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  #11  
Old 5th January 2011, 09:27 PM
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pre65 pre65 is offline
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Default Re: 3 Series smoothing

You could use the EZ rectifier in a hybrid bridge.

That would give you enough volts to go choke input.
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  #12  
Old 5th January 2011, 11:06 PM
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Default Re: 3 Series smoothing

Hi Bondi,
Mine is not the factory kit. It is built in an old chassis I re-used and I only bought the PCB for the audio bit, the PSU is built on tag strip so I can't help you with the space question.
It looks like mine has ended up quite similar to Johns setup. It maybe a bit over the top but the first two sections on mine are also seperated for left and right channel. I don't have the PRE, mine feeds straight into my KEL84.
Attached Images
File Type: jpg Phono PSU.jpg (63.0 KB, 28 views)
File Type: jpg Phono Stage.jpg (56.6 KB, 28 views)
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  #13  
Old 5th January 2011, 11:35 PM
colin.hepburn colin.hepburn is offline
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Default Re: 3 Series smoothing

Quote:
Originally Posted by John Caswell View Post
Hi all,
Yes I added quite a lot of extra smoothing/decoupling both to my Phono II and Phono III see attached drawings. The values are different due to differing HT voltages and were calculated to give the WD figures on the various anodes. Although the drawings state Phono II they equally well apply to Phono III as HT wise the circuit is to all intents and purposes identicl
If you decide to do this bear in mind that tracks will need to be cut and the extra components need to be mounted somewhere.
I also did away with first stage bias and fitted NiCd battery bias, which I think improved it no end, and also fitted Hi quality metal oxide Rs for the anode load.
But everyone to their own taste.

John
Hi John
Interesting I like the idea of these mods I have the WD phono II with Oscon bi-pass cap holco takman resistors for C14/15 decoupling caps I have used solen polypropylene 10uf cap I want to rebuild phono2 up to the phono 3 status but hardwired version also adding the 3180uS 318uS mod
I use battery bias in my 5751/12B4A headphone amp an also like what is does could you post schematic details of this mod john pleas
Thanks’
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  #14  
Old 6th January 2011, 10:52 AM
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David Roberts David Roberts is offline
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Default Re: 3 Series smoothing

Hi Phil,

I was wondering whether you could explain your design choice of EZ80, as opposed to an EZ90 for example? I know that choice is often determined by what's in the spares box, but I was interested in whether there were other factors that you took account of.

Regards,

David
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  #15  
Old 6th January 2011, 10:56 AM
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BOONDI BOONDI is offline
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Default Re: 3 Series smoothing

Quote:
Originally Posted by pre65 View Post
You could use the EZ rectifier in a hybrid bridge.

That would give you enough volts to go choke input.
Que????

Enlighten me oh most wise one.....

Hybrid bridge????
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  #16  
Old 6th January 2011, 11:06 AM
Richard Richard is offline
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Default Re: 3 Series smoothing

Quote:
Originally Posted by John Caswell View Post
Hi all,
Yes I added quite a lot of extra smoothing/decoupling both to my Phono II and Phono III see attached drawings. The values are different due to differing HT voltages and were calculated to give the WD figures on the various anodes. Although the drawings state Phono II they equally well apply to Phono III as HT wise the circuit is to all intents and purposes identicl
If you decide to do this bear in mind that tracks will need to be cut and the extra components need to be mounted somewhere.
I also did away with first stage bias and fitted NiCd battery bias, which I think improved it no end, and also fitted Hi quality metal oxide Rs for the anode load.
But everyone to their own taste.

John
Hi John, Yes it was the first stage decoupling I wondered about, which yours addresses nicely. Voltages aside (mine are ok) I'm happy with the rest. I use 150uF with a 0.47uF film cap across it on the input at C17.
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  #17  
Old 6th January 2011, 11:09 AM
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BOONDI BOONDI is offline
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Default Re: 3 Series smoothing

Quote:
Originally Posted by David Roberts View Post
Hi Phil,

I was wondering whether you could explain your design choice of EZ80, as opposed to an EZ90 for example? I know that choice is often determined by what's in the spares box, but I was interested in whether there were other factors that you took account of.

Regards,

David
I was going to use GZ34 simply cause I like overkill, but Dr John suggested using a smaller rect valve like the EZ80 or 81. This will give me much more power than I need. I can get 90mA from EZ80 and 160mA from EZ81 with 250V. I think it's about 50mA total that I need for Phono3 and pre3. Also, I have one EZ80 sitting in a small PSU that I scavenged up..... I may also have an equivalent in my stash of valve delights. I have a few funny looking voltage regulators somewhere, so I might fit one for a decorative feature. Love the pink glow.....
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  #18  
Old 6th January 2011, 11:34 AM
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pre65 pre65 is offline
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Default Re: 3 Series smoothing

Quote:
Originally Posted by BOONDI View Post
Que????

Enlighten me oh most wise one.....

Hybrid bridge????

A hybrid bridge uses two solid state diodes and a full wave valve rectifier.

A full wave valve rectifier is, in effect, two diodes in one envelope.

This link might be more explanatory.

http://www.freewebs.com/valvewizard/bridge.html

I use hybrid bridges on a few amps of mine but use two 6D22s damper diodes instead of a single full wave valve rectifier.
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  #19  
Old 6th January 2011, 07:36 PM
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Phil Y Phil Y is offline
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Default Re: 3 Series smoothing

Hello David,
I am afraid there was no cunning plan involved in my choice of an EZ80. As well as using the chassis from an old project, I re-used the PSU that was in it as well! After a quick check of the Phono II spec I could see there was plenty of current and volts in the old PSU so I re-used it as it was.


Regards, Phil
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  #20  
Old 6th January 2011, 07:42 PM
John Caswell John Caswell is offline
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Default Re: 3 Series smoothing

Hi all,
The battery bias mod is very simple and consists of removing the first stage cathode bias resistor, (and capacitor if fitted) and replacing it with an "AAA" or "AA" NiCd battery, +ve to cathode of the valve, -ve to ground.
If you use standard NiCds do not use a plastic battery holder, try to get metal ones from CPC as they do not "stretch" Better still get tagged types and then solder them in permanently. They won't discharge when the phono is off.
I think it gives a more defined solid sound but then others may not. Once again I leave it up yo you to listen and decide.

John
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