Q1 and Q2 are the amplifying devices, the arrows of their emitters tied together. This whole circuit consumes five parts, two of which are transistors (though they could be tubes) the other three are resistors. This very topology, with a handful of extra parts and a power supply, is essentially what a few expensive preamplifiers have, and not much else.
Here's the takeaway for today. Power supply noise rejection.
Believe it or not, this simple little handful of parts not only lowers input noise from a balanced cable, it also performs the same magic with the power supply feeding it. Ripple, hum, noise, common to the power supply, are reduced handily by the same means that lowered input noise, common mode rejection—the propensity of a circuit to ignore that which is in common, and amplify that which is not. The positive and negative power supplies connect equally to both sides of the circuit.
Tomorrow we'll cover balanced outputs, then pull all three elements together in the last few posts, before moving on to…hell, I don't know.
It gets even better
Q1 and Q2 are the amplifying devices, the arrows of their emitters tied together. This whole circuit consumes five parts, two of which are transistors (though they could be tubes) the other three are resistors. This very topology, with a handful of extra parts and a power supply, is essentially what a few expensive preamplifiers have, and not much else.
Here's the takeaway for today. Power supply noise rejection.
Believe it or not, this simple little handful of parts not only lowers input noise from a balanced cable, it also performs the same magic with the power supply feeding it. Ripple, hum, noise, common to the power supply, are reduced handily by the same means that lowered input noise, common mode rejection—the propensity of a circuit to ignore that which is in common, and amplify that which is not. The positive and negative power supplies connect equally to both sides of the circuit.
Tomorrow we'll cover balanced outputs, then pull all three elements together in the last few posts, before moving on to…hell, I don't know.
0 comments