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For those of you who use oscilloscopes for car audio: Can you describe the proper methods and procedures of checking voltages of audio components(amplifier level setting, rcas, etc.) as well as proper settings to view the waveforms? I just bought an O-scope and have used one in my electronics class, but for different measurments... Thanks!
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Well to set levels on the HU, EQ, crossovers, etc I have a RCA jack that terminates into two wires to connect to the oscope. To check the HU output I just disconnect the RCA from the EQ and plug it in to my adapter. To level set the amps I disconnect the speakers and hook the scope up to the outputs of the amp. For the settings I use the voltage setting that will show the waveform the largest without cutting off any of it, and the time base setting that will show as few cycles as possible while still showing at least one positive and one negative wave.
Posts: 2575 | From: GA | Registered: May 1999
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Cool.. Ok, JC or anyone else, can you explain where to get a BNC adapter to female RCA, or how to make my own for setting component gain levels? If so should I make one for each channel or use a Y adapter? Also, if so would I need to wire a 1 meg resistor in line with the + lead since the Oscope leads have switchable 1 megohm(x1) and 10 megohm(x10) input impedence? Any help appreciated!
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I just wired up a Female RCA plug to 2 wires and connected those to the alligator clips on the BNC cable. I ran one channel at a time, since the 2 waveforms would be so close together I wanted to catch clipping as early as possible. I didn't use resistors since the input impedance is so high already, I think when you switch the lead to 10X it just adds a 9 Megohm resistance to the internal resistance. But when it is in the 1X posistion I don't think the leads add any noticeable resistance. If you want to make some permanent leads I would get a single BNC to BNC cable, cut it in half put a female RCA on one half, and some terminals to check amplifier outputs on the other half. Where did you get your scope and if you don't mind me asking how much was it?
Posts: 2575 | From: GA | Registered: May 1999
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It's a Beckman Industrial 20 Mhz I got from EBAY last week for $162.00+ Shipping. I have hooked my home theatre speakers up to it and done the probe check the manual describes, so I know it works well.. Thanks for the help JC, I am still learning!
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I'm always willing to help, if you have any questions post it here or email me and I will try my best to help out. An oscope is a purchase I plan to make as soon as I get a job 1. Amps 2. Scope 3. PcRTA
Adapters designed for what you want to do are available from Parts Express &/or MCM Electronics. I got similar ones from there. I also do measurements like the above. You will need a cd with tones recorded full output....actually I recommend the CD (cd102 I think) from autosound, it is designed for setting gains with some overlap built in for opitmal output / SQ. Works well.
I'm not in the this forum often, so email me if you have questions.
------------------ Jeff President, Sweet Sounds Inc. Team Sweet Sounds is gathering information....all are welcome Authorized Dealer for Cerwin Vega, Image Dynamics, Clarion Pro Audio, Stinger, Hifonics, Digital Designs, Memphis and more.....
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Another thing you may need for bench use is a tone generator. Sounds like you got a good deal on the scope. Beckman makes some nice stuff....what else do ya plan on doin with it?
------------------ E=MC2...+/- 3dB Member of N.S.P.L. since Day One 6 Vega 15's, 3 U.S.Amps USA-400's, 154+dB...and Hyraulics....can you say "Ghetto Cruiser"?
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Yea, I plan on getting a tone generator too, also a frequency counter or a good fluke DMM with a counter built in, later distortion analyzer, benchtop power supplies, etc.. Right now I want my scope for level setting betwen components, and checking output waveforms as I do a few installs here and there, as well as my plans to get back into competition shortly. Also I am getting into building small circuits in my spare time(which isn't very much lately ) for fun. Thanks Vega, I did get a pretty good deal on the scope. $180 shipped and all. I am very pleased with the Beckman, I just need to buy another test lead and build my RCA plug in leads for it.
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saw a porable voltmeter/o.scope at parts express , looks pretty cool, 200 bucks , you think this is relyable??
Posts: 732 | From: Reston, VA | Registered: May 1999
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What do you set up for inbetween the componets? I Have a good knolage of test equipment when I'm using it for trouble shooting in school. I have yet to use them in car audio though. I have in the pass just set up gains by ear, but if I new what to look for when hooking up to the out puts of my EQ's, amps, and other equipment I will. Like for instance what dose the output look like on the O-scope when the amp is cliped. Are you setting up the RCA outputs of the various peices of the system to mach the inputs fo the next? Also setting the gains on the amps as the last step to get max output befor cliping at the same tone you use for burping?
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equipment I will. Like for instance what dose the output look like on the O-scope when the amp is clipped. Are you setting up the RCA outputs of the various pieces of the system to mach the inputs of the next? Also setting the gains on the amps as the last step to get max output before clipping at the same tone you use for burping?
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When setting the gains in a system you want the maximum unclipped output from each piece of equipment. So first you find the volume where you get the most output from your headunit without clipping. Then with your headunit at this volume you find the max output without clipping from your EQ, then your crossover, then your amp.
The clipped sinewave is pretty obvious when you see one. It will look like a sine wave with the tops and bottoms flattened.
I don't know about that portable scopemeter, that company makes decent kits but for 200 dollars and the size of the display I can't imagine that it would be too precise. For level setting it will probably work.
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Buzz...why the distorion meter and counter?...do ya do alot of SQ or SPL installs? One of the main things we use is a VERY heavy duty power supply. A company we use is Tripp-Lite. These things are used to test the BIG amps like U.S.Amps USA-400's and MMATS D300HC's...remember, a good bench is like a car, without power..you really have nothing. All the adaptors you need can be ordered through Parts Express or MCM. I prefer MCM for better customer service and stock. I think someone mentioned that a clipped wave will have a flattened top and bottom...which is correct. Another thing to look for as ANY non-curves in the sine wave. They could be due to DC spikes, or power probs.
Posts: 9036 | From: Linden, NC | Registered: Jan 2000
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------------------ Jeff President, Sweet Sounds Inc. Team Sweet Sounds is gathering information....all are welcome Authorized Dealer for Cerwin Vega, Image Dynamics, Clarion Pro Audio, Stinger, Hifonics, Digital Designs, Memphis and more.....
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Generally, no I don't. If the amp has a rating of taking .5 - 5 Volts input I don't measure the crossover output and stop turning it up at 5 Volts. If you exceed the maximum input voltage that a EQ or crossover can handle, the output will be clipped regardless of where the output level of that unit is. For example say you set the HU to max output and the EQ to max. When you go to set the crossover levels the output is clipped no matter where the output level is set. In this case you will have to go back to the EQ and turn down the output level until the crossover output is unclipped.
Posts: 2575 | From: GA | Registered: May 1999
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I looked that CD up a few days ago, it's not 102, I believe it's 104.
------------------ Jeff President, Sweet Sounds Inc. Team Sweet Sounds is gathering information....all are welcome Authorized Dealer for Cerwin Vega, Image Dynamics, Clarion Pro Audio, Stinger, Hifonics, Digital Designs, Memphis and more.....
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Thanks jeff! Do you have any idea about the connectors I need for amp/eq/line driver/etc level setting? I think I need BNC-RCA, which I haven't been able to find.. I have a Parts Express catalog, and MCM electronics and havent seen one anywhere. Or am I overlooking something? I have parts to build my own, or is there a different type of connector I should use? Thanks again!
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