API 312 Thread!
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Rob Flinn
Well-known member
If you`re looking for the reverse log 22k go to electrovalue
Fabio,
you wrote :
I didn?t thought there is limitation in the choice of the Xfrm/Opamp couple.
Which Xfmr input to use with a JFET-992, a JLM99V or a SC25 ? Or which OpAmp to use with a Cinemag CM-75101APC ?
It would be great if we could unite our experiments to build a table with input/opamp/output possibility, preferences and comments.
you wrote :
I didn?t thought there is limitation in the choice of the Xfrm/Opamp couple.
Which Xfmr input to use with a JFET-992, a JLM99V or a SC25 ? Or which OpAmp to use with a Cinemag CM-75101APC ?
It would be great if we could unite our experiments to build a table with input/opamp/output possibility, preferences and comments.
synthetic
Well-known member
What's the source for 22k rev log pots in the USA? I searched for Omeg pots, found their US distributor (vimex.com) and sent them an email. I'm now waiting for them to reply, but I'm not sure if they're a distributor or a retailer. Does another manufacturer make this part and sell it in the USA?
dasbin
Well-known member
Mine's done! Well, almost.
Everything's working well. Also you guys should know that the CMMI-8PCA does in fact plug straight into Fabio's boards. The pinout and spacing are correct. Drops right in.
I'm using CMMI-8PCA input, Cinemag CMOQ-2S ouput, and currently testing opamps (using OPA604 just for now).
Everything worked fantastically first try EXCEPT there seems to be a bit of a gain issue. I'm using a 25K log pot wired in reverse, which seems to taper correctly, but for some reason there is a high-end roll-off when I turn up the gain. The problem is made even worse when engaging the pad (because you have to crank the gain to compensate); the signal becomes completely muddy and everything above 500Hz or so is totally lost. Anyone know what could be happening?
Everything's working well. Also you guys should know that the CMMI-8PCA does in fact plug straight into Fabio's boards. The pinout and spacing are correct. Drops right in.
I'm using CMMI-8PCA input, Cinemag CMOQ-2S ouput, and currently testing opamps (using OPA604 just for now).
Everything worked fantastically first try EXCEPT there seems to be a bit of a gain issue. I'm using a 25K log pot wired in reverse, which seems to taper correctly, but for some reason there is a high-end roll-off when I turn up the gain. The problem is made even worse when engaging the pad (because you have to crank the gain to compensate); the signal becomes completely muddy and everything above 500Hz or so is totally lost. Anyone know what could be happening?
Ultrasonic Osc.
Try increasing feedback cap value a little at a time.
Try increasing feedback cap value a little at a time.
dasbin
Well-known member
Nevermind, I fixed it. Silly me. I apologize for my newbness; this is my first major DIY project. Feedback cap was indeed the problem, I had the wrong value in there in the first place. Thanks for the pointed and quick reply though anyway CJ. You guys are like gods of the electron. The answers to everything just jumps out at you.
Now the only thing left is that the DI auto-switch doesn't seem to be working. I had to substitute the transistor for a 2N3906, which probably has a lot to do with it.
Now the only thing left is that the DI auto-switch doesn't seem to be working. I had to substitute the transistor for a 2N3906, which probably has a lot to do with it.
dasbin
Well-known member
I think you need another opamp in the circuit to do this. OSA has one in their newer designs. They just use a TL072.
therecordingart
Well-known member
If someone could take a guess...about how much do you think it would cost to build each channel? I've been searching parts prices, but have been running in circles. I'm trying to figure out if it would just be more cost effective to purchase the API clone that SCA has.
peter purpose
Well-known member
dpdt
peter purpose
Well-known member
This is how it's done in a 1073.
