Hey guys.
I want to build a fully retro pedal using old board, caps, resistors and wires from 40's/50's. All of the caps I have found in wax paper made in Australia and measure out as I need them too! They are MASSIVE suckers though for say just 10n. Even the small plastic ones for the pF range are realllllllly big.
Due to practical limitations of the time in caps, it will be hard for me to find a decent size output cap (1uF+). I have an electrolytic that's 8uF (labeled MF) but it's way too big. Would there be any unforeseen consequences in leaving it out that I am not seeing? Any following pedal or amp should have an input cap to block DC. We mostly use output caps for good practice and good measure don't we? Or to cut bass maybe in the case of a simple fuzz or something.
I'd like to know what you think...
My guess would be that you'd get MAJOR popping with bypass switching. If this is so retro that it doesn't have a switch, then that's not an issue, but can't you just go to a flea market or thrift store and get something you can pluck a cap from?
There might be some exceptions to the rule, but in my experience no output cap results in a very loud pop.
Quote from: darron on March 31, 2011, 06:57:56 PM
Would there be any unforeseen consequences in leaving it out that I am not seeing?
Nope. Just ugly - but clearly foreseen! - ones.
QuoteAny following pedal or amp should have an input cap to block DC.
Nope. Lots of guitar amps have DC coupled inputs, right to the first triode.
QuoteWe mostly use output caps for good practice and good measure don't we?
Nope. We use output caps to block the output DC levels. Not blocking them lets the output DC charge up whatever is connected to the output when the effect is switched in, and so any caps at inputs following the output get charged up to the effect's DC level. Then when you switch the effect out, that input cap on the other effect has to be discharged through whatever is connected when the effect is switched out. That makes for a big pop. Then when you switch the effect back in, the previously charged input cap in whatever follows the pedal with no output cap has been discharged, and now gets popped again as the DC from the pedal output has to charge it back up. Another big pop.
Retro for fun is a good aesthetic goal, but leaving off an output cap is not something that's going to work well with bypass switching.
you could use a modern one but hide it :icon_twisted:
Quote from: CynicalMan on March 31, 2011, 07:52:13 PM
My guess would be that you'd get MAJOR popping with bypass switching. If this is so retro that it doesn't have a switch, then that's not an issue, but can't you just go to a flea market or thrift store and get something you can pluck a cap from?
i haven't worked out the switch yet. a 3pdt would look too modern. a car dip switch would be cool but finding one in a dpdt is the problem...
no market sort of comes to mind with 40's/50's gear to pick parts from. even if i find one it may be way too big to fit. i'm already way above a 1590b hammond enclosure...
Quote from: blooze_man on March 31, 2011, 08:10:33 PM
There might be some exceptions to the rule, but in my experience no output cap results in a very loud pop.
switching isn't something i clearly overlooked. i was thinking about running performance i guess. clearly with a switch and no cap there will be a sudden change in potential. a leaky cap is normally the first thing to test for a pop. DUH!
thanks. might have to run the biggest caps i have then, but they are only 50n... such a shame...
Quote from: diemilchmann on March 31, 2011, 10:51:59 PM
you could use a modern one but hide it :icon_twisted:
that is a very serious consideration.... I think in one instance I might put a 22uF electro under the board and not in a spot where the legs would be visible... maybe a 1uF MKT for hte output. i can live happily with that i think!
@R.G. Keen
I was under the impression that most preamps were DC decoupled, so that's a very good thing to know. when i meant that we mostly use caps for good measure, at the time i was thinking because the next device will almost certainly have an input cap, so the signal would run straight from one cap through the next. my mind didn't even consider the switch as a problem at the time as passively it was just a piece of wire, albeit a disconnecting one though! :icon_redface:
certainly i'll be VERY excited by the aesthetics... I have some paxolin board coming with this in mind. cotton sheathed wire etc. (everything recycled). and yummy waxy caps that I want to put in my mouth for some reason....
i have 12x CK722's also which i've never dared to use... maybe i should spare one for this.... 10 of them are the original black plastic ones (without labelling) together in 50's packing so maybe i won't open those up... they tell a nice story though. i'll do a respectable job if i use them, don't worry (: