Recent content by jesterbass

I'm having trouble trying to estimate the input impedance each output will "see" (post resistor), going into each 25k MN pot wiper, with the typical passive-pickup-blend wiring applied on the pot. I am almost certain that a) it is a function of the pot's rotation and b) it could be quite low, so...

Thanks for your input! So, what you're describing is: op amp output > output coupling capacitor > 2.7k resistor 25k pot wiper lug? I'm asking because I've arbitrarily added a 25k resistor to ground after the output coupling capacitor, just because it looked nice. :) PS. I will gladly remove...

I agree that a 18V single supply looks odd when you can have two independent batteries for the two rails. In fact, one of my first prototypes was as you describe, with such advantages as having the input/output signals referenced from true ground, less need to isolate the buffer stage from...

That's a good point. This specific op amp can tolerate having its outputs grounded, although I'm sure it would be easier on the chip to always see some resistance at its outputs (part of why I added the external output resistors). Plus, other op amps might fry if connected this way.

Thank you for this! It will be studied carefully as I love seeing how other people approach this stuff. The idea that the outputs may be effectively blended with a simple linear potentiometer is fascinating and an unexpected bonus.

I had to make a schematic with half a TL072 somehow! :)

Hello all, I have come up with this: It is a 18V single supply (bottom left) dual magnetic pickup buffer, based on the TL072 op amp (one half of the chip shown here, for one pickup). Pickup is modeled very simply at the bottom. Since the buffer uses single supply, we need to generate a...

Is it possible to get a Butterworth curve using second order Sallen-Key topology (2 caps, 2 resistors, op-amp) without oscillation? I am trying using this tool: (Sample)Sallen-Key Low-pass Filter Design Tool - Result - (selected resistors and caps at the bottom of the second pic)

I presume this is about the dreadfulness of the woofer. What part of the specs would you pick differently if you wanted to make a small 8" combo? Could a slightly more powerful amp compensate for the low efficiency?

I fully agree with you, they probably don't know what they are selling at that date of the year, and subsequently I'll have to do guesswork and trial and error with that driver. But that's what I had lying around and it made no sense spending for this specific project (toy combo amp). Also, a...

Not disagreeing here, but why is it rather dreadful?

Found it, on this very page (Homer Simpson sounds). No mention of speaker resonant frequency however. How does one proceed without a frequency response for the speaker? What I do know is resonant frequency (29Hz) and frequency response 40Hz-4Khz. And yes, this woofer is going into you know...

If you know the speaker's resonant frequency, would it make sense to configure a second order Sallen-Key hpf with a Butterworth slope, and a cutoff frequency set to the speaker's resonant frequency? Objectives are power efficiency and speaker protection from too much power and excursion, but...

What are the most frequently used exact filters/topologies used in common HPF pedals for bass like Broughton and fdeck for example?

Perhaps in series/parallel they are too hot to be behind a 9V preamp.