Cheap tube mic preamp power supply

[mrtnasty]

Is there any reason why using one of these cheap power supplies to power a tube mic preamp like an RCA Ba1a is a bad idea? It says it produces 280V DC and 6.3V for the filament:

https://www.aliexpress.us/item/3256...srl2EXR8glhoCeVIQAvD_BwE&gatewayAdapt=glo2usa

Thanks! David

 

[mjrippe]

With 5A @ 6.3V and 200mA @ 280V you could power several BA1A. Extra filtering on the 280V rail could also drop it a few volts if needed. I have not used one of these switchers for a tube project yet, but for the price I might try one.

 

[pucho812]

The only reason to avoid it is that it is a switch mode. Will probably need filtering after the psu to eliminate switch noise

 

[mrtnasty]

I bought the power supply and it seems to work great and is dead quiet! I just posted about using it in my RCA BC-2B preamps here:
https://groupdiy.com/threads/rca-bc-2b-restoration-and-power-supply.90135/

 

[pucho812]

Oh really? cool,

 

[emrr]

I have questions about that B+ current rating, a little terrifying and is that really continuous. There are very few historical supplies with such a rating outside of bass amps

 

[mrtnasty]

I have questions about that B+ current rating, a little terrifying and is that really continuous. There are very few historical supplies with such a rating outside of bass amps

I agree, it seems a little too good to be true, unfortunately there is very poor documentation and absolutely no customer support for these power supplies. But it seems to be working very well to power 4 12ay7s, I guess the worst thing that can happen is the power supply blows up one day and I go back to a more conventional power supply?

 

[emrr]

I’m sure it has no problem at all with your usage, but on paper you might power an entire tube console, and that seems questionable. I don’t know enough about the behaviors of switching supplies at full load. Many require a minimum load to get into a lower noise/ripple region I think; i could be wrong, not enough coffee yet.

 

[rock soderstrom]

But it seems to be working very well to power 4 12ay7s, I guess the worst thing that can happen is the power supply blows up one day and I go back to a more conventional power supply?

The 4x 12AY7s are no challenge for that SMPS.

I have seen a similar SMPS module in a hi-fi power amplifier with fat power tubes. I guess 100mA or even more on the B+ rail is no problem. Above a certain load, I guess you have to ensure good ventilation. I've ordered this slightly larger module, I'm curious to see what it can do.


Edit: a comment on Ali

"The power supply works as described. It can drive 2 * e235L at approx. 100mA. It not break down if ther is a peek. It have to be cooled. If if if had a negative grid bias it were perfect."