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Old 26th March 2011, 03:27 PM   #871
Salas is online now Salas  Greece
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The answer is keep 10V Vin-Vout DC difference across the regulators if you can, given the right choices for your AC source.
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Old 26th March 2011, 07:31 PM   #872
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cheers Salas,

I was thinking along the same lines. If I use a 230v primary 15v secondary transformer with a 210v AC supply I should get approx 13.5v on the secondaries. with the same supply voltage the 18v spec version gives me 16.5v. If I could find a 17v transformer I think that I would have a perfect fit.

The reason I asked in the first place was to see if the recommended specification at 15v had any flexibility ie. it was at it upper limits would work well with a slight voltage drop.

Brad
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Old 26th March 2011, 08:08 PM   #873
AndrewT is offline AndrewT  Scotland
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Builder,
I recommend you look at three operational conditions.
When mains is at nominal UK voltage of 240Vac.
When mains is at 254Vac
When mains is at 226Vac.

Look at what happens to each component in the regulator for each of these three situations.
It might also be worth looking at what happens if you have your DCB1 with it's mains transformer connected directly to 254Vac instead of using the balanced voltage dropper.

Have you decided what CCS current you want to use?
The AC current rating of each winding must be at least twice the DC current you plan to draw and preferably four times your CCS currents.
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Old 28th March 2011, 10:14 AM   #874
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What order is best for the following matching 2SK170-BLís,

7.15/7.14 - 7.15/21 (1,2,3,4)

or

7.15/7.15 - 7.14/7.21 (1,2,3,4)
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Old 28th March 2011, 10:18 AM   #875
AndrewT is offline AndrewT  Scotland
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714/721 will give a higher (-ve) output offset. That's a 1% difference.
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Old 28th March 2011, 10:49 AM   #876
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Thank you Andrew.
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Old 31st March 2011, 11:52 PM   #877
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Default Another transformer question

Instead of the BOM specified 15-0-15V 50VA transformer recommended for the 200mA hotrod, is it possible to use a 12-0-12 V 48VA (or alternately 72VA) version instead? (reason is my local store carries only 12V versions, next step up are 18V variants).

For those who have tried both - are there any sonic benefits to using the 15V traffo over a 12V one?

Thank you for all the replies.
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Old 31st March 2011, 11:57 PM   #878
Salas is online now Salas  Greece
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Will work with 12-0-12VAC OK. Does your local power company vary the mains significantly? Not to go much lower.
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Old 1st April 2011, 02:29 AM   #879
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Quote:
Originally Posted by Salas View Post
Will work with 12-0-12VAC OK. Does your local power company vary the mains significantly? Not to go much lower.
Quite stable. Never seen it dip below 230VAC during the times I've measured/monitored it (typically 232VAC). Thank you Salas!
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Old 1st April 2011, 09:16 AM   #880
AndrewT is offline AndrewT  Scotland
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Add two windings giving an extra 2 to 3Vac to add on to the 12Vac.
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