I have both. There is no comparison. IMHO, BOZ-J is better in every respect, with the probable exception of output capability.
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.
merlin's question brings something to mind that I have been wondering about - if you put two really big caps (like the 10,000uf he mentions) on the circuit downstream of the batteries, isn't that just going to drain the heck out of the batteries when it's switched on??
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
Don't use a large cap. Try 1000 to 4700 uf. If it's easy enough, see if using a cap will improve bass response. Try it with and without. Can't hurt. What's a battery cost?
I've got 4700uf caps I'm going to use with the 2x 9v batteries. Mongrel audio guy says he gets about 100hr with them.
I'll build it and find out.
I'll build it and find out.
Merlin2069er,
Let us know if you try it with and without caps; if you hear a difference. I'm curious.
Thanks,
Vince
Let us know if you try it with and without caps; if you hear a difference. I'm curious.
Thanks,
Vince
ok, will do. I'm just waiting on a few battery holders.
I just got a hammond case, I'll need to drill that out.
I just got a hammond case, I'll need to drill that out.
If you are looking for good aluminum cases in the future, check out Antek. They have a link to cases and heat sinks. They sell extra thick front panels too.
And yes, I realize Hammond is in Canada! 😀 Case, heat sinks and transformers in one place! That's half the battle right there! 😀
And yes, I realize Hammond is in Canada! 😀 Case, heat sinks and transformers in one place! That's half the battle right there! 😀
I just received a few of Par-metal (Antek) 20-series cases. They are much nicer than I was expecting... And I was expecting something good. I can unreservedly recommend them!
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.
check your volume control wiring.
That may account for the low range of adjustment and the excessive noise.
That may account for the low range of adjustment and the excessive noise.
Use the 20k pot. Better match, however, that depends on the type of stepped, and will sound better than a standard pot. I switched from a P.E.C. pot to a series stepped attenuator. It's just so much better.
Try a shunt circuit, I'm using line in -> 21k ->wiper of pot & jfet gate, ground of pot to ground.
Roscoe
Roscoe
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.