DIY Audio Projects Forum

HI.

That exactly what I thought it is. I just want to you to confirm to me.

The last PS I would use to power any audio amps is switch mode, a hugh generator of RFI, let alone heating tubes.

Here what I am using to power the 6.3V tube heaters of my tube phonostages:- a digital power pack comprising a 6V sealed lead acid cell, rechargeable by a 7.5V SMPS.

Yes, I've chosen SMPS for its constant regulated voltage O/P, extremely efficient, cool running & very small size. I scrapped the SMPS board from a redundant charger sleeping in my parts bin & used it to build an small outboard 6.3V heater pure DC power pack for my phonostages.

So pure DC heating means no hum from the tube heaters/filaments, which is crucial for DHT like 300B & the likes. I have the heater circuit floated from the phonostage circuit to ensure zero ground loop from the PS.

Knowing SMPS is a well-known RFI generator, it must be 100% isolated from any audio circuitry, including their AC powerlines. To ensure no RFI generated from the digital power pack affecting my auido rig, I've so design/built this digital heater power pack that when the SLA cell inside the power pack is heating the tube heaters when I am playing LPs, the digital charger is always switched off & electrically 100% isolated from the SLA cell.

Under no circumstances the digital charger & the SLA cell work at the same time by proper switching circuitry incorporated in the power pack, which is built in a small plastic equipment box, 7.5" x 3.5" x 2.5". Thanks to the miniature 7.5V 4ADC digital PS board, only 2.5" x 2". which permitted me to build the entire PS (digital charging board + 6V SLA cell + all switching gears, LED indictors & voltage measuring points etc etc) in such a small box !!!!

To further ensure no RFI leaking via its AC powre cord & battery DC cables hooked up to the phonostages, they both have RFI ring suppressor snapped on.

I enjoy the pure DC heating sound let alone cute looking of the small power pack, which sits right beside my super-upgraged Dynaco PS-2 pre-amp.

c-J

PS: IMO, you are playing with (RFI) fire !

SMPS passes the test.

SMPS is a technically smart way of heating tubes, but not muscially wise way to do so.

By the same token, I would not like listening to class D amps despite how smart they are designed built. Extremely high efficiency, low low measured THD blah blab blah..

The wise way I heat up the tubes as described above is to make use of the extremely high efficiency of digital PS (to charge up the heaters battery), without the music digitally intermodulated.

I actually measured RFI contamination of the powerline plugged in by a CD/DVD player.using a wideband powerline & EMI noise analyser. I can read EMI surge up whenever the player is switched on in different home & commercial locations. This proves any digital gears emit EMI/RFT into the powerline.

That's why we NEED RFI powerline filters/conditioners.

Another source of RFI very hard to stop is airborne RFI emitted by any digital equipment.

That's why I always switched OFF my CD & DVD-audio players whenever I play LPs. So airborne/powerline RFI emitted by those digital players can be eliminated.

Why should we open up this huge can of digital worms ???? To incorporate digital electronics in an audio amp is NO NO to me.

NO. I did not say that.

I responded to John who made that statement, not to you at all. Why?

Sorry for off....
To all american guys....Sorry for my tactless remark about transformers. I'm confused....
/sorry for my bad english!/.

Take it easy, bud.

I responded to John who made that statement, not to you at all. Why?

Sampleaccurate, very ambitious for a first build! Most start off with $1 tubes, not 300B

I'll be following this one closely as I'd love to try a SE 300B following much the same ideas.

The output from a SMPS should be just fine for the heaters. If EMI is an issue, you may want to move it out the the main chassis or put some shielding around it.

Sometimes a SMPS can inject noise into your household mains. Computers are really bad for this but as far as using it for heaters, it is a good economical choice that has worked well for many.