Power Amplifier LJM L20SE

[ljm_ljm]

I have a newbie question regarding making my power supply for my L20SE stereo amp. I have an SMPS at +/- 36vdc. My speakers are 4 ohm MTM.

Is there a easy to understand resource on selecting fuse types and values for mains and +/- rails?

Thank you for your help.

You can use +. Between and -.
Use 2 fuses. 4a is recommended.
If you can. I suggest paralleling some capacitors between the power supply + -.
Because the switching power supply output will have some PWM signals. The frequency is about 100kHz.
These PWM signals may cause the amplifier output transistor to heat seriously. Even damaged.

 

[ziffel]

Thank you, LJM,
I was thinking of using a pair of capacitor boards (please see photo). Do I need to add bypass caps to manage the PWM signals? If so, what is a good value?
Thank you for providing these wonderful amp boards and all of your help. - ziffel

 

[ljm_ljm]

Thank you, LJM,
I was thinking of using a pair of capacitor boards (please see photo). Do I need to add bypass caps to manage the PWM signals? If so, what is a good value?
Thank you for providing these wonderful amp boards and all of your help. - ziffelView attachment 1075083

You don't need a rectifier bridge.

 

[philippe guitton]

Oui. L’original a été corrigé et le projet a été ajouté. C’est au début. 1.Juin

Amplificateur de puissance de schéma électronique LJM L20SE

Schéma électronique et analyse

Schéma : Amplif_L20SE.pdf - Google Drive

Projet : Amplif_L20SE.ms14 - Google Drive

Je ne commercialise pas ce produit et je ne suis pas l’auteur du projet. J’ai fait le circuit schématique pour analyser et partager l’information.

Merci pour ce post
quels sont les condensateurs ( capacitors ) qui sont réellement sur le chemin du signal depuis In jusqu’à Out ?

 

[Mooly]

English only please. Rules.

‎Thanks for this post ‎
‎ which capacitors are really on the signal path from In to Out?‎

 

[philippe guitton]

English only please. Rules.

Thank you for this article what
Capacitors are really on the signal path from input to output for l20SE

 

[ljm_ljm]

Thank you for this article what
Capacitors are really on the signal path from input to output for l20SE

L20se has only one capacitor on the signal. 10V1000UF
It basically uses the world's best Rubycon MCZ capacitor.
Or Nichicon Hz, HN capacitor. They are basically the best capacitors in the world. There's nothing better.

 

[philippe guitton]

L20se has only one capacitor on the signal. 10V1000UF
It basically uses the world's best Rubycon MCZ capacitor.
Or Nichicon Hz, HN capacitor. They are basically the best capacitors in the world. There's nothing better.

Tanks for your information and your good Works

 

[electronchaser]

I think the schematic I have shows 1 uf for the feedback cap, must be where the 1000uf cap goes.

 

[electronchaser]

ljm, is there somewhere in the states to buy your boards? or where is best place? thanks

 

[ljm_ljm]

ljm, is there somewhere in the states to buy your boards? or where is best place? thanks

I think I can buy it online. You can compare the prices more.
If you suspect it is fake, you can send me a picture for confirmation.

 

[Marvincf]

Excuse me friends, I have a rookie question, would it improve if we add these two components to the end of the zobel network? Thank you for your answers

 

[ljm_ljm]

Excuse me friends, I have a rookie question, would it improve if we add these two components to the end of the zobel network? Thank you for your answersView attachment 1098424

unable. Because your speaker is a big inductor.
If you are connecting speakers. No additional inductance is required. But if you connect other devices.
Not a speaker. That may require it.

 

[Marvincf]

unable. Because your speaker is a big inductor.
If you are connecting speakers. No additional inductance is required. But if you connect other devices.
Not a speaker. That may require it.

Thank you very much for your answer, one more rookie question, to connect it to a higher voltage source (+80 -80) what elements do you recommend I change? Greetings.

 

[ralphysound]

вопрос новичка: у меня на выходе этого усилителя (-0,020 mv) что делать?
newbie question: what should I do at the output of this amplifier (-0.020 mv)?

 

[Hennady Kovalsky]

Excuse me friends, I have a rookie question, would it improve if we add these two components to the end of the zobel network? Thank you for your

of course, it protects the negative feedback circuit in the amplifier from the non-linear impedance of the speaker, to a large extent this applies to the capacitive nature of the load, i.e. when the impedance increases with frequency.

 

[Hennady Kovalsky]

newbie question: what should I do at the output of this amplifier (-0.020 mv)?

doing nothing is a good thing.

 

[batteryman]

of course, it protects the negative feedback circuit in the amplifier from the non-linear impedance of the speaker, to a large extent this applies to the capacitive nature of the load, i.e. when the impedance increases with frequency.

Also blocks RF picked up by the speaker leads from getting back into the amp so quite important in my opinion.

 

[Hennady Kovalsky]

The values of this circuit depend on the topology of the circuit and are calculated relative to the frequency of 20kHz.
This device has a very distant relation to radio frequencies ...

 

[batteryman]

The values of this circuit depend on the topology of the circuit and are calculated relative to the frequency of 20kHz.
This device has a very distant relation to radio frequencies ...

So what is the purpose of the inductor? A great many audio power amps have one and the reason I gave was the one cited in reviews.