Diodes are a waste, but if you must use them, use a standard bridge rectifier. The standard bridge rectifier will mount with one bolt and most have an isolated case. Use two in series and you have four diode drops.
It should be pointed out that a low dropout regulator would be the best thing to use.
This would provide the maximum voltage out with a drop in battery voltage, and no excess heat at low battery voltage (like diodes would).
A 9V battery could drive the opamp instead of the usual charge-pump IC, it would be simpler. A simple low-current switch on the 9V battery would act as a system power switch.
This would provide the maximum voltage out with a drop in battery voltage, and no excess heat at low battery voltage (like diodes would).
A 9V battery could drive the opamp instead of the usual charge-pump IC, it would be simpler. A simple low-current switch on the 9V battery would act as a system power switch.
I might just stick to the simpler option of going with the 24v SMPS and use it on an inverter, I have to use the inverter anyway as I power a dj mixer and a couple of pioneer CDJ100s off it.
Kind of interested to see if it will be more efficient than using a car amp on 12v batteries in parallel. I used my car amp last time I went camping and was shocked how fast it drained the batteries (deep cycle). When I felt the temperature of the amp, well..... you could fry eggs on it. I wasn't overloading it, it is just terribly inefficient. Hoping this class D will be an improvement.
Kind of interested to see if it will be more efficient than using a car amp on 12v batteries in parallel. I used my car amp last time I went camping and was shocked how fast it drained the batteries (deep cycle). When I felt the temperature of the amp, well..... you could fry eggs on it. I wasn't overloading it, it is just terribly inefficient. Hoping this class D will be an improvement.
Correct! It's quite tight in my chassis tho:TheMG said:
An externally hosted image should be here but it was not working when we last tested it.
so I won't be able to solder them on to the back even when tilted. 🙁
If I was to use thick wire, around 1 or 2 inches long, I could squeeze the 4 caps down the sides, just. Would this cause huge problems? I may be able to use 8 x 500uF caps instead, as they are smaller, but I'd have to order them especially...
Also, my heatsink is grounded to my car battery ground. Should I electronically isolate the big chip on this board, or is it ok? It says nothing in the datasheet about this... 🙁
The inverter will probably be around 50% efficient, but even the diode option isn't 100% efficient, so just go with whatever you are happy with. You can also power this module straight from a single car battery, albeit at reduced power....col said:
MikeHunt79 said:
Depends. Usually the heat spreader on those chips are tied to electrical ground. Nothing that a quick test with a multimeter can't figure out.
MikeHunt79 said:
Or a single car battery with a 24V regulated SMPS. More complicated, but out of all the options is definitely the best one in terms of performance, efficiency, and reliability.
TheMG said:
Ok, just checking... Multimeter on resistance, 1 probe to power ground, 1 probe to heatsink - 0 ohms = tied?
This is exactly what is in the pic I posted above.TheMG said:
It was originally a 28v SMPS, but I took 1 winding off each secondary winding, and now it's 24v. 😎 I haven't measured efficiency, but it will stay above 20v with a 10A load with the engine running.Yup, if you're reading 0 ohms then it's tied.
I assume you got that SMPS from the original car amp? Looks like it.
That class-D amp board is going to be a very nice upgrade. In fact this board is pretty much perfect for a car amp. No so perfect for hi-fi, but great for car.🙂
I assume you got that SMPS from the original car amp? Looks like it.
That class-D amp board is going to be a very nice upgrade. In fact this board is pretty much perfect for a car amp. No so perfect for hi-fi, but great for car.🙂
Yep, the original car amp stopped working, so i butchered it for it's SMPS. The original car amp was poor anyway, it was one of those "purple mosfet" ones.TheMG said:
I have only done some testing, but it all works real well. I'm about 90% there, all I need to do is mount those 4 caps on somewhere, solder on the power and audio input wires, and it will be ready.
This sort of setup would be ideal for col - I wonder if he has any broken car amps hanging around? 😉
yes, very interesting. Don't have any car amps hanging around that would suit but will start looking in second hand shops. Would be good to have something modular, where I can use either the 240v-24v (indoors) or 12v-24v (out bush). Has given me some more ideas, cheers.
Very interested to see further developments with your rig. before I embarked on this project I was looking at Class D car amps but they were all very expensive and not full range. i.e. they are mostly only sub amps, which doesn't really help with my situation as you still have to run the inefficient class AB for above 360hz.
Did you consider just using the power supply without the casing? I mean, might have been better to take the path of least resistance. Maybe put it all in a bigger case where you don't have to do so many mods to the amp.
Very interested to see further developments with your rig. before I embarked on this project I was looking at Class D car amps but they were all very expensive and not full range. i.e. they are mostly only sub amps, which doesn't really help with my situation as you still have to run the inefficient class AB for above 360hz.
Did you consider just using the power supply without the casing? I mean, might have been better to take the path of least resistance. Maybe put it all in a bigger case where you don't have to do so many mods to the amp.
Just my opinion, but since there are always too many projects and not enough time - if a full range Class D car amp is what you want, there are some out there already, with decent components, ICE Power modules, etc. Don't know if they are sold in your part of the world, but something like the Pioneer PRSD2000T.
The Pioneer PRSD2000T would fit the bill but is not available here. I looked at the new Pioneer range of class D amps coming out in Australia but they are mega-bux like, $500 and upwards. I'm only interested in bang4buck, path-of-least-resistance type stuff. I enjoy hardware hacking though 😉
Yeah, in the car audio world, things are generally very expensive for good stuff, and the affordable stuff can be junk. There are a few good bang-for-buck amps out there, I won't deny that, but you really gotta look for em.
Often nothing beats the bang-for-buck of DIY though.🙂
Often nothing beats the bang-for-buck of DIY though.🙂
Yes. The output ripple at 440kHz is not related to the input. It is a by-product of the way class D amplifiers work. The inductor-capacitor pair at the output is meant to filter out this high frequency component from the output. Without this the 440kHz component would be +/- Vsupply at the output rather than a few millivolts!
This has so far been the only class D amp I have my hands on, so I'm not sure exactly how bad the output ripple is since I have nothing to compare to. I'll compare to the UCD400's once I get them.
This has so far been the only class D amp I have my hands on, so I'm not sure exactly how bad the output ripple is since I have nothing to compare to. I'll compare to the UCD400's once I get them.
You don't have to use an old car amp, but if you come across one of the "purple mosfet" amps, they are normally pretty close to 24v I've found.col said:
You should also be able to pick up a 12v to 24v converter, I think lorry drivers sometimes use them to power 24v things from a 12v source. Just make sure it can do the correct current (I tested my SMPS at 9A and it didn't even get warm).
I was hoping to get it finished today, but I'm at work right now, at the weekend! 🙁 When I get some free time, I'll finish it, test it, and put up some pics.
I haven't really considered putting the whole lot in another case. The SMPS has 10 semiconductors that need to be heatsinked, and I'm also making use of the old amps speaker binding posts and things like that. I wish I could stuff a crossover in there as well, but instead I will run +-24v somewhere to else in the car, and have an external crossover...
I've also bolted a block of Alu to the chassis, then bolted the class-D board to this block. This thing will stay nice and cool I hope, even tho I will be using all 4 channels at 4 ohms.
It works! I just soldered the caps on the back in the end, just to see if it works and it does... Once I move the caps, it will be going in the car.😎
An externally hosted image should be here but it was not working when we last tested it.
Thats looking well the business, welldone. Had a look around for a "Purple Mosfet" here. No sign in any of the second hand shops or ebay oz. I guess they were never available here.
Have received a "shipped" email from sure-electronics, only for the amp though, not the 24v PSU. Waiting..........
Have received a "shipped" email from sure-electronics, only for the amp though, not the 24v PSU. Waiting..........
Glad you like it. 😀 I really need to clear off my desk, it would be far better for this sort of thing...TheMG said:
No smoke yet tho, but a black mark on the bed would be far harder to explain than a black mark on the desk. 
Thanks! 🙂 I've seen these amps sold under the "Fury" brand also on ebay... They're around in the UK and US, but there's probably something similar south of the equator...col said:
Anyway, I've finally finished it! I glued the caps down in a gap on the chassis:
An externally hosted image should be here but it was not working when we last tested it.
I soldered up the caps, making sure the polarity is correct. I then hooked it all up and turn it on, music was produced as opposed to smoke, which is always nice. I've also added a molex to carry +-24v for my crossover....
An externally hosted image should be here but it was not working when we last tested it.
A shot from the other side... I had to use long 3mm bolts to hold my Alu block to the chassis. I added a few nuts for good measure, even tho I tapped threads in the chassis (SS is stonger than Alu also).
An externally hosted image should be here but it was not working when we last tested it.
Finally I couldn't get the cover back on! I think my Alu block has changed the shape of the chassis somehow, but it's not the end of the world as I'm gonna bolt the amp to a sheet of plywood.
This did take quite a bit of drilling, tapping and soldering... This definitely wasn't the easiest option, but I learned about how SMPS' work during this project, and I quite enjoyed doing it at the same time. 😎 If I was to do it again, I'd be tempted to go for the 41hz.com amp9 basic kit, as it would be easier to mount to your own heatsink, but I think that I've heatsinked this Sure amp well enough for driving 4 channels at 4 ohms each...
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