If that doesnt resolve the problem, obtain a schematic for the circuit, connect. Tube amp theater how to test amplifiers via oscilloscope. For this purpose, take avo meter or digital multimeter and select resistance in avo meterrotate the knob to the. We will also check that the controls are working as expected. The setup has been the same over all those years, until last week. A guitar amp on 10 should makes its full 50 whatever watts with 20mv input. The following is an excellent article on biasing using an oscilloscope, posted by tom crocker to alt. One jig that i made was a way to connect to the various kinds of output connections to an amp. Using an oscilloscope to test a guitar amp my les paul forum. I am 63, and semiretired as a computer tech and sysadmin, and might like to explore additional income from testing and repairing tube amps as my business continues to dry up as i get older. The primary things i need are a good scope, multimeter and signal generator. How the hantek manages to pack all those features in a box smaller than a lunchbox is beyond me.
After years of procrastination im hoping ill get motivated enough to take on some guitarkeyboardbass amp repair as a part time job at home. However, when i attached the cable that goes to the guitar amp to the probe for the scope, nothing happened. Initial tests wont use a dummy load, but in order to test the amplifier to deliver power, you have to have a load. My previous oscilloscope was a crt scopex from the last millenium. The beat becomes slow and will disappear when it is tuned. Virtins sound card oscilloscope free version download for pc.
Early tube amplifiers often had positive feedback regeneration, which could increase. We are more interested in testing amplifiers under clean fullrated power than at power levels which can be seen as clipped signals on a crude oscilloscope. Beware of cheap meters that are rated for 400v or less. A tube amplifier chassis contains lethal high voltage even when unpluggedsometimes over 700 volts ac and 500 volts dc. For example, an oscilloscope for use in testing amplifiers will fit on a workbench but perhaps not when its used for testing vehicles. The circled figures indicate the points at which oscilloscope checks may be made and the order in which they should be carried out. I am a bit of a novice with oscilloscopes, but i know the basics. Oscilloscopes here you will find a collection of oscilloscope software for analyzing digital signals including audio and music. Assuming there is a one horizontal line across the screen of the monitor and you have checked the surrounding components at the vertical ic and even replaced the vertical ic and still could not find. For example, if you want to verify that the output from a pin of an integrated circuit is. By the way, doing a spectrum analysis of a tube amp versus a solidstate amp tells you all you need to know about why tubes sound different from solidstate. The basic procedure for testing an electronic circuit with an oscilloscope is to attach the ground connector of the scopes test lead to a ground point in the circuit, and then touch the tip of the probe to the point in the circuit that you want to test. I have had many requests for testing amplifiers using a dummy load and oscilloscope.
They make no mention of using oldfashioned test equipment like a vtvm, a dummy load, or even a signal generator. I have performed bench testing on amplifiers both tube and solid state ever. How to signal trace fender champ guitar amp oscilloscope stage. Using an oscilloscope to test a guitar amp page 4 my. In some cases a scope or spectrum analyzer does not have the range required to measure very small noise levels. Just the same as testing a real valve amp, we apply a pure sine wave and check the resulting signal at various stages in the design. The important of oscilloscope electronics repair and. Older style oscilloscopes display the wave on a cathode ray screen whereas a digital storage oscilloscope features a. Tipd147 noise measurement postamp for oscilloscope or. To check if the resistor is in good condition or broken, we use a multimeter.
Under normal troubleshooting and repair i do not use oscilloscope. Going in excess of 45 mills in the typical guitar amp can stress the tubes or power transformer to the point of premature failure. Mellowhead is a guitar amplifier and fx plugin, that replicates the sound and feel of classic guitar tube amplifiers. I will only use scope when i want to measure the waveform output from the ic. When you have answered these two allimportant questions, you can make the first decision in choosing the right audio oscilloscope analog or digital. The data source can be selected in the windows mixer microphone, linein or wave. A sine wave generator can be handy for testing continuous output power and again for verifying operation and fault finding, but i find that the best general test signal generator for a guitar amp is a guitar. Alarms, coupled with mask limit testing, help create a powerful. Randelli asked if i would write a tutorial that explains how an oscilloscope can be used to test and troubleshoot an amp. I only know, that i wont need a scope with digital storage, cause im only going to be reading sine waves potentially clipping or turning into square waves, in real time. This noise measurement postamp boosts the output noise of the device under test dut to allow for measurement with standard test equipment. An oscilloscope will be able to show you the signal from a signal generator and how the signal is modified by the amplifier. For measuring software plugins, the playbackrecording software.
Mention anything about biasing your output tubes utilizing an oscilloscope, and the rest of your day will be spent listening to complaints about how wrong it is to do so. Oscilloscopes measure the changing voltage of an electrical signal over time, and display the signal as a waveform in a graph with sweeps of voltage on a vertical y axis, and time on a horizontal x axis. In order to test our software amp, we will use an oscilloscope to probe the virtual amp at different points in the circuit. Tube guitar amplifier oscilloscope diagnosis overview. Solid state guitar amp diagnostic using signal tracing duration. An idiots guide to oscilloscopes many internet tube gurus will vicariously demonstrate their prowess servicing a vintage tube guitar amplifier. Previously i used an audio signal generator, a distortion analyzer, and an oscilloscope. Ymec software guitar tuning by xy mode of oscilloscope. Joined feb 28, 2014 messages 350 reaction score 247.
Amplifier software free download amplifier top 4 download. I have performed bench testing on amplifiers both tube and solid state ever since i worked in the stereo shop 35 years ago. You have to download the program, and have flash player, but it is definitely worth it. Guitars that arent connected to an amp tend to have pretty weak. Display ch1 v ch2 soft button, and the triggered xy soft button b.
Many internet tube gurus will vicariously demonstrate their prowess servicing a vintage tube guitar amplifier utilizing nothing more than a fluke dmm. An amp simulator amp sim for short is a plugin that imitates the sound of a guitar amp. At this point the amp is biased and ready for testing. But if you just want to learn all about amp sims specifically, keep reading. That unit is a piece of service equipment for testing and calibrating equipment. I really dont want to overbuy this, and get features i wont need for this purpose. Mention the word oscilloscope to any of them, and you are answered with a sneer. If you have not been trained to work with high voltage then have an amp technician service your amp.
Oscilloscope for tube amppedal work id like to get into tube amp and effects pedal designing, and others have said their scopes were very helpful in the learning and troubleshooting process. Picoscope 4262 high resolution oscilloscope software. Guitar tuning by xy mode of oscilloscope instrument tuning 3 during a tuning of guitar, a beat is heard if the guitar sound is approached to a reference note of the tuning fork or a tuner. Unlike most of the sound card oscilloscopes in the market which search trigger event after data collection, it features a specially designed data acquisition approach which is able to monitor the input signal continuously without missing any trigger event before the frame of data is collected. Assembly manual schematic parts list tubes and applications design simulations. Typical connections for measuring rffe parameters in an rf power amp.
An oscilloscope is a device used to test the functionality of equipment that generates an electrical signal. I am in highschool and my comp sci teacher lent me his old tektronix 485 oscilloscope that he no longer uses. The pc based sound card oscilloscope receives its data from the sound card with 44. As circuit boards have become more complex, so has checking them for problems. Checking audio amplifier distortion with oscilloscope. An amplifier, electronic amplifier or informally amp is an electronic device that can increase. A smallsignal ac test current ix is applied to the input or output node. Hey don, i guess i never got a copy the first time around and then my heart sank after i read that you lost the file after putting so much hard work into it. Im doing a project in which i need to record my guitars frequency with an oscilloscope. Af amplifiers can be tested with an oscilloscope by making sequential stage checks, using a. Voltage and time measurements both seem to be right on the money and my testing indicated the actual measured 3db bandwith was around 275 mhz. Whats a good signalfunction generator for audio workamp. How to use signal generator and oscilloscope on amplifier. Learning oscilloscope basics with the rs pro 2205a20.
Since you want all the watts you paid for, and more, even when you pick lightly, this tests sensitivity. Now connect both ends of resistor with the avo or digital multimeter terminals. Debugging and testing of a vacuum tube guitar amplifier. Tube guitar amplifier oscilloscope diagnosis 1102014 7 diagnostic tests platetogrid this is the single most useful and important test of them all. Please refer to figure 2 for the wiring diagram used when performing a square wave test on a component. The oscilloscope contains a protocol trigger capable of decoding the rffe signal and triggering the acquisition of the rf signal from the power amplifier. Virtins sound card oscilloscope is a powerful pc based virtual instrument software. As a starting signal for amp testing, i set my signal generator default to 1khz, 150mv. When its finished i test all the voltages before proceeding.
The custom probes feature allows you to correct for gain, attenuation, offsets and nonlinearities in probes, sensors or transducers that you connect to the oscilloscope. Software effect processor software sampler software synthesizer. Basic amplifier testing with an oscilloscope audiokarma home. You can test a lot different things with that combo and get a good feel for what the amp is doing and is capable of when twiddled or cranked. A comparison between a wellknown guitar tube amplifier and two. Useful for looking at the harmonics of an amplifier output stage. Older style oscilloscopes display the wave on a cathode ray screen whereas a digital storage oscilloscope. I am repairing and upgrading guitar and hifi amplifiers, and i want to take it to the next level, and get myself a scope for that. Audioholics amplifier measurement standard audioholics. Tube amp theater how to test amplifiers via oscilloscope by dlab.
Troubleshoot an audio amplifier with an oscilloscope. On solid state amps it doesnt matter but tube amps need to have a load connected or the. Hi don can you please send me the info on using a ocilliscope to repair a guitar amp jeff. You can give your opinions on that too if you want.
Today i glanced at my electric guitar, and i thought it would be cool to see its waveform on the scopes display. I just started building some really nice class a diy amplifiers which to me sound fantastic. Distortion analysis toolkita software tool for easy analysis of. My unit arrived yesterday and everything seems to work as advertised.
A good multimeter that can withstand plate supply voltages is a must. Tube guitar amplifier oscilloscope diagnosis 1102014 6 steps i follow when i assemble an amp i always start with the power supply. I already own and have read dave hunters the guitar amp. Using an oscilloscope to test a guitar amp page 3 my. The low current has an eye that is too small to fit over most alternator cables and the high curent clamp was delivered with a. World war ii rushed the further development of oscilloscopes. You can use an oscilloscope to test your audio amplifier for blown fuses, improper biasing, signal distortion, and other sources of poor sound fidelity. Using an fft spectrum analyzer to test audio amplifiers. Im looking for a good basic oscilloscope for audio testingtube biasing.
It is probably the most widelyused test instrument because it can be. When finished, i again test all voltages without tubes installed. Failure of an amplifier, or any other device, to perform in this manner is easily visible with an oscilloscope. One channel of the adc216 was connected via a x10 scope probe to the power amplifier speaker output connectors. Oscilloscope for audio testingtube biasing gearslutz. Drop an audio file in the application and watch the waveforms. However, many faults can be tracked down by checking connections and performing a visual inspection. Suggest a good oscilloscope tube amp information, guitar. You take a screened lead and connect the screen to the ground and the live to the red output, and solder a 14 mono trs jack on the other end and plug it into the guitar amp. Later i added an audio analyzer and a spectrum analyzer. This category ranges from sophisticated highend software to more eye candybased applications. Audio amplifier testing a typical high quality audio amplifier circuit. Refer to figure 7 to view the diagram for square wave testing. With the autumn quarter well on its way for high school and college students, now seems like a great time to introduce a few phenomenal oscilloscopes by hantek.
Never touch the amplifier chassis with one hand while probing with the other hand because a lethal shock can run between your arms through your heart. How do i connect my electric guitar to my oscilloscope to. The test signal is induced by an electromagnetic coil placed near the pickupundertest put, with this signal generated by the software on the. Finally, reserved registers improve the efficiency of hardware and software. An oscilloscope can display the shape of an input signal wave, enabling you to observe waves and test electrical currents. Ive got a line on an hp54600a with a warranty from the seller. Although our tabulated results are typically published at 0. The need for servicing radar during the war set the stage for wider use of the oscilloscope after the. Run your guitar through one of these plugins and youll have hundreds of iconic guitar tones at your fingertips. By trying out several different sets of operating conditions in the computer i could eliminate hundreds of possibilities without playing with electricity. Next up is the power amp which includes the output transformer. The frequency range depends on the sound card, but 2020000hz should be possible with all modern cards. Oscilloscope test signal level telecaster guitar forum.
673 191 1609 1120 1190 587 1236 478 583 234 488 915 925 751 68 1544 936 1086 848 176 673 927 421 15 555 332 190 1492 607 703 155 914 444 213 1269