Assuming you're measuring a voltage across one of the source resistors, and if you want a positive reading, just swap the probes. 😉
In all seriousness though, w/o knowing how your probes are arranged / how and where you're measuring, it's hard to answer w/o tongue in cheek.
Show on schematic or describe clearly where red and black DVM probes are placed.
Same exact place on channel A and channel B? Black and Red in same orientation as it relates to rails / GND and across the same resistor from schematic? Measuring R1 on one channel and R2 (from original schematic in Post #1) on the other?
In all seriousness though, w/o knowing how your probes are arranged / how and where you're measuring, it's hard to answer w/o tongue in cheek.
Show on schematic or describe clearly where red and black DVM probes are placed.
Same exact place on channel A and channel B? Black and Red in same orientation as it relates to rails / GND and across the same resistor from schematic? Measuring R1 on one channel and R2 (from original schematic in Post #1) on the other?
I'm overly cautious and still in the light bulb test phase. Will measure again with the probes the right way 🤣
Nice! .651v bias will get hot sitting like that. Keep an eye on it. Also, I know you have the big heatsinks but with only two output devices to distribute the heat on each heatsink, that may be getting close to the limit on bias with the normal voltage power supply. Looks very nice! I wasn't able to get much higher than that anyways.
Have you hooked either up to a speaker yet?
Have you hooked either up to a speaker yet?
I haven't had them on for longer than 30 minutes. The heatsinks get warm, but not hot. Am using dual mono setup with 300VA 18V transformers, 120,000uf caps per channel and IRPF150s.
I thought I read somewhere that I could crank them up to 705mv in bias.
Haven't hooked them up to speakers yet, as I first want it cat proof.
I thought I read somewhere that I could crank them up to 705mv in bias.
Haven't hooked them up to speakers yet, as I first want it cat proof.
Try it. Following 6L6's rules, I haven't been able to get past 0.650ish but I also haven't made a great effort to. Middle pin gets to 65 degrees.
It's worth listening to them at lower bias (say 600mv) before winding them up too far.
With the F6 there has been some discussion about how bias affects the sound. Opinion does seem to vary.
I did not like the sound at higher bias, my impression was that it got harsher. However, someone else might hear it as getting cleaner!
Anyway, "if some is good, more is better" might not always apply.
This is based on listening with my old ears! If you are of the school that says "measurements are more important than listening." Then it may be very different. 🙂
I suppose it also depends on the speakers. I don't like sterile sounding systems, however my Tannoy Legacy Arden might already provide enough colouring to make it sound acceptable 😉. Will initially leave it at 650mv and take it from there.
Don't the irpf150s like more bias compared to the irfp240s?
Don't the irpf150s like more bias compared to the irfp240s?
Except that I would buy a small plastic box, drill some holes in it for air circulation and cables and mount the whole white connector block in the box (together with NTC and cap).
That way there is no obvious risk of touching mains by accident.
That way there is no obvious risk of touching mains by accident.
It looks really neat! I decided to build double mono and even with an 5u case it feels a bit crammed 😄
Thanks!
I finished it when my wife was out for a weekend with her friends when she was eight months pregnant with our first child.
I've got two kids now, so my free-time now is much more limited. I just noticed a popsicle stick managed to make it's way under the left outputs. 😂