Quote: perhaps putting a CRC on board would help with this... along with clear instructions on how to "set the resistor" it would allow for lots of variance in mains voltage, transformers, etc.

The maximum input voltage is usually 37V for most LM3X7 types, unless you shop around. As you suspected, the issue is not voltage drop, maximum input voltage which is just one of the design parameters for the device itself.   100C is too hot for me, and I suspect this number was thrown out...

Quote:   It doesn't work that way. If the heatsinks were at half the max junction temperature, the device would be dead. For a TO-220 device, you want to be able to keep your finger on the heat sink for at least 3 seconds before having to pull away. This will be about Tj = 80C.

what about mounting a pair of chassis mount bridges and then build up a CRC that feeds into C1 (bypass D1-D4)? I think a little more capacitance might be nice to have and this would allow you to deal with your excess voltage. Grab a chassis mount resistor for the "R" as well. Even with doing...

Michael:   Do you happen to have test results (RMAA, for example) on the MicPortPro? Is there any hope of going beyond 24/96? Do you perhaps have an evaluation unit that you send around? I'm interested in using it as a measurement mic pre for developing audio gear.

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I have some that I'd love to get rid of. PM me an offer:  

don't underestimate the fail factor of potential DIYers.   Quote:

Let me ask this another way. How many of NP's "free designs" in the source/preamp/crossover category use coupling capacitors and how many of his commercial designs in this same category use coupling capacitors? Quote:

any other mosfet output I/V? I bet that is what your preference is. Nothing particularly spectacular about this circuit. Quote:

pretty nice devices. I use the Potter and Brumfield W28 series. They're panel mountable just like a fuse, and may even drop into some fuse knock outs. They are available down to 250mA, suitable for just about any project, solid-state or tube. Total cost around $5. For smaller current draws, PTCs...

Quote: unfortunately, you'll have to avoid DIY equipment all together then, if you're worried about insurance adjustors...   Uncle Erik: looks like you've considered other options. Why not try thermal breakers / PTCs?

the dots (or line in later versions) distinguishes if the devices is RoHS compliant. The letter is indeed the lot number, which is a factory, year, batch encoded value.

Quote: even if they are visible different, that's okay as long as the hfe class is the same. There are two versions of these, one with etched identifiers on the case, and one with whiteish-ink-printed labels. The etched ones are the later devices. 

yup, however if you're not matching either at the voltage/current/temperature parameters of the circuit, it might be wasted effort that could be spent in building another one of Alex's designs :)

If I remember correctly, these MOSFETs (IRF550/IRF9540) will not make great complementary pairs... I bet you'll have a ~0.5V difference in Vgs between the two types. If you have a distortion analyzer, you could probably play with R22, R23 to find a null point... probably not worth the effort as...

The big ones are Toshiba 2SJ201/2SK1530. Small ones are 2SA970/2SC2240. Medium ones are 2SA1145/2SC2705.

oh, before someone says something about the use of a crappy meter :) that yellow meter isn't a yellow meter...it calculates hfe directly from wires that go to that box...

Quote: like this?     ...been there done that :)  

yeah, that's not going to work very well. You need to match the devices at their target operating junction temperature and at the target current and voltage. I used a ceramic heater control block of aluminum to do the job. The heating element is in the back and you can see the probe:    ...

Quote: it's a balanced line driver, or differential output amplifier. It converts a single ended input into a balanced output pair.

So, I have been conducting some tests comparing boutique fuses to some other options, namely thermal breakers and other types of resettable fuses. My current favorite is the Potter & Brumfield W28, which absolutely blows traditional *AND BOUTIQUE* ceramic and glass fuses out of the water. I'm...

why not use one of P-A's DRV134 boards on the output?

it's just stacked plexi. The inner layer is mostly missing to accomodate the board. Vertical mount RCA jacks generally suck and if you wanted to do something like the above, perhaps try RCA chassis jacks that actually thread through the PCB itself, like the old Benz PP-1 (sorry, small image...

Thanks guys!   With the small USB connector, casing is always a challenge. Perhaps you guys could consider a stacked plexi case, similar to this: