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Re: Tweaking subwoofer amp - Is it worth it?

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In Reply to: Tweaking subwoofer amp - Is it worth it? posted by Dan W on May 05, 2000 at 16:32:50:

First, does the amp have a power supply regulator? Anyway,
Diodes: what is good for tube amp is not good for SS one. Shottkies should be much better than HEXFREDs in this case. You may use significantly underrated ones for lower PSU impedance, just keep in mind their very high reverse current.
Caps: Not a simple question. Increasing the capasitance has some drawbacks, first, higher start-up current and second, higher current peaks in the power transformer and further in the power lines.
Also: I don't think using the output of a tube amp loaded with a speaker is a good idea. Especially if you remove NFB.
Lesha

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Re: Tweaking subwoofer amp - Is it worth it? Dan W 10:44:30 05/06/00 (2)
Lesha, I appreciate the input, but you are talking a bit above my head in some cases. I am not too familiar with shotke diodes. Why is reverse current a problem?
Why is loading the amp from the ouputs from the tube amp a problem? The amp is seen as nearly a zero load by the amp, as I understand it. And don't worry, I like my NFB, you should know that :)
Your comments about cap size are also a bit baffling. I guess my tweakings have been entirely in the tube domain until now, so I am fishing in dark waters.
Further input would be greatly appreciated.
Dan W
- Re: Tweaking subwoofer amp - Is it worth it? Lesha 11:32:43 05/06/00 (1)
  Diodes: Shottky diodes have very low forward voltage drop and very fast and smooth recovery. However they suffer from two things: low breakdown voltages and high reverse current. I was trying to warn you against using the highest current rated diodes that fit. I don't know the voltage and current of your power supply so I can't say more.
  Sub connection: the impedance curve of the speaker is not very flat at low frequencies especially if they are placed in a real room and with relatively high output impedance of the tube amp it may give a frequency response that is not very flat as well.
  Caps: Of course you may try to calculate the capasitance you need, then simulate the rectifier and calculate if power transformer core would saturate. But I think you'd better double the present capasitance and see if it makes things better.
  Lesha
  - Thanks Lesha (NT) Dan W 17:41:40 05/06/00 (0)
    NT

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