Maker Pro
Maker Pro

I need a low-noise guitar pick-up preamp...

P

powerampfreak

Jan 1, 1970
0
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
 
E

Eeyore

Jan 1, 1970
0
powerampfreak said:
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?

Best ? Depends what you call best. An IC design is going to be very distortion
free which may not be what you want !

What exactly are your criteria ?

Graham
 
P

powerampfreak

Jan 1, 1970
0
Best ? Depends what you call best. An IC design is going to be very distortion
free which may not be what you want !

What exactly are your criteria ?

Graham

Low noise.
Low distortion.
Just a preamp to buffer the high impedance pick-ups, no coloring of
sound.
All tone shaping is done later.
 
Low noise.
Low distortion.
Just a preamp to buffer the high impedance pick-ups, no coloring of
sound.
All tone shaping is done later.

It would help to specify the pick-up. Low noise is generally
associated with high current. Is this a battery powered project?
 
K

Ken Smith

Jan 1, 1970
0
Low noise.
Low distortion.
Just a preamp to buffer the high impedance pick-ups, no coloring of
sound.
All tone shaping is done later.

The LSK170 + a LT1128 may be what you are looking for.



Like this:
Vcc (about 12V)
!
Vcc \
! / 1K
\ \
/100K ! 47u
\ +------!!----------
2.2u ! !- d !
---!!----+-+--->! LSK170 !
! !- s !
/ ! LT1128 !
100K\ +--------!+\ !
/ ! ! >---+--+---+--- Output
! \ ---!-/ ! !
GND / ! ! !
3.3K\ ---------- !
! !
+-------!!-------------
! 47u
\3.3K
/
\
!
GND
 
P

powerampfreak

Jan 1, 1970
0
The LSK170 + a LT1128 may be what you are looking for.

Like this:
Vcc (about 12V)
!
Vcc \
! / 1K
\ \
/100K ! 47u
\ +------!!----------
2.2u ! !- d !
---!!----+-+--->! LSK170 !
! !- s !
/ ! LT1128 !
100K\ +--------!+\ !
/ ! ! >---+--+---+--- Output
! \ ---!-/ ! !
GND / ! ! !
3.3K\ ---------- !
! !
+-------!!-------------
! 47u
\3.3K
/
\
!
GND

--

Yes, it will be battery powered.
 
P

Phil Allison

Jan 1, 1970
0
"powerampfreak"
Hello,
Anyone having good suggestions what kind of preamp is best for use in
guitar pick-up applications.


** A FET input pre-amp.

Do a Google search.



....... Phil
 
T

tempus fugit

Jan 1, 1970
0
powerampfreak said:
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

Check this one out:

http://www.till.com/articles/GuitarPreamp/
 
E

Eeyore

Jan 1, 1970
0
powerampfreak said:
Low noise.
Low distortion.
Just a preamp to buffer the high impedance pick-ups, no coloring of
sound.
All tone shaping is done later.

In which case a FET input op-amp (e.g TL07x family) is ideal.

Graham
 
E

Eeyore

Jan 1, 1970
0
Ken said:
The LSK170 + a LT1128 may be what you are looking for.

Slightly overkill for a guitar pickup though.

Your Zin is way too low btw.

Graham
 
P

powerampfreak

Jan 1, 1970
0
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.- Dölj citerad text -

- Visa citerad text -

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
 
E

Eeyore

Jan 1, 1970
0
powerampfreak said:
What's the problem with 9V (6F22) batteries? Why use AA cells? Tell
me.

I don't know what he had in mind there. I gather that they are sometimes less
reliable since they consist of a stack of cells and the inter-cell connections
can be unreliable.

I will probably need two 9V batteries since I don't like using single
ended supplies,

Ah ! I just drew a scheamtic using a single 9V battery since that's the norm.
Never mind. It's easily adapted.

and I will need higher supply to have a decent output level and headroom.

That's always good practice for sure. The twin supplies also mean you can use an
op-amp intended for split supply operation and these tend to be lower noise than
those intended for single supply (and lower voltage) e.g. TL071 vs TLC271

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.

Well... the problem is that good op-amps don't really have 'a sound'. Many
guitarists do actually like intentionally added (low order) distortion.

For the moment, I think a TL072/TL074 will do just fine, I'm a little
afraid of it's noiselevel though.

Not a problem. They're perfect for this application. From practical experience I
can tell you that a guitar signal is a decent ~ 10mV (when not played hard - you
can get over a volt from some pickups when played hard).

The noise of a TL07x op-amp at 12nV/sqrt Hz is 1.7 uV in the audio band. That'll
give you a 75dB signal to noise ratio.

Besides, going for a NE5532 will make the batteries last much less.

Only about 1.4 times less actually but the 5534/2 wasn't intended for high
impedance inputs. You're better off with a fet input op-amp here.

Graham
 
P

Phil Allison

Jan 1, 1970
0
"Eeysore = the never check a fact plagiarist "


The noise of a TL07x op-amp at 12nV/sqrt Hz is 1.7 uV in the audio band.


** TI spec says 18 nV/rtHz, typical

Noticeably noisier than a most single FETs.




........ Phil
 
E

Eeyore

Jan 1, 1970
0
Phil said:
"Eeysore = the never check a fact plagiarist "


** TI spec says 18 nV/rtHz, typical

You're quite right. I was thinking of an LF357.

Noticeably noisier than a most single FETs.

Perfectly true but easier to use.

Graham
 
J

Jan Panteltje

Jan 1, 1970
0
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

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?
 
Top