems. I wasn't prepared to risk it so I used some ceramic ones I had, no continuity with them, but they were sensitive to splitting torquing the LM3886's down so there was an amount of trial and error to get it right.
I have been using the amp in my system and I am pleased with it. I was using and still have a First One 1.4. They both sound good, there is a difference between them. I haven't made any attempt to compare them more fully as I have had trouble with DC protection tripping the First One with certain tracks. I haven't included any DC protection on this build, no tripping on any track no matter how much low Hz is in the track
If I fix that at some point I might try and do a longer comparison. The pictures are fairly large so I've left them as attachments below.
Attachments
What a fluid build! Seriously!
Looking forward to your subjective comparo between the 686 and First One. Given how unreliable I have seen so many First One amplifiers (to no fault of their owners), that alone would make me veto the design. An unreliable design isn’t conducive to preserving my sanity no matter how good it sounds!
Best,
Anand.
Looking forward to your subjective comparo between the 686 and First One. Given how unreliable I have seen so many First One amplifiers (to no fault of their owners), that alone would make me veto the design. An unreliable design isn’t conducive to preserving my sanity no matter how good it sounds!
Best,
Anand.
+1
Thanks sharing your build here fluid
Thanks for the positive comments
I burnt the zobel on two of mine but that was me being careless
They aren't universally stable so care is needed. I recognised the supplies in your build which was another reason for me to pull the trigger
Good news on the reliability too. No problem. This is the 800W version ?? P800 LLC????? 800W??? ????????????-???
Use google chrome to open the page to make translation easier
Looks great with a fine level of detail. Superb clean looking job!
I'm not surprised you had problems with the ceramic insulators cracking. The Dissipante heatsinks (in fairness in common with any other extruded heatsink) is banana shaped, and it is also difficult to get the two halves of the heatsink in perfect alignment.
Manufacturers of such heatsinks often have a caveat regarding flatness, and if that is important (it always is, of course!) that they should be machined flat. I don't have a machining capability, so the last Dissipante heatsinks I used I laboriously flattened using abrasive strip glued to a piece of plate glass.
I'm not surprised you had problems with the ceramic insulators cracking. The Dissipante heatsinks (in fairness in common with any other extruded heatsink) is banana shaped, and it is also difficult to get the two halves of the heatsink in perfect alignment.
Manufacturers of such heatsinks often have a caveat regarding flatness, and if that is important (it always is, of course!) that they should be machined flat. I don't have a machining capability, so the last Dissipante heatsinks I used I laboriously flattened using abrasive strip glued to a piece of plate glass.
I believe at supply voltages of +/- 35 to +/- 36V DC, you can reach 240w/8 ohms and 360w/4 ohms at 0.1% THD + N. This is right at the onset of clipping.
See here for all measurements, graphs, and details: Modulus-686: 360W power amplifier achieving -120dB (0.0001%) THD – Neurochrome
Best,
Anand.
See here for all measurements, graphs, and details: Modulus-686: 360W power amplifier achieving -120dB (0.0001%) THD – Neurochrome
Best,
Anand.
I recommend staying at or below ±36 V.
There are some rare circumstances, under specific conditions, where I will support pushing to ±40 V (for example to eliminate the whine of the Mean Well RPS-400 series of SMPS). If you do push beyond ±36 V, the power supply must be regulated and the heat sinks must be large (~0.2 K/W or lower).
Tom
Congratulations on a state of the art amp build! I'll be very curious to see how it pairs up with the Don Keele designed CBT speaker I see in the background
Enjoy,
Anand.
Dang, I missed those. Ti Kan brought some of the cbt’s to Burning Amp a couple of times, sounded pretty good!
Thanks, folks. My impressions with the CBT24s are excellent. They have pinpoint imaging, and they create a giant sweet spot that is very evenly filled with sound. I built them about 2 1/2 years ago when the kit was first released.
The Modulus 686s power them as I hoped they would. I have a Modulus 286 stereo amp that I used previously with the CBTs, so I had a good idea of what to expect. I've only had the 686s up and running for a couple of days, so I'll hold off on further impressions until I've spent more time with them.
My stereo system is currently in my garage / billiard area which is a bit messy for staging photos, but here's a pic of one of the CBTs back when I had them in the living room.
The Modulus 686s power them as I hoped they would. I have a Modulus 286 stereo amp that I used previously with the CBTs, so I had a good idea of what to expect. I've only had the 686s up and running for a couple of days, so I'll hold off on further impressions until I've spent more time with them.
My stereo system is currently in my garage / billiard area which is a bit messy for staging photos, but here's a pic of one of the CBTs back when I had them in the living room.