question about condor cab sim

[Marcos - Munky]

I built it using Gringo's layout, and I have a few questions about it.

1- The output is in "common" level or line level?
2- It works if I use it in the chain guitar-condor-preamp-amp? (I ask this because it didn't wordek with my amp, but since this is my first experience with cab sims, I don't know if this is normal or if my built isn't working right)
3- How many volts do I need to bias the J201?

[stm]

Hi, here are the answers and some ideas to your questions:

1) Output is basically "guitar level", which is somewhat lower than typical line levels. There is an easy way to get more output level from the circuit involving two resistors around U1A. Place a 100k resistor between pins 1 and 2 of U1A instead of the jumper, and then place a second 100k resistor between pin 2 of U1A and Vref. This will raise overall gain by 6 dB. If you make this second resistor equal to 47k, then you have 10 dB more output signal, while 33k will give you 12 dB's above the standard level. If you go too high with gain you will have clipping in U1A, which is not necessarily a bad thing, because it happens just before the fourth order low-pass filtering which will remove most of the annoying highs!  Also, a good point of experimentation is to place a couple of silicon diodes or red LEDs between pins 1 and 2 of U1A, a la Tube Screamer!

2) It should work as another stompbox, just as the Sans Amp's GT-2 cabsim does. You may find less highs perhaps, but the notch between 400 and 700 Hz gives a nice character to the guitar.

3) The J201 drain should be close to Vref (typically 4.5V when powering from a 9V battery). As with any FET / MOSFET amplifier stage, the overall characteristics of the circuit when clipping may vary slightly with the bias voltage you choose before going to the extremes where it starts souding splattery. Set gain to max, set the trimpot to 4V first and mark its position; then set it to 6V and mark its position again. Now tune by ear between this range to taste!

Good luck

[Marcos - Munky]

I think I found the problem. I can't get the trimpot to bias the J201. The lower voltage that I'm getting is  about 7.5V. I will change it to a bigger value and try again. Another question, if I use the Condor to make dircet records in my PC, like done in ROG soundclips, should I connect it to the mic in or line in of my sound card?

[transient]

If you can't bias the FET with the 100K trimpot, something is probably wrong. You can try checking the solder connections around the FET.

Both inputs would work, but "line in" would give better results.

...
emre

[stm]

Hi.

1) Use you Line In input to avoid possibility of overload.  However MIC input can be used as well since the Condor has an output volume knob. Just make sure you set the level accordingly both at the Condor and at the Mixer.

2) I second the fact that maybe something's wrong in the circuit if the JFET doesn't bias with 100k.

*Make sure your trimpot is actually 100k and not 10k.
*Recheck J201 pinout (there are two different ponouts out there that depend on the manufacturer. Get the exact manufacturer's datasheet). Make sure Drain and Source are not inverted (!)
*Recheck the value of the source inductor.
*Make sure your 1k pot IS 1k and not other value. Even better, replace with a 1k fixed resistor just to see if you can bias.
*Make sure your 22uF electrolytic capacitor is not wired backwards (inverted polarity). The actual value of the capacitor is not important for biasing. Remove it temporarily and see if you can bias.
*Make sure the 100k bias trim is connected properly and that it is indeed working. Faulty trimpots do happen!

Good luck

[Marcos - Munky]

Found the problem. I used the wrong pinout. I have a few J201s with one pinout, and a few ones that I didn't got out of the pack, I used one of these, but didn't checked the pinout. I will test it in about 7 hours (it's 1:47am here ).