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Goran
Double Platinum Member
Sweden
2203 Posts |
 Posted - 01/18/2006 : 07:35:47
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Yesterday I got a PSM-5 (without supply & daisy-chain), MIT. As the price was about $15 I just bought it to have it�.. directly for the warehouse..
I thought this was a sort of simple A/B-box with an electronic switch and also capable of distributing 9 volts to other pedals by an out-jack.
I opened it up just to see how few components there must be in this sort of pedal, mainly air..
But what I saw nearly made me fall of my chair  , there was components in there enough to make a good overdrive, resistors, ICs, transistors you name it�
Why??? Is the electronics some sort of stabilizing for the power coming in?? And if, why, I think PSA (recommended for this pedal) gives very stable and clean power.
Well, what�s the deal�
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thedarxide
Bronze Member
81 Posts |
Posted - 01/18/2006 : 10:31:08
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I assume most of the components are to cope with the two different modes.
Incidentally, I've just purchased the same, sans daisy and PSU. What can I use for a substitute?
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visserman
Platinum Member
1072 Posts |
Posted - 01/18/2006 : 12:26:21
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| LS-2: You get two loops instead of one, plus a volumecontrol for each loop as well, nice touch!! |
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thedarxide
Bronze Member
81 Posts |
Posted - 01/18/2006 : 13:44:39
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quote:
Originally posted by visserman
LS-2: You get two loops instead of one, plus a volumecontrol for each loop as well, nice touch!!
keh? |
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visserman
Platinum Member
1072 Posts |
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thedarxide
Bronze Member
81 Posts |
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visserman
Platinum Member
1072 Posts |
Posted - 01/18/2006 : 15:16:53
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That can happen to all of us eh? To be honest, I misread very often details in posts as well, then I post with a reply which is..................... guess you know what I mean eh??!!
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stinkfoot
Silver Member
Sweden
181 Posts |
Posted - 01/19/2006 : 02:45:22
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Looking into a simple overdrive pedal like the SD-1, you'd be surprised to learn how few of the components actually have something to do with the overdrive... I'd estimate that at least 60% of the stuff in there has to do with the switching, while a further 15-20% is input/output buffer stages. This leaves just 20-30% of the components doing the actual overdriving (and tone/volume controls).
The PSM-5 acts as a buffered loop pedal, so I'd imagine it has at least four buffer stages in it (main input and output, send and return). Then it probably has two separate mute sections (one for the signal coming straight from the input buffer stage, and another for the signal coming from the return jack), which in turn are controlled by a standard flip-flop circuit, as used in all Boss/Ibanez pedals with electronic switching. There might also be a third mute transistor to kill the signal to the send jack, but I'm not sure about that one. In any case, it is quite a lot of circuitry for the relatively simple task it performs...
The power section is a lot simpler, though - the power out jack is simply wired in parallel to the power in jack, and there's no extra regulator or filter circuitry involved.
/Andreas |
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Goran
Double Platinum Member
Sweden
2203 Posts |
Posted - 01/19/2006 : 06:54:46
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Andreas are you really sure power in and out is wired in parallell??
I mesured the positive and negative terminals on my PSM-5, the positive has zero resistance but there is no connection between the negatives (center pins), the pedal having no power. |
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stinkfoot
Silver Member
Sweden
181 Posts |
Posted - 01/19/2006 : 08:23:17
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I'm fairly sure - not having opened a PSM-5 up to check, mind you. Did you measure with plugs in both jacks? In the more modern "power out" pedals (TU-2, LS-2 etc), they are wired in parallel, and with some elaborate switching (although the center pins are simply wired in parallel, without any switching). I doubt it'd be any different here. But I've been wrong before...
/Andreas |
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Goran
Double Platinum Member
Sweden
2203 Posts |
Posted - 01/19/2006 : 08:34:19
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Well, stupid as I am I hadn�t any plugs in� . Will check when my job is over, but I�m pretty sure you�re right. |
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stinkfoot
Silver Member
Sweden
181 Posts |
Posted - 01/19/2006 : 14:43:28
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Don't be so sure...  As I said, in the newer pedals the center pins in both jacks are connected directly (according to the schematics, at least), so there should be contact even without plugs in the jacks. The sleeve connections are switched, so there it might matter.
But do try it, and also try sticking a plug in the input jack. Boss sometimes likes running the adapter jack negative past the input jack (to turn power on/off), in which case you need a plug in that jack to connect it to ground. The two jacks might not be grounded to the same point, which would explain why they didn't register on the DMM. For instance, if the power input negative is grounded at the input jack "ring" connection (when a mono 1/4" plug is inserted in that jack), the power out jack could be grounded right on the circuit board.
/Andreas |
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Goran
Double Platinum Member
Sweden
2203 Posts |
Posted - 01/20/2006 : 07:13:35
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| Stinkfoot was right, of course, when connecting a plug to the output marked "Amp" there is zero resistance on the positive poles (pin to pin). |
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Inside PSM-5
