hmm, I got an inquiry.
I'll be using 2x 9v batteries in series to power the jfet boz for 18v total.
Should I be adding caps to supplement the dc power supply? I'm not sure it's necessary, but I've read where you can add up to 10,000 uf caps to it?
I'm not sure how that helps?
Just curious.
I'll be using 2x 9v batteries in series to power the jfet boz for 18v total.
Should I be adding caps to supplement the dc power supply? I'm not sure it's necessary, but I've read where you can add up to 10,000 uf caps to it?
I'm not sure how that helps?
Just curious.
You're not going to get a whole lot of run time out of a pair of 9V batteries, find yourself some AA battery holders, and run 12 of them instead....
Not much point adding caps with a battery supply, unless your batteries are some distance from the pre-amp, then they'd help eliminate any noise picked up in the power cabling...
Roscoe
I've put it together and just had a few questions.
I'm using a 24v dc walwart (although it measures 33v dc) anyways, it does sound noisy or my mess of wires in the hammond case must be picking up additional noise.
I'll put together a 18v battery pack and test it with that - the batteries couldn't fit in this case.
The 50k alps pot I'm using didn't seem like it give it much range in volume. I've got 20k stepped pot, should I use that?
Even with the unit off the signal went right thru the amp - lol. Maybe I made an error wiring it up.
I'm using a 24v dc walwart (although it measures 33v dc) anyways, it does sound noisy or my mess of wires in the hammond case must be picking up additional noise.
I'll put together a 18v battery pack and test it with that - the batteries couldn't fit in this case.
The 50k alps pot I'm using didn't seem like it give it much range in volume. I've got 20k stepped pot, should I use that?
Even with the unit off the signal went right thru the amp - lol. Maybe I made an error wiring it up.
Hmm, I had forgotten to ground the input and output jacks. That's why the amp floated.
Anyways, I grounded the in/outputs, and also changed the 50k alps pot with a 20k stepped attenuator (small surface mount resistor type) and it works!
( the 50k alps pot was way to sensitive)... (For sale 50k alps pot, lol).
I'm still using a walwart, and it is a bit noisy.
Oh, power switch works, but it take a while for it to power down because the filter caps are charged (and discharging when powered off).
I've got batteries to test it with, that will be next.
Anyways, I grounded the in/outputs, and also changed the 50k alps pot with a 20k stepped attenuator (small surface mount resistor type) and it works!
( the 50k alps pot was way to sensitive)... (For sale 50k alps pot, lol).
I'm still using a walwart, and it is a bit noisy.
Oh, power switch works, but it take a while for it to power down because the filter caps are charged (and discharging when powered off).
I've got batteries to test it with, that will be next.
problem with newly built BOZ JFET Channel
I just finished a jfet boz using the 2sk170 and the values in the original Schematic, drain resistor 2.2k and source resistor 10 ohms. Supply Voltage is 18v. The 2sk170 came from a matched pair which measured 9.7v.
Here's the problem...I put in 1 volt at 1kh and get out nearly 8 volts. But when I look at the output on an oscilloscope, the bottom going swing is clipping badly. In fact, the bottom going swing starts clipping when output is measured at 1.6v.
What to do???
Thanx
By the way, I used the jfet boz boards from Jim's Audio on Ebay. They are pretty neat, and include a power supply circuit.
I just finished a jfet boz using the 2sk170 and the values in the original Schematic, drain resistor 2.2k and source resistor 10 ohms. Supply Voltage is 18v. The 2sk170 came from a matched pair which measured 9.7v.
Here's the problem...I put in 1 volt at 1kh and get out nearly 8 volts. But when I look at the output on an oscilloscope, the bottom going swing is clipping badly. In fact, the bottom going swing starts clipping when output is measured at 1.6v.
What to do???
Thanx
By the way, I used the jfet boz boards from Jim's Audio on Ebay. They are pretty neat, and include a power supply circuit.
I presume your JFET has the Idss of 9.7 mA. With 10 Ohms source degeneration the Id will be about 7-8mA.
2k2 x 7mA = 15.4V - This means that your JFET works with very low Vds and that's where the early clipping comes from.
Reduce the Drain resistor to get about 8 Volts at the Drain, but don't expect to get more than a few Volts of clean swing from that design.