C3=10μF and no pin7-5 circuit at all.
Shall we say this is FINAL?
(at least for today?)
Shall we say this is FINAL?
(at least for today?)
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Show posts MenuQuote from: J M Fahey on October 29, 2011, 02:25:13 PM
Δημήτριος would be Dimitrios
Παναγιωτίδης would be Panationis
του this one beats me
Γεωργίου would be Georgiou
..........
close enough?
Quote from: DartPlayer170 on October 26, 2011, 05:41:53 PM
Your last statement is not correct. You can hook up a 4 ohm or an 8 ohm speaker to the 2030A.
You can replace the wall-wart to a 20W ( more would be a waste since the 2030A cannot handle it ).
The problem is to figure out how high of a voltage to get for the wall-wart.
There are two problems:
1 - the rating on the wall-wart is nominal. It may be more than the rating even at full load.
2 - the current drain of the 2030A is dependent on the supply voltage, the load and the input signal. And hence, so is the power dissipation.
The 2030A is rated for 44V max and 20W max. However, the current is dependent on the load. If you use a 4 ohm speaker then a 34V supply will dissipate 20W. I=P/V so the current is about 600mA.
What I can tell you is that I have replaced the wall-wart with a 24V 600mA and it works fine.
If you want to create a cleaner sound with the gain at 0, then you need to decrease the gain in the first stage of the amp. The designers set it too high. The clipping diodes that you were told to remove begin distorting the signal at about 800mVpp. You could just remove these diodes as suggested ( d1 and d2 ) if you don`t want to be able to use the distortion circuit. Another solution is to increase the negative feedback to the stage 1 amp. This can be achieved by replacing the feedback resistor with a higher value. The feedback resistor is in series with an electrolytic capacitor between either pin 2 or 6 ( depending on which one they are using as stage 1 ) of the JRC4558D and ground.
Quote from: J M Fahey on October 26, 2011, 05:25:42 PM
Fact is, LM386 was designed with *extreme* simplicity in mind.
So much so, that it includes the gain setting negative feedback resistors.
To provide you an option, one of them is connected between pins and 8.
Open: "normal" gain, good for most uses.
Shorted: quite a lot more.
But there is some DC voltage betwen those pins, so if you add a pot there to vary the gain, you need a cap in series with it or it will scratch.
If you add a gain switch, it will pop when activated.
If the connection is fixed, no problem, can use or not the 10uF cap at will.
a 100nF cap is too small and, best case, will work as a bright control.
Quote from: joecool85 on October 26, 2011, 02:01:22 PMQuote from: Dimi Pana on October 25, 2011, 05:39:16 PM
Also, when jumpering pins 1 and 8 of the LM368, should n't a capacitor be in there as well? I read somewhere about this but unfortunately do not remember any specifics.
On all three LM386 amps I've built I jumpered 1 and 8 directly, no cap or resistor.
Quote from: joecool85 on October 26, 2011, 02:03:10 PM
Quick answer:
You can split it with a Y cable, but it is better to do it with an electronic splitter circuit using a TL074 or similar.
Quote from: J M Fahey on February 03, 2011, 10:58:44 PM
Well, with no volume and minimum gain, what's the DC voltage on LM386 pins 6 and 5?
What's Q1 (Fet) source voltage?
In that schematic, C3 should be 10uF and don't know what C4 is supposed to do.
I would not use it at all.