First guitar preamp... teake a look please.

cufunha · 29th July 2008, 02:43 PM

I'm graduating this year (electronics engineering) and I play guitar for a long time. I like to play metal (symphony X, angra, metallica).

I don't know much about guitar amplifiers; all I know came from google. It seems like guitar pickups act like a lowpass system with a ressonant frequency varying from 1kHz to 5kHz, and this transfer characteristic must be compensated (how?) in the pre-amp stage.

I'm trying to design a pre-amp, as simple as possible, just to start learning about guitar electronics and, in the future, design my own pre-amplifier for my guitar.

I have scketched a very simple pre amp based on poor solid state components, and it has a very good sound.
All I want now is suggestions on what to do next or what is wrong in this schematic and should be changed.

Please take a look:

lineup · 29th July 2008, 03:58 PM

Hola!

I think your little guitar ampifier is good.
You say: 'sound is good'
Why you want to change?
Some problem?

Only thing I do not know about is where you connect output?
Some power amplifier?
What is input impedance of your power amplifier = The Load?

What would I change?
I do not know.
TL081 / TL082 / TL084 will be good for this type of guitar amp.
12 Volt.
What power supply you use?
------------------------------------------------

You want to use battery?
You can use TL06X variant: >>> takes only 200uA supply current! ( 0.2 mA )
And you use one 9 Volt Battery.
And you can put Battery + Guitar Amplifier inside your guitar!
Then you can turn and control, when playing.

Datasheets .. for VARIANT of Op-Amplifiers:
http://focus.ti.com/lit/ds/symlink/tl084.pdf
http://focus.ti.com/lit/ds/symlink/tl064.pdf

cufunha · 30th July 2008, 12:54 AM

thankx for the answer. I forgot to mention some things. First, the output is connected to a standard stereo amplifier, I think a load impedance of 20k to 100k (which is connected to the 22k resistor shunt to the diodes).

the reason of 12V: it's the source I have here... it could be 9V without any problem...

about the 'good sound': the sound is clean (not noisy). It has a good distortion, but it doesn't have that metal sound i want. I have read about pickup electronics and pre-amp pickup corrections. What kind of corrections (filtering) are made in guitar preamps?

and the last question: what do you suggest to add to this schematic and how it is done?

thankx again for the answer.

lineup · 30th July 2008, 01:06 AM

Quote:

Originally posted by cufunha

about the 'good sound': the sound is clean (not noisy).
It has a good distortion, but it doesn't have that metal sound i want.
I have read about pickup electronics and pre-amp pickup corrections. What kind of corrections (filtering) are made in guitar preamps?

and the last question:
what do you suggest to add to this schematic and how it is done?

thankx again for the answer.

I do not see anything add to your schematic, besides some metal effects you want.

One idea I have used,
when have mono signal input + output to stereo:
Put 2 output capacitors and output level potentiometer:
to left + right stereo channel

Same as using a mixer with 1 microphone (mono mic) input.
- you have 2 output to left/right.
- can use those 2 potentiometers to put this sound source into LEFT/RIGHT panorama
... when reording in stereo.
It is like panorama studio mixer.

I give you one good link to find metal guitar effect ... and some other good electronics circuits.
Because I know only little about guitar circuits.

Here I hope you will find a lot links for Guitar Circuits applications
http://www.epanorama.net/schematicsf...uits/index.php
http://www.epanorama.net/links/music.html

Regardas honores.
Lineup

thespeakerguy · 3rd August 2008, 06:59 AM

but a seasoned analog engineer;

C2 can be decreased. 0.22, or even 0.1uF, smaller and cheaper

C5 should be incresed, this is rolling off your gain st 160Hz right now. Becuase there is a fixed DC offset, a 22uF or 47uF electrolytic can be used.

R8 will not provide a reasonable volume range due to its interaction with the feedback diodes.

You will never get more than about 0.6Vpp out of this. Is that enough?

cufunha · 3rd August 2008, 04:15 PM

i changed R8 to 500k now and now i can clearly hear the overdrive effect i want (but too noisy because of the very high gain). the capacitors are now changed as you pointed.
Can u explain me what should be the low cutoff frequency of this amp? I thought it was about 200Hz or more, but you´re talking abaout 160Hz.. and how about the high frequency cutoff? 10KHz is fine?

PS: inductor and capacitor near source simulates guitar pickup plus cables.

29th July 2008, 02:43 PM	#1
cufunha diyAudio Member Join Date: Jul 2008	First guitar preamp... teake a look please. I'm graduating this year (electronics engineering) and I play guitar for a long time. I like to play metal (symphony X, angra, metallica). I don't know much about guitar amplifiers; all I know came from google. It seems like guitar pickups act like a lowpass system with a ressonant frequency varying from 1kHz to 5kHz, and this transfer characteristic must be compensated (how?) in the pre-amp stage. I'm trying to design a pre-amp, as simple as possible, just to start learning about guitar electronics and, in the future, design my own pre-amplifier for my guitar. I have scketched a very simple pre amp based on poor solid state components, and it has a very good sound. All I want now is suggestions on what to do next or what is wrong in this schematic and should be changed. Please take a look:

3rd August 2008, 06:59 AM	#5
thespeakerguy diyAudio Member Join Date: Feb 2001 Location: Silicon Valley	from a relative newbie to guitar stuff.. but a seasoned analog engineer; C2 can be decreased. 0.22, or even 0.1uF, smaller and cheaper C5 should be incresed, this is rolling off your gain st 160Hz right now. Becuase there is a fixed DC offset, a 22uF or 47uF electrolytic can be used. R8 will not provide a reasonable volume range due to its interaction with the feedback diodes. You will never get more than about 0.6Vpp out of this. Is that enough?

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29th July 2008, 03:58 PM	#2
lineup diyAudio Member Join Date: Dec 2005 Location: the north	Hola! I think your little guitar ampifier is good. You say: 'sound is good' Why you want to change? Some problem? Only thing I do not know about is where you connect output? Some power amplifier? What is input impedance of your power amplifier = The Load? What would I change? I do not know. TL081 / TL082 / TL084 will be good for this type of guitar amp. 12 Volt. What power supply you use? ------------------------------------------------ You want to use battery? You can use TL06X variant: >>> takes only 200uA supply current! ( 0.2 mA ) And you use one 9 Volt Battery. And you can put Battery + Guitar Amplifier inside your guitar! Then you can turn and control, when playing. Datasheets .. for VARIANT of Op-Amplifiers: http://focus.ti.com/lit/ds/symlink/tl084.pdf http://focus.ti.com/lit/ds/symlink/tl064.pdf

30th July 2008, 12:54 AM	#3
cufunha diyAudio Member Join Date: Jul 2008	thankx for the answer. I forgot to mention some things. First, the output is connected to a standard stereo amplifier, I think a load impedance of 20k to 100k (which is connected to the 22k resistor shunt to the diodes). the reason of 12V: it's the source I have here... it could be 9V without any problem... about the 'good sound': the sound is clean (not noisy). It has a good distortion, but it doesn't have that metal sound i want. I have read about pickup electronics and pre-amp pickup corrections. What kind of corrections (filtering) are made in guitar preamps? and the last question: what do you suggest to add to this schematic and how it is done? thankx again for the answer.

3rd August 2008, 04:15 PM	#6
cufunha diyAudio Member Join Date: Jul 2008	i changed R8 to 500k now and now i can clearly hear the overdrive effect i want (but too noisy because of the very high gain). the capacitors are now changed as you pointed. Can u explain me what should be the low cutoff frequency of this amp? I thought it was about 200Hz or more, but you´re talking abaout 160Hz.. and how about the high frequency cutoff? 10KHz is fine? PS: inductor and capacitor near source simulates guitar pickup plus cables.