Hi guys,
I just discoverd this "site/forum" to my great delight...well I wasn't living in the jungle all these years!
Well,I am planning on building an acoustic guitar preamp incorporating
1; a Piezo under saddle pu,an AST type ex;B-Band AST1470
or a schertler bluestik under saddle pu.
a Panaonic WM 61A elecret condenser mic (found some on the e-bay) I've a few more to experiment with....
For the tone control..thought of using the TDA 1524A IC since it has stereo in/out!
I 've been looking at some published designs,so would like to combine some of them.
My problem is, although I can read,& construct from schematics
have no knowledge of circuit theory or analysis!
My major expected hurdles will be buffer/driver/output impedence matching,phase switching etc!!
So any/all help and encouragement in this venture would be both welcome & appreciated...i've seen some of you guys are quite amazingly knowledgable!
In my next post I shall give you the basic diagrams etc
Thanks & wish me luck!
Acousic guitar blender preamp
Hi All!
Here I'm after doing quite a bit of reading/researching on op-amp designs for the past 6 months!
My intention is to build a Piezo + mic blender acoustic g. preamp.
Part1
iezo Preamp(tone control)
I' lifted this schematic from http://www.next.gr & have already tried this on a proto-board & it worked the first time!
But since I wanted to drive it on +/- 9v supply for better dynamic response,(wishful thinking?) I then removed resistor R12.
It sounded little clearer than when it was run on only + 9v. although still lacking a wee bit in bass.But it sounds rather lifeless,(only 10dB gain)but sounds much better than most piezo preamps I've heard so far!
By the way I'm using a Roland AC60 for testing this.
Also tried as a current follower by increasing R1 from 1M to 4M7 & shunting it to ground, with higher values of C1 but it still sounded very harsh & typical piezo!So have now reverted back to as before.
GAIN SWITCH:
No sound on either 0dB or-10dB settings!Quite adequate sound only on +10dB setting
TONE CONTROLS:
Bass Pot:Hardly any change,only slight boost at max. level.
MID:quite good response
TREB:more response towards max. setting.
Question
Would it be possible/better to run the input/buffer as a comparator instead?
Is it possible get +40dB gain in this configuaration?
What component changes/additions would it involve?
How do I calculate the queisent current?
Can any one out there please give me any suggestions/ideas?
All inputs/ideas are gratefully taken onboard.
Thanks.
Hi All!
Here I'm after doing quite a bit of reading/researching on op-amp designs for the past 6 months!
My intention is to build a Piezo + mic blender acoustic g. preamp.
Part1
iezo Preamp(tone control)I' lifted this schematic from http://www.next.gr & have already tried this on a proto-board & it worked the first time!
But since I wanted to drive it on +/- 9v supply for better dynamic response,(wishful thinking?) I then removed resistor R12.
It sounded little clearer than when it was run on only + 9v. although still lacking a wee bit in bass.But it sounds rather lifeless,(only 10dB gain)but sounds much better than most piezo preamps I've heard so far!
By the way I'm using a Roland AC60 for testing this.
Also tried as a current follower by increasing R1 from 1M to 4M7 & shunting it to ground, with higher values of C1 but it still sounded very harsh & typical piezo!So have now reverted back to as before.
GAIN SWITCH:
No sound on either 0dB or-10dB settings!Quite adequate sound only on +10dB setting
TONE CONTROLS:
Bass Pot:Hardly any change,only slight boost at max. level.
MID:quite good response
TREB:more response towards max. setting.
Question
Would it be possible/better to run the input/buffer as a comparator instead?
Is it possible get +40dB gain in this configuaration?
What component changes/additions would it involve?
How do I calculate the queisent current?
Can any one out there please give me any suggestions/ideas?
All inputs/ideas are gratefully taken onboard.
Thanks.
I did some search as you did not tell what circuit.
You probably refer to this www.RedCircuits.com 'Guitar Control'
http://www.redcircuits.com/Page69.htm
You probably refer to this www.RedCircuits.com 'Guitar Control'
http://www.redcircuits.com/Page69.htm
Acoustic Guitar pre amp blender
As you can see,it is an inverting amp.If my limited knowledge serves me right I want to change this to a non-inverting config;
for the following reasons.
Looking at the diagram,is it correct that R4/R1 would give only a marginal gain given such low values of these resistors?
Low impedence?
Am I correct in assuming that a non inverting amp would give
1.higher impedence?
2.more gain?
By the way I am using a 20mm ceramic piezo disc for this.
Supply is +/- 9v(two PP3)
As you can see,it is an inverting amp.If my limited knowledge serves me right I want to change this to a non-inverting config;
for the following reasons.
Looking at the diagram,is it correct that R4/R1 would give only a marginal gain given such low values of these resistors?
Low impedence?
Am I correct in assuming that a non inverting amp would give
1.higher impedence?
2.more gain?
By the way I am using a 20mm ceramic piezo disc for this.
Supply is +/- 9v(two PP3)
Piezo discs require very high input impedance. You may take a look at: http://www.carvinmuseum.com/pdf/guitarbass/506p-activepiezobassmodule.pdf or http://www.carvinmuseum.com/pdf/guitarbass/503a-activepiezomodule.pdf
The circuit from RedCircuit may not meet this requirement - it is rather for magnetic pickups.
Mark
The circuit from RedCircuit may not meet this requirement - it is rather for magnetic pickups.
Mark
Hello Mark,
Thanks for the Carwin schematic,which I've just had a look at...
as you will agree, this too is only a 2 stage + tone control design apart from the FET in the input buffer section + seperate active/ passive pickup drive circuits.
I am using a 20mm ceramic disc..as described in the original article.& it sounds quite good too!
I have tested " mine" on a Roland AC 60 ac.amp & IT DOES WORK! albeit with rather reduced bass & gain response.However,
it feedsback with all the tone controls turned up full & the AC 60 turned up half +!It also sounds much better so unlike most piezo preamps I've tried,including the Artec Tri-Blender on one of my guitars!
My AC60 has a 1M impedence in the dedicated piezo input,may be
this is too low for an under saddle/Piezo film pu's..but works well with this ceramic disc.
If you have a look at the resistor R1 which sets the impedence,I'd agree that this is quite low compared to the feed-back resistors..hence the low gain?
Any thoughts on that?
Thanks.
I only wanted more gain/head-room for better dynamic response.
Thanks for the Carwin schematic,which I've just had a look at...
as you will agree, this too is only a 2 stage + tone control design apart from the FET in the input buffer section + seperate active/ passive pickup drive circuits.
I am using a 20mm ceramic disc..as described in the original article.& it sounds quite good too!
I have tested " mine" on a Roland AC 60 ac.amp & IT DOES WORK! albeit with rather reduced bass & gain response.However,
it feedsback with all the tone controls turned up full & the AC 60 turned up half +!It also sounds much better so unlike most piezo preamps I've tried,including the Artec Tri-Blender on one of my guitars!
My AC60 has a 1M impedence in the dedicated piezo input,may be
this is too low for an under saddle/Piezo film pu's..but works well with this ceramic disc.
If you have a look at the resistor R1 which sets the impedence,I'd agree that this is quite low compared to the feed-back resistors..hence the low gain?
Any thoughts on that?
Thanks.
I only wanted more gain/head-room for better dynamic response.
Hi Lineup,
Could you please explain the effect og high gain vs. dynamic range?Am I correct in supposing that increasing th voltage gain would give more dynamic range aswell due o more headroom avilable to the signal?
Is this the reason that studio mixers/ high spec;mic channel preamps have this "large sound"?
I've tried about 20 odd acoustic guitar preampsso far..yet almost all of them sound the same,regardless with either a cermic or a undersaddle pickup!This may not be very critical on solid electric bass,since i presume,the vibrations come mainly from the bridge area & not from the body? But on hollow string intruments,the whole body vibrates,hence more resonance frequencies?
Besides the piezo generates only a very small amount current! ,
which cannot provide adequate signal boost to the input/buffer opamp?
I also gather that API & the Presonus AcouticQ preamps have 60dB & 40dB gain respectively!
1.How can I achieve more gain without loosing higher freq.
2.would it help to run it on +15/-15v instead?
3.could I cascade more stage(s) to achieve this?.
My preamp would hopefully have the folowing:
1 piezo disc input using the JFET IC.
2.A modified Panasonic MW61 capsule driving a AN217 IC mic pre-
amp which is already published in their website & claims to have
a gain of 60dB!!!
3.Include a notch filter with both lo/high controls.
4.An inverter/ phase switch
5.A simple 2 input 2 stage mixer (virtual earth?)
After readig some of your comments on audio amp colums elswhere, I now realize the enormity of my undertaking!
I would only be thankful for your insight /advice or suggestions.
.
Could you please explain the effect og high gain vs. dynamic range?Am I correct in supposing that increasing th voltage gain would give more dynamic range aswell due o more headroom avilable to the signal?
Is this the reason that studio mixers/ high spec;mic channel preamps have this "large sound"?
I've tried about 20 odd acoustic guitar preampsso far..yet almost all of them sound the same,regardless with either a cermic or a undersaddle pickup!This may not be very critical on solid electric bass,since i presume,the vibrations come mainly from the bridge area & not from the body? But on hollow string intruments,the whole body vibrates,hence more resonance frequencies?
Besides the piezo generates only a very small amount current! ,
which cannot provide adequate signal boost to the input/buffer opamp?
I also gather that API & the Presonus AcouticQ preamps have 60dB & 40dB gain respectively!
1.How can I achieve more gain without loosing higher freq.
2.would it help to run it on +15/-15v instead?
3.could I cascade more stage(s) to achieve this?.
My preamp would hopefully have the folowing:
1 piezo disc input using the JFET IC.
2.A modified Panasonic MW61 capsule driving a AN217 IC mic pre-
amp which is already published in their website & claims to have
a gain of 60dB!!!
3.Include a notch filter with both lo/high controls.
4.An inverter/ phase switch
5.A simple 2 input 2 stage mixer (virtual earth?)
After readig some of your comments on audio amp colums elswhere, I now realize the enormity of my undertaking!
I would only be thankful for your insight /advice or suggestions.
.
I Found this schematic on http://devices.sapp.org/circuit/piezo, hence thought I could try this with my earlier piezo circuit above to increase the sensivity & gain.
This circuit breaks up the sound!,although I can hear a lot of gain.
Tried removing the diode,but then it sounds like a fuzz box!A lot of distortion!
I've connected it as it is to the previous piezo preamp.(above)
Is there any incompatibility between these two?
By the way I'm running this too on +9/-9 v supply.
Can anyone please tell me why this doesn't work?
This circuit breaks up the sound!,although I can hear a lot of gain.
Tried removing the diode,but then it sounds like a fuzz box!A lot of distortion!
I've connected it as it is to the previous piezo preamp.(above)
Is there any incompatibility between these two?
By the way I'm running this too on +9/-9 v supply.
Can anyone please tell me why this doesn't work?
Attachments
I think that this is not a circuit for instruments. Piezo sensors are used for various measurements and this is just one of such circuits. In my opinion you don't need any gain - you just need a circuit with very high input impedance > 10 MOhms (it was stated here already several times). And the circuit from Carvin will work without any problems.
Mark
Mark
Thank you Markus,
Yes you're right,It eventually dawned on me that the circuit was
for some sort of purcussive instrument.But then I just tried the input section only with my current circuit..& both the switches & the tone controls started functioning atlast!
So it could be the impedence/gain incompatibility problem!
I've now printed out the Carvin schemetic, will try it & will let you know in a few days (I got to take a break!!!)
Thanks again & hope you'll have a peaceful festive season.
Yes you're right,It eventually dawned on me that the circuit was
for some sort of purcussive instrument.But then I just tried the input section only with my current circuit..& both the switches & the tone controls started functioning atlast!
So it could be the impedence/gain incompatibility problem!
I've now printed out the Carvin schemetic, will try it & will let you know in a few days (I got to take a break!!!)
Thanks again & hope you'll have a peaceful festive season.
This Artec Tri Blend HTL-TBL model on one of my guitars,..but I
never could get a good sound on my Roland AC60. Reading from the Artec spec.sheet in front of me;
Although this has 3 seperate inputs for Piezo,Mic & magnetic pu's..They have given just one input impedance figure! Amazing!
This is all you get on their spec; sheet anyway.
Input impedance -10M ohm
Output Imp; -10K ohm
Since Roland too have conveniently ommited to give the input impedane specs. on the "Owner's Manual..I just tried to measure it with my Fluke dig.Multimeter...ooops it's well above the Mega ohm range...no reading! doesn't even show the resistive
value!
never could get a good sound on my Roland AC60. Reading from the Artec spec.sheet in front of me;
Although this has 3 seperate inputs for Piezo,Mic & magnetic pu's..They have given just one input impedance figure! Amazing!
This is all you get on their spec; sheet anyway.
Input impedance -10M ohm
Output Imp; -10K ohm
Since Roland too have conveniently ommited to give the input impedane specs. on the "Owner's Manual..I just tried to measure it with my Fluke dig.Multimeter...ooops it's well above the Mega ohm range...no reading! doesn't even show the resistive
value!
I cannot comment on the sound since it's so difficult to define the word "good". But I don't see anything wrong or amazing regarding the same input impedance at least for piezo and magnetic pickups inputs (I assume it's the same for three inputs). The higher, the better. What do you see amazing in this?teleman said:
I don't know how did you try to measure the input impedance. I just hope that you know that it cannot be measured by simply puting meter wires on the preamp input.teleman said:
Mark
teleman said:
For the Panasonic WM 61A you can find good electret mic preamplifiers schematics.
This mic is commonly used by DIY audio people.
You can use just one opamp
http://www.linkwitzlab.com/images/graphics/microph1.gif
http://www.johncon.com/john/wm61a/
--------------------------------------
For your guitar pickup, you would need a circuit with high impedance input.
This can be done.
Using one opamp with JFET inputs, like TL071 TL061 OPA2134.
--------------------------------------
At output of those source input amplifiers, you can add whatever other effects or amplifiers.
Thanks Lineup!
yes,I have already downloaded the schematics you've mentioned
& one more by H.P.Friedrich, which I've already built (prototype) & it works quite well with an unmodified,unknown electret mic.Very quiet too!( I will give the results with a "Linwitz" modified Panasonic WM61A asap.
Q.I remember reading somewhere that it is better to wire the input circuitry to the 2nd opamp rather than the 1st in the same package in a dual opamp!What's the significance of this practice?
I also found a series of superbly written articles on "Choosing operational amps" on http://www.dclf.dsl.pipex.com. which was of immence help to me & I'm sure will be to many others too!
yes,I have already downloaded the schematics you've mentioned
& one more by H.P.Friedrich, which I've already built (prototype) & it works quite well with an unmodified,unknown electret mic.Very quiet too!( I will give the results with a "Linwitz" modified Panasonic WM61A asap.
Q.I remember reading somewhere that it is better to wire the input circuitry to the 2nd opamp rather than the 1st in the same package in a dual opamp!What's the significance of this practice?
I also found a series of superbly written articles on "Choosing operational amps" on http://www.dclf.dsl.pipex.com. which was of immence help to me & I'm sure will be to many others too!
Sorry!The correct web link to "Designing with opamps" is;
http://www.dself.dsl.pipex.com/ampins/webbop/opamp.htm
This is the most recently updated link,where most of the popular BJET & JFET mono & dual opamps -16 in all- are included with test reports.
http://www.dself.dsl.pipex.com/ampins/webbop/opamp.htm
This is the most recently updated link,where most of the popular BJET & JFET mono & dual opamps -16 in all- are included with test reports.
I bought (or at least thought I was buying)10 Panasonic WM61A mic capsules on the E-Bay which the seller advertised/sold as the original capsules at that time.
The numbers which are embossed on the capsules read, 61H71.
The Digikey part numbers are P9925-ND & P11974-ND.Is it their inventry/stock no.or WM61A's original part/serial no?
I am no longer certain if my mics are genuine stuff or not!!!!!
Can anyone please throw some light on this or tell me if I've got the original WM61As..or been had by yet another unscrupulous mortal!
I tried the "mic pre with an unknown & not yet "Linkwitz" modified mic yet it sounded quite impressive.With the modified so called WM61 cap' it wasn't as impressive as with the previous one.This is why I got little suspicious about the WM61A!!
The numbers which are embossed on the capsules read, 61H71.
The Digikey part numbers are P9925-ND & P11974-ND.Is it their inventry/stock no.or WM61A's original part/serial no?
I am no longer certain if my mics are genuine stuff or not!!!!!
Can anyone please throw some light on this or tell me if I've got the original WM61As..or been had by yet another unscrupulous mortal!
I tried the "mic pre with an unknown & not yet "Linkwitz" modified mic yet it sounded quite impressive.With the modified so called WM61 cap' it wasn't as impressive as with the previous one.This is why I got little suspicious about the WM61A!!
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