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Pc Board Layout Mag/piezo Mixer


KeithHowell
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Are you set on that particular circuit, or just looking for a preamp/mixer with a layout already done? In the second case, the MIMF preamp (go to mimf.com, register, and look for the library link at the bottom of the page) is ready to go.

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I would think that the buffer is not really needed, the active circuit of the mixer is probably enough. The circuit was designed for basses so the frequenciy especially of the master tone may need some tweaking, but the use of a single opamp is cool...thanks for posting that...where did it come from?

pete

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The mixer circuit as drawn still needs the buffer. Otherwise you're trying to passively blend the magnetic and piezo pickups using a pair of 500k pots -- the piezo tone will suffer badly. The mixer circuit is straight from a Fender bass, and, IIRC, Walter had to add a buffer to get the piezos to sound good. Both schematics are from Cafe Walter.

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Hrm, if someone doesn't get to it sooner, I might be able to do this this weekend. Simple circuit like that shouldn't take to long. I've been thinking of using a buffered, active mixing circuit, as I'm not entirely pleased with the results using passive mixers with certain pickup combos. (This is only with mag. pickups, I haven't played around with piezo yet)

Are you set on the transistor buffer? I usually use opamp buffers.

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Hrm, if someone doesn't get to it sooner, I might be able to do this this weekend. Simple circuit like that shouldn't take to long. I've been thinking of using a buffered, active mixing circuit, as I'm not entirely pleased with the results using passive mixers with certain pickup combos. (This is only with mag. pickups, I haven't played around with piezo yet)

Are you set on the transistor buffer? I usually use opamp buffers.

How about something really different for the piezo preamp/buffer? Here's a subminiature valve (tube) circuit in kit form.

K261.jpg

More info, including a pdf with circuit here.

http://secure.oatleyelectronics.com//produ...3dea00ebef48950

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I want to use the circuits in a bass I am building for a colleague. I dont have decent software to do the layout and I dont really have layout experience or the desire to learn another software package. I do that all day at work.

After much searching I came up with Walters circuits which he has tested and pronounced OK. So I thought I would use those, why reinvent the wheel. Yes the mixer is from a Fender Bass.

Have a look at Cafe Walter for the full story.

There's a downloads section?

Yes there is. You get access if you make a donation.

Keith

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I don't don't have the time just at the moment, but I can highly recommend DIY Layout creator which is free, extremely easy to use and was created in consultation with Aron's stompbox forum so a huge range of layouts already done for common effects...all free. It is kind of drag and drop, and can be picked up in minutes and rendered and edited in MSpaint or similar to Jpeg for posting here in seconds. It will draw a circuit board in PCB, vero or (my fave), stripboard. It now includes off board components like pots and wires, so that makes it even easier to understand over simple labeled connection points.

Many people who have been involved in the sustainer project have picked this up and got layouts in a very short time. As always, checking everything is correct and verified, that takes some work and often only building it will be absolutely sure of the layout.

Yes, I see, you are right about the 500k pots on the piezo. A better approach would be to use a quad op-amp instead of the dual one in the mixer running as an inverted buffer, very few components and still a one chip device to provide a buffer for both the mags and the piezo before the mixer section.

There may even be something out there along these lines if you look for mixer circuits.

Sorry I can't help more, but I will be interested if someone comes up with something, the question keeps cropping up.

best of luck...pete

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I want to use the circuits in a bass I am building for a colleague. I dont have decent software to do the layout and I dont really have layout experience or the desire to learn another software package. I do that all day at work.

Just out of curiosity, do you have all the stuff you need to make the boards, and are you planning to make more than one? For one-off circuits (especially simple ones like this), it's often easier to just assemble it on perfboard. DIY Layout Creator is a nice tool for coming up with perfboard layouts, but it seems a bit lacking for designing true PCB's. Also, I have to agree with Pete that a slight redesign using a quad opamp to replace the JFET preamp section would help keep the parts count down.

I have to make one last plug for the MIMF preamp, too. The design is at least 7 years old now, and pretty well tested. It was designed to do exactly what you're looking to do - mix piezo and magnetic pickups, and it works well.

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