#1 Simple Active Low Pass Filter/Buffer
Posted: Thu Mar 04, 2021 10:00 pm
I'm looking for some advice/steer on an active Low-pass filter for my Open Baffle project. Crossover of bass to full range unit will be circa 150-180Hz.
I've covered some of this in the SLOB thread but, just as a reminder, I'm hoping to run the full range unit essentially without a separate crossover using its natural rolloff and driving it with a bandwidth limited amplifier (a MoFo) by adjusting the input cap and inductor load, I've built up a single MoFo module, so configured, but found my source compenents have insufficient output to drive it well enough to be able to take FR measurements of the drive units mounted on a make-do baffle and driven by the MoFo - fortunately I always expected to build a suitable preamp just not quite as soon.
Anyway, I'm now working on a 2P29L preamp with about 19dB of gain. After the volume control I split the signal, one connection goes to the 2P29L preamp stage and the other goes to a unity gain buffer using a BUF-03 device (we're talking about one channel here) so essentially this gives me a passive buffered volume control that will feed the bass amplifier (the bass amp has slightly more gain than the 2P29L/MoFo combination).
I need a LP filter in front of the bass amplifer (a chip amp) and this is where I'm hoping I can some help. I have some spare BUF-03 devices and I'm thinking of using the same buffer arrangement as I described above but preceded by a line level low-pass filter. Does that sound viable or am I missing something fundamental? Here's the BUF-03 buffer schematic:
https://www.stereophile.com/content/aun ... schematics
An alternative solution to the same general approach would be to use the JLSounds JG Buffer module with a suitably configured LP filter in front.
http://jlsounds.com/buffer.html
I hope to be able to explore the crossover specifics with MiniDSP before building the actual end LP filters.
Where is the gotcha?
If this approach looks viable I can sketch a schematic for further connebts.
Thanks chaps.
I've covered some of this in the SLOB thread but, just as a reminder, I'm hoping to run the full range unit essentially without a separate crossover using its natural rolloff and driving it with a bandwidth limited amplifier (a MoFo) by adjusting the input cap and inductor load, I've built up a single MoFo module, so configured, but found my source compenents have insufficient output to drive it well enough to be able to take FR measurements of the drive units mounted on a make-do baffle and driven by the MoFo - fortunately I always expected to build a suitable preamp just not quite as soon.
Anyway, I'm now working on a 2P29L preamp with about 19dB of gain. After the volume control I split the signal, one connection goes to the 2P29L preamp stage and the other goes to a unity gain buffer using a BUF-03 device (we're talking about one channel here) so essentially this gives me a passive buffered volume control that will feed the bass amplifier (the bass amp has slightly more gain than the 2P29L/MoFo combination).
I need a LP filter in front of the bass amplifer (a chip amp) and this is where I'm hoping I can some help. I have some spare BUF-03 devices and I'm thinking of using the same buffer arrangement as I described above but preceded by a line level low-pass filter. Does that sound viable or am I missing something fundamental? Here's the BUF-03 buffer schematic:
https://www.stereophile.com/content/aun ... schematics
An alternative solution to the same general approach would be to use the JLSounds JG Buffer module with a suitably configured LP filter in front.
http://jlsounds.com/buffer.html
I hope to be able to explore the crossover specifics with MiniDSP before building the actual end LP filters.
Where is the gotcha?
If this approach looks viable I can sketch a schematic for further connebts.
Thanks chaps.