Re: Power Supply Filtering: Is More Better ?




"John King" <kingsx@xxxxxxxxxx> wrote in message
news:obdtg.129942$dW3.1470@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Chief_Billy@xxxxxxxxxxx wrote:
I'm building a Marshall JTM-45 clone. The BOM calls out 16uF filter
caps
at the pre-amp C- and D-feeds (to PI and pre-amp, respectively) from
the PS. I'm thinking of bumping these up to 40uF, same as the B-feed
(to screen grids) . I'm thinking that this will give me a tighter
bottom end and a more lively tone. I'm using a GZ34 tube rectifier.

Would increasing the filter , as I plan to do, be a 'good thing' ? Any
detriments ?



There are several reasons not to drift too far away from spec
on such an amp build. While it is true that capacitors in general
have a wide tolerance band which allows some leeway, in the case
of power supply filters, there are consequences. Tube rectifiers
have specs as to what capacitance they are tolerant to. Even with
SS (diodes) for rectification, raising the capacitance value will
have some sonic impact. Generally in the form of 'tightening' up
the dynamics of the amp. (Which seems to be the effect you are
after.) Just be mindful of the spec of the GZ34? recto tube, and
what its capacitance limits are. You could always do a 'dual recto'
on it; and have switchable SS (diode) rectification feeding bigger
caps to produce a different sound than the stock setup. No risk
to the recto tube that way. Probably really 'tighten' it up too!

John King


I'll build it stock, then try adding a little more capacitance one stage at
a time.
Luckily, caps in parallel are additive..makes it easy.


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