I don't like cutting traces.

Thank you for ME not being the only one.

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I really do hate 'ruining a clean board' by doing a knife or dremmel trick.

a wire, otoh, is fully reversable with no ill traces (so to speak)

could I put in one more tiny vote for non-traces and a big sentence in red in the how-to saying 'please user, DO install a wire short here'. I know answering user questions is annoying but the wire option means that no board is ever harmed in the call of duty I kind of like that design over the surgery approach.

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[Quoting NelsonVandal]

It looks like a final version, doesn't it?

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[Quoting bdhornback]

IF you're going to short the C1 traces... could you please at least do it on the bottom of the PCB (instead of shorting the SMT pads) so it doesn't show from the top?

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I did it not just because of the appearance issue, but because people are more likely to use leaded film caps than SMT, and might forget to cut the trace first, so you want them to be able to get at it without removing the cap.

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[Quoting cobaltmute]

what is the layer beneath the top now?

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do you think you have to worry about someone cutting through the full layer if they Dremel C1?

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[Quoting linux-works]

a big sentence in red in the how-to saying 'please user, DO install a wire short here'.

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First, it makes the docs ugly and insulting.

Second, it doesn't address the real problem, which is that not everyone fully reads or comprehends the documentation. Making it glow and blink and dance isn't going to change that. In fact, it's probably more likely to hurt...when was the last time you studied the "warnings" section in a manual? Don't your eyes just sort of slide over that, with your brain going "yeah, yeah, whatever"? Mine do.

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I know answering user questions is annoying

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[Quoting bdhornback]

I would think that if someone can take on this project, they won't miss a jumper and if they did... it'd be the first thing they'd check.

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I can't say these arguments from experienced DIYers make much impact on me, for an issue like this. The PIMETA is frequently recommended as a "second project" when someone completes their first simple project and is asking "what next". These people's needs are what I'm trying to address.

My mind's not absolutely made up on this. You'll need better arguments to change it, though.

no, a red blinking banner is not needed but a photo would really hit the concept home.

if this is a 2nd build for new DIYers then maybe its GOOD for their education to have the unit not work on first power up *IF* they miss an important step. no harm comes to the circuit and this teaches them at least a little thought process and troubleshooting. so there's that going for it, which is nice

I might add a section before final power up (you probably already have one) stating to check diodes and chips for proper orientation and also ensure that all jumpers (all 2 of them, lol) are in place. just mention it once in the instructions at the build section and once more at the pre-power up check.

designing for supportability is a good thing but installing or not installing the jumper won't cause damage to the unit and so its not critical that the user be 'protected from himself' in this manner.

So, I'm teetering on the edge. Anyone wanting to give me a kick, go ahead.

I agree with MisterX. I have to say that it is sensible to decide things based the practice in 95% of all cases. Instead of 95 people installing a wire and 5 people installing a cap, we have 5 people cutting a wire and installing a cap. Less total work saves the planet!

You cap lovers may want to consider yourself lucky for having a place for caps on the board at all

very few people will *want* to install a cap.

so it is optimized or the real-world. I see that.

suppose someone intends to use the cap and they forget to shave off the etched trace. to me, this is the worst possible situation as the user *expects* to have the protection of a cap and yet is NOT getting any protection simply because they overlooked the need to shave off that trace connection. if their source had DC on it and they run the pimeta with gain, well, that's a problem for most phones ;(

if the line is 'pre-shaved' (not connected) then the worst-case is that the user gets no sound. the other worst-case is that they do damage to their phones.

is *that* argument at all compelling?

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[Quoting Mister X]

caps that are unnecessary 95% of the time.

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You are almost right -- it is probably closer to 99%, though.

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suppose someone intends to use the cap and they forget to shave off the etched trace. to me, this is the worst possible situation as the user *expects* to have the protection of a cap and yet is NOT getting any protection simply because they overlooked the need to shave off that trace connection. if their source had DC on it and they run the pimeta with gain, well, that's a problem for most phones ;(

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It's a lot of if's. As a DIYer, you have to be responsible for your own actions -- if you don't understand how to build and measure an amp before plugging in headphones, it is your own fault. Moreover, I've been around these boards for a long time, and I have *never* seen a post where someone damaged their phones due to offset from a source passed through an amp. In the real world, this doesn't happen.

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[Quoting MisterX]

Is that enough of a kick?

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[Quoting linux-works]

suppose someone intends to use the cap and they forget to shave off the etched trace. to me, this is the worst possible situation

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[Quoting dsavitsk]

it is probably closer to 99%, though.

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You can't prove a negative -- "I will never need an input cap" -- so out of an abundance of caution, one may choose to add an input cap even though they may not need it right now.

Still teetering...

fine - remove the option, then! seriously.

use the space for something else.

just seems odd to have space allocated and a wire pre-installed to BYPASS the whole point of the space

if 'no one needs or builds with caps' then take it off the board entirely!

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[Quoting tangent]

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[Quoting dsavitsk]

it is probably closer to 99%, though.

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99% is a really dangerous number. Forgive me, but when someone uses it, they're saying "I actually have no idea." I also have no idea.

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"if you're right 90% of the time, why argue about the remaining 3%?"

(sorry)

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[Quoting tangent]

You can't prove a negative -- "I will never need an input cap" -- so out of an abundance of caution, one may choose to add an input cap even though they may not need it right now.

Still teetering...

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has anyone thought about those jumper-shunt style jumpers?

instead of having a pc-board etch short, why not just leave the 2 holes as they are for the caps but also route a trace from each hole to component-side computer style jumper shunts, where the user can install or remove those little black plastic shunts?

they will be the only shunts on the top of the board and there might even be room (?) on the silkscreen for a small legend.

short the shunt to take the caps out of the circuit. remove the shunt to use the cap (if any). you can install caps and then 'tune' by removing and replacing the shunt and people can have 'fun' with that (again, its a 2nd diy and its good to let them see or play with this, perhaps?)

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[Quoting linux-works]

remove the option, then! seriously.

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First, what do you propose using a space only about the size of your pinkie's longitudinal cross-section for? It looks big on screen, but it's really not all that much.

Second, those who do want caps need the mechanical support of a PCB for them. They're not something that should be air-wired.

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just seems odd to have space allocated and a wire pre-installed to BYPASS the whole point of the space

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if 'no one needs or builds with caps' then...

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This whole thing is fraught with uncertainty: the potential need for input caps, the wisdom of populating them in advance of need, the question of how often they're installed...

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has anyone thought about those jumper-shunt style jumpers?

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A thought, however: you can buy resistor-like jumpers (0 ohms) from all the distributors. Maybe if I include those in the part list as an alternate for C1?

[Edited by dsavitsk on 03-04-2009 at 04:18 PM.]

well, it was just a thought. I can't see them being any worse than the molex connectors that people seem to use.

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I had no idea people would get all fussy about jumper blocks and shunts. no idea at all.

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I use them all the time. Not in signal path though. I can't see why would people have an issue with it either, let alone make it a Holy Wars one. I must've missed a few fiery threads here in the few years I've been absent .

I have a new appreciation for the job tangent is doing.

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[Quoting aos]

I must've missed a few fiery threads here in the few years I've been absent .

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[Quoting tangent]

Your computer's motherboard probably has a few unpopulated chip footprints. Does that bother you, too?

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if there were things that could have been in the real estate but got pushed out for a de-populated option then yes, I would mind a little bit.

just wondering if a set of relays could fit in those cap areas and be used to control gain (provide a high/low remote gain setting for diff kinds of phones) or a selectable remote bass boost.

thinking aloud - not saying its a great idea but just exploring what *could* go in that combined area if the caps are done away with.

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[Quoting tangent]

A thought, however: you can buy resistor-like jumpers (0 ohms) from all the distributors. Maybe if I include those in the part list as an alternate for C1?

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Maybe you could sell .9999 silver wire in your shop by the inch?

I honestly think it's pretty simple. *Something* needs to go in the holes for C1 (either a cap or a jumper). If this is an intermediate DIY project... I don't see a problem. I've measured the DC offset from a lot of various PRO audio gear and have found anywhere from 10 mV to 28 mV on *PRO* gear. I know you don't like input caps... but you even state on your site, "A source that has a low DC offset today may develop a problem tomorrow." Safe is much better than sorry any day.

I have not used rechargeable 9v batts before, but I assume they will fit the standard case that you're targeting?

what do you do about the DC in/charge jack? where would that go on the case?