So, starting from the beginning of the line.
All measurements are referenced to secondary GND.
I found out my multimeter is not really exact.
RCA jack: 0.41v
U101-1: 0.043v
U101-7: 0.043v
U100-7: 0.018v
U102-1: 0.08v
U102-7: 0.054v
U110-9: 0.027v
U103-7: 0.035v
U103-1: 0.036v
U104-1: 0.048v
U104-7: 0.048v
U109-1: 0.048v
U109-7: 0.048v
U105-7: 0.11v
U105-1: 0.11v
U106-7: 0.12v
U106-1: 0.11v
U107-1: 0.11v
U108-1: 0.11v
U108-7: 0.11v
U107-7: 0.11v
Since the secondary GND to primary GND resistor has been changed, the sine wave going to the input of the main driver board is even lower.
All measurements are referenced to secondary GND.
I found out my multimeter is not really exact.
RCA jack: 0.41v
U101-1: 0.043v
U101-7: 0.043v
U100-7: 0.018v
U102-1: 0.08v
U102-7: 0.054v
U110-9: 0.027v
U103-7: 0.035v
U103-1: 0.036v
U104-1: 0.048v
U104-7: 0.048v
U109-1: 0.048v
U109-7: 0.048v
U105-7: 0.11v
U105-1: 0.11v
U106-7: 0.12v
U106-1: 0.11v
U107-1: 0.11v
U108-1: 0.11v
U108-7: 0.11v
U107-7: 0.11v
Since the secondary GND to primary GND resistor has been changed, the sine wave going to the input of the main driver board is even lower.
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Measure the output of your phone at full volume with the meter probes on the shield and center conductor of the RCA cable that you use to drive the amp.
It's 1.05v
Phone signal is 100% good. I can clip all amps with that phone.
Seems like the multimeter is way more exact when GND reference is measured to the RCA shields.
Phone signal is 100% good. I can clip all amps with that phone.
Seems like the multimeter is way more exact when GND reference is measured to the RCA shields.
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I don't know.
There is unlimited resistance between the RCA GND and the secondary GND.
I checked the DC voltage referenced to the minus 12v supply voltage
RCA GND: 0.054v
Secondary GND: 0.00v
Maybe this has some influence?
There is unlimited resistance between the RCA GND and the secondary GND.
I checked the DC voltage referenced to the minus 12v supply voltage
RCA GND: 0.054v
Secondary GND: 0.00v
Maybe this has some influence?
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RCA jack: 0.19v
U101-1: 0.001v
U101-7: 0.006v
U100-7: 0.007v
U102-1: 0.007v
U102-7: 0.058v
U110-9: 0.037v
U103-7: 0.037v
U103-1: 0.053v
U104-1: 0.051v
U104-7: 0.051v
U109-1: 0.051v
U109-7: 0.051v
U105-7: 0.118v
U105-1: 0.114v
U106-7: 0.126v
U106-1: 0.12v
U107-1: 0.12v
U108-1: 0.115v
U108-7: 0.114v
U107-7: 0.114v
Referenced to secondary GND. These measurements are accurate. I rechecked all pins with the oscilloscope.
The charger was plugged in the phone. Seems like some strange GND problems occured. There was a strange 50Hz tone on the speaker terminal constantly. Disconnecting the charger made it disappear.
U101-1: 0.001v
U101-7: 0.006v
U100-7: 0.007v
U102-1: 0.007v
U102-7: 0.058v
U110-9: 0.037v
U103-7: 0.037v
U103-1: 0.053v
U104-1: 0.051v
U104-7: 0.051v
U109-1: 0.051v
U109-7: 0.051v
U105-7: 0.118v
U105-1: 0.114v
U106-7: 0.126v
U106-1: 0.12v
U107-1: 0.12v
U108-1: 0.115v
U108-7: 0.114v
U107-7: 0.114v
Referenced to secondary GND. These measurements are accurate. I rechecked all pins with the oscilloscope.
The charger was plugged in the phone. Seems like some strange GND problems occured. There was a strange 50Hz tone on the speaker terminal constantly. Disconnecting the charger made it disappear.
Measure the AC voltage with the probes on the RCA shield and the RCA center conductor for both channels. Do you read the same voltage you read on the RCA from the phone? Do this on the solder connections for the RCA jack.
Measure the voltage with one probe on pin 1 and the other on pin 7 of U101. What's that voltage?
Measure the voltage with one probe on pin 1 and the other on pin 7 of U101. What's that voltage?
I restarted my phone, the AUX gives a higher amplitude now.
Measured the AC voltage between RCA GND and middle pole, 0.759v (RCA disconnected from the amp)
Measured the AC voltage between RCA GND and middle pole, 0.756v (RCA connected to the amp)
Between U101-1 and U101-7 is 0.005v (RCA voltage is 0.19v)
Between U101-1 and U101-7 is 0.026v (RCA voltage is 0.759v)
So, when the RCA signal becomes louder, the potential difference between U101-1 and U101-7 becomes bigger.
Measured the AC voltage between RCA GND and middle pole, 0.759v (RCA disconnected from the amp)
Measured the AC voltage between RCA GND and middle pole, 0.756v (RCA connected to the amp)
Between U101-1 and U101-7 is 0.005v (RCA voltage is 0.19v)
Between U101-1 and U101-7 is 0.026v (RCA voltage is 0.759v)
So, when the RCA signal becomes louder, the potential difference between U101-1 and U101-7 becomes bigger.
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This amp has a differential RCA input, if your source ground is not at the power supply ground, I think this could be the cause the problems?
Just use a headunit with RCA ground connected to it's power supply ground.
Just use a headunit with RCA ground connected to it's power supply ground.
Bertje, do you think this is fixable by connecting the RCA's GND to the secondary or primary GND?
With JBL BPX series or some Alpine's connect RCA ground to power supply ground (primary ground) . In a car this always like that. Or just use an old 4V output headunit for testing, they are cheap...
Bertje, I connected the RCA GND to the PS GND. But this results in even lower speaker terminal volume (I think 3x lower).
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Perry, removed U101, the amp pulls 1.20a more when max volume is applied. Is it safe to measure pins 6 and 2 with max volume?
With 0.111v RCA signal applied, between U101-2 and U101-6 reads 0.071v (amplifier pulls 80mA extra).
With 0.212v RCA signal applied, between U101-2 and U101-6 reads 0.138v (amplifier pulls 500mA extra)
With 0.111v RCA signal applied, between U101-2 and U101-6 reads 0.071v (amplifier pulls 80mA extra).
With 0.212v RCA signal applied, between U101-2 and U101-6 reads 0.138v (amplifier pulls 500mA extra)
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You'll have to decide if it's safe. Watch the temperature of the FETs.
Are you measuring the RCA voltage with the black probe on the shield and the red on the center conductor?
Are you measuring the RCA voltage with the black probe on the shield and the red on the center conductor?
Are these values usefull for you? 🙂
I rather not try full volume if it's not necessary, because I don't know where the excessive current is going to..
I rather not try full volume if it's not necessary, because I don't know where the excessive current is going to..
What's causing the increased current draw? Is noise being produced by the next op-amp?
Connecting the output terminals of the op-amp you removed together may prevent noise from causing a problem farther down the circuit.
Higher voltage is more definitive.
Connecting the output terminals of the op-amp you removed together may prevent noise from causing a problem farther down the circuit.
Higher voltage is more definitive.
I checked the speaker terminals when U101 is removed. There now is a big 50Hz sine wave present at the speaker terminal. Not clipped, but much bigger already.
43VAC measured with the multimeter with an 0.28VAC worth of input at the RCA's
About 800mA drawn extra.
I highered the RCA input to 0.316VAC. This is just below the clipping limit of the speaker terminal (48.6VAC at the speaker terminal). Anything above will let the amplifier clip with all the potentiometers tuned to the max volume). That is were the extra current draw is coming from I think.
It actually seems to work pretty good when U101 is removed��...
With bass boost turned off and my daily phone on max volume (0.346VAC on RCA) it is almost clippable, so the total amplification in the filter section is a bit on the low side with U101 removed.
43VAC measured with the multimeter with an 0.28VAC worth of input at the RCA's
About 800mA drawn extra.
I highered the RCA input to 0.316VAC. This is just below the clipping limit of the speaker terminal (48.6VAC at the speaker terminal). Anything above will let the amplifier clip with all the potentiometers tuned to the max volume). That is were the extra current draw is coming from I think.
It actually seems to work pretty good when U101 is removed��...
With bass boost turned off and my daily phone on max volume (0.346VAC on RCA) it is almost clippable, so the total amplification in the filter section is a bit on the low side with U101 removed.
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