Do you know if the engine is 1200 or 1100 CC?
I'm eagerly awaiting for your photos. My friend's radio (which I talked before) had a defective vibrator. He threw the thing away!!! Can you believe it? Nowadays, it would be a real collectible.
The TDA2003 datasheet has a graph that shows its distortion with a 14.4V supply and a 4 ohm load. It clips at about 4.2W and at 5W its distortion is 0.3% and is becoming audible.
If the supply is only 13V then it clips at only 3.5W.
The 34063A can switch the low input voltage to the inductor at up to 1.5A but the output current is much less because the voltage is stepped up. It cannot manufacture additional Watts.
Yes indeed, you need a boost converter.
My suggestion on this one, since you are not familiar with the design of switchmode power supplies, is to use a Simple Switcher device from National Semiconductor.
They have an on-line simulator that works amazingly well. You only enter the input/output parameters, it will suggest devices from its extensive lineup, and it will calculate the required component values and provide all sorts of plots and data.
1) Power out must equal power in, minus some losses.I understand that power is conserved. It's just that I have a VERY basic understanding at best of boost converter theory.
An amplifier has low distortion until its output runs out of supply voltage and clips which produces severe distortion (the audio waveform is "clipped" into a square-wave). Unfortunately all amplifier manufacturers exaggerate the output power by spec'ing 10% distortion where the volume control is turned up too high so the output is a badly clipped square-wave that sounds awful.I think I understand your comments about the clipping at 3.5W with a 13 V supply. I also think based on your comments that if I use a higher supply voltage say 17V, I can achieve 5W output with much lower distortion. Is this a correct statement?
A resistor in series with a speaker makes it sound boomy because the resistor destroys the damping of resonances provided by the extremely low output impedance (0.04 ohms or less) of an amplifier.If that's true, then there would be a problem because with a 17V supply, the maximum output of the amp could go to ~ 8.5 W with a 4 Ω load which would likely blow my 5W speaker. Could I protect my speaker by adding an extra resistor at the input (resistor labeled Rp in attached schematic)?
In the datasheet the graph for power with a 14.4V supply and into 4 ohms with 10% distortion shows 6W. But the graph for distortion with a 14.4V supply and into 4 ohms shows the distortion suddenly climbing (clipping) at only 4.2W. So the ratio is 4.2W/6W= 0.7.
It shows 8.5W with a 17V supply and a 4 ohm load with 10% distortion so it clips at 8.5W x 0.7= 5.95W.
Based on your explaination above, wouldn't a 15V supply clip at 4.5W?
The ratio from no distortion to 10% clipping distortion is 0.7 times. So 6.5W at 10% distortion with a 15V supply means that the amplifier begins clipping at 4.55W (simplified calculations). The difference in volume between 9W and 4.5W is small. You will not hear the difference between 4.55W and 4.5W.
Amplifiers have a power supply hum rejection spec where the ripple is attenuated. It should be very low at the output of the amplifier.Also, the ouput of the LM2588 is regulated but according to the datasheet on page 21 it does have some voltage ripple at what looks like about 100-200 mV. I sthat not going to affect the amp? Do I not need to worry about that?
- The current plan is to connect the voltage going into the switching converter directly to the car’s battery, however this voltage will not be constant. The battery voltage of the car varies between 6 and 7.5V depending on engine RPM. Is it necessary and/or beneficial to place a voltage regulator in between the vehicle battery and the switching converter so that the converter sees a nice stable voltage at its input?
- I’m unsure, because of my inability to use National’s software, what component values to use for the switching converter. I attached a schematic of my preliminary circuit. The components shown with red labels are the ones I’m unsure of.
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P.S. Schmitt Trigger, sorry I’ve been busy with work but I haven’t forgotten about you. I have some pictures of the old VW radio I’m going to post tonight.
The ratio from no distortion to 10% clipping distortion is 0.7 times. So 6.5W at 10% distortion with a 15V supply means that the amplifier begins clipping at 4.55W (simplified calculations). The difference in volume between 9W and 4.5W is small. You will not hear the difference between 4.55W and 4.5W.
Amplifiers have a power supply hum rejection spec where the ripple is attenuated. It should be very low at the output of the amplifier.
-The Nat Semi's software WILL PROVIDE you with both an annotated schematic and a Bill of Materials which lists the value AND full description of each component.
See the attached file of an example circuit which I had run previously.
The plan seems too complex and somewhat wrong for the task.
If it will stay with one speaker to keep originality, the MP3 source can have both earphone or better line-out channels merged and fed to the radio volume potentiometer with a selector switch.
Is that a vacuum tubes radio ? Is it 6 V ?
The 5V MP3 power source can be obtained from the 6V VW electrical with a couple of 1A Si diodes in series to bring it to around 5V. A 7805 is not a good choice. Perhaps a 2950-05 if you really want regulation.
It will sound like an AM radio. Bad sound quality.
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