Hi guys, I,m back again! I'm not sure if I am posting this in the right section, If it's not, let me know and I'll try to figure out how to move it.
Anyway, I have built a VCA using a TL074CN as a CV mixer and a LM13700N transconductance op amp. The circuit is performing as it should but I'm getting very low volume on the output. I have checked to see what is going on with an oscilloscope and everything seems to be fine with the TL074N and the signal is fine going in to the input of the LM13700N. The signal going in is around 4 volts, but it is in the millivolts on the output, resulting in a very quiet signal. I have also checked the signal on the oscilloscope after the input goes through the 47K resistor, but that doesn't give me any sort of reading I can understand. It just looks like static, but as I say the circuit is working and coming out of the output so I don't think this is the problem.
This circuit is from the MFOS website and Ray mentions; "I attempted to get a gain of one at maximum control voltage although due to variation between LM13700 chips your mileage may vary." Could the chip be the problem? I have already tried 2 different ones and I'm getting the same result, so I'm not so sure it is the chip. Any help on this matter would be greatly appreciated. Thanks.
Here is the schematic:
Anyway, I have built a VCA using a TL074CN as a CV mixer and a LM13700N transconductance op amp. The circuit is performing as it should but I'm getting very low volume on the output. I have checked to see what is going on with an oscilloscope and everything seems to be fine with the TL074N and the signal is fine going in to the input of the LM13700N. The signal going in is around 4 volts, but it is in the millivolts on the output, resulting in a very quiet signal. I have also checked the signal on the oscilloscope after the input goes through the 47K resistor, but that doesn't give me any sort of reading I can understand. It just looks like static, but as I say the circuit is working and coming out of the output so I don't think this is the problem.
This circuit is from the MFOS website and Ray mentions; "I attempted to get a gain of one at maximum control voltage although due to variation between LM13700 chips your mileage may vary." Could the chip be the problem? I have already tried 2 different ones and I'm getting the same result, so I'm not so sure it is the chip. Any help on this matter would be greatly appreciated. Thanks.
Here is the schematic: