Hello, Anyone having good suggestions what kind of preamp is best for use in guitar pick-up applications. These pick-ups has very high impedance. Would a I.C based circuit or a discrete provide the best results? Your ideas are most appreciated, Regards PAF
"powerampfreak"
** A FET input pre-amp.Do a Google search.
...... Phil
Check this one out:
"tempus fugit"
** The 2.2k in the source can be bypassed with an electro of about 10uF for increased gain. 10 times gain or 20 dB is easily possible........ Phil
Hmmmh, doesn't like the sound of op amps, but big ass polarized caps in the audio path are just fine. Uh, right.
I have this general distaste for circuits that use 9V batteries unless the current draw is on the order of self-discharge. Always design with AA cells if possible.
** Piss off - you pathetic audiophool wanker.
........ Phil
What's the problem with 9V (6F22) batteries? Why use AA cells? Tell me. I will probably need two 9V batteries since I don't like using single ended supplies, and I will need higher supply to have a decent output level and headroom.
Also, how could anyone say "don't like to sound of op-amps". It all is up to how to op-amp is wired up.
For the moment, I think a TL072/TL074 will do just fine, I'm a little afraid of it's noiselevel though. Besides, going for a NE5532 will make the batteries last much less.
Regards PAF
On a sunny day (11 Mar 2007 04:37:51 -0700) it happened "powerampfreak" wrote in :
Hi PowerAmpFreak, I have been thinking, and it is so many years ago I had a guitar with electric pickup coils, and those were inductive.
So if the 'sensor' is like this:
-R-L-------- | ------------
where R is the resistance of the windings, why not drive into a LOW impedance: +9V | [ ] 10k 470k |-----------------0 --===---| c | b |/ ---||-----------| |\\/ e -- | | | /// ///
The idea is, that as freq goes higher, the impedance of the picup coil _also_ increases, so the Ib is actually set by the R in the coil in series with the Zi of the transistor circuit.
There are several advantages in using a low impedance circuit, no effect of cable capacitance, low noise if input open, linear freq ??? response? (I am not sure if lower frequency snares make the same EMF..., but seems sensible).
Also, with the correct wrong bias this cicuit will give the so much loved correction of the waveform, sometimes by some non musicians bluntly referred to as 'distortion'.
This aside, in the old vidicon (camera picture tube) days, great effort was made to make a high impedance input amplifier, one day I just stuck the signal in a cicuit as above, and it worked just as well.. (vidicons have many MOhms output impedance, makes it pretty much a current source, ideal to drive a base of a transistor, if impedance is high enough then no distortion.
Anyways I have no guitar now, so I cannot test it, maybe somebody can?
in
I have this 9V jihad. It is the most expensive battery for the power you get out of it AA cells are the best bang for the buck.
Before you get too concerned with signal swing, you need to determine what voltage will clip the amplifier downstream. No use driving it deeper than need be into clipping.
You realize the sensor (pickup) isn't going to be noise free. Thus there are diminishing returns in making the electronics very low noise. The deal with analog design is to select the right engineering compromises.
Masters of understatement: "... in general, the distortions introduced by opamps are not musical."
No Sh-t, Sherlock! ;-)
Cheers! Rich
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