Re: PCB interest
Wait a minute, you are asking me to sell you something like 10-16 PCB's of this power amp??
I havent got one completed !!
Well, i can have some pcb made, but without any silk or legend, no smobc too. Range is aroud 20$usd each.
There have to be some serious orders and some real money shown before making any of them, and that is without any waranty from my side as it is something real DIY.
Bent said:Hi, I for one am very interested.
I have a sag if IRF540's and +/-48v SMPS in my shed waiting for a home, and these are just the answer
Please let us know when the CB's are ready, I will likely buy 10-16 for my surround sound project.
Cheers, Graeme
Wait a minute, you are asking me to sell you something like 10-16 PCB's of this power amp??
I havent got one completed !!
Well, i can have some pcb made, but without any silk or legend, no smobc too. Range is aroud 20$usd each.
There have to be some serious orders and some real money shown before making any of them, and that is without any waranty from my side as it is something real DIY.
pb12 PCB for sale?
Sorry Pat,
I had been following the posts and thought your results were very encouraging and in the excitement thought the project was further advanced than it is.
I would be prepared to wait a while (not that I have any choice), but I was interested in your results and the output mosfets you are using (since I have so many of them...)
I have 10 SMPS +/- 48v at constant 3.3 amps/rail and and +/- 25v at 2 amps max.They may do better at 50v, but that is ll I have tested them to.
Since they are all 110v, and I live in Australia (and cant work out if they can be converted to run on 240v) I may post them on the list for sale section.
$20 seems reasonable for the boards, what is the current size of the pcb's?
All the best with it, I am really looking forward to hearing more.
Cheers, Graeme
Sorry Pat,
I had been following the posts and thought your results were very encouraging and in the excitement thought the project was further advanced than it is.
I would be prepared to wait a while (not that I have any choice), but I was interested in your results and the output mosfets you are using (since I have so many of them...)
I have 10 SMPS +/- 48v at constant 3.3 amps/rail and and +/- 25v at 2 amps max.They may do better at 50v, but that is ll I have tested them to.
Since they are all 110v, and I live in Australia (and cant work out if they can be converted to run on 240v) I may post them on the list for sale section.
$20 seems reasonable for the boards, what is the current size of the pcb's?
All the best with it, I am really looking forward to hearing more.
Cheers, Graeme
Doesn't want to work
Hi All!
Pat!
I've also made an iraudamp1 without any protection. It's almost the same as you published first time in this thread (see the attachment). I used THS4051 from TI because here in Hungary I couldn't buy LT1220... IR2010 and MMBT5401 are also unavailable
. As last chance I replaced C7 with a 100u capacity and R7 with a 100k resistor. It doesn't do anything 
. Could you help me?
As I observed the opamp couldn't push out voltage higher than 4V if it has 5V positive supply so Q2 never close so U3 always sense logically high level at its input (pin 1)... So, my question is if your LT1220 can push out voltage enough to close Q2?
Regards, lkadar
classd1
Hi All!
Pat!
I've also made an iraudamp1 without any protection. It's almost the same as you published first time in this thread (see the attachment). I used THS4051 from TI because here in Hungary I couldn't buy LT1220... IR2010 and MMBT5401 are also unavailable
. As last chance I replaced C7 with a 100u capacity and R7 with a 100k resistor. It doesn't do anything . Could you help me?As I observed the opamp couldn't push out voltage higher than 4V if it has 5V positive supply so Q2 never close so U3 always sense logically high level at its input (pin 1)... So, my question is if your LT1220 can push out voltage enough to close Q2?
Regards, lkadar
classd1
Hi, thanks for the interest in my project.
As far as i have tested, yes the output of the opamp was about close to +vcc, it is part of its specifications to be able to go very close to its +vcc swing. Maybe the opamp you use is not able to do so, you might try to add a resistor from B-E of Q2 as a pull-up, like 10k or so...
Did you check if Q1 is not part conducting ?
you migh try to disconnect the collector of Q1 and apply some signal to the input to see if it swing ok.
what is the gain of the BF942? might be the source of the problem, to duno.
i realy suspect that the opamp is simply not able to swing more than that. The LT1220 is precisely specified to do that.
They claims that the ouput swing voltage of the 1220cs is=±VS.
LT1220cs data sheet
Pat Allen
As far as i have tested, yes the output of the opamp was about close to +vcc, it is part of its specifications to be able to go very close to its +vcc swing. Maybe the opamp you use is not able to do so, you might try to add a resistor from B-E of Q2 as a pull-up, like 10k or so...
Did you check if Q1 is not part conducting ?
you migh try to disconnect the collector of Q1 and apply some signal to the input to see if it swing ok.
what is the gain of the BF942? might be the source of the problem, to duno.
i realy suspect that the opamp is simply not able to swing more than that. The LT1220 is precisely specified to do that.
They claims that the ouput swing voltage of the 1220cs is=±VS.
LT1220cs data sheet
Pat Allen
It works, but...
Hi all!
Pat!
Thanks for your help... It was my fault... I've put D3 into the PCB with reverse polarity.
So, it works now with about 300kHz carrier... I'm going to change R6 (freq. pot.) with a higher resistance one to get higher carrier frequency. But there are some problems.
The first problem is that the coil at the output gets realy hot. I use T106-40 (Al=81) against the suggested T106-2 (Al=13.5). I think the problem is the toroid core gets saturated.
The second problem is when the input is shortcutted I change the output to 28mV in average with the help of R3 pot., but the output swings between 3.6V and -3.6V at the carrier freq. Can it be caused by the first problem?
Thanks and regards, lkadar.
Hi all!
Pat!
Thanks for your help... It was my fault... I've put D3 into the PCB with reverse polarity
.So, it works now with about 300kHz carrier... I'm going to change R6 (freq. pot.) with a higher resistance one to get higher carrier frequency. But there are some problems.
The first problem is that the coil at the output gets realy hot. I use T106-40 (Al=81) against the suggested T106-2 (Al=13.5). I think the problem is the toroid core gets saturated.
The second problem is when the input is shortcutted I change the output to 28mV in average with the help of R3 pot., but the output swings between 3.6V and -3.6V at the carrier freq. Can it be caused by the first problem?
Thanks and regards, lkadar.
Hi.
What is the vcc rails you have?
i have figured that below 25v rail, the freq. was lower than it should.
My inductor also gets hot, but only after 1h of playing.
i dont have my module handy, i think the 3,5v figure for the residual noise is higher than mine, a lot. You may have something wrong with either the inductor or the capacitor.
Mine work best with higher voltages like 30-35v rails. Freq. is 400.0000khz.
DC offset could be set with a multimeter, like a flike or so, like i did. I been able to set it a 0.0mv dc ofset, with something like +1 -1v rail residual noise,
hth.
What is the vcc rails you have?
i have figured that below 25v rail, the freq. was lower than it should.
My inductor also gets hot, but only after 1h of playing.
i dont have my module handy, i think the 3,5v figure for the residual noise is higher than mine, a lot. You may have something wrong with either the inductor or the capacitor.
Mine work best with higher voltages like 30-35v rails. Freq. is 400.0000khz.
DC offset could be set with a multimeter, like a flike or so, like i did. I been able to set it a 0.0mv dc ofset, with something like +1 -1v rail residual noise,
hth.
Hi Pat!
Thanks again for your reply.
Thanks and regards, lkadar.
[OFF]what does it mean 'hth'?[/OFF]
Thanks again for your reply.
The Vcc rail is 40V, so it must not be a problem. Below 25V the 12V regulator doesn't want to work.
The lower carrier frequency can be caused by the fact that instead of using IR2011 I used IR2110, which has a higher switch delay (about 1.3 times, so the frequency can be 300kHz, which is 0.75*400kHz (0.75 = 1/1.3)).
OK, I'll try to use a simple multimeter to set the output DC offset too, but the +-3.6V residual noise is worrisome. The C16 cap is a WIMA 0.47uF/100V one, so I'll play with the coil...
Thanks and regards, lkadar.
[OFF]what does it mean 'hth'?[/OFF]
How many turns are you winding in your coil? You have a T106-40, don't you?
I assume you know that the inductance is calculated as L(uH)=(N^2*Al)/1000
You should have something in the 15-40uH range. If you can tell us the number of turns, I can tell you the residual ripple level you should have for that rails voltage.
Please confirm: +-40V, and 0.47uF filter, right?
Pierre
I assume you know that the inductance is calculated as L(uH)=(N^2*Al)/1000
You should have something in the 15-40uH range. If you can tell us the number of turns, I can tell you the residual ripple level you should have for that rails voltage.
Please confirm: +-40V, and 0.47uF filter, right?
Pierre
You should have around 2.66Vpp of ripple at 300KHz, or about 4.5Vpp at 250KHz with that values. (calculated with 6 ohm load, although it is very much the same on 4 ohm)
The heating of the inductor can be due to core losses. The ripple current in the inductor is about 4.3A pp.
If you use micrometal's software, you will find that, for a given current, voltage, and inductance, you have much higher temperature rise with T106-40 than T106-2, for example.
BTW: It is normal that your 12V regulator doesn't work below 25V rails, due to the series resistor that drops about 12V, so the input to the 7812 starts to fall below 13V and it doesn't regulate anymore. But I suppose you already knew that.
Hope this helps.
Best regards,
Pierre
The heating of the inductor can be due to core losses. The ripple current in the inductor is about 4.3A pp.
If you use micrometal's software, you will find that, for a given current, voltage, and inductance, you have much higher temperature rise with T106-40 than T106-2, for example.
BTW: It is normal that your 12V regulator doesn't work below 25V rails, due to the series resistor that drops about 12V, so the input to the 7812 starts to fall below 13V and it doesn't regulate anymore. But I suppose you already knew that.
Hope this helps.
Best regards,
Pierre
. But without load? In my case the coil gets very hot when there was no load... - Status
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