dear fivefishdiy:
First off, congratulations on such a fantastic design project and what's turning out to be a model success story for a product that's custom tailored to the target market. How better to do it than you are? I'll buy one of your preamps for that reason alone!
I've read the input here and there as it's gone along, but I'm not really tech saavy enough to provide much input. However, just today I spent that last three hours really reading and absorbing everything that's been offered up to this point. I hope you don't mind at this late stage some new eyes on this project and maybe a couple of new thoughts...take the input for what it's worth and it's probaby too late to matter. However, I do have some input that might be useful.
I have an Apogee Mini-MP preamp that I recently inadvertently toasted because I accidently applied reverse polarity to the power jack. Actually, I am thinking (based on other threads that I've read on this same subject related to this preamp) that the whole preamp isn't cooked, but probably just an internal fuse that is located at the output jack as reverse polarity protection. I don't know circuit design, but on the one hand, I'm glad that I probably have only a blown fuse. However, on the other hand, my preamp is now DOA until I have it serviced which of course is a PITA.
For pretty much every other electrical component I own, if reverse polarity is applied, the only thing that happens is...well, nothing. In other words, the component doesn't power on, but it also doesn't fail. So, maybe the fuse is an additional form of reverse polarity protection on the Mini-MP (in addition to a diode), but FWIW I don't like it because I still have a dead preamp.
So, I guess my input is:
a) make sure that your preamp is fully reverse polarity protected (you mentioned output diodes, so I guess you have that covered???), and
b) make the design respond passively if reverse polarity _IS_ applied. Yeah the fuse might be an additional form of protection, but now that it blew, I still have a dead preamp that's gonna cost me $100 to get fixed by Apogee, so from my perspective, I'm not sure what's been saved with this design.
Of course, your final case design should indicate in the cover artwork at the power input what are the polarity and voltage requirements are...surprisingly, a good number of my electrical gadgets don't give polarity requirements at the jack.
A second input on the case design is that I REALLY like the idea of standoffs at the rear of the unit, but I understand and agree with your efforts at permanent installation and how they are be in the way. A thought I had when I saw your pics was some sort of removable or screw-on standoffs. Or maybe some brackets or something that's kinda 'C' shaped and snaps onto the back with some detents to snap into place. Or maybe a bracket that swivels out of the way...say it swivels flush to the sides of the preamp when not in use, but then swivels out around the back so that it acts as a stand-off.
Of course the goal of the stand-offs would be something that doesn't get in the way, but something that would provide stress relief on everything in the back (not only stress relief but 'movement' relief in the case of battery connectors becoming accidently disconnected) while also allowing the preamp sit in a gig-bag with the face upward so we can see easily see the lights and settings. Of couse the problem with 100% of existing preamps is that in that position, everything is resting on the wires or the RA plug of the XLR.
Regardless, of my input, congratulations on the great job you've done. Sorry for the latest mishap with board design, but from the looks of it, you're WELL on your way to having the one of the most significant success stories in net history (as for as
TS.com is concerned anyway!).
Topic: Greetings... my new mic preamp. (Read 176,917 times)