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Yes, it can be fixed, but wouldn't it be better if it didn't happen? Should we ask for it to be changed to only show the model filename?

That is "easily" fixed and by now I have gotten accustomed to doing that after group members upload their schematics.? It is an unfortunate consequence of letting LTspice auto-generate symbols.?

• Right-click on the text "1N4007" and change it to "1N4007 N=6"; or
• Ctrl-right-click on the diode symbol and add "N=6" (without quotes) in the Value2 line, and optionally add an X in the Vis. column.

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Yes, correct. You have not been banned, so you can still ask for help. But I give you another tip - in future use more explicit subjects than 'test'. Everyone and his cat has a file called 'test'.

I don't understand you circuits. What are they supposed to do? Where is the output? I can see it might be the top ends of the diode stacks, but that doesn't work for the circuit that doesn't have a diode stack.

I can't run your sims because your LM317 symbol has the full path to its model which is on your computer only.

? In the future, I should continue to post my schematic files in the temp folder. All emails related to my topic should have a unique one and only subject. Correct?

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No, you didn't correct it. You continued the same thread, but with a different subject.

By "start a new topic", I mean you start a new email thread by either:

1. Clicking "New Topic", if you're using the group website, or
2. Clicking "New Message", if you are using Thunderbird, or "Compose", if you're using Gmail.

If you don't do this, the (normally) hidden email header signifies that you have answered an existing message, even if you've changed the subject.

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Can you please not hijack a thread. Start a new topic. What you did was reply to a message in the "Model of BF970 ?" thread, and simply change the subject.

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I never pretend or intend for someone else to do the hard work. That
is for me to try, because that way I learn.

What I did need help on that thread was with adding a HP filter for a
specific very low frequency rumble some Thorens TTs had. And I was
trying to use a two stage passive RIAA filter, as shown on Walt Jung's
book and later, and another passive/active design, also two stage,
inspired on a discrete RIAA preamp by Erno Borbely in The Audio
Amateru magazine. One pal on the thread, Marcel, helped me with that.
Designing a RIAA filter is much beyond my knowledge.

I'm not sure someone here would like to see the .asc sims, with and
without filters, as that's not a matter for this "problem solving"
site (to describe it somehow). If someone is interested, do let me
know. Going to that DIYaudio thread would be much better, and
suggestions from those that ask and respond to questions here would be
very useful there.

When I ask for help on something, everywhere, I do not expect others
to do the hard work. That is what I want to do.

Carlos

On Sun, Mar 30, 2025 at 10:04?AM Andy I via groups.io
<AI.egrps+io@...> wrote:

On Sun, Mar 30, 2025 at 08:23 AM, Carlos E. Martínez wrote:

According to one of my colleagues at DIYaaudio, "Laplace is the most
accurate but can only be used in the .AC mode.
For the .Tran mode you will have to use the RC model.

That is not quite true.

The Laplace version has the disadvantage that the Laplace transform from frequency domain to time domain sometimes does not produce the right result - but sometimes it does, and the reasons why it works or does not work are not well understood. It seems to be a problem with fine-tuning the Laplace settings in the simulator. Those settings are WINDOW, NFFT, and MTOL. This is described (tersely) in LTspice's Help. As it states there:

The time domain behavior is found from the sum of the instantaneous current(or voltage) with the convolution of the history of this current(or voltage) with the impulse response. Numerical inversion of a Laplace transfer function to the time domain impulse response is a potentially compute-bound process and a topic of current numerical research. ... This process is prone to the usual artifacts of FFT's such as spectral leakage and picket fencing that is common to discrete FFT's. ... LTspice must guess an appropriate frequency range and resolution. It is recommended that the LTspice first be allowed to make a guess at this. The length of the window and number of FFT data points used will be reported in the .log file. You can then adjust the algorithm's choices by explicitly setting nfft and window length. The reciprocal of the value of the window is the frequency resolution. The value of nfft times this resolution is the highest frequency considered. ...

In other words, it might work, but you may need to manually adjust the settings to get a good transform to the time domain. It is incorrect that "you will have to use the RC model", but it is probably better and easier if you do. An RC model with correctly calculated components has exactly the same response as the Laplace form anyway.

Your colleagues at DIYaudio are incorrect when they say that "Laplace is the most accurate." It is not more accurate than the RC version. It is just easier to calculate since you know in advance where the poles and zeros should be.


I did try some of the SW settings that you suggested, and for now
found different responses according to the opamp being used. Now I
need someone to translate those results into actual distortions or
limits, and if possible play with the variables.

Can you do that yourself? Since this is your project, you ought to be able to examine your preamps' distortions and other effects. Or, you could pay someone to do it for you. :-) Wouldn't it be better to work on it yourself? Getting assistance is good, but don't expect someone else to do all the work.

Andy