Hi, i'm Facundo from Argentina.
I'm trying to make a small guitar head using a tpa3118 sanwu module, using a simple circuit as a preamp.
I've already tested the module with other sources of sound like differents guitar stompboxes or floor multieffects (like line 6 hd500, fractal ax8, axe fx rack unit, etc). All theese units worked flawless
But when i use an analog preamp, like a fetzervalve from runoffgroove if i hit hard the strings of my guitar, the class d module gets into protection (it makes a hard and loud "click" per second)
http://www.runoffgroove.com/fetzervalve.html
i'm thinking that may be there is a problem with the input signal of the class d module. So, i've removed one SMD resistor, to let the input gain in 20db. It worked a little bit better, but still have the "protection" issue.
i'm using the same power source, a notebook charger, 24v 4A for the preamp and class d module.
What i am doing bad?
The preamp sounds gorgeous, i love it, but i cant trust on it if i have to "play softly"
I'm trying to make a small guitar head using a tpa3118 sanwu module, using a simple circuit as a preamp.
I've already tested the module with other sources of sound like differents guitar stompboxes or floor multieffects (like line 6 hd500, fractal ax8, axe fx rack unit, etc). All theese units worked flawless
But when i use an analog preamp, like a fetzervalve from runoffgroove if i hit hard the strings of my guitar, the class d module gets into protection (it makes a hard and loud "click" per second)
http://www.runoffgroove.com/fetzervalve.html
i'm thinking that may be there is a problem with the input signal of the class d module. So, i've removed one SMD resistor, to let the input gain in 20db. It worked a little bit better, but still have the "protection" issue.
i'm using the same power source, a notebook charger, 24v 4A for the preamp and class d module.
What i am doing bad?
The preamp sounds gorgeous, i love it, but i cant trust on it if i have to "play softly"
It seems you are having too much input signal to the TPA3118 amplifier module. A guitar has got a huge dynamic range.
You may try to put a volume potentiometer in-between the pre-amp and the TPA3118 module. I know very little about use with guitars and perhaps it is normal to use a dynamic limiter to remove the worst transients.
Voltwide seems to know a lot about the use of guitars with TPA3118 amplifiers.
You may try to put a volume potentiometer in-between the pre-amp and the TPA3118 module. I know very little about use with guitars and perhaps it is normal to use a dynamic limiter to remove the worst transients.
Voltwide seems to know a lot about the use of guitars with TPA3118 amplifiers.
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You'd better insert a soft limiter between pre-amp and TPA3116 input. You may have a look at this thread
the trAmp - my latest and smallest guitar amp
the trAmp - my latest and smallest guitar amp
That looks very nice voltwide. I've not used an analog based preamp into my tpa3118 yet, havent had any trouble with a zoom multieffect unit so far. I did make the gain selectable via a toggle switch between ~25db & 30dB range, no hiss related issues after that mod.
These work nicely for me into an 4ohm speaker of 40W, i power the tpa with 12V 2A, it gets loud for practice. It sounded much better after changing the smd electrolytic caps to a higher value & voltage rating.
These work nicely for me into an 4ohm speaker of 40W, i power the tpa with 12V 2A, it gets loud for practice. It sounded much better after changing the smd electrolytic caps to a higher value & voltage rating.
sorry for late response.
i've made some corrections to my preamp.
The fetzer valve is still being feeded with 24v, but i put a buffer with a tl071 working at 9v via a LM7809. That enhanced the problem when i remove the SMD resistor on the power amp board. It's nearly solved. If i use the board as it comes (around 34dB input gain) still get the "click" protection sound.
its weird because i've made one time ago and that problem was not there. So... mistery
Thanks for all your answers! and sorry for my English
i've made some corrections to my preamp.
The fetzer valve is still being feeded with 24v, but i put a buffer with a tl071 working at 9v via a LM7809. That enhanced the problem when i remove the SMD resistor on the power amp board. It's nearly solved. If i use the board as it comes (around 34dB input gain) still get the "click" protection sound.
its weird because i've made one time ago and that problem was not there. So... mistery
Thanks for all your answers! and sorry for my English
i'm still having the "protection" or clicking problem. If i remove the 100k SMD resistor the problem goes away, but just because of the change in the input gain settings.
i just dont understand why is this happening.
i'll try with another preamp. But didn't expect any changes... im just stuck there
i just dont understand why is this happening.
i'll try with another preamp. But didn't expect any changes... im just stuck there
Section 7.3.4 of the TPA3116D2 datasheet mentions power limitation and may be relevant for this case. Can you see if such a power limitation has been implemented? Check if the PLIMIT-pin (pin 6) is directly connected to the GVDD-pin (pin 7) or if if the PLIMIT-pin has a voltage lower than the GVDD-pin. Next, check if the PLIMIT-pin is well decoupled to ground by at least 1uF. If this decoupling is missing, a temporary spike may cause the “clicking”.
The correct functioning of a TPA3116 amplifier is described by that it can provide a rather distortion-free sine-wave of about 1KHz, with nominal output loading, at the output until the supply rail causes “clipping”. Such can be tested if you have access to an oscilloscope. The problem with the present setup is that we do not know if the problem relate to the TPA3116 amplifier or the “fetzer-valve” (the first time I have heard that word).
It seems likely that a 24V feed “fetzer-valve” (a single-FET amplification stage) can saturate the input of the TPA3116 amplifier. As a simple experiment, try to connect two 1N4148 diodes, coupled in anti-parallel, across the input terminals of the TPA3116 amplifier. Such 1N4148 diodes will act as a signal limiter and may remove the “clicking” but may introduce some distortion at high levels.
hi! thanks so much for that info!
In the sanwu tpa3118 module i'm using, the pins 6 and 7 are connected together, goes thru c26 and then to ground. I'll check if c26 is 1uf as you say.
so... for what i've understand i have to put a resitor divider so i can adjust the output voltage of the amplifier. am i right?
True, with the PLIMIT-pin voltage you can control at which voltage-level the output starts clipping.
Not exactly. You would have to make a voltage divider and use the midpoint of that voltage divider for the PLIMIT pin (has to be disconnected from the GVDD pin). But, I cannot see how this would help on your clicking-problem. At present, PLIMIT is connected to GVDD such that you have a maximum of dynamic range before any limitation kicks in. If you set the PLIMIT differently, you just invoke "clipping" (voltage) at an earlier point.
My guess at present is that you overload the amplifier input and the protection-click relates to protection at the input with signals outside the valid range. Try the 1N4148 trick.
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I tried the trick of placing the 1n4148 but without good results.
I was reading a little bit of the datasheet and in a part it says about adding decoupling capacitors in the input. Today I will try to put a 10uf between the input of the amplifier and ground and see what happens.
But I'm seriously considering setting everything on fire. I hope I do not get to that point hahahaha.
Is there anything else that I may be forgetting to check?
This is the preamp i'm using
I was reading a little bit of the datasheet and in a part it says about adding decoupling capacitors in the input. Today I will try to put a 10uf between the input of the amplifier and ground and see what happens.
But I'm seriously considering setting everything on fire. I hope I do not get to that point hahahaha.
Is there anything else that I may be forgetting to check?
This is the preamp i'm using
I just learned that a "fetzer-valve" is part of a distortion-pedal ( A closer look at the Fetzer Valve ). Looking for strange sounds in an audio-circuit involving intentional distortion is a bit awkward.
You have a power amplifier (TPA3118 based) that is supposed to reproduce the input signal with low THD and the pre-set gain until clipping. Let's test it as such. You use a 24V/4A power supply, which is fine, but I have read nothing about your decoupling of the supply line voltage (the output of your 24V SMPS). You have 4x330uF on-board (amplifier) but they will be capable of little when you hit the strings hard. Try with some 4700uF-10000uF as supply line decoupling. Then, put a well recorded MP3 of the type of guitar you play on your smart-phone and connect your smart-phone headphone output directly at the input of the TPA3118 amplifier. Use the same speaker as you use for your own guitar and try the amplifier to a volume corresponding to what you expect when you play with your own guitar. Any "clicking sounds"? If yes, it is the TPA3118 amplifier that makes the noise. If no, it is probably caused by your pre-amplifier circuit which I will address afterwards.
No fire yet, please!
You have a power amplifier (TPA3118 based) that is supposed to reproduce the input signal with low THD and the pre-set gain until clipping. Let's test it as such. You use a 24V/4A power supply, which is fine, but I have read nothing about your decoupling of the supply line voltage (the output of your 24V SMPS). You have 4x330uF on-board (amplifier) but they will be capable of little when you hit the strings hard. Try with some 4700uF-10000uF as supply line decoupling. Then, put a well recorded MP3 of the type of guitar you play on your smart-phone and connect your smart-phone headphone output directly at the input of the TPA3118 amplifier. Use the same speaker as you use for your own guitar and try the amplifier to a volume corresponding to what you expect when you play with your own guitar. Any "clicking sounds"? If yes, it is the TPA3118 amplifier that makes the noise. If no, it is probably caused by your pre-amplifier circuit which I will address afterwards.
No fire yet, please!
Dear FauxFrench, thank you very much for the amount of help and tutoring that you are giving me.
Today I am going to test the decoupling of the input through a 10uf capacitor as I have read in the datasheet and I will also see if I get a high value electrolytic capacitor for the power supply.
I'll keep you updated.
For now, without fire.
A hug from Argentina.
You forgot the caps close to input and output of 7808.
Btw this regulator is of little benefit here, the supply of the op-amp does not require very stable supply so you could tie it to 18V as well. On the other hand drain resistor-poti require low-noise supply as any supply noise is fed directly into the tone stack, but this is fed from unstabilized? 18V rail.
Gain setting resistors of the opamp are way too high and will increase noise. Replace them by 1/10 of their current value.
Additionnally it is good practice to place some 100nF ceramic cap as close as possible to the supply leads of the OpAmp.
Btw this regulator is of little benefit here, the supply of the op-amp does not require very stable supply so you could tie it to 18V as well. On the other hand drain resistor-poti require low-noise supply as any supply noise is fed directly into the tone stack, but this is fed from unstabilized? 18V rail.
Gain setting resistors of the opamp are way too high and will increase noise. Replace them by 1/10 of their current value.
Additionnally it is good practice to place some 100nF ceramic cap as close as possible to the supply leads of the OpAmp.
I could make it work!
it was not power limitation
it was not power supply failure
It was nothing of everything I had tried!
It was high frequency!
I just put a low pass filter on the output of the preamp and everything was solved.
I used a capacitor of 10nf and a resistance of 1k, which gave me a frequency cut close to 11k, ideal for my project.
thanks you very much for all the time invested in this topic and I send you a huge greeting from Argentina.
it was not power limitation
it was not power supply failure
It was nothing of everything I had tried!
It was high frequency!
I just put a low pass filter on the output of the preamp and everything was solved.
I used a capacitor of 10nf and a resistance of 1k, which gave me a frequency cut close to 11k, ideal for my project.
thanks you very much for all the time invested in this topic and I send you a huge greeting from Argentina.
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