Schatten Design thumbwheel controls question

[Jazz_175]

And yes.. I cheated and looked some stuff up (hey, college was a very long time ago). Dailey's 'Electronics for Guitarists' has a very good discussion in Chapter 2.

Ah Ah....that's a very good suggestion. Thanks, and it can also be found....

[PTChristopher]

S'410,

>>> I think a piezo is a high pass. Looks like:

Yes, indeed. I misunderstood you before. Nice artwork too.

[NS Ninja]>>> looks like the best option would be to use an onboard preamp for the piezo whether I'm adding a volume pot or not.

That would be best. Again, it is not absolutely impossible to keep the guitar passive, but yes - far easier to work with the system when the piezo is not exposed directly to the magnetic PU, or to a cable of any significant length. In my opinion.

>>> what do you mean by extreme high frequency loss? above 10khz?

I meant to suggest noticeable losses at the upper end of what we typically expect to hear from guitar, which I would describe as 5K to 10K. So yes, noticeable, but also in a range where many players would want to roll things off a bit anyway.

In my opinion, it is not practical to expect anything above 10K Hz from a guitar amp speaker, and many speakers are rolling off response like crazy by even 5K Hz.

Anyway, back to the original subject:

The idea is to avoid two problems:

1. Running a very high Z (impedance) signal on a long cable.

2. Mixing mismatched impedance signals.

Now you can actually do both of these things, and get a rather usable sound out of it as well - despite some info loss. But it is a real pain to tweak using the onboard passive pots. I can imagine some players feeling that there was one very touchy volume balance at which the sound was right.

Chris

[PTChristopher]

To calibrate frequencies:

Low E open is 82.4 Hz.

High E at a possible 24th fret is 1,318.4 Hz.

So when we talk about 5K to 10K Hz we are talking about harmonics and attack transients that BEGIN almost 2 octaves about the high E if it were fretted at a 24th fret. Up there.

There frequencies still definitely are audible and contribute to most player's sound.

The common thinking is that human hearing is 20 to 20K Hz, although many of us fall apart well below 20K.

[Jazz_175]

Where would you physically install the onboard pre-amp?
Inside the f-holes?

[PTChristopher]

Hi Paolo,

Who are you asking?

What pre-amp are you using?

I have only used pre-amps I made myself in archtops. They are very small and light and can be attached to the inside of the body with velcro. I have also just taped the pre-amp to the PU wire. Really small and light.

The battery is the pain, because it is heavy. I have used clips epoxied to the inside of the body, and also just suspended the battery in foam and stuffed it into the body. This sounds terrible but works well.

Most flat top acoustic guitars have a pre-amp assembly (slider pots, pre-amp, battery holder, etc.) mounted on the side, on the upper bout.

Chris

[nosoyninja]

S'410,

>>> what do you mean by extreme high frequency loss? above 10khz?

I meant to suggest noticeable losses at the upper end of what we typically expect to hear from guitar, which I would describe as 5K to 10K. So yes, noticeable, but also in a range where many players would want to roll things off a bit anyway.

Ha! I guess it was my bad... I read "extreme-high-end" loss, as opposed to extreme "high-end" loss. It´s the loss thats extreme, not the frequency!

[Spook410]

I think some different things are getting jumbled up here. The piezo attached to a load (like an amp or volume pot) won't lose high frequencies. If the resistance isn't very high (needs to be like 8M-10M) you will lose low frequencies and not in a range you would want to lose.

You may lose high frequencies through some other mechanism like cable capacitance or something, but it won't be much. The problem with piezo's seems to be those edgy, fingernail on a blackboard highs. I think you'll find yourself rolling them off with EQ rather than losing them to your passive setup.

[PTChristopher]

[S'410]>>> I think some different things are getting jumbled up here.

Yes. And my post #21 in this thread is the culprit. It contains a fundamental mistake, and I have now added a comment back in that post about my mistake.

While going on about trying to work with passive controls and mixed high impedance I got sloppy about the practical problem with the piezo PU in an extended passive circuit.

So thanks S'410 for steering this back on track.

To take it way back to the original question about a passive combination of a piezo PU and a magnetic PU - I have tried it and found that it can work (you get sound, and it can sound just fine) but it is very difficult to get a workable mix with the passive controls. It is very hard to balance the volume between the two pickups and then also use a passive tone control.

I can see why Schatten would specifically not recommend it, but would suggest a single buffer for just the piezo.

I have never used a single buffer, only a dual buffer - one for the piezo and one for the magnetic PU.

Thanks again S'410 for noticing my sloppy comments earlier.

Chris