Bash 500 High Pass Calculator - AVS Forum
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post #1 of 7 Old 11-08-2011, 02:08 PM - Thread Starter
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Just got my new PE Bash 500w amp. Got a little frustrated trying to determine what the stock settings for Cutoff (Fc) and boost were since the values for the stock resistors didn't appear in the table. (Yah I could extrapolate but I'd really rather have the actual values).

Anyway, I searched around on the internet for some equations and built a spreadsheet that will allow you to calculate resistor values for a specified Fc and Q or calcuate the Fc and Q for specified resistor values.

I know complete zilch about electronics, this is all just math to me, so if there's a boneheaded error in the spreadsheet let me know and I'll fix it. Also if everyone already knows how to do this and I'm the only just figuring this out... well just humor me.

If you need to setup a highpass filter on your Bash 500, or any amp that uses a 2nd order HP filter where you know the inductance value, or want to know the cutoff for the stock values you can use this... enjoy.
**************************************************
11/9/11 - Updated the file to include boost and gain information

 

Second_OrderHPCalc.zip 6.1376953125k . file
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post #2 of 7 Old 11-08-2011, 03:17 PM
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Out of curiousity, what HPF setting did your BASH500 ship with? I saw a post on a forum recently (recently = within last 1.5 month) suggesting the BASH500 is now shipping with the same stock HPF filter as the BASH300 (Fc=17Hz; Q=1) instead of Fc=32Hz; Q=1.2 that the BASH500 has used for years. With a sample size of 1 and no updated documentation to corroborate, it's always possible that poster got a restocked unit that had been modified by the first purchaser.

-Brent
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post #3 of 7 Old 11-08-2011, 03:31 PM - Thread Starter
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It shipped with R17 = 25K5 and R18 = 68K1 (25,500 & 68,100) this give an Fc of 17.36Hz and a Q of 0.817. As I understand a Q of 0.7 is no boost so the stock setup is only about a .3db boost.

I don't know how to calc the Boost Freq but PE said the stock setup boosts 31 -35Hz, but only minimally. I assume the stock setup is designed for effectively no boost.
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post #4 of 7 Old 11-08-2011, 06:02 PM
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Quote:
Originally Posted by GlibHarbinger View Post

It shipped with R17 = 25K5 and R18 = 68K1 (25,500 & 68,100) this give an Fc of 17.36Hz and a Q of 0.817. As I understand a Q of 0.7 is no boost so the stock setup is only about a .3db boost.

I don't know how to calc the Boost Freq but PE said the stock setup boosts 31 -35Hz, but only minimally. I assume the stock setup is designed for effectively no boost.

Interesting. It does appear P-E has changed the BASH500's stock HPF, but the documentation hasn't been updated. Hopefully, they've put a Rev# somewhere on the amp board as well to help identify the change. Warning people about the older HPF's Fc=30.6/Q=1.2 has become SOP anytime a DIYer mentions buying the BASH500 for a subwoofer project.

You can use WinISD Pro to see what the HPF does to the signal. Create a project and then add a "Highpass/SOS, user specified" filter to it...enter Fc and Q. Flip to the "Transfer function/magnitude (EQ/Filter) graph. If you were guessing at .3dB, then you guessed correctly...WinISD shows a maximum peak of .282dB @ 35.2 Hz for the filter only.

You can also use Jack's spreadsheet for the WF-100K's rumble filter to back into the Sallen-Key values and EQ. Looks like I had to unlock and clear the formula for Q (cell C7) and I changed the cap to .22, which I think is typically used in most of Dayton's amps. Then, you can just enter the desire Fc into cell C4 and the dB down (-3 for Fc in a Sallen-Key). The spreadsheet will then calculate the resistor values and graph the EQ'd signals shape.

-Brent
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post #5 of 7 Old 11-08-2011, 06:58 PM
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IIRC .22µf is not used in most of the Dayton amps.
The Bash 300 is .15µf, and the old 240 watt plate was a .1µf.

Regards,
Dan
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post #6 of 7 Old 11-09-2011, 02:26 PM - Thread Starter
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Quote:
Originally Posted by riverwolf View Post


You can also use Jack's spreadsheet for the WF-100K's rumble filter to back into the Sallen-Key values and EQ. Looks like I had to unlock and clear the formula for Q (cell C7) and I changed the cap to .22, which I think is typically used in most of Dayton's amps. Then, you can just enter the desire Fc into cell C4 and the dB down (-3 for Fc in a Sallen-Key). The spreadsheet will then calculate the resistor values and graph the EQ'd signals shape.

-Brent

Thanks Brent. I liked some of the stuff in Jack's spreadsheet and added it in mine. Specifically the Boost/Gain information. Hope he won't mind...
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post #7 of 7 Old 02-14-2012, 10:32 AM - Thread Starter
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Bumping this because there still seems to be some confusion about the HPF on this amp...
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