Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: JGk on April 10, 2015, 02:10:28 pm
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I am building a single channel DR based on the hoffman board and considering a set of 100uf 350 volts caps in a series for the first filter stage will this change the feel and sound of the amp and would it be better to use 40uf in parallel. I've just have some 350 100uf sparagues handy. Thanks
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I doubt that you could hear (or feel) the difference between 50uf created by your two Sprague caps and 44uf created by two 22uf caps in parallel. The power supply might be a little bit "stiffer" with the slightly greater net capacitance.
Kevin O'Connor says that the parallel caps do a slightly better job filtering ripple than one big cap for the "reservoir" cap (IOW first in line out of rectifier). Original AB763 Deluxe only had two 16uf caps in parallel, so I'm sure a net cap of 50uf would be better filtering than the original.
You probably know all about this, but don't forget the parallel balancing resistors in your cap stack. Like the AB763 Super Reverb:
http://el34world.com/charts/Schematics/files/fender/Fender_super_reverb_ab763_schem.pdf (http://el34world.com/charts/Schematics/files/fender/Fender_super_reverb_ab763_schem.pdf)
Now if you want really good ripple filtering with perhaps a touch more sag, you could put those 22uf caps in series separated by a resistor and create a CRC filter. Resistor value 470 ohms or 1K maybe? Need to be careful about wattage rating though since the entire amp is running through that resistor.
Cheers,
Chip