35 Volt wall wart?

[Solidhex]

Anyone know where to get a 35 volt wall wart power supply?

--Brad

[Minion]

I have never seen a 35v DC one but I have seen 24v AC ones that can be rectified to give you about 35v DC , Sould be easier to find a 24v ac one ....

[R.G.]

Mouser 412-224034; "24Vac" with 1000uF cap and diode bridge gives 37Vdc unloaded, 35Vdc at 50ma.

That's the part in the parts list for the Vox preamps, anyway. 

[Solidhex]

Ah

  Haha R.g. you read my mind. Thanks guys!

--Brad

[R.G.]

By the way, for the 7-series preamps, you need a 220 ohm/2W resistor and a 25V/5W zener to make the 25Vdc the 7-series circuit wants.

[slideman82]

I don't know if there are 35, more than 30 for sure in some printer power supplies, I have a pair. Really cheap.

[Solidhex]

Hey R.G.

  If the Vox preamp (Conqueror, Defiant, Supreme) wants 25vdc could I just use a 24vdc adapter? I was just reading both the schem for the preamp and the power amp show the preamp section being supplied with 35vdc so I was going after that. Sticking to the plan though I should connect the terminals of the 24vac power supply to a diode bridge ( I have one leftover from a Neovibe build, that would work right?) then place the 1000uf cap across the output of the diode bridge, then both the 220ohm and Zener would be in series? Not to unleash a flurry of questions but is there a minimum voltage rating I should stick to for the circuit for the caps?

--Brad

[R.G.]

If the Vox preamp (Conqueror, Defiant, Supreme) wants 25vdc

It doesn't. It takes in the 35V from the main power supply, drops that to a variety of voltages through resistors. The 715/730/760/7120 preamp runs on 25V from the main amp, not the Supreme/Conqueror/Defiant.

could I just use a 24vdc adapter?

For the 7-series, yes.

I was just reading both the schem for the preamp and the power amp show the preamp section being supplied with 35vdc so I was going after that.

Good plan.

Sticking to the plan though I should connect the terminals of the 24vac power supply to a diode bridge ( I have one leftover from a Neovibe build, that would work right?)

A 24VAC adapter should be OK. I bought a 24Vac/300ma adapter from Mouser, and it gives me 36.3V unloaded, pulls down to 35V under load.
By the way, the project boards, if you get one, will come with parts list and Mouser part numbers. A 24Vac adapter rated for 300-400ma appears to be about perfect. This is enough that the maker had to make the low-load voltage a little high, and so it makes our 35Vdc under light load.

then place the 1000uf cap across the output of the diode bridge,

Yes, that gets you 35Vdc for the Supreme/Conqueror/Defiant preamp.

then both the 220ohm and Zener would be in series?

The 220 ohm resistor and the zener form a shunt regulator. The 220 ohm resistor is the right size to let about 52ma of current flow from a 35Vdc source if the other end is held at 25Vdc. The zener does this by eating all the current needed to keep the voltage across it down to 25V. So the 220 ohm is in series with the output of the 35Vdc power supply. The zener is in parallel with the 7-Series preamp board.

Not to unleash a flurry of questions but is there a minimum voltage rating I should stick to for the circuit for the caps?

All capacitor applications have a minimum voltage rating that should be used. The rating is that voltage that never gets exceeded, plus a little safety margin. In the case of the power supply filter, that's 50V; it's 50, not 35, because if you run it unloaded, the power supply can make 36-37Vdc, and that will be stressful - although probably not disastrous - to a 35V rated cap. So use the next voltage rating larger.

The ..um.. parts list for the project will list all the cap voltages as well as the Mouser part numbers.