Then you have about 10mohms of DC resistance in the coil wire (2mm dia/2m length). With load and audio signal, for instance, 160Vpp at 4 ohms the losses in the wire mean about 2W wire loesses (you should add core losses to that). That's more than enough to make it warm.
The wire has a higher hf resistance, due to skin effect (that's why 4x0.9mm is better).
With no load, it shouldn't dissipate almost nothing, you must have something bad there.
Best regards
The wire has a higher hf resistance, due to skin effect (that's why 4x0.9mm is better).
With no load, it shouldn't dissipate almost nothing, you must have something bad there.
Best regards
I have assembeled one of my pcb's i am really happy with how clean the waveforms are. Infact with the IR2110 10R gate drive resistors and 15V supply for the driver IC. The output of the Half bridge swings 160v in 28nS, there is a VERY small amount of ringing with no snubbers at the speed. i can slow that down by running the driver IC off 12V.. Thats pretty impressive given the high gate charge of the IR260N's.
Peter
Peter
Question with regards to Grounding / Earth Loops
I just have a quick question with regards to the best way to ground the module etc.
Currently the module is grounded to the heatsink & earth, hence they are at the same potential at GND on the circuit.
When an external source is connected a small gound loop must be being set up though the mains earth. As Extra humming / hissing can be heard.
How can i get around this.? Do i need to let the GND in the amp module, float away from the mains earth? The output GND for my speaker must be grounded to the Case..
Regards
Peter.
I just have a quick question with regards to the best way to ground the module etc.
Currently the module is grounded to the heatsink & earth, hence they are at the same potential at GND on the circuit.
When an external source is connected a small gound loop must be being set up though the mains earth. As Extra humming / hissing can be heard.
How can i get around this.? Do i need to let the GND in the amp module, float away from the mains earth? The output GND for my speaker must be grounded to the Case..
Regards
Peter.
Nah I wouldn't do that.
Sounds like it's a ground loop with the source so let's ignore the module itself to start with.
http://www.epanorama.net/documents/groundloop/index.html
All the info you can stand on ground loops.
Turn you volume down before you go.
You'll find this link there as well
http://www.jensen-transformers.com/an/an004.pdf
I think it does a good job of detailing the issue at hand, however let's not forget they do sell transformers. I've seen another site recommend a small resistor from 10 to 100 ohms in series with the signal ground to help limit the loop current, or tying the chassis together through another low impedance cable that isn't the signal cable.
Hope that helps.
Sounds like it's a ground loop with the source so let's ignore the module itself to start with.
http://www.epanorama.net/documents/groundloop/index.html
All the info you can stand on ground loops.
Turn you volume down before you go.
You'll find this link there as well
http://www.jensen-transformers.com/an/an004.pdf
I think it does a good job of detailing the issue at hand, however let's not forget they do sell transformers. I've seen another site recommend a small resistor from 10 to 100 ohms in series with the signal ground to help limit the loop current, or tying the chassis together through another low impedance cable that isn't the signal cable.
Hope that helps.
Thanks for that,
I am thinking I will just make up a pcb for my pre-amp and have balanced / unbalanced inputs, that should help reduce any possible ground loops.
I've really only had a problem while connected to my laptop while its on AC power, something funny must happen with the ground on the laptop. My desktop PC works pretty well, only a very very slight hum at full gain.
BTW, i measured the Loop current while pluged into my laptop, I measured about 100mA, while connected to my desktop PC its down to about 11mA.
I have not yet gounded the module directly to the Mains Earth, it is connected to a gnd connector on the front of one of my power supplys.
Regards
Peter.
I am thinking I will just make up a pcb for my pre-amp and have balanced / unbalanced inputs, that should help reduce any possible ground loops.
I've really only had a problem while connected to my laptop while its on AC power, something funny must happen with the ground on the laptop. My desktop PC works pretty well, only a very very slight hum at full gain.
BTW, i measured the Loop current while pluged into my laptop, I measured about 100mA, while connected to my desktop PC its down to about 11mA.
I have not yet gounded the module directly to the Mains Earth, it is connected to a gnd connector on the front of one of my power supplys.
Regards
Peter.
Yeah that sounds like a great idea.
Computers.. I've had interesting results. First time I connected an amp to an old SB16 the hum easily overtook the audio!
With an Audigy, as long as the computer is turned on, it's perfectly silent. Must be using balanced outputs? With the computer turned off though, 60Hz hum.
Good link huh? Used to be better before they had all that add ****, but it's too good a collection of info to be able to ignore.
It sounds like a small resistor would be an easy fix for you btw, have you tried it?
Regards
Computers.. I've had interesting results. First time I connected an amp to an old SB16 the hum easily overtook the audio!
With an Audigy, as long as the computer is turned on, it's perfectly silent. Must be using balanced outputs? With the computer turned off though, 60Hz hum.
Good link huh? Used to be better before they had all that add ****, but it's too good a collection of info to be able to ignore.
It sounds like a small resistor would be an easy fix for you btw, have you tried it?
Regards
OK, a few more questions to ease my mind...
I found some Bridge Rectifiers for my 2xUcD400. Still debating on using 1 or 2 rectifiers, would need some help deciding (UcD180 thread talks about possible tones generated between 2 modules with double rectifier)
The type I got is KBPC3508, is this any good? They are 35A, 50-1000V, no idea if they are "fast" types or not, only info i got is "Single-phase silicon bridge" - Looks nice & heavy with faston connectors.
The guy at my HW store thought a slowstart wasn't needed for 1000VA transformer at 230V - I tend to disagree, what do you guys think? My house circuits have automatic circuit breakers, 2x16A.
Next question...
Velleman M4701 DC protection modules, I've got 2. Specs say: Max 300W, max contact current 10A. Is this good enough? The UcD400 can deliver 200W (I think 185W at my rail voltage) into 8 ohms. Will this thing do well loaded heavily into 4 ohms (possible >360W channel) - UcD modules can go to 20A as well.
The relay is the only thing in the speaker signal path, the "detection" seems to be in parallel over the signal. Hard to make out but the relay is a HG4124.
Thanks for the input
PS. For people wanting to use this, I think it's easy to remove the miniature relay and replace it with something heavier
I found some Bridge Rectifiers for my 2xUcD400. Still debating on using 1 or 2 rectifiers, would need some help deciding (UcD180 thread talks about possible tones generated between 2 modules with double rectifier)
The type I got is KBPC3508, is this any good? They are 35A, 50-1000V, no idea if they are "fast" types or not, only info i got is "Single-phase silicon bridge" - Looks nice & heavy with faston connectors.
The guy at my HW store thought a slowstart wasn't needed for 1000VA transformer at 230V - I tend to disagree, what do you guys think? My house circuits have automatic circuit breakers, 2x16A.
Next question...
Velleman M4701 DC protection modules, I've got 2. Specs say: Max 300W, max contact current 10A. Is this good enough? The UcD400 can deliver 200W (I think 185W at my rail voltage) into 8 ohms. Will this thing do well loaded heavily into 4 ohms (possible >360W channel) - UcD modules can go to 20A as well.
The relay is the only thing in the speaker signal path, the "detection" seems to be in parallel over the signal. Hard to make out but the relay is a HG4124.
Thanks for the input
PS. For people wanting to use this, I think it's easy to remove the miniature relay and replace it with something heavier
Looks like a beast. I take it you bought it on recommendation? Must trust the guy alot, but he's dead wrong about 1000VA not needing soft start, especially at 200+ volts.
Data sheet:
http://www.datasheetarchive.com/datasheet/pdf/23/233744.html
Should handle the job fine, no ultra fast soft recovery here, the price of it likely reflected that, don't forget the snubber caps for it. I think you can solder them right onto the leads.
Would have been better off posting this in the PSU thread, so others can find it later when they're hunting for info.
Can you post the reference you found to the dual rectifier hum problem in there? I dont' recall it having said anything about multiple modules, and haven't found it myself.
Soft start... opinions vary:
Plitron:
"Inrush Current
The high remanence of grain oriented silicon steel, lack of air gaps, and the excellent magnetic properties of toroidal transformers can cause a high magnetizing current on turn on, limited only by the low impedance of the primary winding. However, the duration of the inrush current is rarely longer than a half a cycle.
The effect of this inrush becomes greater with an increase in toroidal power. 8 VA to 300 VA transformers should not require any protection. For transformers 300 VA and up a slow-blow fuse, delayed action circuit breaker, or some form of soft start circuitry should be considered."
I believe when they say a slow blow fuse or delayed action breaker, they mean in the house... basically, the "let it flow" philosphy, how would that affect your PSU caps?
Here's a table I think I've posted before, from:
http://www.tortran.com/Transformer_Design.asp#inrush
"Transformer Rating Suggested Protection
Up to 300VA None
300VA to 1000VA Use slow-blow fuse in primary circuit
1000VA to 2000VA Add a small value resistor in series with primary circuit.
2000VA and up Add a by-pass relay that will momentarily short out the resistor after 100-200 milliseconds. An NTC thermistor may be sufficient for some applications."
Why would you want to leave a resistor in series with the primary? May as well switch it out when you don't need it, but I guess it "can" be done.
Another site found makes a real good point. Inrush on a "regular" toroidal 1000VA transformer was found (calculated or measured?)to be in the realm of 500A! They don't say what the primary voltage used was. I'd think you'd want to limite that. But on a limited in-rush type of toroidal, it never surpased 20 or so. Through the use of different materials and techniques some toroids simply are inrush limited and no further circuitry is required. Personally, I'd like to know if the extra cost of this type of transformer would be warranted with what you'd save in inrush circuitry or whatever. More research required.
Other factors to note, the inrush limited transformers seem to be bigger, heavier, less efficient, and have a poorer regulation factor..... yuck.
http://powerelectronics.com/mag/power_magnetic_solutions_solving/
Note, the author of that is from plitron. They aren't your only options if you want to consider this low in-rush type of transformer either, maybe someone else has done a better job of it, but if they had they'd be showing off the better regulation factor and efficiency and smaller size etc. So I doubt it.
So personally, I would say it is required, unless you have an in-rush limited transformer.
I had one of those HW guys argue with me before because I asked him for some header pins, he told me there's no such thing and I just didn't know how to ask for what I wanted by it's proper name. He fished through his books for over 10 minutes looking for pictures as he looked for "leaders" or whatever, I kept saying "header pins". Finally I saw a picture that looked like I wanted... pointed to it... he read out the title above, nice bold letters .. "Header pins". I didn't say anything, just smirked a little.
Point is, there's a reason most of these guys work in parts.
Regards
ClassD4sure, thanks for your input, like always. I did post it in the wrong thread, was too quick.
I'll build a slow start circuit, better make a good design. I'm thinking of adding another relay in the slow start, that turns on the UcD's (grounding /ON) after the slow start - This should be possible with a transistor as well but i'm no hero when it comes to electronics.
About the 2 rectifiers instead of one, it was mentioned in one of Bruno's posts - the threads are nearly impossible to read over because of their size. A FAQ would be a great thing, but will require a bit of work.
As for the DC protection... Time will tell. I think I'll have to do a "disco" test, my friend has 2 free air subwoofers @4 ohms, putting these in parallel on a channel could be fun
- then check if anything heats up...
I'll build a slow start circuit, better make a good design. I'm thinking of adding another relay in the slow start, that turns on the UcD's (grounding /ON) after the slow start - This should be possible with a transistor as well but i'm no hero when it comes to electronics.
About the 2 rectifiers instead of one, it was mentioned in one of Bruno's posts - the threads are nearly impossible to read over because of their size. A FAQ would be a great thing, but will require a bit of work.
As for the DC protection... Time will tell. I think I'll have to do a "disco" test, my friend has 2 free air subwoofers @4 ohms, putting these in parallel on a channel could be fun
- then check if anything heats up...Hello,
Can someone tell me what would be an maximum temperature rise for an inductor, ie is it okay for it too run at 70'C. I will add fan cooling, only i have too. For small loads 4-8ohms heating is not really a problem, but for running at 1.3kW continous at 2 ohms, the inductor heats quite a fair bit, it probably gets up to 70-80deg C. I will have to measure this to be exact.
Is this acceptable or should i design and build an even heavier duty inductor?
Regards
Peter.
Can someone tell me what would be an maximum temperature rise for an inductor, ie is it okay for it too run at 70'C. I will add fan cooling, only i have too. For small loads 4-8ohms heating is not really a problem, but for running at 1.3kW continous at 2 ohms, the inductor heats quite a fair bit, it probably gets up to 70-80deg C. I will have to measure this to be exact.
Is this acceptable or should i design and build an even heavier duty inductor?
Regards
Peter.
Hello, Peter.
You have said you have measured 28ns rise time on your mosfets. How have you performed that measurement? Did you look at the PWM signal rise/fall times or something as the Vgs waveforms?
BTW: What mosfets are you using? I can't find anything named "IR260N" in order to check the datasheet.
Best regards,
Pierre
You have said you have measured 28ns rise time on your mosfets. How have you performed that measurement? Did you look at the PWM signal rise/fall times or something as the Vgs waveforms?
BTW: What mosfets are you using? I can't find anything named "IR260N" in order to check the datasheet.
Best regards,
Pierre
Hello Pierre,
The exact number is irfp260n made by international rectifier.
I am not measuring the gate waveform, I am measuring the Rise time from the output of the Half Bridge with my Tektronics TDS220 digital scope.
I have actually slowed it down a little bit, down to about 70nS in order to reduce the high frequency noise / ringing.
I will have to post some photos of my amp board. It is running extremely well. Sooooooo much better than my prototype. The sound is crystal clear, The frequency response is much flatter too, I havn't measured it yet, but the -3db point is > 20kHz.
Regards
Peter
The exact number is irfp260n made by international rectifier.
I am not measuring the gate waveform, I am measuring the Rise time from the output of the Half Bridge with my Tektronics TDS220 digital scope.
I have actually slowed it down a little bit, down to about 70nS in order to reduce the high frequency noise / ringing.
I will have to post some photos of my amp board. It is running extremely well. Sooooooo much better than my prototype. The sound is crystal clear, The frequency response is much flatter too, I havn't measured it yet, but the -3db point is > 20kHz.
Regards
Peter
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