Fitting a subsonic filter to a plate amp - Page 5

Collo · 28th September 2008, 08:44 PM

Looking at the schematic for the amp, it does indeed have +/- 15v rails, so it would be an ideal match for the filter circuit.

Not only do you save on a separate power supply which can introduce hum if not implimented well, but you get the option of mounting the filter inside the sub for a seamless installation.

I have one of those amps myself, but never had the circuit, so this exercise truly has been a 2-way street!

As for using the TL072/LF353N op-amps, I'm no expert. I know Rod Elliot uses the TL072 in his filters, and he's an Aussie circuit guru, so I think it would be fine. Someone else might be able to confirm that though!

djk · 29th September 2008, 12:57 AM

This should be obvious.

The ESP filter has an input buffer, two 12dB filter sections, and an output buffer.

The plate amp has an input buffer, one 12dB filter section (C13, C14, R23, R24), and a second 12dB filter section C1, R1, R2, and add a resistor from the connection point of C1, R1 to the base of Q2, the power amp is the output buffer.

C1 will now be the same as C13, change R1 to the same as C14, the added resistor is R23, R2 is R24.

Now we have the same functions as the ESP filter with no extra board, opamps, etc.

otto88 · 30th September 2008, 12:00 AM

Thanks for the link http://www.subwoofer-builder.com/active-filter.htm to your excellent guide to 0.1 filters 101

Your wish list for the ideal subwoofer processor is good.

If I could suggest a wish for formula on LR HP filters, which calculates the component values. As well as 24 dB/octave, a formula for 36 dB/octave.

That’s also really good that WinISD models the changes to cone excursion and frequency response. Though I’ll wait till their next production release!

Cheers

28th September 2008, 08:44 PM	#41
Collo diyAudio Member Join Date: Nov 2004 Location: Newcastle, Australia	Looking at the schematic for the amp, it does indeed have +/- 15v rails, so it would be an ideal match for the filter circuit. Not only do you save on a separate power supply which can introduce hum if not implimented well, but you get the option of mounting the filter inside the sub for a seamless installation. I have one of those amps myself, but never had the circuit, so this exercise truly has been a 2-way street! As for using the TL072/LF353N op-amps, I'm no expert. I know Rod Elliot uses the TL072 in his filters, and he's an Aussie circuit guru, so I think it would be fine. Someone else might be able to confirm that though! __________________ Ports rule!

29th September 2008, 12:57 AM	#42
djk diyAudio Member Join Date: Feb 2001 Location: USA	This should be obvious. The ESP filter has an input buffer, two 12dB filter sections, and an output buffer. The plate amp has an input buffer, one 12dB filter section (C13, C14, R23, R24), and a second 12dB filter section C1, R1, R2, and add a resistor from the connection point of C1, R1 to the base of Q2, the power amp is the output buffer. C1 will now be the same as C13, change R1 to the same as C14, the added resistor is R23, R2 is R24. Now we have the same functions as the ESP filter with no extra board, opamps, etc. __________________ Candidates for the Darwin Award should not read this author.

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30th September 2008, 12:00 AM	#43
otto88 diyAudio Member Join Date: Dec 2007	Thanks for the link http://www.subwoofer-builder.com/active-filter.htm to your excellent guide to 0.1 filters 101 Your wish list for the ideal subwoofer processor is good. If I could suggest a wish for formula on LR HP filters, which calculates the component values. As well as 24 dB/octave, a formula for 36 dB/octave. That’s also really good that WinISD models the changes to cone excursion and frequency response. Though I’ll wait till their next production release! Cheers