Automated Amp Freq Response plot question

I am wondering if I am doing something wrong when doing an automated Amp Freq Response plot on an integrated amp. Here are the settings:
Here is the plot I got after setting the axes:

I have 2 questions:

  1. Is there a way to label each trace for the different input power levels- it was not apparent to me?
  2. How do you get rid of “Pen not going up” trace is what I would call it. Back in the days of pen plotters like the HP7470A you needed to send a “Pen Up” command to the plotter when you were done plotting a trace…


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Hi @VAR, that’s a bug I just repro’d too.

  1. To label a trace you make the trace you want to change the current trace, and then you do Trace->Rename Trace

  2. Bug as noted above, will fix for next release

Thanks Matt. However, It will only let me rename one of the traces, it does not appear to know there are two of them so I cannot differentiate which trace is at which input power level. Is that part of the bug ?

@VAR your reference to the HP GL “Pen Up” command made me smile. I knew exactly what you meant. We had a number of HP-7220C in our control systems lab in the early 80s and I remember making that very error - on more than one occasion. Install a new set of pens and a sheet of quality white paper and it was a pleasure to watch it plot.

Yes, that’s part of the bug. The lack of “pen up” that you note is the two traces being merged into one. Hopefully this week the new release posts.

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Thanks Matt. Built my speaker impedance test cables so trying them out is today’s fun…

I am glad to know I am not the only guy here who knew what I was talking about. I never had to pleasure of using the 722c, but did use the 6pen 7475a. They were pretty slick- using a static system to hold down the paper. Having the pens run out of ink or get dull was common place. I started out programming with the HP9825 instrument controllers- those were so cool back then.

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Hi @VAR, 0.998 was just posted HERE which should fix this.

That is good news. Will download and install shortly :grin:

Matt- thanks again for the way you support this product, and it has provided me with a lot of enjoyment, and will continue to do so I am sure. I think the main thing that is missing for me, at least, are not having are markers for the EXPO Chirp FR- is that something that is in the works or not that easy to do ?


Hi @VAR,

Yes, the cursor code has been prototyped for the graph tool (see below), and needs to be merged in with a few changes. In short, you will have the ability to turn on Cursor 1 and Cursor 2 independently, drag as needed, and if both are on you will see the delta between C1 and C2 (like most spice programs). I don’t know the exact timeline, but it’s coming.

That is good news, Matt. The example you show above has just a delta X being shown and no delta Y- I assume there would be both delta X and Y. Also you mention that it is part of the Graph Tool- will we be able to at least set Markers when in the Expo Chirp FR mode ? That would be a nice holiday present :slightly_smiling_face: