Passive and active power supplies for phonos

What people are working on at the moment
simon
Thermionic Monk Status
Posts: 5600
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

#1 Passive and active power supplies for phonos

Post by simon »

Diverting from an existing thread on Colin's integrated pre is the discussion between passive and active power supplies for phonos, in particular the one here, wot I built:
http://www.atrj13.dsl.pipex.com/images/ ... _rev_d.pdf
izzy wizzy wrote:What was the passive circuit you used?
I've had a dig around and found this. It was cobbled together from the few bits I had. I actually also added 4 No. 1R 3.3uF RC sections which aren't shown; two per stage, one per channel.
Image
izzy wizzy wrote:
simon wrote:Going from AC heaters to DC heaters using a simple PI filter made little difference also, but going to the reg heater supply surprised me just how much of an improvement there was.
What was the heater reg? Was there any iron in the passive supply?
The passive was a simple pi filter, so something like 4700uF small R 4700uF. No iron. I tried it mostly to find out how much hum was coming from the AC heaters, and it made little difference.

I haven't tried chokes in heater supplies, guess I've got bigger nuts to crack at the moment :). I'm guessing you like them? CLC or something like that? Have you been able to use a smallish last C of nice quality rather than the usual cheap large 'lytics?

The heater reg is a bog standard Morgan Jones type jobbie with an LM338 for a little more current capacity than an LM317. This is pretty much it though I've bypased the Schottkies now, and added a small R on top of the 1uF.
Image
izzy wizzy wrote:
simon wrote:Next to try is the SS HT reg. Once I've built two channels I'm sure I'll want to build two more, unless I really don't like the sound they're making.
Do you mean you will expand the regs as in maybe one per stage? If so, why?
Yeah, to find out how it sounds, especially as I haven't built a SS HT reg yet :D.

Why not? Serious question.
izzy wizzy wrote:
simon wrote:What might be interesting is to have a passive, a valve reg and a SS reg supply ready for Owston to see what people think.
It would be interesting. If you do, the circuit for each needs to be a little different which may make things a little complicated.
Yes, one never has enough iron and decent caps :(. It's also difficult to do a "definitive" comparison as who's to say I will have built the best of each variant (I won't have). But it might be interesting to get a "feel". But I do agree with you that with some of these things I need a long time to decide which is better and which is merely different.
izzy wizzy wrote:It's hard to design a passive supply without it being an integral part of the audio circuit i.e. they are not seperate things. Fer instance, a passive supply has decoupling at each stage. It can be daisy chain config as in feed the 2nd stage and then the first is RC decoupled from that or the two stages can both be fed RC decoupled from a common source.

In my phono, I've tried numerous configurations and in the end have liked rectifier-LCLC. Call this last C a common point. then one LC for stage 1 then RC to each channel and from the common point, LC then RC to each channel. The last C is right on the audio circuit to close the AC loop for that stage.
That's not too different from what I ended up with in the end. I used a couple of smallish 10uF caps for the first 2 Cs as this modelled best in PSUD. I didn't have any big caps spare to try then - I have some WKZs now I could try, though with the final Cs being decent-ish films maybe the WKZs would be wasted here?
izzy wizzy wrote:The thing I like about passive supplies vs the active stuff is the ease and lack of a kinda mechanical sound in the presentation. I think regs do sound impressive at first. IMHO, when using regulators, the sound of the circuit becomes dominated by their signature. Each reg has its own sound just like an audio circuit; maybe even more so. My preference is to have the PSU as benign as possible rather than the star of the show :-)
The heater reg was my first reg, the valve the second so I'm just starting out with them to find out how they differ for myself. Regs do seem to be a rather personal taste though.
Will
Old Hand
Posts: 497
Joined: Mon Jun 11, 2007 10:35 pm
Location: Northumberland

#2

Post by Will »

The best I have at the mo. LCRC phono supply this I have found has the least restriction on the music, when it gets louder the image gets larger this is what I like, there are 2 10h chokes in series from 250v to 0v on the mains Tx secondary. ripple is 1.3mv av'g. without the series chokes 2.3mv and some hum.
simon
Thermionic Monk Status
Posts: 5600
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

#3

Post by simon »

Not sure I understand you Will :(. Do you mean that the 2 chokes take the place of the first cap in a cap input supply???
Will
Old Hand
Posts: 497
Joined: Mon Jun 11, 2007 10:35 pm
Location: Northumberland

#4

Post by Will »

They go between the 240v and 0v mains Tx output before the rectifier.

Maplin 240v Tx and 2 Hammond 10hry 100ma.

cant think 240or250v
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8879
Joined: Mon May 21, 2007 9:42 pm

#5

Post by Paul Barker »

between the transformer and the rectifier is different, you would need a choke after the rectifier for lc to work.
simon
Thermionic Monk Status
Posts: 5600
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

#6

Post by simon »

Ah! I think I get it now.

Like this?

Image

I haven't seen this before. Do the two chokes help to remove any, erm don't know how to describe it, imperfection?, on the mains?
Will
Old Hand
Posts: 497
Joined: Mon Jun 11, 2007 10:35 pm
Location: Northumberland

#7

Post by Will »

Heres a pic not a thousand words..
Attachments
scan0002.jpg
scan0002.jpg (4.52 KiB) Viewed 9731 times
Will
Old Hand
Posts: 497
Joined: Mon Jun 11, 2007 10:35 pm
Location: Northumberland

#8

Post by Will »

I found this on the AA, used as a mains filter using a large 10hry 200ma Hammond choke between L and N.
I thought there was a post about this application but I cant find it so could have been in a dream, search for Hammond Choke in the Tweaks section.
Andrew
Eternally single
Posts: 4206
Joined: Thu May 24, 2007 2:18 pm

#9

Post by Andrew »

I'm sure we talked about this on here......

cheers,

-- Andrew
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#10

Post by pre65 »

Hi-why does that work ? (or is it just that it does ?)
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
Andrew
Eternally single
Posts: 4206
Joined: Thu May 24, 2007 2:18 pm

#11

Post by Andrew »

We had a debate about that too....
Andrew
Eternally single
Posts: 4206
Joined: Thu May 24, 2007 2:18 pm

#12

Post by Andrew »

Will
Old Hand
Posts: 497
Joined: Mon Jun 11, 2007 10:35 pm
Location: Northumberland

#13

Post by Will »

Just saying it works for me, its been in a long time but remember benefits in harmonics, decay and space.
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8879
Joined: Mon May 21, 2007 9:42 pm

#14

Post by Paul Barker »

Probably works because inductors reject transients and noise by their nature. Should be better placed at the primary so as to take the worst of spikes before they can saturate the transformer core, or at least assist it in rejecting them. But you can't ground the centre you would first need an isolating transformer.

Long ago we talked about making power transformers gapped. I had some decent sized c cores sent me for my power transformers but never did get that round tuit. The benefit of the cut core being the ability to handle a little dc..

The push pull EI core (interleaved assembly method) can handle vertually no dc.

In those days most people disliked conditioning applied in line with the audio equipment but found that such filters mounted on the same ring main elsewhere most effective.

The cheapest trick is to put the microwave oven )(and hence it's effective emi suppression circuitry) into the ADJACENT outlet.

A lot cheaper than shopping in the Lake district and just as effective heresay has it.
Last edited by Paul Barker on Mon Jan 14, 2008 10:23 pm, edited 1 time in total.
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8879
Joined: Mon May 21, 2007 9:42 pm

#15

Post by Paul Barker »

Of course some of us have cut core power transformers, I have one right here now.

500ma ht capability on a core capable of a little dc to provide 200mA. Quite minimalist really. Same one I used to put the resistorless capacitorless power supply on as it has sufficient reserve for all that wasted energy.

I never did sign up to kyoto.
Post Reply