Use of diode in projects M-Levision

[Rafael L]

What is the reason designer of the Mark Levision using many diodes in their projects.
Would be for thermal stability?
Or only voltage drop?

That schematic has quite diodes across the amp:

http://www.audio-circuit.dk/images/schematics/Mark-Levinson-23-pwr-sch.pdf

 

[Nelson Pass]

Perhaps the designer was being paid by the part.

 

[Artie]

Diodes are a cheap and easy way to produce a voltage reference. 1 diode drop is roughly 600mv's. Where you see 2-in-a-row, would be approximately 1.2 volts. 4 would be 2.4 volts, and so on and so forth . . .

 

[Rafael L]

Perhaps the designer was being paid by the part.

Or leave the amp more difficult, to anyone copy

 

[Rafael L]

Diodes are a cheap and easy way to produce a voltage reference. 1 diode drop is roughly 600mv's. Where you see 2-in-a-row, would be approximately 1.2 volts. 4 would be 2.4 volts, and so on and so forth . . .

I know that diodes are used as reference voltage, current sources for example, generally is used one or two diodes.
For voltage drop could use a resistor metal film that would give the same result

 

[blueskynis]

But putting a bigger resistor would increase LTP gain and therefore possibly making amplifier less stable. Diodes have low Rd (in order of ten ohms) and they do not alter gain so much, they only shift DC value. Maybe they are also used for thermal compensation also...

EDIT: Ohh, I didn't noticed more diodes on other pages...well I don't know why the designer used so much diodes...

 

[cbdb]

Looks like most of these diode chains are voltage refrences. (voltage level shifters). Diode voltage drops are not as dependent on current changes as resistors. This helps with the power supply rejection ratio. And I think regular diodes are less noisey than zener diodes.

 

[Rafael L]

Looks like most of these diode chains are voltage refrences. (voltage level shifters). Diode voltage drops are not as dependent on current changes as resistors.

Look the picture attached, there are two diodes to drop VBE in output stage (class-B),to a greater bias simply increasing the number of diodes, would be better that resistors?

 

[cbdb]

simply increasing the number of diodes, would be better that resistors?

Adding another diode is too large a voltage jump, thats why most use Vbe multiplier wich lets you dial in the exact amount of bias. The main reason diodes or transistors are used to bias the out put is so the bias becomes temperature stable. These diodes are mounted right on the out put tranies or on the heat sink so they are the same temp. these diodes do not have the same purpose as the other diode chains. the other ones in the above cct. are V refs for the current sources.