westaust55
Moderator
I found the volume level for the SPE030 speech synthesis module (Devantech SP03), even on the maximum volume setting, to be rather quite. In fact could not envisage ever using less than max volume setting (=0)
(okay, okay - make a mental note to buy hearing aid
)
Now a warning - Anyone who proceeds to modify their SPE030 module does so at their own risk. I take no responsibility for errors or damage that could follow.
Removing the small 30mm diameter 0.4 Watt 8 Ohm speaker and using far better quality 63mm diameter 3 Watt 8 Ohm speaker gave a louder and far better tonal quality output.
However my goal was to use a 90mm piezo speaker. This is primarily to keep magnets away from my PICAXE box to minimise magnetic influence on the CMPS03 compass module (yet to be mounted)
A few "by ear" volume level checks found that the volume level from the PICAXE using the TUNE command into a Piezo speaker was still much higher than the SPE030 speech module.
The SPE030 uses a LM386 Audio Power Amp to drive the output.
A check of the LM386 datasheet and the SPE030 module found that pins 1 and 8 for gain are seemingly unused so the default gain is 20 (according to the datasheet).
Could not find a formula for determining the gain so decided on web surf plus trial and error approach.
Scrounging in my electronics junk box tonight for a few components I found I had a 22uF capacitor and a whole range of resistors.
Using just the capacitor across the LM386 pins 1 and 8 supposedly gives a gain of ~200 but trying that increased the volume but also the distortion (over driving the amp so it is clipping I would suspect).
Found a site that suggested 22uF in series with 5k Ohm gives a gain of 30.
Another site indicated a 100uF capacitor in series with a 104 Ohm resistor gives a gain of 44 and changing the resistor to 33 Ohm gives a gain of 74.
Using a 1.5 KOhm resistor in series with the 22uF capacitor only resulted in minimal volume increase (barely perceptible). However decreasing the resistor value to the ubiquitous (for LED's) value of 330 Ohm resistor in gave a very reasonable increase in the volume level without distortion.
lower values like 100 Ohms further increased the volume but obvious distortion coming into the output as well.
So for those brave or fool hardy enough to try it, adding a 22uF capacitor in series with a 330 Ohm resistor from pin 1 to pin 8 on the LM386 power amp on the SPE030 will give a respectable increase in volume (and all volume settings).
To locate the The LM386 IC. With the Winbond speech chip to the top and connector PL1 at the bottom (see the SPE030 datasheet), the LM386 amp is the 8 pin SOIC surface mounted IC at the bottom right corner. Pins 1 and 8 at the the bottom. I have soldered a couple of fines wires to these two pins and connected the resistor and capacitor to these wires.
(okay, okay - make a mental note to buy hearing aid
)Now a warning - Anyone who proceeds to modify their SPE030 module does so at their own risk. I take no responsibility for errors or damage that could follow.
Removing the small 30mm diameter 0.4 Watt 8 Ohm speaker and using far better quality 63mm diameter 3 Watt 8 Ohm speaker gave a louder and far better tonal quality output.
However my goal was to use a 90mm piezo speaker. This is primarily to keep magnets away from my PICAXE box to minimise magnetic influence on the CMPS03 compass module (yet to be mounted)
A few "by ear" volume level checks found that the volume level from the PICAXE using the TUNE command into a Piezo speaker was still much higher than the SPE030 speech module.
The SPE030 uses a LM386 Audio Power Amp to drive the output.
A check of the LM386 datasheet and the SPE030 module found that pins 1 and 8 for gain are seemingly unused so the default gain is 20 (according to the datasheet).
Could not find a formula for determining the gain so decided on web surf plus trial and error approach.
Scrounging in my electronics junk box tonight for a few components I found I had a 22uF capacitor and a whole range of resistors.
Using just the capacitor across the LM386 pins 1 and 8 supposedly gives a gain of ~200 but trying that increased the volume but also the distortion (over driving the amp so it is clipping I would suspect).
Found a site that suggested 22uF in series with 5k Ohm gives a gain of 30.
Another site indicated a 100uF capacitor in series with a 104 Ohm resistor gives a gain of 44 and changing the resistor to 33 Ohm gives a gain of 74.
Using a 1.5 KOhm resistor in series with the 22uF capacitor only resulted in minimal volume increase (barely perceptible). However decreasing the resistor value to the ubiquitous (for LED's) value of 330 Ohm resistor in gave a very reasonable increase in the volume level without distortion.
lower values like 100 Ohms further increased the volume but obvious distortion coming into the output as well.
So for those brave or fool hardy enough to try it, adding a 22uF capacitor in series with a 330 Ohm resistor from pin 1 to pin 8 on the LM386 power amp on the SPE030 will give a respectable increase in volume (and all volume settings).
To locate the The LM386 IC. With the Winbond speech chip to the top and connector PL1 at the bottom (see the SPE030 datasheet), the LM386 amp is the 8 pin SOIC surface mounted IC at the bottom right corner. Pins 1 and 8 at the the bottom. I have soldered a couple of fines wires to these two pins and connected the resistor and capacitor to these wires.
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