So how should I wire it all ? the safety ground, the purple wire, the dc power supply ground and the speaker rca's. Been through this discussion a few times here on diyAudio and I am still confused what to do. I wish someone would tell me to do to make it right. I keep getting different answers that confuses me.
Yes, I'd include the diodes and the main electrolytic filter capacitors in the PS box,
and have reasonably clean DC exiting it. Have more of the electrolytics
in the amplifier box for low inductance, though.
This is the kit I have:
Non-Inverting LM3886 Stereo Kit | Chipamp Electronics
So the transformer and power supply board in one box an the other two boards with other electrolytic in the adjacent box.
Wire the purple wire and ac safety ground both to the same point? i.e. transformer mounting bolt?
The way it's wired now is everything is tied together at one point on a temporary metal backplate: AC safety ground, purple wire from ante, dc ground wires.
Last edited:
Shielding with adhesive copper coil shoild be enough. It is used in electric guitars.
Consider that the melting point of PLA is 180°. MY F5's 10kg heatsinks are around 60° C, but the mosfets are probably hotter than that.
Consider that the melting point of PLA is 180°. MY F5's 10kg heatsinks are around 60° C, but the mosfets are probably hotter than that.
Everyone sees it a little (or a lot) differently. I like to have at least one large electrolytic for each rail
right on the amplifier pcb. Additional parallel electrolytics for each rail can be at a more remote location,
perhaps with a small value (0.1-0.5 Ohm) series R for some additional filtering.
The input ground, the DC ground, and the speaker ground all go to the common junction of the +/- rail
electrolytics on the amplifier board.
In a metal chassis, the safety ground bolts next to the IEC inlet. For a plastic chassis,
I would suggest a metal plate under the transformer. To this plate you would mount the transformer,
and bolt the safety ground. The plate would attach to the plastic box with 4 bolts.
I wouldn't use the transformer's mounting bolt for any wire connections.
Instead, install a metal plate under the transformer and attach the transformer to it.
Bolt the ground wires near the corners of the plate, with a separate bolt for the safety ground.
Amazingly enough the purple wire which I gather is to the interwinding shield does not need to be connected to reduce the incoming line noise! I have measured this. The theory says it should be connected to the safety ground, except even the length of the power cord has enough inductance to be useless never mind the rest of the house wiring. Now the DC output common is called ground but it really does not need to be connected to any kind of ground. It is just the common point for the power supply.
My most sensitive amplifiers are battery powered and only may be grounded by the equipment connected to the output. But I do have AC line isolation transformers for when needed.
The shell of the RCA connectors should be wired directly to the amplifier PC card at the point closest to the input of the IC ground reference.
My most sensitive amplifiers are battery powered and only may be grounded by the equipment connected to the output. But I do have AC line isolation transformers for when needed.
The shell of the RCA connectors should be wired directly to the amplifier PC card at the point closest to the input of the IC ground reference.
Last edited:
Would I attach the antek purple wire to the same point as the safety ground?
EDIT: just read another reply. So don't attach the purple wire at all?
Last edited:
Okay so let me get this straight.
I have one plastic box (let's say to the left). It has a 110V ac power input (w/ filter, fuse & switch) on the back left side of this box. The ac power runs along the very left edge of this box to the front of this box. It connects to the Antek transformer, which is bolted to a metal plate (the plate residing inside the case).
The metal plate has the safety ground attached to it on the edge of this plate. The purple wire is useless and is left alone, shrink tubed & zip tied.
The 4 output wires of the antek are twisted in pairs running to the chipamp.com lm3886 dc power supply board, which is sitting behind near the back of the case.
The outputs of this supply are twisted and connected to an umbilical jack in the back right side.
An umbilical cable connects from the right side of the left case to the left side of the right case.
Common of the dc power supply is connected to the shell of both the input and output shell rica connectors.
All the wires, including line level wires, aren't shielded but twisted. (Line level wires are currently solid core tinned copper 20 awg or so.)
How would this work?
dc supply board (left case):
amp boards (right case):
I have one plastic box (let's say to the left). It has a 110V ac power input (w/ filter, fuse & switch) on the back left side of this box. The ac power runs along the very left edge of this box to the front of this box. It connects to the Antek transformer, which is bolted to a metal plate (the plate residing inside the case).
The metal plate has the safety ground attached to it on the edge of this plate. The purple wire is useless and is left alone, shrink tubed & zip tied.
The 4 output wires of the antek are twisted in pairs running to the chipamp.com lm3886 dc power supply board, which is sitting behind near the back of the case.
The outputs of this supply are twisted and connected to an umbilical jack in the back right side.
An umbilical cable connects from the right side of the left case to the left side of the right case.
Common of the dc power supply is connected to the shell of both the input and output shell rica connectors.
All the wires, including line level wires, aren't shielded but twisted. (Line level wires are currently solid core tinned copper 20 awg or so.)
How would this work?
dc supply board (left case):
An externally hosted image should be here but it was not working when we last tested it.
amp boards (right case):
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
Yes there will be a heatsink as well in the right case, but how does the rest look :
http://www.diyaudio.com/forums/parts/289088-3d-printed-chassis-5.html#post4664368
No power supply connection to the input RCA connectors. They have the shell wire go to the PC Card. The power supply provides current to drive everything. The input shield wire should only carry signal current.
Ok so only connect dc power supply common to output rca shells, that's it? And AC safety ground to transformer base plate. No other grounding?
I wonder what all this talk is about tying it all together at one point--star configuration or whatever. This included connecting output rca shell and dc power supply common I thought. Seems like I won't have this star config. But just like 3 wires grounded at 3 different points.
Last edited:
The RCA grounds all go to the pcb, each as part of a twisted pair, as does each DC supply ground.
Forget about all the "star ground" stuff, it's mostly an urban legend.
Maybe we should consider, for safety reasons, a 30A diode block connecting the pcb ground
to the safety ground. This acts as a high current voltage clamp to blow the fuse if an abnormal
voltage appears on the pcb common.
Last edited:
Would this be a good type of connector to use for the umbilical between the two?
An externally hosted image should be here but it was not working when we last tested it.
Seems ok, you definitely want a locking type that can't detach easily.
Ideally, you want a chassis mounting female DC outlet on the power supply box,
and a chassis mounting male DC inlet on the amplifier box. This is the safest way.
Last edited:
I use the above connector in a custom commodore 64 linear power supply I built. I didn't want the cord permanently attached to the unit -- so I could store it better. So I lopped the end off the old c64 power supply cable and attached the above. I like that it locks in place.
(Btw, the c64 linear power supply is the first one I ever built on my own, not in a kit form. I actually sat down and studied the current flow and went through it my mind several times before I turned it on.. it didn't blow up -- powered up my c64 heh. The c64 needs 9v ac and 5v dc so I used an antek torroidal 9v and sent 9v ac straight through and 9v ac to a beefy 4 way rectifier I built with 4 diodes. And then to a 6700k uf cap and 2A 78S05C voltage regulator -- with a small filtering cap on the output of the VR. Fun stuff! )
(Btw, the c64 linear power supply is the first one I ever built on my own, not in a kit form. I actually sat down and studied the current flow and went through it my mind several times before I turned it on.. it didn't blow up -- powered up my c64 heh. The c64 needs 9v ac and 5v dc so I used an antek torroidal 9v and sent 9v ac straight through and 9v ac to a beefy 4 way rectifier I built with 4 diodes. And then to a 6700k uf cap and 2A 78S05C voltage regulator -- with a small filtering cap on the output of the VR. Fun stuff! )
Last edited:
Is it possible to just filter the power before it comes to the switch in some external box? Because these 3 require a panel that is less than .07 in thick and well my panel is 5mm thick in the back. Wish there was a screw in option.
- Status
- Not open for further replies.