Same reason cable guys lift the wires off the floor.
😉
😉
Hi Bro, can you share your kicad/gerber files? happy that you can send to me by email [*Redacted]. Thank you very much.
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Firstly, I am by no means an experienced guy, just like to build some small stuff and have a good listen. So I maybe ask stupid questions...
So, I recently built a ACA Mini and like it very much, so much so that I decided to build another one in a case with heatsinks to be able to crank current up a bit.
So far so good, here is the current state...
Then I realized that the whole circuit is grounded through the 4 mounting holes, so the ground of inputs and speaker connection is connected to the case now.
This doesn't feel right...
Also because I want to use this power supply, which is also grounded by the mounting screws by the famous yellow/green wire.
Question: is it ok to mount the amp board with nylon screws for isolation, and connect the supply as on the picture, so the case is connected to safety ground by it?
And then...the supply can put out 26V, is it ok to run the amp like that, also with some more current?
So, I recently built a ACA Mini and like it very much, so much so that I decided to build another one in a case with heatsinks to be able to crank current up a bit.
So far so good, here is the current state...
Then I realized that the whole circuit is grounded through the 4 mounting holes, so the ground of inputs and speaker connection is connected to the case now.
This doesn't feel right...
Also because I want to use this power supply, which is also grounded by the mounting screws by the famous yellow/green wire.
Question: is it ok to mount the amp board with nylon screws for isolation, and connect the supply as on the picture, so the case is connected to safety ground by it?
And then...the supply can put out 26V, is it ok to run the amp like that, also with some more current?
It may run to hot. 24 to 26 volt may sound like a very small increase in voltage but because power (dissipated) has voltage squared as a term in the equation it makes a big difference.
You could see getting on for 20% more dissipation per device even if you don't alter anything current wise. Somewhere in the region of around 18.5 watts to 22 watts per transistor. That makes a big difference to the heat.
Give it just a 100ma or so more bias and that figure jumps even higher to around 27% increase per device.
You could see getting on for 20% more dissipation per device even if you don't alter anything current wise. Somewhere in the region of around 18.5 watts to 22 watts per transistor. That makes a big difference to the heat.
Give it just a 100ma or so more bias and that figure jumps even higher to around 27% increase per device.
@Mooly: thanks for those figures, I'll increase the current carefully then, but those sinks are pretty big compared to the small Aavid ones so there should be some headroom. Just don't want to destroy it🙂
So the active devices can take 26V I assume then? Want to squeeze out a little more out of it.
@AJedi: they are in place, I moved them upright to the capacitor spot, and connected the caps to the resistor spot. Otherwise it's difficult to use bigger input caps. It's even a boutique Audio Note tantalum, which I really like for input duties.
So the active devices can take 26V I assume then? Want to squeeze out a little more out of it.
@AJedi: they are in place, I moved them upright to the capacitor spot, and connected the caps to the resistor spot. Otherwise it's difficult to use bigger input caps. It's even a boutique Audio Note tantalum, which I really like for input duties.
I better correct that 🙂 I was thinking of the standard ACA...
Same applies but the numbers are very different. You would see around a 10 to 12% increase in dissipation per device by increasing the supply and correspondingly more if you increase the bias as well.
Sorry about that...
But the important issue is the grounding scheme, I don't want to be electrocuted or having a ground loop humming along. So far I always mounted the cinch connectors isolated from the case to avoid loops, execute all connected
Heat is the enemy, the transistors themselves can handle far far more than they see here... as long as they are not running to hot.
You can easily put some numbers in to see how big things get for small increases.
If you have 12 volts across the transistor and it passes 400ma then you have 4.8 watts of heat for that transistor.
Increase the supply so you have 13 volts across it and you also up the bias from 400 to 500ma and you now have 6.5 watts of heat. That is per device and is nearly 36% of an increase.
Ok, good to know that it's about getting rid of the heat. So I'll go by Nelson's finger thermometer😊...being able to touch for some seconds comfortably.
Nylon standoffs and a ground lift should work well. CL-60 would be easy.
So I built a pair of dual mono ACA Mini boards up with a dual'ish mono power supply. Although I only had 24 volts, I cranked the bias up to something like .450 per device and with the large heatsinks, the MOSFETs didn't even get above say 35-40 Celcius with an ambient of around 17 Celcius. That was with the heatsinks faced down on my test bench. So crank her up and use the back of one of your finger knuckles to get a sense of how warm it is
This amp does not dissipate a lot of heat being push-pull and only 5 watts stock. In fact, I decided to make mine a nice summer amp using the large heatsinks for my workshop becuase of these results 🙂
So I built a pair of dual mono ACA Mini boards up with a dual'ish mono power supply. Although I only had 24 volts, I cranked the bias up to something like .450 per device and with the large heatsinks, the MOSFETs didn't even get above say 35-40 Celcius with an ambient of around 17 Celcius. That was with the heatsinks faced down on my test bench. So crank her up and use the back of one of your finger knuckles to get a sense of how warm it is
This amp does not dissipate a lot of heat being push-pull and only 5 watts stock. In fact, I decided to make mine a nice summer amp using the large heatsinks for my workshop becuase of these results 🙂
And a tasty treat to be consumed before you begin soldering!
Sorry for slight OT on the DIY ACA Mini thread...
Puffin,
You still have those Fostex FE206E in the FE208 BLH cabinet? Plan to run those with the ACA Mini?
Puffin,
You still have those Fostex FE206E in the FE208 BLH cabinet? Plan to run those with the ACA Mini?