Talk:Valve audio amplifier technical specification

message: were the article mentions that SETs operate a lethal voltages it should be changed. Its not the volts that will kill you, its the amps(milliamps in this case). The average static shock people commonly get can be thousands of volts yet not do any damage because the amperage is so low.
You're wrong. Ohm's law applies. Watch this video for clarification: http://www.youtube.com/watch?v=8xONZcBJh5A  — Preceding unsigned comment added by 62.80.140.10 (talk) 11:13, 3 October 2013 (UTC)
thread_title: lethal voltages

message: "For this reason class B amplifiers are arguably well suited to eg pop and rock music where high sound levels predominate"
This seems to give the impression that class AB and B are unsuited to other music types, which is clearly not the case.
More to the point, the suitability of class B to high power music has nothing to do with the quoted reason, rather it is down to practicalities, including costs. When running huge output powers, high efficiency means less power consumption, more manageable levels of heat dissipation, and lower component diss equals lower amp cost. The relationship between output and distortion is minor in comparison.
Tabby (talk) 01:02, 18 December 2007 (UTC)
thread_title: Class B and rock concerts

message: "Following its invention by Black, negative feedback (NFB) has been almost universally adopted in most amplifiers (of all types) and universally in amplifiers operating other than in class A, to provide substantially improved measured distortion performance, flatter frequency response, and more repeatable performance irrespective of component variations."
Almost, but I had a pocket dictaphone using class B and no nfb. It sounded terrible. Early 70s, with very minimalistic discrete transistor circuitry, though class B because it was battery powered. At least the use of germanium rather than silicon reduced the xover distortion a fair bit, making it terrible rather than unintelligible.
I tweaked the article.
Tabby (talk) 01:02, 18 December 2007 (UTC)
thread_title: nfb and class B

message: "Today's circuits in most cases remain similar to circuits from the golden age, however they benefit from dramatic advances in ancillary component quality (notably capacitors)"
Surely the main component quality issue in old kit is not caps, but switches.
AFAIK modern caps are no better than old, despite the fact that there seems to be a lot of mythology built up around bad caps since the 90s.
Tabby (talk) 01:02, 18 December 2007 (UTC)
thread_title: Component Quality

message: Using term "SET" to describe the common cathode voltage amplification stage is not standard practise in texts. The term SET almost always refers to power amplification, specifically the output stage.
Also note the word triode within its definition. This article largely ignores the pentode device and therefore falls woefully short of justifying its title description. Using the term "common cathode" gain stage and noting that the explanation is based upon the triode might be a first step in rectifying these shortfalls.  —Preceding unsigned comment added by 121.72.27.120 (talk) 22:25, 5 June 2008 (UTC)
thread_title:  SET 

message: These are DC systems.  From the impedance page:  When the circuit is driven with direct current (DC), there is no distinction between impedance and resistance; the latter can be thought of as impedance with zero phase angle.  Therefore impedance is resistance.  I am just starting in this field, but I am already developing a concept: AudioFOS.--John Bessa (talk) 00:16, 2 October 2011 (UTC)
replies: text: They may be powered from DC, but the signals that audio amplifiers are called on to amplify are AC.  Thus the impedance most certainly does not necessarily have a zero phase angle because there is reactance present in the circuit.  The reactance comes not only from the capacitors and inductance (transformers) in the circuit, but is also present in the valves.  Capacitance from the proximity of the valve components, and inductance in the valve lead in wires.  There is also a less obvious source of phase change through a valve that comes about because the electron stream carries the signal between the control grid and the anode relatively slowly (transit delay), but this is really only a problem in R.F. valves.  86.157.171.34 (talk) 16:48, 24 January 2013 (UTC)
thread_title:  Why impedance?