“Yeo, I want to build the circuits on your
projects page but you only show signal circuitry but
no power supply circuitry.”
Err, you are right.
An amplifier is basically a modulated power
supply, so the power supply circuitry should get your utmost attention, then
only followed by the signal circuitry, not the other way round. I have built a
few different versions so I could tell you more about each of them, with some
example circuits you could try yourselves. As always, take everything you read
with many grains of audiophile salt, me included. The circuits shown on this
page has been simulated using the excellent Power Supply Designer.
Okay, here goes.
Cheap, cheap, cheap.
The above is a basic “brute force”
method. Least in cost and bulk. For the diode, use whatever super-fast,
soft-recovery, hexfred blah blah blah as see fit. To improve on it without
spending too much, sandwich a snubber circuit in. Snubber circuit courtesy of
John Camille from Bottlehead.
To make it even better, you could opt to swap the
220ohm resistor with a choke. Any choke with DCR (DC resistance) ~200 ohm would
do.
Less cheap, more mojo.
Use a tube rectifier! Kinder to tubes, they don’t
leap to full B+ at turn on, but I don’t welcome the added expense, and the
voltage drop.
The above uses tube rectifier and is 2-stage
filtering. If you prefer to remove one stage, remember to compensate with more
capacitance. If you replace one choke with a resistor, you need to increase the
capacitance too. The above uses 5U4G but if you wish to try something else, go
ahead. Just simulate it with the Power Supply Designer.
If you don’t want to spend too much on tube
rectifiers, since NOS versions could cost a bomb, use TV damper diode like I
did! They are BIG, they can handle lots of voltage and lots of current and they
are CHEAP. Read this.
You could play around with the sound by adding
more capacitance, say use 100uf instead of 50uf but be careful with the first
cap right after the tube rectifiers. Lots of them don’t like high capacitance.
The 5U4G don’t like more than 20uF.
My take for what it’s worth…
I could think of 2 conventional power supply
filters. Choke input and capacitor input. I find that choke input is quieter,
but capacitor input seems to be more dynamic, albeit noisier. Choose whichever
you are comfortable with.
You could hear what you put in the power supply
circuitry. I like chokes. Presence of chokes smoothen the mids and highs, deepen
the lows but at a loss of speed. The Presentation seems to be more relaxed,
slower. Kenneth once told me he likes the bass of cap input but prefers the mids/highs
of choke input. There you go.
Electrolytic capacitors get a lot of flak for its
sonic characteristics. Well, we live in a real world where, unfortunately, cost
per micro-farad is the lowest for electrolytics. Elna Cerafine and Black Gates
are raved as the best sounding electrolytics but the prices is too high for a
cheapskate like me.
Okay, my approach to good sounding, not too
expensive power supply circuitry is this. I like lots of chokes and very little
capacitance. When you don’t have lots of capacitance, you really need lots of
chokes. Unfortunately, this makes your amp really heavy. Chokes are cheaper than
quality capacitors.
Unfortunately as well, you don’t see lots of
chokes in commercial designs. This makes the amp too heavy. Nor do you see the
usage of oil capacitors in the power supply. The combination of chokes and oil
capacitors make a VERY heavy power supply. My power supply is heavier than my
signal circuitry.
Okay, how important is the power supply?
Alright, consider this. My Darling amp originally
uses “cheap, cheap, cheap” as shown above. Diodes, resistors and 2
very high capacitance capacitors. RCA tubes sound musical but thin and
compressed. The GE 5 star beats it by a mile.
Then I rebuilt
my Darling with an extra-mojo power supply. Lots of chokes and lots of oil caps.
This time, the difference between the RCA and the GE 5 star is subtle. Not day
and night like before. Huh? I couldn’t believe it!
So, before you pay expensive moolah for NOS tubes,
consider uprading your power supply. You may be in for a treat.
