Design for manufacturing is fascinating. I've learned a lot from my assembly guys. I learned a lot about that at TI before then as well.
Think about that next time you hear someone saying that you can just heat the board up in a frying pan and everything will be well.
Yeah... Life at -120 dBc THD.
Tom
So what's the general consensus when it comes to mounting the Mod-686 boards in a chassis that has two heatsinks - one on each side, like the Deluxe 4U?
I'm trying to decide whether I should have one board mounted upside down so that the wires are roughly the same length, or mount them both upwards.
If I mount them both upwards, then the one input wire will have to be like 6 inches longer then the other, and it will have to cross over the power input and speaker output. I could do my best to keep them separated, but it will be tricky.
Are there any downsides when it comes to mounting it upside down? Should I put a dab of electronics grade silicone on those coils and big caps to help with mechanical stress, or is that a non-issue?
EDIT: After looking at some of the other builds, I think I'm going to mount the one upside down. Going to drill and tap the heatsinks tonight...
I'm trying to decide whether I should have one board mounted upside down so that the wires are roughly the same length, or mount them both upwards.
If I mount them both upwards, then the one input wire will have to be like 6 inches longer then the other, and it will have to cross over the power input and speaker output. I could do my best to keep them separated, but it will be tricky.
Are there any downsides when it comes to mounting it upside down? Should I put a dab of electronics grade silicone on those coils and big caps to help with mechanical stress, or is that a non-issue?
EDIT: After looking at some of the other builds, I think I'm going to mount the one upside down. Going to drill and tap the heatsinks tonight...
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Hi Guys,
I was reading some of your recent posts and have decided to share some of my experience building my first Modulus-686. I will add the link to my google album as I didn't want to clutter this page with so many images. If you are interested in my build you can take a look here Modulus-686 - Google Photos
As you can see in the pictures I have decided to mount the amplifier modules diagonally and also centered between two heat sinks. This way I was able to drill and tap the holes right in between the fins and also achieve even distribution of heat dissipation. I have tested the temperature on all 4 heat sinks after 2 hours of driving the amp at high load and the temperature was even at around 63-65°C across all of them. This setup works very well for me and I'm very happy with the end result. Once all of my components were delivered it took me 2 weekends to finish this build. It was very easy and very satisfying project. Tom was very helpful to answer my questions and to select the right components for my build.
My listening impression is very positive. No audible noise or any type of distortion after hours of critical listening. For those that are interested in some "numbers" I can probably follow up in a few weeks posting my measurement results once I have a chance of finishing building my Autoranger MK II from linear audio.
I'm currently waiting on my second order from Modushop and would like to build the second matching mod686. Two of them will be driving my pair of bi amped Audio Artistry CBT36K Line Array. Can't wait to listen to the end result...
Please let me know your thoughts or any improvements you think I can make in my next build.
Regards,
Walter
I was reading some of your recent posts and have decided to share some of my experience building my first Modulus-686. I will add the link to my google album as I didn't want to clutter this page with so many images. If you are interested in my build you can take a look here Modulus-686 - Google Photos
As you can see in the pictures I have decided to mount the amplifier modules diagonally and also centered between two heat sinks. This way I was able to drill and tap the holes right in between the fins and also achieve even distribution of heat dissipation. I have tested the temperature on all 4 heat sinks after 2 hours of driving the amp at high load and the temperature was even at around 63-65°C across all of them. This setup works very well for me and I'm very happy with the end result. Once all of my components were delivered it took me 2 weekends to finish this build. It was very easy and very satisfying project. Tom was very helpful to answer my questions and to select the right components for my build.
My listening impression is very positive. No audible noise or any type of distortion after hours of critical listening. For those that are interested in some "numbers" I can probably follow up in a few weeks posting my measurement results once I have a chance of finishing building my Autoranger MK II from linear audio.
I'm currently waiting on my second order from Modushop and would like to build the second matching mod686. Two of them will be driving my pair of bi amped Audio Artistry CBT36K Line Array. Can't wait to listen to the end result...
Please let me know your thoughts or any improvements you think I can make in my next build.
Regards,
Walter
Looks great!
I'm a great fan of Modushop. Being in the UK I just order direct from the manufacturer. They do a great job of customization too, which is not expensive. So post machining, silk screen printing, engraving etc, which they have also done for me and makes the case look really professional.
My only criticism is that everything is anodized, so electrical continuity between the panels is not guaranteed, and in extreme circumstances might compromise electrical safety through lack of bonding. I usually spend some time with a dremel to get back to metal in key attachment areas so the safety ground connects to all the metalwork.
Craig
I'm a great fan of Modushop. Being in the UK I just order direct from the manufacturer. They do a great job of customization too, which is not expensive. So post machining, silk screen printing, engraving etc, which they have also done for me and makes the case look really professional.
My only criticism is that everything is anodized, so electrical continuity between the panels is not guaranteed, and in extreme circumstances might compromise electrical safety through lack of bonding. I usually spend some time with a dremel to get back to metal in key attachment areas so the safety ground connects to all the metalwork.
Craig
Just completed this for a client. 4x Modulus-686 powered by 2x Connex SMPS800RE (±36 V). ModuShop 5U Dissipante chassis. It's intended for driving two 8 Ω and two 13 Ω drivers.
The power is controlled by an Intelligent Soft Start.
The amp will be rack-mounted. It weighs in at 11.1 kg.
To my surprise ModuShop have improved the Dissipante chassis. The brackets that hold the chassis together now feature PEM nuts, which allow the top and bottom panels to be attached with some nice machine screws rather than the cheap-looking self-tapping screws they used to use. Nice work, ModuShop.
Tom
The power is controlled by an Intelligent Soft Start.
The amp will be rack-mounted. It weighs in at 11.1 kg.
To my surprise ModuShop have improved the Dissipante chassis. The brackets that hold the chassis together now feature PEM nuts, which allow the top and bottom panels to be attached with some nice machine screws rather than the cheap-looking self-tapping screws they used to use. Nice work, ModuShop.
Tom
Attachments
Thank you!
Yep. ModuShop made the front panel. Unfortunately they don't offer customization of the steel panels, so I drilled and labeled those myself. I found a 24 mm hole saw (HSS steel) on Amazon for $10ish. It worked really well for the cutouts for the XLR and speakON connectors.
If you buy a hole saw for cutting steel you want HSS steel or something with carbide teeth. Not the bimetal hole saws.
Glad you like it. Those LS50s are amazing. I'm glad to see that KEF is still developing that product line.
Tom
Never quite sure how they were supposed to work. I have always drilled and tapped the brackets out to M4 and attached the top and bottom plates that way.
About 350-365mA/ch. And probably a little more if you are running sinewaves through the thing and pushing hundreds of watts - see spec sheet from Ti below.
This makes sense since each LM3886 device has an idle draw of about 50-60mA (max of 85mA). Page 4 under 'Total Quiescent Power Supply Current': https://www.ti.com/lit/ds/symlink/lm3886.pdf
There are six LM3886 devices in each Modulus 686 amplifier channel. They should constitute the bulk of the idle current draw. A few mA here and there will be drawn by his input stage devices which should bring the total up to about 350-365mA/ch.
As I recall, Tom had a 2ch Modulus 686 in a small 3U chassis at a Burning Amp GTG and the heatsinks were lukewarm at most.
Tom answers here:
https://www.diyaudio.com/forums/ven...er-amp-extremely-low-thd-139.html#post6481313
Best,
Anand.
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I know this is kind of stupid, but can someone explain the math used for calculating the power of this amp. I know I’m missing something. Maybe because it’s a BTL amp?
If I assume a 36V rail and there’s a 4 Ohm load, wouldn’t the power be:
((36 * 0.707) / 4) * (36 * 0.707) = 161 watts?
How is the 360 watt rating derived in this case?
If I assume a 36V rail and there’s a 4 Ohm load, wouldn’t the power be:
((36 * 0.707) / 4) * (36 * 0.707) = 161 watts?
How is the 360 watt rating derived in this case?
BTL gives you twice the output swing for the same rail voltage. So the math should be P = (2*Vs)^2/(2R). That works out to 72^2/8 = 648 W into 4 Ω for a ±36 V power supply.
The LM3886 can't swing all the way to the supply rail, so you're probably looking at more like 60^2/8 = 450 W into 4 Ω at hard clipping. I measure 360 W into 4 Ω at <0.1% THD+N. If I rated the amp at 10% THD+N like many other manufacturers I could claim 400+ W into 4 Ω.
Tom
The LM3886 can't swing all the way to the supply rail, so you're probably looking at more like 60^2/8 = 450 W into 4 Ω at hard clipping. I measure 360 W into 4 Ω at <0.1% THD+N. If I rated the amp at 10% THD+N like many other manufacturers I could claim 400+ W into 4 Ω.
Tom
Thanks! I bought some dummy loads for my amp and I plan to do some testing to measure the temperature at various spots while the amp is under steady state full load.
I’m running some Meanwell UHP-750-36 supplies in an unvented Deuxe 4U chassis, so I’m curious to see how hot the supplies get. They’re bolted to the bottom plate, but that bottom plate doesn’t have the best thermal conductivity to the rest of the chassis.
I’m running some Meanwell UHP-750-36 supplies in an unvented Deuxe 4U chassis, so I’m curious to see how hot the supplies get. They’re bolted to the bottom plate, but that bottom plate doesn’t have the best thermal conductivity to the rest of the chassis.