External psu question

[Schmilsson]

In the case of a tube unit, with an external psu, how do you guys deal with the connectors and charged caps?
If all the stabs are in the psu, then fine, simple have the psu end be female and the other male. But if both contains stabs, like in a pre with a caps between each stage, then what?

 

[emrr]

Any safe design should have some bleeder resistances, though it's rare to see them in a tube preamp module. 

I generally use female as the PSU output and male for the device.  Situation may dictate otherwise. 

 

[Schmilsson]

To be specific, a NYD two-bottle.

 

[sahib]

It really depends how far you want to take the safety issue. As mentioned the female connector on the psu side is one way or as Doug suggested the bleeder resistor is the other.

But if you do not wish the bleeder resistor connected continuously you can use a relay to disconnect it after you plug in the power supply. For this you can have two additional pins on the power connector and obviously two additional wires on the power lead. Short these two pins on the equipment side connector so that as soon as you plug in the female psu connector the relay turns on, and disconnects the bleeder resistor. When you unplug the connector the relay turns off, and connects the bleeder resistor to safely discharge the capacitor.

Obviously you can also use the relay to actually switch the psu output on or off.

 

[shabtek]

diodes too

 

[Schmilsson]

Relays sounds like like a hassle, but neat idea.
Would a bleeder on the preamp side affect the performance?

 

[sahib]

From the total current consumption point of view you'll have just another (resistive) load added onto the psu output. From the noise point of view you'll have another component that generates thermal noise. But how much does it affect the performance of a valve device? Just try if you hear any difference.

 

[johnR]

How about using an input connector with shrouded pins? Bulgin PXO95x or PXO55x series might do the job. They're common on small stage lighting systems here. (Don't know how easy they are to buy where you are).

From the noise point of view you'll have another component that generates thermal noise.

The bleeder would be across an electrolytic cap so any thermal noise would be shunted out.