Is it possible to make one voltage source go two ways? - Page 1
Forum section: electronics / beginners

author: TRS-90
author_rank: Regular Contributor
timestamp: August 30, 2016, 08:30:29 pm
content: I'm trying to figure out how to make one potentiometer control two seperate amplifier chip's volume.They are not connected to each other.Is this possible?

author: MK14
author_rank: Super Contributor
timestamp: August 30, 2016, 08:36:32 pm
content: One way is to use special potentiometer, called multi gang potentiometers (or dual gang). These are multiple ones which turn together. It saves getting into significant complexity, by trying to use a voltage to control a number of different things. Which can be done, but it can get very complicated, having to use voltage controlled gain stuff.

author: Maxlor
author_rank: Frequent Contributor
timestamp: August 30, 2016, 08:39:45 pm
content: What you need is a ganged potentiometer, something like this:http://www.mouser.ch/ProductDetail/Alpha-Taiwan/RV122F-20-15F-A100K-0072/?qs=sGAEpiMZZMu7u4aXTvZ%252bjx1nJbHWsEkbYq3jcGbMJop5VWZhAcKCRA%3d%3dThey works like 2 potentiometers that are controlled by a single knob, but are otherwise isolated from each other. You can get them in configurations other than 2-gang too, Mouser lists up to 8-gang ones.

author: TRS-90
author_rank: Regular Contributor
timestamp: August 30, 2016, 08:41:11 pm
content: Okay.I'm just seeing what to do if the thing I'm trying to control only has one voltage coming out to put in to the potentiometer in the first place.

author: wraper
author_rank: Unknown
timestamp: August 30, 2016, 08:42:50 pm
content: Unless you want to complicate it, you need stereo potentiometer. If you want to use mono potentiometer, as minimum, one additional specialized IC would be required.

author: TRS-90
author_rank: Regular Contributor
timestamp: August 30, 2016, 08:49:11 pm
content: Basically I need a potentiometer with one in and two outs.one volume voltage, two amplifier chips.

author: MK14
author_rank: Super Contributor
timestamp: August 30, 2016, 08:56:50 pm
content: Quote from: TRS-90 on August 30, 2016, 08:49:11 pmWhat problem are you expecting ?Are you worried that the signal is too weak ?Or are you worried that the two amps will fight each other ?Maybe you are missing many details here, so I can't understand what is going on.Often a voltage can be split up, as many times as you like. But it depends on the exact details, which I can't seem to find in this thread.

author: TRS-90
author_rank: Regular Contributor
timestamp: August 30, 2016, 09:01:18 pm
content: There is an edge connector that I'm pretty sure has a voltage output on it because two pins are that are next to each other are connected.I'm assuming that is the only edge connector voltage I will be able to use and I need it for volume control.This means I have to control two things with one voltage source.I just don't know how to make two voltage sources out of one, that's all.

author: MK14
author_rank: Super Contributor
timestamp: August 30, 2016, 09:05:51 pm
content: Quote from: TRS-90 on August 30, 2016, 09:01:18 pmThe two amps. How exactly will you be connecting to them, and what sort of signals/voltages (inputs to them), do we need to control them ?Most amps, have their own built in potentiometers (volume control or remote control signals), to control themselves. So it is not that easy to control them via an external voltage source. But there are ways of doing it.EDIT:Or it might be more practical to attenuate the input signals (adjust their volume), before they enter the amps (but that method may create more stray noise and maybe distortion, depending on your setup). It depends on your exact setup. I still can't really see the overall setup you have/want.

author: TRS-90
author_rank: Regular Contributor
timestamp: August 30, 2016, 09:18:37 pm
content: The previously mentioned edge connector has pins that go to the volume control on the amps.The amplifier I dealing with is a TDA7052A-A 1 watt amplifier with DC volume control.And I just realized that I'm REALLY DUMB, the both volume control pins are connected to each other.But how do you split one voltage to go two ways in any situation?Just for future reference.

author: MK14
author_rank: Super Contributor
timestamp: August 30, 2016, 09:32:12 pm
content: Quote from: TRS-90 on August 30, 2016, 09:18:37 pmFor future reference.(Example) If you had a 6 volt battery, so the (output if you like, plus terminal +) voltage was 6 volts from it. You could connect that 6 volt line to as many things as you like, as long as they don't in total, use more amps (current) than the battery is suppose to supply.Instead of the 6 volt battery, it could have been your volume voltage level signal, etc etc.

author: TRS-90
author_rank: Regular Contributor
timestamp: August 30, 2016, 09:36:23 pm
content: So you literally just hook up more wires to the source?I did not think it would be that simple.Thanks!

author: MK14
author_rank: Super Contributor
timestamp: August 30, 2016, 09:37:33 pm
content: Quote from: TRS-90 on August 30, 2016, 09:36:23 pmYes, it is that simple!

author: Brumby
author_rank: Unknown
timestamp: August 31, 2016, 04:58:46 am
content: Quote from: TRS-90 on August 30, 2016, 09:36:23 pmYep. If they are controlled by a simple DC voltage, it is that simple.If you were directly controlling the audio signal itself, however, then you would be back into the problem area (but one that is easily solved)

author: Zero999
author_rank: Super Contributor
timestamp: August 31, 2016, 08:43:35 am
content: The TDA7052A looks like a nice IC. It's a shame only the SOIC package sill seems to be made which has a power output of 0.5W, rather than 1W of the DIL package.Yes, the gain control inputs can simply be connected together and the voltage to them both varied.

author: TRS-90
author_rank: Regular Contributor
timestamp: September 05, 2016, 09:49:18 pm
content: I now have another small problem.How do I combine to signals from two separate wires to one wire that carries both?Something that normally uses two separate signals on two separate pins use the both on one (i.e. a TV using horizontal and vertical sync on one wire of a special connector instead of two).Is it as simple as hooking the wires together? Or is it more complicated?

author: Zero999
author_rank: Super Contributor
timestamp: September 05, 2016, 10:17:50 pm
content: You need a mixer, which can be passive (just resistors) or active.In a passive mixer there's always some voltage loss: a minimum equal to the number of signals combined, so for two you're looking at half the voltage.In an active mixer an amplifier is required so there can be voltage gain but a separate power supply, other than the signals is required.

author: TRS-90
author_rank: Regular Contributor
timestamp: September 05, 2016, 10:30:50 pm
content: Well what I'm dealing with is a CRT monitor I'm trying to solder wires to (it has a proprietary edge connector) and there is a pin labled "composite signal" not composite video signal just composite signal and there are no HSYNC or VSYNC connectors on the board.How do you make a passive mixer?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 06, 2016, 04:28:26 am
content: If I might gently bring this to your attention,http://xyproblem.info/Please, for your own sake, and for the sake of our sanity... tell us what you want to do, first!Tim

author: Brumby
author_rank: Unknown
timestamp: September 06, 2016, 05:04:04 am
content: Quote from: TRS-90 on September 05, 2016, 10:30:50 pmIf you see a pin labelled..."composite signal""composite video signal""composite video"- or even just "composite" on a piece of equipment that obviously processes a video signal... then you will be dealing with the same thing.But this is, perhaps, THE most important recommendation I would support:Quote from: T3sl4co1l on September 06, 2016, 04:28:26 amThe specifics of your answer to this will allow us to give you more direct assistance. Otherwise we are just guessing - which can add a lot of frustration and confusion ... on both sides.

author: TRS-90
author_rank: Regular Contributor
timestamp: October 21, 2016, 11:09:41 pm
content: I need to make HSYNC and VSYNC into CSYNC for a monitor.My video source has seperate sync, my receiver has composite sync.Monitor has vey little information available on it.

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: October 23, 2016, 05:03:30 am
content: If you have an output that says "Composite" or "Composite video" then CSYNC is included in that composite video. If you want composite sync with video then just using that output may be all you need.However, if you need just a CSYNC signal, which has no video included then combining VSYNC and HSYNC is NOT a trivial exercise. It requires some involved logic and timing circuitry to get it right. That circuit will also be different depending on whether the video in question is NTSC, PAL, or analog HDTV or what.Just putting the two through an XOR gate and inverting the output and using that may get you close but it still will not be correct and the resulting picture will have bends and wonks in it but if all you want to do is get an idea of the picture it may be good enough in the short term.