Split L/R display for frequency response

Is it possible, and if not, WOULD it be possible, to provide a “visualizer” display that gives separate L and R frequency response? Basically, the idea would be for the current SA display to be split in two, with the top half showing the L channel, the bottom half the R channel, when you are running for example a frequency response test on an amplifier?

Additionally, it would be wonderful to be able to use the two signal generators separately for this, i.e. Left Channel generator set to 1KHz, R Channel generator set to 2KHz, to show the L and R channel separately instead of virtually superimposed (when doing a THD test for example). OR … as above, some kind of split display.

And lastly, does increasing the Windows computer in any way increase the processing speed of the analyzer? My guess is no, all of the calculations are done within the analyzer, but the question came up at a meeting yesterday.

Thanks so much

I am curious why you would want a separate display for left and right channels’ frequency response. I am assuming that you would be sweeping the same frequency range? It seems more useful to have them on the same display- You can always save the data for each channel situation and export it as a .csv file and graph what you want in Excel if it is for report purposes. Likewise, I do not see the usefulness for a single frequency test with each frequency displayed separately for each channel, though it would be nice to have that capability I suppose.

The usefulness is for our customers, not any engineering or tech functions. In a properly repaired amplifier, the L and R traces are almost identical and therefore superimposed on each other.

The secondary usefulness is so the final testing can be done a lot faster. Given dual screen display for L/R, a simple one step print is possible of the frequency response display.


I guess that makes sense, but in my experience I doubt the customer is really going to appreciate having the two graphs overlaying & seeing the two channels being very close to one another, which is what you want to see.

I understand. But what I want to see, is actually what I want to see :). I was hoping for some pointers towards a solution, not a questioning of why I was asking for what I want. I’m not without experience dealing with customers, actually. Just new to the QA analyzer, a wonderful piece of engineering btw.

Hi, using a small dB range (3 dB or less, for example) wouldn’t show L-R differences?

Yes, that could work, but at that dB setting, the response curve is far from a straight line. To be clear, this is more of a marketing use, not strictly an engineering one. Customers will have no idea what a dB is, let alone what it means.

The intended use of this request for dual display is to give a customer a piece of paper showing essentially a flat response from 20Hz to 20KHz. In the “Visualizers” menu, there is a bar graph for THD, which is perfect. But that won’t work for my intended use of a flat frequency response curve to present to the customer.

It may help to know that this is for a shop that repairs VINTAGE equipment, not new stuff. So, a 70 year old Marantz, for instance, is probably never going to be perfect. But as I said, the intent is more marketing than science.

Hi @BBTV, there’s not a way to do that currently. But there’s plenty of software that will let you take a capture of the left trace, and then a capture of the right trace, and tile them side by side. Additionally, if you right click on the graph, you can select “copy as EMF” which will be a vector representation of the graph. That means you can scale it just about any resolution and still keep great fidelity. The EMF export was added precisely for reports. Now if I could only find a schematic tool that would export in a vector format.

In the attached PDF, there are two plots, both copied as EMF, placed in a Word doc and exported as PDF. Zoom in on the PDF and note how clear everything stays (focus especially on the text on the graph). The QuantAsylum logo in the upper right will fuzz as you zoom in, because it’s a bitmap. But that can be turned off in the Settings.

A really key setting in Word is the ability to click on a graphic and specify the the precise width while maintaining aspect ratio. It’s a very quick way to unify a bunch of EMF drawings.

combinedchannels.pdf (54.2 KB)

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I was just curious why you wanted what you were asking for. The excel csv data method, while a few extra steps, would be easy to do once you get the spreadsheet template all set up and your left and right channels could be shown with the spec lines as well. Plus your company logo, test conditions etc- better marketing ? Speaking of 70year old Marantz, here is the FR for a 60yr old 8B that I tested a few days ago for an upcoming video for my channel (5w/8ohms). Pretty much original except for the tubes as best I can tell. Impressive, IMHO:

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I see you also have the repetitive ADC Overflow message which sure is a strange one. @matt mentioned it was a bit pessimistic of the software, but I get it quite often, even just changing ranges and with no input. If you start an aquisition is goes away, but it is annoying not know what is causing it and why. Hopefully it will be fixed. I wondered if it is a DC offset issue internally?

@restorer-john @matt- That ADC overflow error only occurs after I stopped the measure and click on the trace. When I am screen capturing the data (usually for a video) the measurement has actually stopped and I am trying to point something out. The software will put a circle over the point that I clicked on, but even though I am stopped, that ADC message may be triggered, or something else, like only the left channel can be used for something- annoying for my video work and I have mentioned it to Matt that it would be nice to just freeze the display so you can click on it. I suppose I could save a .jpg of the screen on click on that, but I am so busy with being retired that i would prefer such a setting to save a little time. .

Hi @restorer-john, the overflow message refers to USB buffers, not levels.

Hi @VAR, when you stop an acquisition by pressing the space bar, for example, watch carefully on the lower left and you might see a “canceling…” message go by. The space bar (or run/stop) button will cancel the current acquisition and that can leave some buffers in limbo. Now, if you are running small FFT sizes, then there’s no reason to abruptly stop the acquisition–it will be done a a few hundred milliseconds anyway. And so, just let it finish. But if you are running a 10 second FFT, then you’d probably want to abruptly stop the acquisition rather than wait around for it to finish.

But, in any case, you can do a control+space after canceling an acquisition, and that will run a single cycle and you can avoid the overflow message on screen.

Probably what makes the most sense here is if you cancel an acquisition, don’t display the overflow message because you canceled the acquisition that overflowed…

@matt- I rarely run a long FFT. I will try to use the control Space method until the fix you mentioned is implemented. It would still be nice to have the display screen area frozen at that point so clicking on it does not do anything…

Hi @VAR, can you please try release 1.198 when time permits and see if this solves the issue?

I should be looking at something later today and will let you know- thanks for all your hard work!

@matt- I did get around to using the 1.198 software and did not get any DAC overflow errors popping up in the corner once the program was stopped. Though I am probably one of the few users who would appreciate having “display lock” button so I can click on signals on the screen w/out getting some kind of warning, I am hopeful it will be considered at some point :smiley:

Hi @Var, thanks for the update. For the display lock, are you referring to the ability to lock the axis to stop the panning?

I think the only warning you get now is if you click near a a trace while both channels are active.

But if you don’t click then you won’t get a warning, and if you don’t click and drag it won’t pan…is that right???

@matt- thanks for taking the interest in this. Let’s say I am measuring an amp’s power output, and stopped the measurement. If I am making a video and have my screen capture software going with a mic hooked up so I can narrate all the exciting performance details, and click around the trace, I will get marker warnings, and possibly another warning if it was an expochrip FR. Sometimes the “expanded scale warning” arrow might show up in the bottom right. I could always do a screen capture of the trace area and come back and narrate over the picture, which I used to do when I first started my channel, but it is much easier to have the video segment with sound done while the measurement was taken. It is a small problem to be sure and probably not worth the time to create a solution for it unless it is very simple. This is the area that I would propose having a “screen lock” for:

Of course, there would be some sort of annunciator that would tell you that the “screen lock was activated” and a button or toggle for it. BTW, the screenshot is from a Sansui 5000a receiver from around 1971, that I just finished testing for an upcoming video.

Hi @Var, noted, thanks. I think what you need will come, but probably not until in the next big release.

BTW, on your MC2125 review, do you know of a spec that McIntosh used for noise? Was unweighted common back then? An A-weighting (which is how TI measures noise on their Class D) would improve that a lot. Another great video, BTW!

Thanks for considering the “freeze screen” for an upcoming release. As for the 2125, there was only a spec for Hum & Noise, which was 95dB below rated output.I just showed the system noise level as something that I do with the inputs terminated into 50ohm loads- kinda a reference type measurement to compare to other units, but does give you an idea of the power supply hum. Sometimes I will run the amp at its rated power level- almost always into 8ohms- and point out have far down the noise is and the 60/120/180hz- I am trying to do that more often as the hum and noise if often listed as below rated output. Unless A weighting is specified I do not apply it. As for what you pointed out, I am not familiar with that, but guess it would be newer spec and not used back when most of the stuff I test was made. Not sure what an AES17 filter is.