Square Wave Testing of Audio Vacuum Tube Amplifiers

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  • Опубликовано: 27 авг 2024
  • This video was inspired by a question I was asked some time back on RUclips. It is more of a lab experiment than anything really conclusive. Square wave testing is more subjective than THD and IMD measurements but it is much simpler as all that is required is an oscilloscope and a square wave generator.Hopefully, these three examples can provide some reference for others that test audio amplifiers using square waves. Hope it helps.

Комментарии • 59

  • @dhpbear2
    @dhpbear2 6 лет назад

    Thanks for this posting. I searched for the term "square wave testing" and arrived here. I've seen several YT posters who build tube amps. Most of them test their amps with a 1 KHz-or-so sine wave. The ONLY things a sine wave will show you is non-linearity and clipping. A square wave shows frequency response.

  • @Pootycat8359
    @Pootycat8359 Год назад

    That's amazing! When you consider that the second term in the Fourier series of a square wave, after the fundamental, is three times the fundamental frequency, that Marantz has good response out to 210 KHz! I'm sure that ringing in the Fisher is due parasitics. That can be easily fixed, by adding a little negative feedback, at the right frequency. Hams deal with that problem, a lot, with RF power amps.

  • @basspig
    @basspig 12 лет назад +1

    On the 3rd amp, the ringing is still there, but is nearly invisible due to the long trace sweep cycle time. If you look at the rising edge at the same uS scale as you used for 20khz, the ringing would look the same, assuming the generator was providing the same rise time at 16hz as at 20khz. The Fisher has a lot of L-C resonances at work as evidenced in these tests. Poorly damped resonance. It also has a shorter time constant, so more LF tilt. Interesting videos. Enjoyed them all.

  • @MichaelBeeny
    @MichaelBeeny 9 лет назад +3

    Using a square wave is a useful test because it give a good guide to frequency response and the overall stability of the amplifier. Many amplifiers give a reasonable square wave into a resistive load but a loudspeaker has a very inductive load. Try looking at the same square way with an inductive load, it can be a real mess.
    One of the best amplifiers (valve) I have tested was the QUAD 11. Wide frequency response and very stable square waves. The slopping tops and bottoms at below 100Hz is due to low frequency roll off. Very few valve amplifiers go down much below 40 Hz. In those days there was no reason to go down to such low frequencys. A vinal disc has nothing to give at these frequencies in fact you need to cut such frequencies as all you would get is high levels of rumble from the turntable which in turn would give large bass cone movement and intermodulation distortion. The ringing is mostly due to the output transformer and negative feedback, or lack of it!

    • @mikesamra9126
      @mikesamra9126 9 лет назад

      Indeed Mike. I even test for the 10KHZ sq wave. I look at ringing on sq waves and any buckling because it does dictate the FR as you say and any slopes you may see in FR.

    • @gino3286
      @gino3286 6 лет назад

      Hi thanks a lot for the interesting advice. What about solid state amps ? do they have a better performance at SW test with real loads ?

  • @peshmadscientist1833
    @peshmadscientist1833 7 лет назад +3

    The space station called. They want their dashboard back.

  • @swinde
    @swinde 5 лет назад +2

    5:09 ... If you include a preamp and do this test, you can turn the "Bass" control up and down and see how it affects the 10 and 100 Hz square wave. The tilt you are showing here indicates a roll off at low frequencies. (subsonic). If you check it with a sine wave you will not see a lower amplitude. If this tilt in in the opposite direction, it indicated a boosted bass level.

  • @joralebedev8608
    @joralebedev8608 9 лет назад +5

    It'd be nice if you showed how it's hooked up for those of us trying to learn how to use our scopes.

  • @Signal_Glow
    @Signal_Glow 7 лет назад +1

    Nice to see this tests. I've recreated some of late 40's or early 50's tube microphone preamps with DC into output transformer. Most were without negative feedback and give quite similar response to Fischer. At first it made me think preamp with square response like this has nothing to do with high quality repoduction, although studio tests revealed they are some of the best sounding ones i built. Quite particular sound, squares revealed bent edges were sign of high and low pass, so most of them will go from 35-45Hz to about 18kHz +-3dB with little ringing or overshoot. Very revealing.
    Only cap coupled into output transformer gave me nice square response from like 10Hz to 50kHz or even higher.

    • @ElPasoTubeAmps
      @ElPasoTubeAmps  7 лет назад

      That is really interesting about capacitor coupling into the output transformer. Do you think this improvement if FR is due to eliminating the DC bias on the transformer? I used a very large PP OPT that will deliver over 1KW of good audio in PP circuits at 3 KV on the plates of the tubes but when I tried to use that transformer in a SE amplifier running an 833A, I found that the core saturated very quickly at about 150 mA and was pretty worthless. I would assume in a small voltage level output transformer, from a preamp, would saturate at just a few mA and have essential no inductance as I experienced with the big transformer. Do you think this is the case with your preamp, and square wave response ? ... assuming I am understanding your situation correctly.

    • @Signal_Glow
      @Signal_Glow 7 лет назад

      English is not my native language, so let me explain that i only use gapped transformers when they are DC biased. I tried really huge cores meant for parafeed and all of them saturated to a point where it could be clearly heard. Couldn't find any use in studios for such sound. This are high quality microphone preamps, with proper pad also for line signals...
      I'm sure most amps with DC into output transformer in general have more restricted bass response, if compared to cap coupled. Such transformer needs air gap to prevent core saturation, consequence of this is lower inductance and restricted bass response. So core mass has to be bigger to get inductance back, which also gives better bass. Cathode bypass cap can help with bass further, although just a bit. But this are hints when replicating old designs because we also have to have this cap of higher value, because in 50's when lytics were available, stated capacitance was actually about 100% higher, which influences bass response too. There are other things in designing gapped transformers, but i let them to my winders which are mostly people from Cinemag. Sometimes i buy vintage models, mostly when clients want them.
      There are different core materials to get desired sound with SE designed preamps, for some designs i tend to use mixture of iron or nickel where laminations are interleaved like 2x2 or so instead of classic butt stacked iron cores. Ni/Fe tends to get even better mid frequencies which is probably the main reason people still use such amps and preamps. I'm not saying butt stacked iron core in such design is bad, it just sounds different and i guess is way, way cheaper for power amps. For power levels you are talking about there are probably no cores with any nickel on the market, you might want to check for that. My preference in general probably goes towards parafeed resistor loaded designs because they tend to sound more linear, have more punch in bass, but SE has so good mids that parafeed never even came close. Very nice on vocals and also many other things. For high end Hi-Fi my preference goes towards resistor loaded parafeed for sure, especialy when amps are PP.
      I'm not surprised at all that your core saturated at 150mA because PP transformer in preamps can take about 1/10 or even less DC, compared to gapped one. And if tubes aren't well matched sound isn't good enough for studio use.
      You are right, preamps with DC biased transformer without air gap saturate even with only a few mA. Model with lowest current i built was RCA BA-2 which has 3,5mA/250V HT, every ungapped transformer saturated. Typical gapped transformer takes about 7mA if we talk about microphone preamps. PP ones in the same application can take ~0,5-1mA, so this are no welding machines like yours :)
      Square responses mostly show a bit restricted frequency response for SE, in general it is easier to get better results with parafeed.
      Physics are the same for very high power audio amps like you have and studio mic preamps i do, so hope i'm right with explanation of my experiences. If anyone has other opinions it would be nice to discuss this matter further.

    • @foureyedchick
      @foureyedchick 7 лет назад

      I believe the downward sloping of the output square wave of the amplifiers is caused by a high-pass effect of the capacitive coupling between stages. A series capacitor with a shunt resistor, or a series resistor with a shunt inductor should function as "differentiator" rather than an "integrator". The downward "sloping" is a capacitor discharging through a resistor (sort of a small section of an exponential curve). What do you think?

  • @ElPasoTubeAmps
    @ElPasoTubeAmps  11 лет назад

    Yes, the peak value (the top and bottom of the square wave) has the same RMS value so it is kind of like putting a DC source or a battery across the speaker and will make the speaker voice coil have to dissipate more heat. I have always felt that square wave testing of amplifiers has pretty limited value but it may be an instrument along with an oscilloscope that some hobby labs have. Thanks for your input.

  • @thehobe2111
    @thehobe2111 9 лет назад +1

    The slope at low frequency of the square wave is related to the low frequency response normally limited by (and actually designed in) the coupling capacitor time constants. The leading edge ringing is probably due to your lead length to and the inductive nature of you load resistors. This could also be the lower damping factors (related to the amplifier output impedance) of tube type amplifiers. I like your instrumentation: Tek 7904 and Tek 485!

  • @cheissenberger
    @cheissenberger 7 лет назад +4

    The trailing edge down is low frequency rolloff

    • @allanfrancis9603
      @allanfrancis9603 3 года назад

      a trick: you can watch series at Flixzone. Been using it for watching all kinds of movies these days.

    • @cadendesmond7044
      @cadendesmond7044 3 года назад

      @Allan Francis Yup, have been watching on Flixzone for months myself :)

    • @juliuscolton9419
      @juliuscolton9419 3 года назад

      @Allan Francis Definitely, been watching on flixzone for since december myself :D

    • @terrancegrady699
      @terrancegrady699 3 года назад

      @Allan Francis Definitely, have been using Flixzone for since november myself :D

  • @wa4aos
    @wa4aos 9 лет назад

    Hello David,
    I hope you are doing well and enjoying the Spring before it gets hot.. I have done a good bit of square wave testing before and like the previous fellow said, the same test into an inductive load is more of a mess. But having a good response into a resistive level is a good starting point. What I have seen in my work at lower frequencies when the line slopes down on the top and slants up on the lower part of the display, is low frequency roll off. As the signal starts to transition from a square wave to more of a sin-wave is high frequency roll off. Most of these anomalies are tube specific but sometimes playing with the bias and B+ you may be able to set the tube to have a better response at higher frequencies. However, when you have a design that was done years ago such as a Dynaco, it's a little late to reinvent the wheel...Hi hi.
    I was designing an amp once using a 45/2A3 interchangeable config and was able to find a more linear part of the tubes power curve and improve the high response over what seemed to be the standard voltage ranges of other designs I had looked at.. That was such an interesting project while being a real PITA.
    Thanks so much for sharing your results and time with all of us audio enthusiast. You really explain your material so well. I suspect you have done some training professionally in the past. Vry 73 from SC de WA4AOS dit dit

  • @ElPasoTubeAmps
    @ElPasoTubeAmps  11 лет назад +2

    It is difficult to say definitively but I think the "warmth" that we hear in tube vs SS equipment is in the harmonic profile of the tube amp. Clearly, if THD were the only true value in an amp, All high end SS amps would "sound better" than All tube amps - but that is not the case. Tube amps distort differently than SS amps and simply put, we like it - also, tube amps have a more rolled-off high frequency response and I think, generally, that is less harsh or tinny sounding - just my thoughts

    • @lazzer408
      @lazzer408 6 лет назад

      The "warmth" (tubby bass) the low damping factor. The "lack of harshness" (warmth?) is poor HF response, fewer high order harmonics, and lower IMD.

    • @johnc8910
      @johnc8910 5 лет назад

      The HF roll off is a function of the output transformer. The distributed capacitance of the primary coils just eats the high frequency components of the square wave.

  • @basspig
    @basspig 12 лет назад

    The tilt at the low frequencies is the time constant of the amplifier's ability to hold a DC voltage potential. Since tube amps are ac coupled, the time constant of the circuits will show tilt at lower frequencies. The tilt is always there, but at 1KHz, the sample time is too short to see this tilt. At high frequencies, you're seeing the slew rate. The amps under test demonstrate remarkable square wave for a transformer coupled amp.

  • @EJP286CRSKW
    @EJP286CRSKW 9 лет назад

    A lean or curve on the left hand riser is an HF limitation (caused by a pole). A downward slop on the top is an LF limitation (caused by a zero). Ringing at the top LH corner is marginal instability. Same goes for the bottom traces in reverse. Any difference between top and bottom is a push-pull issue of some kind.

  • @sonick808
    @sonick808 11 лет назад

    whoah! that duckfoot wave at 10khz was wild

  • @das250250
    @das250250 6 лет назад +2

    The room background noise is pretty distracting

  • @mikesamra9126
    @mikesamra9126 8 лет назад

    David
    I meant to tell you that on this amp,you need to add a little more capacitance on the feedback resistor. Usually on the MK3s you have to use anywhere from a 390pf to a 720pf silver mica depending on the circuit..I guarantee that you can get that ringing out in the upper left corner with that trick of you haven't already.As far as the 100hz and the 10z sq wave,you can get it better with beefier power supply but that is very common on many amplifiers at those frequencies.

  • @Dario01101
    @Dario01101 5 лет назад +1

    What is that anomaly in the output form at high frequencies due to? Why does it look more like a sine wave?

    • @simonkormendy849
      @simonkormendy849 3 года назад

      It's basically due to the amplifier's frequency response, and the fact that the amplifier's gain is decreasing as the frequency goes up, it also has to do with the output-transformer's frequency response too.

    • @Wolfgang3418
      @Wolfgang3418 3 года назад

      It's caused by limited bandwidth of the amp. At 70kHz you have just a few odd harmonics left for creating a square wave, since perfect square waves are made of an infinite number of sinewaves (ground wave plus odd harmonics)
      ruclips.net/video/TNiA0Y5tHQQ/видео.html

    • @bigcbradio
      @bigcbradio 10 месяцев назад

      To me, it appears that the anomaly seems to be nothing more than the rinigng seen in the lower frequencies. If you watch starting around 13min or so, you see as he goes up in frequency, only the flat dc line gets shorter and all he is left with is the ringing.

  • @lazzer408
    @lazzer408 5 лет назад

    Find the capacitor that is parallel with the feedback resistor off the output. Increase it slightly. You can knock down that overshoot.

    • @ElPasoTubeAmps
      @ElPasoTubeAmps  5 лет назад +1

      There is a procedure for determining the value of this capacitor but I can never remember it off the top of my head. Some suggest using a square wave at 1 KHz and adjust the value for best square wave. Sounds reasonable but I have not tried it yet.

    • @lazzer408
      @lazzer408 5 лет назад +1

      No need to calculate. It's never right. :) Start with a value of 100pf or so and adjust as needed to tame the overshoot. To simplify, overshoot is just a delay in the NFB signal due to phase shift (lag) in the amplifier's circuits. Say you had an open-loop gain of 26, and closed loop brought that down to 20. With the loop closed, the gain is still 26 until the feedback finally shows up. That make sense? It always made more sense for me to explain it this way vs. explaining dominant poles, phase shifts, and attempting to calculate it.
      I would enjoy a video showing the location of the capacitor (easy to locate) and how it's value effects the leading edge of the waveform. Many a DIY'er has had to deal with this.

    • @Wolfgang3418
      @Wolfgang3418 3 года назад

      @@lazzer408 Hi! You are an expert, I understand. May be my video on the topic is interesting to you, leave a coment, please: ruclips.net/video/TNiA0Y5tHQQ/видео.html

  • @78awhite
    @78awhite 8 лет назад

    @ElPaso TubeAmps To get the 8V output, you are just turning up the volume control on the Amp correct? I get a little confused sometimes if the output voltage is a function of turning up the amp volume or increasing the amplitude of the signal generator. Any light you can shed on this would be appreciated! I have learned so much from you and I look forward to learning a lot more! Thanks for making these videos:)

    • @ElPasoTubeAmps
      @ElPasoTubeAmps  8 лет назад

      +Adam White One way to start out is turn the volume of the amplifier all the way up while keeping the signal generator output very low, i.e. a millivolt (mV) or less and then start increasing the output of the signal generator while watching the output of the amplifier across the 8 ohm load with your oscilloscope.. I say it this way because you do want to be careful that you don't overdrive the first stage of the amplifier because then nothing will make sense at the output. If it is just a power amplifier like the ones in this video it will take 1 or 2 volts or more to over drive the first stage of the amplifier so you may set the output of the signal generator at about a volt or so and use the volume control of the amplifier to increase the output. If it is a guitar amplifier, just a few mV input will overdrive the first stage so you have to be really careful in that case. Hope this helps.

  • @adamwolfram6126
    @adamwolfram6126 4 года назад

    Great video! Thanks!
    What is the model of oscilloscope used in this video that is positioned on the left?

    • @ElPasoTubeAmps
      @ElPasoTubeAmps  4 года назад

      Here is a video on that scope.
      ruclips.net/video/y7uMl-erdCk/видео.html

  • @zbyszekskibinski
    @zbyszekskibinski 8 лет назад

    I can see you've got some nice toys out there
    Slants in the waveform amplitudes at 100Hz are caused by low quality speaker transformers in tube amps. But in your videos its not too bad, most amps will have frequency response like that.

  • @kubockferre5532
    @kubockferre5532 4 года назад

    hello ,id like to know what the ringing means for an amp !

    • @ElPasoTubeAmps
      @ElPasoTubeAmps  4 года назад

      It generally ringing means that the load impedance (the speaker or dummy load) does not match the output transformer perfectly.
      Damping has a good analog in cars. If a car does not have a shock absorber, then the car will oscillate up and down as it goes over bumps or ups-and-downs making it ride like a ship on the ocean. If the spring is way too stiff or the shock absorber is too stiff, it will ride like a pioneer wagon and the rider will feel every bump. If the spring and the shock absorber is properly matched to the weight of the car, it rides relatively smooth and straight on the road. A similar thing occurs with amplifiers. Ringing in the output generally manifests in "boomy" bass much like a juke box. This often is caused by a cheaper transformer with a higher impedance secondary that can not control the voice coil of the speaker and the speaker oscillates like the car with out a shock absorber.
      Here is a very good article on square wave testing I think you will enjoy.
      sound-au.com/articles/squarewave.htm

  • @richpaul8132
    @richpaul8132 6 лет назад

    I don't know if it's the same but, the human hearing range falls between 20Hz and maybe 22Khz so isn't it pointless to run the test beyond 20 or 22Khz? As I said, I don't know if the frequencies you refer to are the same as the audio frequencies in a stereo amp.
    I do know that McIntosh amps are among the best in the world, (I only wish I could afford a couple of 700w mono Macs circa 1985... I WISH!). Therefore, I would guess that they would focus on keeping the distortion to a minimum in the 20Hz to 22Khz range and anything higher or lower than that wouldn't be too important to them.
    I also agree with Jora Lebedev; it would have been great to see how you configured your connections. I'm trying to learn how to use a scope and I am in the very early stages of that understanding. I don't have any other equipment except for the basic oscilloscope, (BK Precision 2120), and I'm using an old Radio Shack 25w per channel stereo amp as a 'test monkey'.
    I see you have several additional components there and I wonder if that's a "mandatory" setup for testing anything using a scope. I'm sure some of, (if not all), the equipment improves the input/output voltage stability and the accuracy of the test results on the scope, but is it really required for a more "casual" test session?
    Thank you,
    Rich

    • @ElPasoTubeAmps
      @ElPasoTubeAmps  6 лет назад +2

      Hi Rick,
      If you have a scope you are 90% there.
      You will also require a resistor for a dummy load (one for each channel) capable of dissipating the maximum amount of power your amplifier(s) will deliver and you need a driving voltage that is adjustable from a few mV to maybe 2.5 volts and you have all that is necessary for a set of basic measurements.
      You drive the amplifier input (usually the AUX input) with the adjustable voltage source usually at 1 KHz at about 1 volt with dummy loads across the output of your amplifier. You can connect your scope across the dummy load and increase the volume on the amp until you see the waveform just starting to clip at the tops.
      When connecting the scope across the dummy load be careful to not connect the ground lead of the scope to the "hot" side of the speaker output terminals where the dummy load is connected. This could short your output to ground and damage a solid state amp.
      If the waveform looks good and symmetrical to that point and starts clipping the top and bottom of the waveform the same amount, you have just reached the 1 or 2% harmonic distortion level. If your scope is calibrated you can measure the peak to peak voltage on the scope and multiply that value by 0.353 which will give you the RMS voltage across your dummy load and assuming your dummy load is 8 ohms, you square the RMS voltage and divide by the 8 ohms and you get the average power in watts. Example: assume your PP voltage on your calibrated scope is 40 volts. Multiply by 0.353 and get approx 14.12 volts. Square 14.12 and get 199.37 then divide by 8 and get 24.92 watts. (PS - probably best to not leave the amp running at max power for very long as it may damage the amp. Also, the dummy load resistors can get really hot is they are run at their maximum power level). That is petty much were everybody starts and you can obtain more sophisticated equipment from there. Hope this helps.

    • @richpaul8132
      @richpaul8132 6 лет назад

      Thank you sooooo Much!! a few hours ago, I ordered a Signal Function Generator from Amazon.com (smile.amazon.com/gp/product/B07211YWMK/ref=od_aui_detailpages00?ie=UTF8&psc=1). It may be more than I really need but I'm considering the high probability that I'll be buying a better scope as I continue to learn this field, (as a 'base-level hobbyist').
      Anyway, in the past 40 years or so, I've collected, (and continue to collect), many various electronics including breadboards, resistors, diodes, caps, transistors, etc. Based on your reply, I'm pretty sure I have all the components I need. I plan to setup a breadboard with the configuration you've mentioned.
      As for the Radio Shack amp, it's a 'working' 25w x 2 amp but I got it for free years ago. It's not in any shape for me to use so if I blow it up, I won't mind, (I have a much higher end Sansui amp that I definitely won't try anything on). I also have a pair of 'test-monkey speakers' that give me the same affordability, lol.
      I have three questions:
      "you need a driving voltage that is adjustable from a few mV to maybe 2.5 volts"
      (A): Should I use DC or AC power for the adjustable voltage? I'm guessing that it should be AC but I do have a nice, small, DC regulator if DC power is to be used.
      I also have various resistors from 10 ohm to 1M ohm.
      (B): Do you have a recommendation as to what size resistors, (or the amount of resistance), I should use? Considering that the amp is 25W per channel, how much resistance would you use in the dummy load?
      (C): What is the value ".0353" refer to? Is it a constant figure that never changes?
      Thanks again for the pointers.
      Rich

    • @ElPasoTubeAmps
      @ElPasoTubeAmps  6 лет назад

      The driving voltage must be AC and the standard is 1 KHz. Your oscillator you purchased will probably go from 20 Hz to 20 KHz so you will have all you need in that. I am sure the output of the oscillator is adjustable also.
      The most common load resistor is 8 ohms. Radio Shack sold 8 ohm load resistors when they were in business and I think they were rated at 20 watts so those can be used as long as you don't pump lots of power into them for more than a minute or so. 8 ohm load resistors are all over Ebay and not expensive. They will be listed as non-inductive 8 ohm resistors.
      The peak to peak voltage as read on a scope has to be changed to RMS voltage so you can look at it a couple of ways. Typically we think of peak voltage which would be one half of peak to peak. In the example of 40 volts peak to peak that would be 20 volts peak. To convert peak voltage to RMS voltage you multiply the peak voltage times 1/(sqrt(2)) which is approx 0.707. 1 volt peak would be 0.707 volts RMS, 10 volts peak would be 7.07 volts RMS and so on. If you use peak to peak as read directly off the scope you would half that voltage again so you would divide the 0.707 by 2 and get the 0.353. Hope that makes sense.

    • @richpaul8132
      @richpaul8132 6 лет назад

      Yes, it absolutely makes sense and I very much appreciated the time you took to explain that. The signal function generator will be here Saturday and by then, I should be able to acquire the non-inductive resistors.
      In other words, I should be able to try this out by Saturday afternoon!
      Thanks again,
      Rich

    • @richpaul8132
      @richpaul8132 6 лет назад

      Oh, I meant to update my results and of course, you were spot-on! It's hard to explain but I was fascinated by the results of additional tests I did after I completed this configuration first.
      As for the Radio Shack 25w per channel amp; well, it's a very old, (circa 1990, maybe) and somewhat worn-out amp that I got for free about 5 months ago. Whoever owned it didn't put a lot of energy applying 'upkeep & care' to the unit. That said, I was surprised to find that I could get to about 80% of the volume level before the output wave became distorted. The amp's best power output was held to about 19 watts.
      I know that it would get to about 22 watts when I would first turn it on and run the test. However, after about 5 to 8 minutes, the wave would begin to distort and I would have to cut back the volume to settle on 19 watts. Nothing got hot, not even warm, throughout the time I had it connected for testing. Most of the time, I sent no more than about 1.75v through the Tape inputs from the DDS.
      A few times, I forgot to cut back the volume level and even at near 75%, nothing got hot, the 8 ohm resistors certainly stayed cool as well. Anyway, this test and subsequent variations I tried, has taught me a lot more than I would have learned from using only a DVMM.
      Thanks again,
      Rich

  • @sonick808
    @sonick808 11 лет назад

    that ringing appears to be consistent with all tubes. try putting a solid state on there, i bet that artifact disappears. have you identified "the warmth" ?

    • @johnc8910
      @johnc8910 5 лет назад

      That ringing is caused by the output transformer. A transformerless design (yes, they exist, but they depend on low-mu, power triodes such as the 6080) probably would minimize the ringing.

  • @KIRBZVIDS
    @KIRBZVIDS 11 лет назад

    ant aqware wave realy bad for speakers ?

  • @dynacoA25
    @dynacoA25 8 лет назад

    too bad you cant test the output of a speakers and test brands against eatchtother the dynaco A25's would mop the floors and then some

  • @bonniekapischke210
    @bonniekapischke210 5 лет назад

    To bad you have no idea what you are doing and what the display is telling you. All the fancy test equipment in the world is useless if you can't interpret what it's telling you.

    • @ElPasoTubeAmps
      @ElPasoTubeAmps  5 лет назад +2

      I will admit that my videos are less than perfect much of the time but NASA and White Sands Missile Range thought I was pretty good for 26 years as an engineer before I went into management. Guess I was just lucky and had them fooled. Maybe you could be so kind and interpret what is on the oscilloscope screen for us and share your knowledge with the RUclips community.

    • @swinde
      @swinde 5 лет назад +1

      ElPaso Tube Amps ... Bonnie is being a jerk and perhaps doesn't even know herself. I posted above what these tilted square waves are indicating. If one has rarely or never used square waves to test amplifiers, it is not uncommon to not understand the waveform. As I said above these wave forms are showing roll off of low frequencies. (in this case subsonic at that). Another useful waveform to use is a triangle wave.
      With the triangle wave you can observe the linearity of the amplifier at different frequencies. A function generator is a useful tool for evaluation amplifiers. Mine also will do saw tooth and linear and log sweep functions.