Fender Deluxe 5D3

[gldtp99]

A friend brought over his old 5D3 amp and i'm extremely impressed, this one has 9 pin preamp tubes------- i've built several different takes on the 5E3 and several similar 5E5-type heads (@30 watts with 6L6GC x 2).
so i'm thinking about building a 6V6 x 4 head version of the 5D3 circuit----maybe the paraphase PI just is a little more to my liking.
I've got a cast-off '90's Vox AC30 OT that should do ok---- and i've been looking at PT and B+/current capacity options.
That orig 5D3 has one of the sweetest natural OD's i've ever heard so getting a similar amount of PT sag seems important in this build.
I built a 35 watt 6L6GC x 2 version of a BF Princeton Reverb for a guy and he's very happy with it---- but i know that i went too stiff on the Power Supply because it sounds more like any other larger BF Fender w/reverb rather than the saggy sweetness of the real Princeton Reverb---- i recently rebuilt a '68 SF Princeton Reverb i got in a trade---it went to a jazz player friend----- that PR is one sweet sounding amp.
So i don't want to repeat the "mistake" that i made with the 35 watt PR with this 6v6 x 4 5D3 head build and have the power section too constipated sounding------ just some amp planning i've been thinking about lately............................gldtp99

[soundguruman]

If you want sag, just use smaller uF capacitors. It was 10 uF in the older, smaller amps.
As time went on people complained about the 60 cycle hum and the capacitors became larger values.
So more sag, more hum. Hmmmmm.

[printer2]

Keep the large cap but add another stage of filtering with a medium sized resistor and a small capacitor to feed the power transformer. The voltage will sag as you draw current out of the small cap and through the resistor but rather than AC from the transformer you will be drawing DC from the preceding stage.

[loudthud]

Sag is a function of the rectifier impedance and the capacitance of the first filter cap. If you watch the voltage at the first filter cap when the output stage suddenly demands current with an oscilloscope, you'll see the ripple increase. While the positive side dips a little bit (rectifier and transformer losses), the bottom of the ripple dips significantly (the amount of capacitance). A choke will find the average of the ripple and deliver a voltage about half way between the positive and negative peaks of the ripple to the screens. So screen voltage dips quite a bit when ripple increases. A tube rectifier will round off the ripple and soften some of the harmonics contained in the ripple.

Too much capacitance on the first filter and the amp seems stiff and too clean. Some ripple needs to bleed through to the output when an amp clips. Too little capacitance and the amp seems spongy and lacks bass. So getting the right amount of capacitance on the first filter plays a major role in controling the dynamics of an amp. A resistor in place of a choke slows the recovery of the screen voltage and that plays a role in gain compression and recovery. Experiment and have fun.

[gldtp99]

Thanks for the info, guys----- i'm just getting my head around planning this build--- but it will be a while before i can get to it------ several locals want me to build other types of amps for them----so this planned build, even though it's interesting to me, is on the back burner--- the locals want a few different versions of Marshall 2204 circuits (stock/various mods)---no problem, but i like to build amps that i've never built before---building the same old thing isn't interesting anymore.......................gldtp99

[jmaf]

You can use a 100 to 220 OHM resistor before the rectifier bridge, on one of the leads of the AC side, simulating a smaller transformer.