A diode drops ~600mV to 700mV depending on the current passing the diode.
A series pair will drop ~ 1.2V to 1.4V.
The diodes acts like a shunt regulator, much the same as a Zener Diode shunts away excess current.
The CCS sets the total current flowing to the load and flowing through the shunting diodes.
If the CCS is set to a current that exceeds the load current then the diodes shunt away the excess current and as a result, drop a voltage, Vf. Vf can be set by adjusting the CCS current. Vf is your output voltage to feed the load.
A series pair will drop ~ 1.2V to 1.4V.
The diodes acts like a shunt regulator, much the same as a Zener Diode shunts away excess current.
The CCS sets the total current flowing to the load and flowing through the shunting diodes.
If the CCS is set to a current that exceeds the load current then the diodes shunt away the excess current and as a result, drop a voltage, Vf. Vf can be set by adjusting the CCS current. Vf is your output voltage to feed the load.
The question is what is the noise level of a pair of diodes compared to a single LED?
Thanks. What is the noise of a single 1N4148 diode, compared to a single LED?
Hi Salas, listening better, the sound is rolled off at hi frequencies, the cymbals are too silky and beyond the soundstage, like there was a gently low pass filter
in the hi treble region.
I'm using a led string (5x12v) bypassed with 680uF.Some years ago, working on
a CCS, I tried to bypass a single zener(was a 12v one) with different values of capacitance and I noted subjectively that when the cap was big,there was more
bass and viceversa.
Today I made some try; I used a 220R+ led string and bypassed all with a Pan
220uF. Now the sound it's a bit better, the noise is a bit less, but the timbre it's not correct again.Finally I changed the cap with a BG 10uF. Now the sound is more vivid and real and the noise it's the same with the 220uF cap.
Question:bypassing a zener, different values of capacitance can change the
timbre( i.e. the freq response) of a circuit?
PS , I'm talking of listening impressions, I made no measurements.
Because you talk electrolytics and Zeners, yes there are differences for noise level, its shape, the filtering capacitors values, their THD, bandwidth. With LEDs & 220R the capacitance value can be substantially lower than with a Zener. Depends on the audio circuit's gain and PSRR a lot also. If 10uF was enough in the particular application, you can even try a plastic cap.
It was the fifth harmonic of your clock if I remember correctly and was there with the previous psu too. When you are at 100MHZ region it can be picking by the probe's gnd crock inductance even. I don't think that the 1.2R can produce anything that high on itself anyway. Did you try ferrite beads on suspicious places?
Yes, I did that too. Both regular and smd ferrite beads were put on the test. I read the article provided by ikoflexer (big thanks!), and found this is not an easy task to just find out the cause. Due to my lack of knowledge, I ordered 'Electromagnetic Compatibility Engineering ' - a book by Henry Ott. It seems there are certain techniques to deal inteference problem. I hope I can solve it one day.
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