hey
i want to make an array of super ebows for an instrument i'm making.
in the past ive been using LM386s, but they have proven to be too weak and/or distort too much.
the LM1876 seems like a good choice to go for the new instrument, and i've been doing experiments with gainclone schematics (actually haven't been working properly for me yet... doh!!)
however, i was wondering if these Hi-Fi amp schematics might be a little too complicated for this kind of application.
what i want to do is amplify a signal from a piezo - or magnetic pickup - and drive a solenoid actuator positioned under a string - causing it to vibrate/feedback.
would you guys be able to help me with sorting out a more simple schematic for this kind of application? or at least throw some ideas at me?
i have a 100va 2x 18v transformer, and some LM1876s. what do you think?
all the best,
úlfur
i want to make an array of super ebows for an instrument i'm making.
in the past ive been using LM386s, but they have proven to be too weak and/or distort too much.
the LM1876 seems like a good choice to go for the new instrument, and i've been doing experiments with gainclone schematics (actually haven't been working properly for me yet... doh!!)
however, i was wondering if these Hi-Fi amp schematics might be a little too complicated for this kind of application.
what i want to do is amplify a signal from a piezo - or magnetic pickup - and drive a solenoid actuator positioned under a string - causing it to vibrate/feedback.
would you guys be able to help me with sorting out a more simple schematic for this kind of application? or at least throw some ideas at me?
i have a 100va 2x 18v transformer, and some LM1876s. what do you think?
all the best,
úlfur
Solenoid loading vs peak current from the amplifier is one thing to consider.
Solenoid impedance would be another.
There were some ap notes somewhere in the APEX Micro site that addressed reactive loading and SOA for amplifiers...Might want to take a look at that:
Apex Application Note Library - Apex Microtechnology
Solenoid impedance would be another.
There were some ap notes somewhere in the APEX Micro site that addressed reactive loading and SOA for amplifiers...Might want to take a look at that:
Apex Application Note Library - Apex Microtechnology
hey, thanks!
Electromagnet Catalog - Magnetic Sensor Systems - MSS Electromagnets
The model I will be using is E-77-82, 28 AWG wire. i know andrew macpherson uses these coils with the LM1876 for his magnetic resonator piano - Magnetic Resonator Piano | Music . Entertainment . Technology
Electromagnet Catalog - Magnetic Sensor Systems - MSS Electromagnets
The model I will be using is E-77-82, 28 AWG wire. i know andrew macpherson uses these coils with the LM1876 for his magnetic resonator piano - Magnetic Resonator Piano | Music . Entertainment . Technology
I think you are overstressing everything, both amp and solenoid.
Your 2x18V transformer will provide 2x25V rails, way too much considering you will be driving what practically amounts to a pure inductor.
Your LM1876 will not like it very much.
And that solenoid is factory rated for 1.25W (using DC current).
Don't know what frequencies you will use, (nor the inductance), so can't calculate current through that coil, but the potential exists to fry that solenoid.
Yours is an inusual application, so I guess you won't get much input easily from others, but I suggest you build a normal, by the book, 1875 circuit, load it with a solenoid, and sweep it at different voltage levels (to know what's *really* necessary) and watch for overheating, measure current (insert a 0.1 ohm resistor in series and scope it), etc.
As a side note: even if the driving frequency clips, it's not bad, the string will pick the fundamental anyway .
Note 2: place the solenoid close to the string and check how much power is really needed to make it vibrate.
Your 2x18V transformer will provide 2x25V rails, way too much considering you will be driving what practically amounts to a pure inductor.
Your LM1876 will not like it very much.
And that solenoid is factory rated for 1.25W (using DC current).
Don't know what frequencies you will use, (nor the inductance), so can't calculate current through that coil, but the potential exists to fry that solenoid.
Yours is an inusual application, so I guess you won't get much input easily from others, but I suggest you build a normal, by the book, 1875 circuit, load it with a solenoid, and sweep it at different voltage levels (to know what's *really* necessary) and watch for overheating, measure current (insert a 0.1 ohm resistor in series and scope it), etc.
As a side note: even if the driving frequency clips, it's not bad, the string will pick the fundamental anyway .
Note 2: place the solenoid close to the string and check how much power is really needed to make it vibrate.
hey jim, thanks for the reply! your insight is very valuable!
driving my strings with clear harmonics, full frequency range is optimal. however, i could probably do fine with something like 2000 - 14.000hz. im not sure what inductance means (sorry, im looking it up right now!) but the coil resistance of the solenoids i bought will be a little under 8 ohms.
i need significally more power than the LM386 i used prior to this design... today i made some progress - i actually got the LM1876 chip working with a custom handwound 8 ohm solenoid. the output using my iphone music jack is perfect, but the coil was heating up A LOT. might have to heatsink the manufactured coils when they arrive at my studio.
one question that i need help with -
is there a preamp schematic you would suggest i could build to pre-amping a signal from a piezo, /and or magnetic pickups for the LM1876?
thank you!
úlfur
driving my strings with clear harmonics, full frequency range is optimal. however, i could probably do fine with something like 2000 - 14.000hz. im not sure what inductance means (sorry, im looking it up right now!) but the coil resistance of the solenoids i bought will be a little under 8 ohms.
i need significally more power than the LM386 i used prior to this design... today i made some progress - i actually got the LM1876 chip working with a custom handwound 8 ohm solenoid. the output using my iphone music jack is perfect, but the coil was heating up A LOT. might have to heatsink the manufactured coils when they arrive at my studio.
one question that i need help with -
is there a preamp schematic you would suggest i could build to pre-amping a signal from a piezo, /and or magnetic pickups for the LM1876?
thank you!
úlfur
Are you making musical instruments for bats?
Are you sure about those frequencies?
As an example, guitar strings vibrate (fundamentals) between 80 and 1200/1500Hz
Not surprising, I think you must re-evaluate what you are doing.
The very successful EBow which I think you are trying to emulate, is a hand held device powered by a 9V battery, must use a few milliwatts at most.:
The Amazing EBow :: Home
I think you must re-evaluate what you are doing.[2]
Yes, I might suggest a preamp, please be a little more specific about your instrument so I can guess what the signal levels will be.
And please check the frequency range.
@JMFahey sorry, i hadn't slept for hours when i posted those frequencies. they should have been 20 - 1400 hz.... duh... my bad!
the instrument is a new version of this acoustic electromagnetic harp i designed last year - as seen here :: ÚLFUR
i used LM386-4n's for the old version, but i want to go for something louder like this guy - Magnetic Resonator Piano | Music . Entertainment . Technology
he uses the LM1876, thats why im opting for that chip. the chip doesn't heat up at all with proper heatsinking.
i would like to use piezos for the feedback circuit instead of magnetic pickups because of interference from the heavy magnetic actuation fields going on. thats why im looking for a pre-amp for the piezo! any thoughts on that?
also - to drive 10x LM1876 at once, do i need an insane power supply system? or should i just wing it?
thanks guys!
-úlfur
the instrument is a new version of this acoustic electromagnetic harp i designed last year - as seen here :: ÚLFUR
i used LM386-4n's for the old version, but i want to go for something louder like this guy - Magnetic Resonator Piano | Music . Entertainment . Technology
he uses the LM1876, thats why im opting for that chip. the chip doesn't heat up at all with proper heatsinking.
i would like to use piezos for the feedback circuit instead of magnetic pickups because of interference from the heavy magnetic actuation fields going on. thats why im looking for a pre-amp for the piezo! any thoughts on that?
also - to drive 10x LM1876 at once, do i need an insane power supply system? or should i just wing it?
thanks guys!
-úlfur
1) I loved the concepts at ulfur.com
Is it some Art Cooperative or something?
Cool pictures too.
2) draw a simple diagram of your instrument.
I still don't know *what* are you driving.
Also to what levels.
Are you picking vibrations and amplifying elsewhere (amps+speakers) or trying to have loud acoustic output out of the instrument itself?
Because in that case you might need hundreds of watts.
3) a simple piezo preamp is easy, later I'll draw some.
You can build it for peanuts, standard TL072 and common parts are more than enough.
4) you must collect some needed data yourself.
As said earlier, build *one* channel and experiment.
Measure actual power needed (we don't want to kill mosquitoes with grenades).
Also measure voltage and currents involved (remember this is *not* a resistive load), draw a voltage/current graph relative to frequency.
Is it some Art Cooperative or something?
Cool pictures too.
2) draw a simple diagram of your instrument.
I still don't know *what* are you driving.
Also to what levels.
Are you picking vibrations and amplifying elsewhere (amps+speakers) or trying to have loud acoustic output out of the instrument itself?
Because in that case you might need hundreds of watts.
3) a simple piezo preamp is easy, later I'll draw some.
You can build it for peanuts, standard TL072 and common parts are more than enough.
4) you must collect some needed data yourself.
As said earlier, build *one* channel and experiment.
Measure actual power needed (we don't want to kill mosquitoes with grenades).
Also measure voltage and currents involved (remember this is *not* a resistive load), draw a voltage/current graph relative to frequency.
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1)
thanks! my name is úlfur, and the website is a portfolio of my work.
2)
i am driving guitar strings. so basically, its an acoustic electronic instrument. i drive them via feedback, but another feature i have in mind and have tested with great results is having an "outboard feature" - where you can route any kind of audio through the instrument for a resonant "string reverb" effect.
3)
thanks!!! i really appreciate that! would i be able to use one preamp for all the LM1876 inputs?
4)
yeah today i successfully made a neat one channel system with an LM1876! im working day and night on this for the next couple of months..... i think ill use the power supply i made until it decides otherwise. we will see
also
i am finishing my order of solenoids online as we speak here :: Tubular Electromagnet E-66-75 Magnetic Sensor Systems.
do you think i should go for the 28AWG with a nominal internal resistance of 2.9 Ohms, or the 33 AWG with a nominal internal resistance of 30.7 Ohms? maybe the middle road makes sense - 30 AWG... ahrg! i just dont know!
thanks! my name is úlfur, and the website is a portfolio of my work.
2)
i am driving guitar strings. so basically, its an acoustic electronic instrument. i drive them via feedback, but another feature i have in mind and have tested with great results is having an "outboard feature" - where you can route any kind of audio through the instrument for a resonant "string reverb" effect.
3)
thanks!!! i really appreciate that! would i be able to use one preamp for all the LM1876 inputs?
4)
yeah today i successfully made a neat one channel system with an LM1876! im working day and night on this for the next couple of months..... i think ill use the power supply i made until it decides otherwise. we will see
also
i am finishing my order of solenoids online as we speak here :: Tubular Electromagnet E-66-75 Magnetic Sensor Systems.
do you think i should go for the 28AWG with a nominal internal resistance of 2.9 Ohms, or the 33 AWG with a nominal internal resistance of 30.7 Ohms? maybe the middle road makes sense - 30 AWG... ahrg! i just dont know!
This is as simple as can be.
Gain depends on R3 / R6
10K for 10X gain ; 1K for 100X gain.
Set as needed .
If you use very small Piezos, increase R1 / R4 to 3M3 or even 10M, but you'll have to be very careful with input wiring shielding and ground, place preamp as close to pickups as possible.
Good luck.
Gain depends on R3 / R6
10K for 10X gain ; 1K for 100X gain.
Set as needed .
If you use very small Piezos, increase R1 / R4 to 3M3 or even 10M, but you'll have to be very careful with input wiring shielding and ground, place preamp as close to pickups as possible.
Good luck.
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