Author Topic: Question about RC Filter values / volume drop  (Read 276 times)

cdwillis

Question about RC Filter values / volume drop
« on: January 31, 2021, 02:14:46 PM »
This is something I was thinking about with a Blues Breaker clone I'm about to build. The low pass filter right after the tone control is 6.8k/.01uf for a 2.3khz frequency knee. Can I could use a 680 ohm/.1uf combination to get a smidge more output level than the stock 6.8k/.01uf while keeping that same frequency response? Is there going to be a difference, even minor like 1db or less I guess, between using those two different combinations?

iainpunk

Re: Question about RC Filter values / volume drop
« Reply #1 on: January 31, 2021, 02:23:13 PM »
that really depends on the schematic, but lowering the resistance and increasing the capacitance wold load down the preceding stage more an you'll probably lose volume, instead of gaining.

cheers

edit: you would probably gain some volume by changing the diodes, maybe use Led + 4148 in both directions, but you lose a little bit of distortion, but that only makes a tiny difference as long as you don't dime the gain
« Last Edit: January 31, 2021, 02:35:49 PM by iainpunk »
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antonis

Re: Question about RC Filter values / volume drop
« Reply #2 on: January 31, 2021, 02:44:08 PM »
You'll result into different LPF corner frequency for any Tone pot setting other than fully CW..
6k8 resistor is set in series with Tone pot upper lug - wiper resistance (plus 1k op-amp output resistor) forming the "R" part of RC filter, which part should be entirely scaled..
« Last Edit: January 31, 2021, 02:52:33 PM by antonis »
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anotherjim

Re: Question about RC Filter values / volume drop
« Reply #3 on: February 01, 2021, 10:47:38 AM »
The existing output stage seems quite well chosen. That 6k8 isn't loaded much by what follows and it's transparent above the filter knee.
As said, you could increase the clipping threshold with higher Vf diodes, but you could also increase the 6k8 in the diode feedback path so the existing diodes don't limit the gain so much.
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cdwillis

Re: Question about RC Filter values / volume drop
« Reply #4 on: February 01, 2021, 07:58:53 PM »
I've thought about putting a 10k linear pot in place of the 6.8k in the feedback loop as a sort of softness control. I guess that would also add a little volume, but at the same time more clipping?

iainpunk

Re: Question about RC Filter values / volume drop
« Reply #5 on: February 02, 2021, 07:57:05 PM »
I've thought about putting a 10k linear pot in place of the 6.8k in the feedback loop as a sort of softness control. I guess that would also add a little volume, but at the same time more clipping?
no, when you make the resistor larger, you get more volume because you kinda mix clean in to the distorted signal more, and if you make the resistance smaller, you get less volume and more clipping, because there is less clean added back.

cheers, Iain
half man - half snail - 6 feet to scale - Snail man's - not frail - He's been - to jail - snail man is fuccing real
『snailpilled』