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Meridian 103 clone
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Old 10th April 2019, 03:53 PM   #51
RCruz is offline RCruz  Switzerland
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Maybe... probably more impact in the bass.... let us know the outcome
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Old 10th April 2019, 04:29 PM   #52
keantoken is offline keantoken  United States
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I can't determine what D2 and D4 are for, but I would think they have something to do with tuning the amp behavior during startup or prolonged clipping. They seem to be keeping the input transistors slightly on at low supply voltages. They could also be affecting temperature compensation.
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Old 10th April 2019, 07:27 PM   #53
RCruz is offline RCruz  Switzerland
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Thank you kean.

Please view the last mods that increased damping at low freq apart from your suggestions.
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File Type: asc Meridian 103 exicon power amp EVO13 DAMPING FACTOR.asc (15.8 KB, 19 views)
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Old 10th April 2019, 08:00 PM   #54
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Quote:
Originally Posted by keantoken View Post
The funny thing about lytics is that they usually already have a 10nF or so cap inside them which bypasses the ESR at high enough frequencies where the oxide layer behaves more like a dielectric than a conductor.
I have never heard such a tale, where do you get your information, I am curious?
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Old 10th April 2019, 09:00 PM   #55
keantoken is offline keantoken  United States
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It is there in some obscure capacitor manufacturer app notes which discuss the electrolytic equivalent model to higher detail. If you measure the ESR of a lytic you will find it starts to decrease above a certain frequency. You can see it here on page 8:

http://www.hoffmann-hochfrequenz.de/...capacitors.pdf

In this case it's more like 1nF, but it's still there. It looks like I didn't save the original references.
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Old 13th April 2019, 01:25 PM   #56
RCruz is offline RCruz  Switzerland
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New work done.

Jfet cascoded IPS

IPS bias now set with CCS found here: TSSA - The Simplest Symmetrical Amplifier

Needed to reduce lead lag capacitor in the feedback loop to retain a good phase lag.

That also increased bandwidth and -3dB is now near 300khz.

IPS emitter decoupling capacitors where increased to 1000u.

THD reduced from 0.005 to 0.0035% ...

Now my question is... can I use 62V rails with only two output lateral mosfets per rail or should I reduce voltage ?

Is it normal that I find a damping factor of 33000 at 1khz ?
Output impedance is 247uohm at 1khz .... never simed nothing like it before.
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Last edited by RCruz; 13th April 2019 at 01:27 PM. Reason: Need to post images
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Old 15th April 2019, 06:15 PM   #57
RCruz is offline RCruz  Switzerland
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Adding an output coil and damping resistor lowers damping to lower than optimal damping....
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File Type: png MClone Damping factor @ 20kHz With output coil.PNG (113.6 KB, 57 views)
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Old 15th April 2019, 06:20 PM   #58
RCruz is offline RCruz  Switzerland
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Adjusted bias current to much lower and acceptable values.

Adding some additional info for those who do not have the models.

Just place everything in the same directory and open with LTSpice....
Attached Files
File Type: asc Meridian 103 exicon power amp EVO15 CCS IPS CASCODE TRANSIENT.asc (18.4 KB, 7 views)
File Type: txt Cordell-Models.txt (19.6 KB, 3 views)
File Type: txt MYamp.txt (59.1 KB, 4 views)
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Old 15th April 2019, 06:22 PM   #59
RCruz is offline RCruz  Switzerland
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Trying zip with TL431 files to be dropped on the same directory...
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File Type: zip TL431.zip (780 Bytes, 5 views)
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Old 15th April 2019, 07:45 PM   #60
keantoken is offline keantoken  United States
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Output impedance can be down in the uohms depending on the feedback, but this is moot as one inch of wire swamps it out.

At 20KHz there is nothing to damp, the speaker parasitics are preventing any damping from taking place through the voicecoil at those frequencies. If you look at the numbers, the more likely reason if the output inductor affects sound is that it causes some HF rolloff. And/or it is preventing oscillation or RF demodulation.
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