calling all the power supply gurus

[changes]

hey guys i need some help here
i have a modded paia stack in a box.
i didn't use inverters to charge up the voltage but the typical diode/cap configuration.
the heaters of the the tube are being powered from 12V AC but the problem is that there is no refernce to ground so i have a lot of hum.
i know this ain't a layout problem cause when i powered the heaters with another trannie i had no hum at all

1) i tried to put 100ohm resistors to ground but that didn't work cause the charged up voltage went down to almost 3V or so(should be 40)
2) tried a diode bridge and a regulator for dc powered filament but had the same results as above.

any guidance?

[Minion]

Maybe add a Voltage referance to the Input...

[Paul Perry (Frostwave)]

Are you powering the rest of the circuit from the same transformer as the heater?

And how much hum is there.. are we saying 'an annoying hum that I can hear in the quiet bits" or "it sounds like the mains are connected to the input, there is nothing but HUMMMM".

Always posible: the heaters draw so much current, the transformer is overloaded and can't supply a steady supply for the amplifier part.

[R.G.]

i didn't use inverters to charge up the voltage but the typical diode/cap configuration.

Maybe there's a reason they used the inverter that way, eh?

any guidance?

Without seeing exactly the schematic you wired, no.

You already have two solutions available: using a second transformer to power the filaments and using an inverter.

I'm guessing you want a solution which is only "add a resistor here...", right?

[changes]

the hum is not that loud but audible all the time, especially when not playing



things are wired up like that, with the heaters being powered straight from the secondary.

the reason i didn't use the inverters was that i ripped off all the opamps and used an extra tube.

if i go back to the inverters will the noise be less audible?

any solution is welcome

[R.G.]

That helps.

If it were mine, I would first put a big capacitor from + to -, maybe 100uF to 470uF, 63V. That may help. You don't list any component values so I can't tell what the ripple will be.

You also don't show where ground is connected, so I can't tell if ground hum is a problem.

[changes]

for ground i used the "-" of the cap on the right side
all diodes were 1n4007
and all caps shown above are 470u/63V
i have one 220u from + to -
and after that a 1k/100u  filter

[R.G.]

OK. That helps.
First suggestion: flip all the polarities. Reverse all the diodes, all the caps. That puts the + output at the right side where the - side is now, but more importantly makes one end of the transformer winding be at ground. When you are doing this, be sure that the ground side of the wiring to the heaters and the ground side of the multiplier meet at one and only one point. Also, take one and only one wire from that same point over to your tube circuits. That last wire is "signal ground" and must not share any conductive path with the wires to the filaments or the multiplier.

[toneman]

look at the schematic here---

http://www.paia.com/prodimages/siabsch.pdf

looks like in your substitution of a xfmr for the inverter, U have not gnded one side of the secondary(?)

So,...... the "HiV" side has no gnd reference.

guess U are not using a PAIA pcb(?)

try rewiring the HiV to look like the PAIA schematic.

Also, Using DC for the filaments is better in that it reduces the noise.

afn
T

[R.G.]

So,...... the "HiV" side has no gnd reference.

Yeah, that would do it. I guess I just assumed it was grounded SOMEWHERE.

[changes]

so if i get it right i should ground the upper side of the secondary(in the circuit shown above).Will it work that way?

[R.G.]

No. Well, OK, it will do something, so it will work in some fashion. But it will not do what you want.

Do this:

1.Change the multiplier schematic. Reverse the polarity of each diode and each capacitor. In terms of actually rebuilding the thing, there is a way to make what you have already wired up match the new schematic by moving one diode and reconnecting the transformer wires. But it will probably be less confusing to rebuild it to the new schematic.
2.When you have this done, the terminal on the lower right will be 60V more positive than the terminal nearest the transformer on the left. Connect the left terminal with a single wire to signal ground. Connect the right terminal, which we can now call B+, to the plate supply of your tubes.
3. Connect the transformer leads across pins 4 and 5 of your tube. Leave pin 9 open.

If you still have hum problems, you can insert a 1K resistor between +60V and another 470uF cap between the outer end of the 1K and ground, and use the new 470K as your plate supply. This will cut ripple on the power supply from about a volt and a half (says Mr. Circuit Simulator) to under 20mV.

[changes]

wow seems like the solution to my problem. i'll try that asap. thanks