Recent content by rossbalch

Based on the quality of the PCB course I'm not keen on another Wampler course.

I thought it would be a good exercise as I learn more about circuits to annotate a schematic and describe and calculate the important features. Though in calculating some of the filter values, there's clearly some impedance considerations I'm not accounting for because some of these filters are...

I picked up these pots and the associated bobbin https://nz.mouser.com/ProductDetail/871-B65661W0000R030 What's the best way to calculate how many turns you need for a given inductance?

You've heard or even used plenty of circuits with X7R caps in the signal path. One way to minimise the "downsides" is to over spec the voltage of X7Rs and Electros.

That's actually a great idea.

The inductor is almost certainly part of some kind of power regulation and filtering circuit.

Awesome thanks for your help, I think I'm beginning to understand a bit more about DC and biasing here.

Ok so let's say instead the FET/BJT combo circuit is connected to the output of my "Recovery Tube" from the initial circuit, after R16, would I still need a coupling cap? Assuming you remove R11 to replace it with R1 from the FET/BJT circuit.

I tried a JFET with lower IDSS and that biases much nicer.

Even though the input voltage is a perfect 1v ac sine wave in the simulation?

For completeness you can see the original 1v input run +6 to +12v after the JFET stage which is buffered by the BJT

Hmm, now the whole thing just acts as a buffer. Without -12v on the emitter of Q1 there is zero voltage on the output. At least before I was getting a gain of ~3 which is what I had wanted in the first place. Thanks, I think I will just scrap the first JFET buffer, it doesn't seem necessary...

Bonus question, can C14 discharge through R3? or do I need something like a 1M between C14 and the first Op-amp?

Having 9 different germanium diodes pairs is less helpful to you than having a good number of the one specification IMO. D9E is probably the most "average" amongst them. Germanium can be a little fragile being made with glass so if you break one better to have backups of the same type. As for...

Do any of your builds require Germanium transistors? I would normally have a circuit in mind before buying them. If you just want them in hand fair enough. The BAT diodes will sound pretty much the same in those circuits, you can even add a small resistor in series to make them a bit more...