Ucd for s/woofer appln

newvirus2008 · 13th October 2010, 03:37 PM

Hi friends,

I want to build a UCD with the following specs:

freq=250kHz.
s/woofer = JBL CS1215, 4 ohms, 275W max.
req amp power = 200W.

Unfortunately, i have no access to an oscillioscope

. and would like to get help on the following:

1) How to calculate values L, C for output filter?
2) Is a gain of 56 problematic?
3) How to provide the GD power supply with good peak-current capability?
4) How to work out values for the resistors around the level-shift transistor?

Schematic attached.
Thanks in advance.

m-tech · 13th October 2010, 03:56 PM

First, use some software for simulations. LTspice is free, and very good for this things.
You can find a lot of finished projects which are almost same as yours.

savu · 13th October 2010, 04:43 PM

@newvirus2008
related to question 4 try this:
http://ufdemo.uni-information.com/au...evel-shift.gif
it is from here:
ucd 25 watts to 1200 watts using 2 mosfets

regards,
savu

newvirus2008 · 14th October 2010, 10:19 AM

thanks for the link savu. i think the level-shift problem is over.
Any suggestions regarding the output filter / loop gain etc.?

newvirus2008 · 14th October 2010, 04:43 PM

Also IRF530 is rated at 100 Vdsmax. Is it advisable to apply +/- 45V into an IRF530?

savu · 14th October 2010, 06:15 PM

I have no clue how to calculate it.

just use LTspice

regards,
savu

ViennaTom · 15th October 2010, 10:25 AM

If this is only for sub application, why go 250kHz? 50 kHz is way enough!

reg 1) : if only one pre-defined load (woofer) is to be applied, it is relatively easy to find good LC values. In fact, this gets even more easy as the factor between your LF bandwith (assuming <=200Hz) and your fs is sooo big.

savu · 15th October 2010, 10:28 AM

Yes but let's presume that you will want to use the sub woofer to listen to dubstep or drum and bas. you will need that extra sw freq ... 250Khz is easily achieved, so i do not see a problem there.

regards,
savu

newvirus2008 · 02:21 PM

Yes savu, I want it to be around 250kHz!
I will be initially testing it with full range audio and ordinary speaker, so i want it to be 250kHz. I mentioned 's/w' so that the target distortion levels are clearly understood.

thank you Vienna tom, but would you please share your idea on getting LC values for the filter?

m-tech · 03:35 PM

Do you think you need some special LC filter because it's going to be subamp ? No, you are wrong. Use 30uH and 680nF. These values are used typically ( at least in diy ).
If you want to use it as subwoofer amp, then you need active low pass filter on the input side. Btw.
Lout = Rsp / (2 x Pi x Frolloff), Pi=3.14
Cout = Lout / (4 x Rsp x Rsp x K x K ), K=0.707 typically value.

13th October 2010, 04:43 PM	#3
savu diyAudio Member Join Date: Feb 2007 Location: Cluj - Napoca	@newvirus2008 related to question 4 try this: http://ufdemo.uni-information.com/au...evel-shift.gif it is from here: ucd 25 watts to 1200 watts using 2 mosfets regards, savu __________________ 1'st rule of chess: The only way to get smarter is by playing a smarter opponent.

14th October 2010, 06:15 PM	#6
savu diyAudio Member Join Date: Feb 2007 Location: Cluj - Napoca	I have no clue how to calculate it. just use LTspice regards, savu __________________ 1'st rule of chess: The only way to get smarter is by playing a smarter opponent.

15th October 2010, 10:28 AM	#8
savu diyAudio Member Join Date: Feb 2007 Location: Cluj - Napoca	Yes but let's presume that you will want to use the sub woofer to listen to dubstep or drum and bas. you will need that extra sw freq ... 250Khz is easily achieved, so i do not see a problem there. regards, savu __________________ 1'st rule of chess: The only way to get smarter is by playing a smarter opponent.

15th October 2010, 02:04 PM	#9
newvirus2008 diyAudio Member Join Date: Jun 2008 Location: India	Yes savu, I want it to be around 250kHz! I will be initially testing it with full range audio and ordinary speaker, so i want it to be 250kHz. I mentioned 's/w' so that the target distortion levels are clearly understood. thank you Vienna tom, but would you please share your idea on getting LC values for the filter? Last edited by newvirus2008; 15th October 2010 at 02:21 PM.

15th October 2010, 03:33 PM	#10
m-tech diyAudio Member Join Date: Feb 2006 Location: Belgrade	Do you think you need some special LC filter because it's going to be subamp ? No, you are wrong. Use 30uH and 680nF. These values are used typically ( at least in diy ). If you want to use it as subwoofer amp, then you need active low pass filter on the input side. Btw. Lout = Rsp / (2 x Pi x Frolloff), Pi=3.14 Cout = Lout / (4 x Rsp x Rsp x K x K ), K=0.707 typically value. Last edited by m-tech; 15th October 2010 at 03:35 PM.


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13th October 2010, 03:56 PM	#2
m-tech diyAudio Member Join Date: Feb 2006 Location: Belgrade	First, use some software for simulations. LTspice is free, and very good for this things. You can find a lot of finished projects which are almost same as yours.

14th October 2010, 10:19 AM	#4
newvirus2008 diyAudio Member Join Date: Jun 2008 Location: India	thanks for the link savu. i think the level-shift problem is over. Any suggestions regarding the output filter / loop gain etc.?

14th October 2010, 04:43 PM	#5
newvirus2008 diyAudio Member Join Date: Jun 2008 Location: India	Also IRF530 is rated at 100 Vdsmax. Is it advisable to apply +/- 45V into an IRF530?

15th October 2010, 10:25 AM	#7
ViennaTom diyAudio Member Join Date: Apr 2010	If this is only for sub application, why go 250kHz? 50 kHz is way enough! reg 1) : if only one pre-defined load (woofer) is to be applied, it is relatively easy to find good LC values. In fact, this gets even more easy as the factor between your LF bandwith (assuming <=200Hz) and your fs is sooo big.

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