Hi,
so in my Corsa D car (2008) there was a DELPHI-GRUNDIG car radio, model CD30 with a TDA 7385 chip (at least based on what some forums said, since the chip is identified with an industrial code and not with the official name).
The sound was always very muffled and not very loud. It also was distorted at maximum volume, so after replacing the horrific factory loudspeakers I decided to upgrade the amp chip inside the radio: I decided to use the TDA 7560 which was the most suitable replacement because of the pinout compatibility, altough some modifications was still necessary.
I tought that the new chip would give me at least some more SPL, since from the datasheet the TDA 7560 is actually much powerful that TDA 7385. The speakers are 4 Ohms.
Unfortunately there is virtually no difference between the two chips: the volume is practically the same and the distorsion is still present at maximum volume. The only beneficial upgrade was the replacing of the speakers, the originals were really bad in quality.
Did I something wrong?
so in my Corsa D car (2008) there was a DELPHI-GRUNDIG car radio, model CD30 with a TDA 7385 chip (at least based on what some forums said, since the chip is identified with an industrial code and not with the official name).
The sound was always very muffled and not very loud. It also was distorted at maximum volume, so after replacing the horrific factory loudspeakers I decided to upgrade the amp chip inside the radio: I decided to use the TDA 7560 which was the most suitable replacement because of the pinout compatibility, altough some modifications was still necessary.
I tought that the new chip would give me at least some more SPL, since from the datasheet the TDA 7560 is actually much powerful that TDA 7385. The speakers are 4 Ohms.
Unfortunately there is virtually no difference between the two chips: the volume is practically the same and the distorsion is still present at maximum volume. The only beneficial upgrade was the replacing of the speakers, the originals were really bad in quality.
Did I something wrong?
So you replaced a chip in the head unit?
Speakers are by far the biggest bang for your buck. After that usually source then amp. If it sounds muddy it’s probably the whole head unit not just the amp section.
Did. You really just replace the chip or am I reading that wrong?
Speakers are by far the biggest bang for your buck. After that usually source then amp. If it sounds muddy it’s probably the whole head unit not just the amp section.
Did. You really just replace the chip or am I reading that wrong?
Hello,
First, cudos (is that a okay word?) for being able to make this work, I did not look at pin config, but even very similar, this must have a advanced soldering job🙂. I unfortunately it is easy to explain (the basic) of why you are not happy. You can split it into 3 reasons:
- This is IC designed to be the amplifier in a car stereo or similar. Its already very crowded inside a DIN size unit, and heat is a massive problem, so in 98% of the car radios, the designer do not choose to cramp in a dc to dc converter (small switching device) and are stuck with your cars dc voltage as a source, and less on the rails. There is some tricks here to improve (bridging two units (that is normal), or lower the imp on the load, which Audi have done in my car, all speakers are 1 ohm (less common)) but 10-13W continuous output pr channel (with less than 1% in a 4 ohm load) using AB designed IC is normal.
- After quickly scrolling the datasheet its easy to believe that both of these delivers much more, (and they can given a 25 volt DC input and a large heatsink look at Figure 5: Output Power vs. Supply Voltage)
TDA7560 Superior output power capability: – 4 x 51 W/4 max. – 4 x 45 W/4 EIAJ – 4 x 30 W/4 @ 14.4 V, 1 kHz, 10 % – 4 x 80 W/2 max. – 4 x 77 W/2 EIAJ – 4 x 55 W/2 @ 14.4 V, 1 kHz, 10 %
These are the gived output parameters at the top of the doc in BOLD, (But nobody know drive around playing a sinus 1000 Hz wave at 10% distortion). And output, in your use case, is provided in same sheet:
Power Output: THD: 1%; VS: 13.2 V = 13 W for the 7385 (and 1 W higher from the other if I remember correctly)
- Changing a amplifier from 10 to 20 Watts gives you theoretically 3 dB more output - not much. People usually says something is twice as loud when SPL is increased by 10 Db. So go for something that has 30 dB gain, and you will hear it.
I think feeding the input to the 7385s into a separate amplifier with a switching module to increase the rail voltage is the easiest.
But if you want to continue, read and understand the ICs ABS Max Values, solder the IC(s) out of the unit to ensure cooling (Figure 10: Power Dissipation & Efficiency vs. Output Power) and feed it 25 volt input and it will perform much better.
Good luck
Simon
First, cudos (is that a okay word?) for being able to make this work, I did not look at pin config, but even very similar, this must have a advanced soldering job🙂. I unfortunately it is easy to explain (the basic) of why you are not happy. You can split it into 3 reasons:
- This is IC designed to be the amplifier in a car stereo or similar. Its already very crowded inside a DIN size unit, and heat is a massive problem, so in 98% of the car radios, the designer do not choose to cramp in a dc to dc converter (small switching device) and are stuck with your cars dc voltage as a source, and less on the rails. There is some tricks here to improve (bridging two units (that is normal), or lower the imp on the load, which Audi have done in my car, all speakers are 1 ohm (less common)) but 10-13W continuous output pr channel (with less than 1% in a 4 ohm load) using AB designed IC is normal.
- After quickly scrolling the datasheet its easy to believe that both of these delivers much more, (and they can given a 25 volt DC input and a large heatsink look at Figure 5: Output Power vs. Supply Voltage)
TDA7560 Superior output power capability: – 4 x 51 W/4 max. – 4 x 45 W/4 EIAJ – 4 x 30 W/4 @ 14.4 V, 1 kHz, 10 % – 4 x 80 W/2 max. – 4 x 77 W/2 EIAJ – 4 x 55 W/2 @ 14.4 V, 1 kHz, 10 %
These are the gived output parameters at the top of the doc in BOLD, (But nobody know drive around playing a sinus 1000 Hz wave at 10% distortion). And output, in your use case, is provided in same sheet:
Power Output: THD: 1%; VS: 13.2 V = 13 W for the 7385 (and 1 W higher from the other if I remember correctly)
- Changing a amplifier from 10 to 20 Watts gives you theoretically 3 dB more output - not much. People usually says something is twice as loud when SPL is increased by 10 Db. So go for something that has 30 dB gain, and you will hear it.
I think feeding the input to the 7385s into a separate amplifier with a switching module to increase the rail voltage is the easiest.
But if you want to continue, read and understand the ICs ABS Max Values, solder the IC(s) out of the unit to ensure cooling (Figure 10: Power Dissipation & Efficiency vs. Output Power) and feed it 25 volt input and it will perform much better.
Good luck
Simon
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I would like to add why not just get an aftermarket amp? It will get you what you want. A good head unit wouldn’t hurt either.
New amp is like going too far for my currently available money. And if you buy a good quality amp then you have to source better speakers, better head unit and also good door damping and so on. I tought a new chip would have make at least some difference but I was wrong.
That’s fair, the other commenter made great points. The input voltage is your limiting factor.
You don’t need to go all crazy with dampening and all that, depending on the drivers you picked you could just get a used 100 w stereo amp and be decent with a good line adapter.
As was stated, speakers are the weak point in virtually any system.
Don't expect any head unit's speaker level output to go to the end of the volume control's range without it going to full clipping. Even at half of the volume control's range, if you have the bass set higher than flat, you could be driving the internal amplifier to clipping. A scope will show you when it clips.
You may be able to find a used amp for free if you ask around.
If you use a line output converter, you will still run into the problem of clipping and distortion unless you limit the volume control position to about 1/2. You will get higher output because the amp will have gain and will boost the level above what the head unit could produce.
Don't expect any head unit's speaker level output to go to the end of the volume control's range without it going to full clipping. Even at half of the volume control's range, if you have the bass set higher than flat, you could be driving the internal amplifier to clipping. A scope will show you when it clips.
You may be able to find a used amp for free if you ask around.
If you use a line output converter, you will still run into the problem of clipping and distortion unless you limit the volume control position to about 1/2. You will get higher output because the amp will have gain and will boost the level above what the head unit could produce.
Why 13.2V? When engine is on my voltmeter shows 14.3V, but the two datasheets lacks of data for direct comparison. To be clear: i didn't expected a huge improvement, but at least some minor improvement
If both were modern ICs that used the same circuit topology that could drive to speaker load to the full supply voltage (no matter what it is), there would be no difference in the output.
Yes, you assumed the Chip by itself CREATES Power ...it does not, at all.
All an amp does is manage the power available from the power supply.
Very experienced Tech Enzo always says: "the amplifier is just that thingie between the power supply an the speaker" .... and of course he´s right.
So after your upgrade I expect exactly same power, clipping etc. , or maybe a very very slight increase (a couple %) if the new one is way more efficient.
So a louder power amp will require a stronger power supply, period.
Which in practice means buying a new power amp, with its own supply, because modding/improving the old one is not practical.
Lead acid batteries used in cars can offer widely differing voltage at different times.
Nominal is 12.6V ; feeding them MANY amperes from a full speed alternator rises that a lot, it can easily reach 15 or 16V, so a voltage regulator is used to avoid "cooking" batteries.
Which one you choose to display on datasheets?
Some use 14.4V (a common regulator voltage output) but it´s often considered "cheating" or at least impractical because it requires the engine guzzling expensive Gasoline.
12.6V would be most "honest" of all but it shows lowered specs; so a common compromise is using 13.2V which is what a recently charged battery can give, but without inefficient engine running.