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Class A vs Class AB |
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Analog Kid
Senior Member Joined: 07 Mar 2008 Location: Germany Status: Offline Points: 209 |
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Posted: 19 Nov 2008 at 5:43pm |
As a guitar player I greatly prefer the sound of class A valve guitar amplifiers. The guitar valve amplifier I had to sell to buy my Reflex, had a switchable class A mode. In class A it sounded warmer, sweeter and more organic than in class AB. It was a much nicer and more pleasant sound.
What about for HiFi amplifiers, is there a significant audible difference between class A and AB amps? Does class A also sound better in HiFi? And why don't HiFi amps have a switchable class mode like some guitar amps? Is this not possible to implement? |
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mrarroyo
Moderator Group Joined: 28 Jul 2008 Location: Miami Beach, FL Status: Offline Points: 1401 |
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The one feature from guitar amps that I wished was available in home stereo tube amps is the "standby switch". I have not seen one in home tube amps, yet.
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Miguel
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Analog Kid
Senior Member Joined: 07 Mar 2008 Location: Germany Status: Offline Points: 209 |
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Do any of the amplification experts on the forum want to offer their answers for the above questions? I am still curious to learn more. |
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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Forcing Hi-Fi amps to get hot by moving the bias into class A quarters can help get rid of the "transistor sound", but I think sometimes it is a crutch.
The transistor sound is usually because of instability - messing about with increased bandwidth can take a design to the edge of high frequency instability - and that should also answer why things sound bright. What made matters worse was the RoHS - many components lost much of their warm character with the removal of alleged hazardous substances. From my point of view, rather than pushing bandwidth (taking pole splitting techniques to extremes), with RoHS it's about bringing bandwidth down very slightly to buy a bigger stability margin. In my opinion this gives better results than class A bias. |
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That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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Analog Kid
Senior Member Joined: 07 Mar 2008 Location: Germany Status: Offline Points: 209 |
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Maybe the best way to get rid of the "transistor sound" is to replace the transistors with valves.
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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I guess they'll all have to do that eventually... ...then I'll get ALL their sales! (who dares wins) |
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That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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Analog Kid
Senior Member Joined: 07 Mar 2008 Location: Germany Status: Offline Points: 209 |
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This question still remains, so I will try again: is it not possible to design a HiFi power amplifier, either valve or solid-state, that can be switched between Class A and Class AB at the flick of a switch? Never seen this in a HiFi amplifier before, but in guitar amplifiers it is a quite common feature.
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