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Old 10th September 2008, 02:49 PM   #1
johnm is offline johnm  United Kingdom
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Default External PSU for Quad 22 pre-amplifier

Hi folks.

I need some help/pointers in designing an external power supply for a Quad 22 control unit.

After much searching I came across the diagram which I've posted. Not sure of the value of the choke but I presume it is the same as the one in the Quad II, as this is where the drawing appears to have been culled from.

I have several EZ80s lying around - would it be better to use these to keep the tradition of using a valve regulated PSU instead of diodes?

Whilst I've rebuilt my Quad IIs several times, and have recently completed a Dynaco ST70 kit and VTA driver board, I really don't have much of a clue in designing power supplies, so any help would be grately appreciated. In particular are there any suitable transformers I could pick up from somewhere like Maplins or RS which wouldn't break the bank? The PSU requirement of the Quad 22 is 330V 4.5mA.

The Quad IIs will be using independent mains leads now BTW, and no longer powered by the Quad 22.

Thank you,

- John
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Old 10th September 2008, 02:59 PM   #2
poynton is offline poynton  United Kingdom
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maplins do (or did) a couple of transformers and also a choke.

Andy
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Old 11th September 2008, 01:35 AM   #3
johnm is offline johnm  United Kingdom
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Just had a look and their transformer doesn't look suitable alas. May have to get a custom job?
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Old 11th September 2008, 02:26 AM   #4
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John,

It might be worth your while to order from this side of the salty "pond".

The prices AnTek charges are attractive and the exchange rate is still in your favor. AnTek's model AN-1T150 looks like it could be adapted to your needs.

Wire the 2 secondaries in series and hybrid bridge rectify using snubbed UF4007s on the ground side and an EZ80/6V4 on the B+ side. Use 1 of the 2X 6.3 VAC windings for the rectifier and the other for the signal tubes.

Obviously, you will wire the dual primaries in series. 4 lbs. is approx. 1818 grams.
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Old 11th September 2008, 12:13 PM   #5
johnm is offline johnm  United Kingdom
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Thanks for that Eli that looks great

I'll draw up a diagram before I do any wiring to make sure I've got it right and post it here.

Thanks again mate,

- John
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Old 17th September 2008, 12:07 PM   #6
johnm is offline johnm  United Kingdom
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Hi Eli.

Would it be possible for you to post a diagram of the circuit you describe above please? Want to make sure I understand the circuit before I blow meself up

Mucho thanks,

- John
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Old 28th September 2008, 05:53 PM   #7
johnm is offline johnm  United Kingdom
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Hi Eli.

Have I got this correctly drawn out?

Many thanks,

- John
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Old 29th September 2008, 01:18 PM   #8
johnm is offline johnm  United Kingdom
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Anyone?? (he asks his lower lip quivering - Boooooohohohoho wahhhhh etc! )

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Old 29th September 2008, 03:44 PM   #9
kevinkr is offline kevinkr  United States
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Hi John,
Yes that is just fine as drawn.. Observe the maximum rated input capacitance for the 6V4 and you are all set.
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Old 29th September 2008, 03:45 PM   #10
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Why not try your hand at a regulated PSU for the tube pre-amp? It will make the worlds difference in sound quality and will be much more compact than a CLC style PSU.
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