PSUIII regulated supply.

Graeme · Post by **Graeme** » Fri Aug 02, 2013 11:04 pm

I was chatting with richard this evening and he suggested it may be worth looking into a voltage regulated supply for my phono stage.
Phono is wd III clone, as is the PSU.
I have spare voltage but will have to check how much.

Has anyone done this?
Worthwhile?

Can anyone point me towards any pages where i can learn whats involved?

Thanks

colin.hepburn · Post by **colin.hepburn** » Sat Aug 03, 2013 12:35 am

Hi Graeme
Here a list of links for most things WD phono and PSU
http://www.world-designs.co.uk/forum/sh ... hono+links

IslandPink · Post by **IslandPink** » Sat Aug 03, 2013 11:15 am

Graeme
A regulated supply for a phono can be as simple as the modification shown in the upper right corner of the circuit on page 1 here :

http://www.audio-talk.co.uk/phpBB2/view ... 88&start=0

This is a simple shunt regulator formed from a supply of about 340V , feeding a constant current source ( Gary Pimm in my case, or DN2540 cascode if you like ) which feeds the signal circuit and a pair of OD3 gas tubes.
The OD3's keep a stable 300V after the CCS .
The CCS is adjusted to supply the normal circuit demand , for example 60ma, plus an extra 20mA that goes through the VR tubes.
Any change in demand of the circuit due to signal is balanced by an equal and opposite change in the VR tubes.

Not drawn on here is a small 'zobel' of 0.1uF/330R which by-passes the VR tubes and provides some extra transparency .

I've used this sort of PS for about 8 years without wanting to upgrade to anything more complex . It was a big improvement on the previous passive supply, particularly in the bass.

Post by **Nick** » Sat Aug 03, 2013 11:28 am

IslandPink wrote:Graeme
A regulated supply for a phono can be as simple as the modification shown in the upper right corner of the circuit on page 1 here :

http://www.audio-talk.co.uk/phpBB2/view ... 88&start=0

This is a simple shunt regulator formed from a supply of about 340V , feeding a constant current source ( Gary Pimm in my case, or DN2540 cascode if you like ) which feeds the signal circuit and a pair of OD3 gas tubes.
The OD3's keep a stable 300V after the CCS .
The CCS is adjusted to supply the normal circuit demand , for example 60ma, plus an extra 20mA that goes through the VR tubes.
Any change in demand of the circuit due to signal is balanced by an equal and opposite change in the VR tubes.

Yep, I did exactly the same to power a phono II copy.

Edited for clarity, to avoid making no sense of Marks post.

IslandPink · Post by **IslandPink** » Sat Aug 03, 2013 11:42 am

In case you missed Nick's comment in there it was "Yep, I did exactly the same to power a phono II copy" .

Graeme · Post by **Graeme** » Sat Aug 03, 2013 4:07 pm

Im sure ive seen a pic of your supply nick, but cant find it now.

Edit, been searching and still cant find it. Do you have it to hand nick?

Can it be done with SS or is it easier/better to do it with valve?

davebms · Post by **davebms** » Sat Aug 03, 2013 7:50 pm

poss this

IslandPink · Post by **IslandPink** » Sat Aug 03, 2013 10:41 pm

That's just an ordinary PS from the WD phono, Dave.

Graeme, how much space do you have to work with ?
All a shunt-reg variant of the power supply needs is cRC or cLC smoothing at the front, then the CCS ( solid-state ) then the VR tubes . You can probably do the shunt with the smaller 7-pin valves ( OA2 ) as the current demand on the WAD phonos is quite small - hence the demand variation is also small .

I don't know if the difference between 280V and 300V is a problem ( probably not ) . The next easy step down is 255V unless I've missed a 125V or 135V VR tube.

Greg · Post by **Greg** » Sat Aug 03, 2013 10:47 pm

I'd like to see Nick's circuit again if possible. I failed to make a copy last time Nick published it and like Graeme, can't find it now. Any chance of putting it up again, Nick?

colin.hepburn · Post by **colin.hepburn** » Sat Aug 03, 2013 11:06 pm

Here you go

Graeme · Post by **Graeme** » Sun Aug 04, 2013 3:28 pm

CCS, constant current source?

I need to do some reading as i dont really understand. I might be getting ahead of my ability LOL.

IslandPink · Post by **IslandPink** » Sun Aug 04, 2013 4:20 pm

Thanks Colin for finding that .

Don't worry Graeme - there's only 5 bits in the CCS . Nick has drawn it out for you there. It does what it says - keeps a constant current once it's set to the value you need.
It's like a choke with a very high inductance that works down to DC .
The diodes shown there are LED's .

We can help you through it.
It's a mod well worth doing. It will improve the sound across the board, but particularly in the bass .

Graeme · Post by **Graeme** » Sun Aug 04, 2013 4:25 pm

Great, thanks.
Ill study it later, measure how many spare volts ive got, then work out what i understand, what i dont, and we'll go from there

Appreciated.

Paul Barker · Post by **Paul Barker** » Sun Aug 04, 2013 5:40 pm

Graeme wrote:Great, thanks.
Ill study it later, measure how many spare volts ive got, then work out what i understand, what i dont, and we'll go from there

Appreciated.

You can use a resistor instead of the CCS as a starting point 5k 3 watt.

Neal · Post by **Neal** » Sun Aug 04, 2013 7:15 pm

I think the battery is unnecessary if using the CCS a resistor is fine, there was a discussion on the old WAD forum about it, I think Max worked out is wasn't needed. I don't use one in mine now just the CCS...

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