castlewalls Posted November 13, 2013 Share Posted November 13, 2013 hey ya'll, i'm in the design process of building a combo amp that'll have two 10 watt practice amps in a cabnet. Each amp will have it's own internal speaker cabs (left & right cabs each with an 8" & a 10" speaker) plus an internal center speaker cab housing a 10" dual coil subwoofer speaker. I'm looking to add a VU meter to each 'side' cab (for the 'looks cool' factor, plus there will be lights as well) and got some from a cassette deck but i'm sure there will be a needed circuit to run the meters off the speakers. Any idea where I can find a schematic for such a thing? Thanks, -Jim My roughly scale design: http://home.comcast.net/~castle.walls/scamp/index.html What does not kill you makes you stronger if you cook it properly. Link to comment Share on other sites More sharing options...
CouchBed Posted November 14, 2013 Share Posted November 14, 2013 Don't know about the VU meters, but I must admit that your whole design is very different from anything that I've ever seen. Cool idea. Just out of curiosity, how do you connect the woofer to both amplifiers? Link to comment Share on other sites More sharing options...
castlewalls Posted November 14, 2013 Author Share Posted November 14, 2013 it's a dual coil speaker from a home stereo system subwoofer. it's a real sub, not just a speaker you normally see on a home system where only one side (usually just a single rca cable with either the left or right stereo side bass signal is sent to a normal 'sub' speaker cabnet) is plugged into it (in effect, they lie). i'll feed both amp speaker outputs to it as well as their dedicated 'side' cabs speakers. What does not kill you makes you stronger if you cook it properly. Link to comment Share on other sites More sharing options...
CouchBed Posted November 14, 2013 Share Posted November 14, 2013 Oh alright. Hope you can find what you're looking for, and hope it works! Best of luck. Here's an idea that I just thought of that you might want to consider: I think it'd be cool if you designed this guy with the two side cabs removable, so that if you're playing somewhere, and you want to get a better stereo effect, you can remove the cabs, plug in a 1/4" to both of them, and set them farther apart to create more separation of the two channels. Just an idea. I'm not sure how you could make the side cabs removeable... you'd have to design some sort of latch system or something, but it seems like you're pretty creative! Link to comment Share on other sites More sharing options...
castlewalls Posted November 14, 2013 Author Share Posted November 14, 2013 already thought out,...;>) plus I have thought of the clear plexi version (with cool interior lights) & the removable head version (as well as side cabs) & adding a collapsible rear handle (like on a travel suitcase) with built in rear wheels - smaller but similar to an Ampeg cab & some rubber feet up front. I've tons of ideas but can do only a little with cardboard & no money for the wood & drumshell (yet...:>) btw, i'd use magnets in key places to hold the cabs to the main sub/head assembly (Star Trek access hatch inspired that...;>) What does not kill you makes you stronger if you cook it properly. Link to comment Share on other sites More sharing options...
CouchBed Posted November 14, 2013 Share Posted November 14, 2013 Okay. Good luck! Link to comment Share on other sites More sharing options...
Dr. Ellwood Posted November 14, 2013 Share Posted November 14, 2013 Locate the output circuit on your amp. This circuit will be the connection between the amplifier and the output jack, so the last set of wires you see running to the output are the cables you are looking for. On a unit that is built into a speaker, the circuit is the connection between the speaker itself and the amplifier, rather than the output.5 Find the last two wires leading directly to the speaker output. One will be grounded, and the other will be live. Connect the VU meter to the amplifier by connecting the live wire to the terminal marked with a negative sign and the ground wire to the terminal marked with a positive sign. Connect the output from the meter back to the speaker output, connecting the positive output to the ground and the negative output to the speaker. http://www.thestringnetwork.com Link to comment Share on other sites More sharing options...
castlewalls Posted December 1, 2013 Author Share Posted December 1, 2013 Sorry for the late reply, bad back & lotsa pain....;>) Doc, can you please clarify your description with a dwg? Are you saying to just put the meter in series between the amp & speaker or parallel across the speaker wires...? Will the meter just be pegged all the time with any amount of signal to the speaker? I'd like the meter to 'register' the volume (more or less) as with a meter on a cassette deck. What does not kill you makes you stronger if you cook it properly. Link to comment Share on other sites More sharing options...
Dr. Ellwood Posted December 1, 2013 Share Posted December 1, 2013 http://i16.photobucket.com/albums/b48/ellwood1/VUmetercircuit_zps8209392a.jpg Yes it would be pegged if you didn't use a Op-Amp in the circuit http://www.thestringnetwork.com Link to comment Share on other sites More sharing options...
castlewalls Posted December 2, 2013 Author Share Posted December 2, 2013 Thanks for the schematic but I have some questions. Where does the B+ go to? I assume (my wife says i'm good at that....;>) that the inputs are for the positive sides of each speaker out from the two amps but there's only one common ground...? Here's my layout: http://home.comcast.net/~castle.walls/lassiteramp.jpg What does not kill you makes you stronger if you cook it properly. Link to comment Share on other sites More sharing options...
Scott Fraser Posted December 2, 2013 Share Posted December 2, 2013 Where does the B+ go to? B+ is the positive output of the power supply. Scott Fraser Link to comment Share on other sites More sharing options...
J. Dan Posted December 9, 2013 Share Posted December 9, 2013 I don't think we know enough about the "VU" meter - there are lots of different versions out there. Just because it says "VU" meter doesn't mean in actuality that the input is the same as the earliest VU meters, which were actually ammeters with a range of 200 microamps. More modern versions could have been voltmeters, ammeters, strain gauge inputs, etc. to work with the tape deck circuit, but been labeled as a "VU" meter. Can you verify that it is a standard VU meter and not something else? How old was the tape deck? Theoretically, given the peak output of the amp and the speaker impedance, you ought to be able to come up with a simple passive resistor network if it is in fact a VU meter. Dan Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth. Link to comment Share on other sites More sharing options...
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