In Reply to: RE: Nope, no coupling cap with the battery bias posted by mqracing on July 29, 2014 at 14:32:23:
Hi Mikey, long time no see. Hope you're doing well. If I'm not mistaken, the 1570 uses zero-bias triodes in Class B. I'm not a big fan of this topology, but I admit its been many years since I've heard them. As I'm sure you know, Class A2 is very different. In an A2 amplifier, operating conditions at most power levels (including "the first watt") are essentially Class A. The signal may not be exactly centered in the curve, but it's usually close. This means nothing untoward happens (grid current) until power levels are very high, well into the area where nuance and detail are usually masked anyway by the higher dynamics of the sound. More important, being IT or direct coupled, the A2 input circuit creates minimal recovery issues. The design is enhanced from this perspective if the cathode is also connected to ground with a low impedance and no bypass cap. The fact that an A2 design can not only resolve the recovery issue, but also eliminates the audible liability of grid and cathode caps, makes it my favorite topology. ;)
Edits: 07/30/14 07/30/14
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Follow Ups
- RE: Nope, no coupling cap with the battery bias - Triode_Kingdom 07:37:23 07/30/14 (4)
- RE: Nope, no coupling cap with the battery bias - Naz 16:49:29 07/30/14 (3)
- Class A2 - Triode_Kingdom 18:25:19 07/30/14 (2)
- RE: Class A2 - Naz 19:26:22 07/30/14 (1)
- RE: Class A2 - Triode_Kingdom 08:23:31 07/31/14 (0)