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Modulus-686: 380W (4Ω); 220W (8Ω) Balanced Composite Power Amp with extremely low THD

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If I may ask, how much are those Tortrans transformers?

That is a nice heatsink - also locally sourced?

If I may ask, how much are those Tortrans transformers?
Torotrans charged me just over Rs.4,000 for the transformer, and then added 18% GST and shipping.

That is a nice heatsink - also locally sourced?
Yes, this is from a vendor called Akash Heatsinks, also in Pune.

Home | Akashheatsink.com

These guys (and almost anyone anywhere in the world) have extruded heatsinks of 8" width or less. (If you get wider sections, they are usually cast, not extruded, and have poorer heat sinking ability.) So they are willing to join two pieces edge to edge using friction welding. Then they polished the base surface and anodised them. I paid Rs.3,300 for two such pieces, each 40cm long, including taxes.
 
Hi all.
I am soon going to build a 686. My first full DIY build.
I have ordered most of the parts already. Just waiting for the "Black Friday" sales at modushop before I order my case.

I have a couple of questions , should I order the case with Iron covers, or are the aluminium covers worth the additional cost?

I have modiifed the case layout slightly, but having just learnt that the heatsinks are in two pieces, should I split the 686 modules evenly between the two?
 
I do not know. I systematically use this process to avoid the vibrations of the capacitors.

There is the butyl sheet but also butyl between each capacitor.

Similar things can be found on switching power supplies.
What happens if the power supply smoothing capacitors vibrate a bit? I've heard that there could be microphonics with the signal carrying caps, but not about the power supply caps.
 
If they vibrate enough, metal fatigue will set in and the pins will break. That's mostly an issue with smaller capacitors if they're mounted a hair above the PCB surface. That's why you often see capacitors held together with silicone in SMPSes and Class D amp modules. I doubt vibration is an issue with snap-in capacitors. That's what I use in the Power-86 and Power-686.
I also doubt vibration is a big issue in most residential settings. But it likely would be an issue in active speakers intended for PA use.

The NOVER caps are snap-in types. The data sheet does not mention where the vent is located.

Tom
 
In high reliability gear, such as aerospace, there is a process known as "staking" in which components are bonded in a defined and precise way to the circuit board.

For example CONFORMAL COATING AND STAKING (BONDING)<br>ADHESIVE BONDING/STAKING

In domestic and commercial gear that might end up in a high vibration environment - such as sound reinforcement electronics - use of silicone or hot melt is the workaday thing to do, particularly to high-mass items like board mounted reservoir capacitors.

Craig
 
Hello,
Thanks for your feedback.
By reading the capacitor datasheet we see on the sketch a dotted line on the top of the capacitor marked "vent".
I'm afraid that having a butyl covering plate is a potentially dangerous idea ...
I will put a disclaimer on my presentation. But I think it will be difficult for me to remove those in place ...:(
 
Hi all.
I am soon going to build a 686. My first full DIY build.
I have ordered most of the parts already. Just waiting for the "Black Friday" sales at modushop before I order my case.

I have a couple of questions , should I order the case with Iron covers, or are the aluminium covers worth the additional cost?

I have modiifed the case layout slightly, but having just learnt that the heatsinks are in two pieces, should I split the 686 modules evenly between the two?

A follow up on this. If you want Modushop to modify your chassis, you need the 3mm aluminium cover version, as the cheaper 1mm “iron” cover has an
“Iron” rear panel, which Modushop cannot drill.