THAT4301 troubleshooting

[electric_diaries]

Hi all,

I got some THAT4301s the other day and went about making a test circuit.... but I must be doing something stupid.

I am powering it with +/-12V and using the circuit below . At lower volumes I am only getting distorted positive cycles. Then at a higher volume there is a threshold where it tries to jump to it’s positive rail.

Sorry I can’t provide more specific information on where this threshold is because I was using someone else’s test equipment. However I managed to make a small audio clip of a 200hz sine wave that is temporarily pushed into this threshold. (lets assume this threshold is somewhere around +4dbu to give you an idea). I will post a picture of the waveform in the first comment.

I tested OA3 and it appears to be working properly. I can see the proper voltage on pins 10 and 11 and have tried connecting pin 16 to a high impedance voltage source, ground, and no connection.

I also tried changing the chip so I must be doing something stupid with my circuit.

Any ideas where to start looking?

Many thanks!

 

[electric_diaries]

Here is the 200hz sin wave being pushed into it's "freakout" threshold.

 

[JohnRoberts]

EC- should be grounded for unity gain.

JR

 

[electric_diaries]

EC- should be grounded for unity gain.

I tried that but I still get the same problem unfortunately  :-\

 

[JohnRoberts]

EC- should be grounded for unity gain.

I tried that but I still get the same problem unfortunately  :-\

Do more than try it...  both EC ports need to be connected to low impedance nodes within mV of 0V.

what are DC voltages at pins 13 and 12 with no signal playing?

Have you confirmed resistance of the two 20.0k resistors?

JR

 

[electric_diaries]

Thanks JR I finally got back to test it last night and it worked fine after I grounded pin 16. I guess I didn't try that properly after all.  :-X

I tried it with a low-impedance/low-level CV and it works great!

Thanks again!