Tube HW question from a software guy

[rgoodnight]

I have a piece of tube equipment (a Bellari vp129 tube phone stage) that came equipped with a 12VAC - 600mA power supply (i.e. wall wart). The spec says that the unit can take 12-18VAC.

I misplaced the power supply during a move. I cannot find a replacement supply with the exact specs (and don't want to wait weeks and spend $40 for a replacement from the manufacturer) and I have some questions about using power supplies with a higher voltage rating (but still within the 12-18VAC in the spec).

I assume that the spec indicates that I cannot "fry" the unit by having up to 18V instead of the 12V. I don't know enough about tubes or the architecture of the Bellari, but I have to believe that powering with, say 16V, instead of 12V will change its sonic characteristics quite dramatically.

Question 1) What is the impact of the supply voltage on the sonics/performance of tube gear?

Question 2) Can I simply put a resistor in series to drop the voltage of my 16V replacement power supply to 12V, or is that going to affect the quality of the power and affect the performance of the tube unit.

Question 3) Am I going to do any damage to the Bellari by trying different power supplies and voltage ranges as long as they are within the specs? This way I can use my ears to judge.

Thanks,

Randy (who remembers when we didn't worry about power conditioners, power cords, etc.)
rgoodnight is online now Reply With Quote

 

[SHiFTY]

If it's in the specifications it should be fine.

Just make sure that your power supply is rated for 600mA or more.

It's too hard to say what difference it will make- you need a schematic for that.

 

[dsavitsk]

I would guess there are voltage regulators in there that take whatever you give it and turn it into what it wants. So, a higher voltage PS probably will not influence the sound at all. However, since the tube's heater draws 300mA at 6.3V (likly the largest draw in the amp), and a voltage regulator needs to drop from the input voltage to 6.3V, as the PS creeps higher, the voltage regs will need to dissipate a lot more heat -- almost 2 extra watts moving from 12 to 18V. Probably not a huge deal, but worth being aware of and probably giving it some extra ventilation.