I Recently purchased TDA7492 IC board
and discovered that there are no volume control buttons/knob. I wonder how would I be able to vary the volume of my music. Any suggestions?
You want a 'Dual Gang' potentiometer with each half wired up like this. Use a 10k or 22k logarithmic pot.
Volume Control - Circuit Bricks - The easy way to design electronic circuits
Edit 12th Feb 2017... the picture was taken from the web and on closer examination is wrong. The outer two terminals of the pot are reversed.
Edit 2... 14th Jan 2018 Image replaced by correctly drawn version.
Volume Control - Circuit Bricks - The easy way to design electronic circuits
Edit 12th Feb 2017... the picture was taken from the web and on closer examination is wrong. The outer two terminals of the pot are reversed.
Edit 2... 14th Jan 2018 Image replaced by correctly drawn version.
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A log pot matches the way our ears work and so (appear) to give a progressively equal increase in volume per degree of rotation of the control. A linear pot still goes as loud and quiet but the increase in volume per degree of rotation wont seem to match how you perceive the level.
Linear pots tend to match better between the two channels which can be an advantage. You can also fake a log law by adding a single resistor per channel from the wiper (middle pin) to ground.
Linear pots tend to match better between the two channels which can be an advantage. You can also fake a log law by adding a single resistor per channel from the wiper (middle pin) to ground.
Thanks for the prompt response Mooly.
I have one more question. I am thinking of using TDA7492 board with my old speaker system ss-rs77v which consists of 2 woofers (in series) and 1 tweeter( in parallel to the 2 woofers).I guess it becomes a Full-range system.
As I have read somewhere that whole component is rated at 70 W and also on the back label it's mentioned that it's 24ohm. Will it be possible to make that work with this amplifier board?
I have one more question. I am thinking of using TDA7492 board with my old speaker system ss-rs77v which consists of 2 woofers (in series) and 1 tweeter( in parallel to the 2 woofers).I guess it becomes a Full-range system.
As I have read somewhere that whole component is rated at 70 W and also on the back label it's mentioned that it's 24ohm. Will it be possible to make that work with this amplifier board?
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It will certainly work but those impedance values are not standard at all. Maybe because they are 'surround sound speakers' and deliberately configured for high impedance to limit the output from them.
You might find them quieter than you expect but that is a 'fault' of the speaker, not the amp.
You might find them quieter than you expect but that is a 'fault' of the speaker, not the amp.
So how should I proceed? By Connecting one woofer to each amp output channel? and what about tweeter? I recently realized that I am not sure that it is rated at 70 W. It was all that I could make out from this guy's reviews Sony's MHC-GN88D DVD Component System. correct me if I am wrong.
If there is just one pair of connections on the back of the speaker then you can feed the speaker normally. I'm guessing this is how they are.
If by chance the woofer and tweeter are available via separate sockets on the back of the speaker then you must determine if a cross over is built into the speaker cabinet before applying full range audio to them.
If by chance the woofer and tweeter are available via separate sockets on the back of the speaker then you must determine if a cross over is built into the speaker cabinet before applying full range audio to them.
Yes there is only one pair of wire to this speaker box and inside it is as I have described i.e. Two woofers in series and the tweeter in parallel (and yes a capacitor is already there for crossover so I need not bother about determining capacitance I guess.)
My queries are as follows
1) Shall I connect these two woofers directly to each channelof the amp? won't it result in distortion due to mismatch of the impedance since AFAIK this TDA7492 supports 4 ohm, 6 ohm and 8ohm speakers only? (I am assuming each woofer is of 12ohm since whole box is labeled as 24 ohm and woofers are in series. Correct me if i am wrong).
And If at all it causes distortion with 12ohm speaker, will the distortion be significant? Or it will just result in less output volume?
2) Since originally both of these woofers were ment for same channel and so was the tweeter. But now as described I want to use one woofer for each different channel. how should I connect the tweeter? Is there any way to make one tweeter work for both channels. I guess I have to use two tweeters for each channel but then it will cause imbalance (increase in high frequency component) as compared to what it was intended for originally .
My queries are as follows
1) Shall I connect these two woofers directly to each channelof the amp? won't it result in distortion due to mismatch of the impedance since AFAIK this TDA7492 supports 4 ohm, 6 ohm and 8ohm speakers only? (I am assuming each woofer is of 12ohm since whole box is labeled as 24 ohm and woofers are in series. Correct me if i am wrong).
And If at all it causes distortion with 12ohm speaker, will the distortion be significant? Or it will just result in less output volume?
2) Since originally both of these woofers were ment for same channel and so was the tweeter. But now as described I want to use one woofer for each different channel. how should I connect the tweeter? Is there any way to make one tweeter work for both channels. I guess I have to use two tweeters for each channel but then it will cause imbalance (increase in high frequency component) as compared to what it was intended for originally .
The higher the impedance a load is, the easier it is for the amp to drive. It might be worth measuring the DC resistance of each woofer (that is not the same as impedance) and seeing what they are.
A capacitor in series with the tweeter is the very simplest type of crossover. Always retain the cap as the tweeter will be damaged in seconds without it. You need one tweeter per channel but you can add a series resistor to lower the tweeter volume if needed. You would have to experiment with the value.
A capacitor in series with the tweeter is the very simplest type of crossover. Always retain the cap as the tweeter will be damaged in seconds without it. You need one tweeter per channel but you can add a series resistor to lower the tweeter volume if needed. You would have to experiment with the value.
Thanks Mooly.
1) Can you suggest me the power supply to be used for optimal operation. The ebay TDA7492 page describes that it works for a wide range of input voltages from10v to 26v (i guess higher is better, correct me here if I am wrong) .
2) What curent rating of PS I shall look for when I am at the store? Can use some standard supplies like, A desktop smps, A laptop charger, Or should I make a power supply of my own?
3) You asked me to find resistance and not the impedance. Isn't "24 ohm" printed on the box the resistance? I haven't seen the mention of impedance anywhere. Is impedance really required to be known?
It think that's pretty much of what I need to know. Let me know if I am missing something.
1) Can you suggest me the power supply to be used for optimal operation. The ebay TDA7492 page describes that it works for a wide range of input voltages from10v to 26v (i guess higher is better, correct me here if I am wrong) .
2) What curent rating of PS I shall look for when I am at the store? Can use some standard supplies like, A desktop smps, A laptop charger, Or should I make a power supply of my own?
3) You asked me to find resistance and not the impedance. Isn't "24 ohm" printed on the box the resistance? I haven't seen the mention of impedance anywhere. Is impedance really required to be known?
It think that's pretty much of what I need to know. Let me know if I am missing something.
Old laptop power bricks will work fine. They typically range from 16-20v. I'd look for a 19-20v model. Anything more than 60W should be sufficient with such high-impedance speakers. 24v power bricks are a little harder to find, but they'll be able to squeeze more power out. Old Apple Macintosh PowerPC PowerBook bricks are 24v, good quality, and available in 40 or 60w. I see quite a few in thrift-stores near me (in the US). There are also inexpensive 24v power supplies intended for LED lighting. I wouldn't go higher than 24v to allow a little headroom for the chip and other components on the board.
I'm curious about how your amp will do with those speakers.
I'm curious about how your amp will do with those speakers.
I'd go along with using laptop type PSU as well. Its complete, compact and ready built.
Don't get hung up over the impedance/ resistance thing. Resistance is very specific in its meaning and is the DC resistance of the unit. It is whatever you measure it to be.
Impedance is the 'resistance at AC' and varies depending on the applied frequency. An '8 ohm speaker' may vary from from as little 3 ohms to as high as perhaps 20 or 30 ohms and yet still be called 'an 8 ohm speaker'.
The real guide to how loud it will be is given by the efficiency and that is quoted as an SPL (sound pressure level) per watt. For example 92dB/watt for an efficient one and perhaps 82dB/watt for an inefficient one.
Don't get hung up over the impedance/ resistance thing. Resistance is very specific in its meaning and is the DC resistance of the unit. It is whatever you measure it to be.
Impedance is the 'resistance at AC' and varies depending on the applied frequency. An '8 ohm speaker' may vary from from as little 3 ohms to as high as perhaps 20 or 30 ohms and yet still be called 'an 8 ohm speaker'.
The real guide to how loud it will be is given by the efficiency and that is quoted as an SPL (sound pressure level) per watt. For example 92dB/watt for an efficient one and perhaps 82dB/watt for an inefficient one.
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