Salas hotrodded blue DCB1 build - Page 88

Salas · 26th March 2011, 03:27 PM

The answer is keep 10V Vin-Vout DC difference across the regulators if you can, given the right choices for your AC source.

Builder Brad · 26th March 2011, 07:31 PM

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

AndrewT · 26th March 2011, 08:08 PM

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.

johnwmclean · 28th March 2011, 10:14 AM

What order is best for the following matching 2SK170-BL’s,

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

or

7.15/7.15 - 7.14/7.21 (1,2,3,4)

AndrewT · 28th March 2011, 10:18 AM

714/721 will give a higher (-ve) output offset. That's a 1% difference.

johnwmclean · 28th March 2011, 10:49 AM

Thank you Andrew.

brainf · 31st March 2011, 11:52 PM

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.

Salas · 31st March 2011, 11:57 PM

Will work with 12-0-12VAC OK. Does your local power company vary the mains significantly? Not to go much lower.

brainf · 1st April 2011, 02:29 AM

Quote:

Originally Posted by Salas

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!

AndrewT · 1st April 2011, 09:16 AM

Add two windings giving an extra 2 to 3Vac to add on to the 12Vac.

31st March 2011, 11:52 PM	#877
brainf diyAudio Member Join Date: Feb 2007 Location: Manila, Philippines	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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26th March 2011, 03:27 PM	#871
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	The answer is keep 10V Vin-Vout DC difference across the regulators if you can, given the right choices for your AC source.

26th March 2011, 07:31 PM	#872
Builder Brad diyAudio Member Join Date: Jan 2006 Location: Kent, UK	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

26th March 2011, 08:08 PM	#873
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	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.

28th March 2011, 10:14 AM	#874
johnwmclean diyAudio Member Join Date: Oct 2009	What order is best for the following matching 2SK170-BL’s, 7.15/7.14 - 7.15/21 (1,2,3,4) or 7.15/7.15 - 7.14/7.21 (1,2,3,4)

28th March 2011, 10:18 AM	#875
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	714/721 will give a higher (-ve) output offset. That's a 1% difference.

28th March 2011, 10:49 AM	#876
johnwmclean diyAudio Member Join Date: Oct 2009	Thank you Andrew.

31st March 2011, 11:57 PM	#878
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Will work with 12-0-12VAC OK. Does your local power company vary the mains significantly? Not to go much lower.

1st April 2011, 09:16 AM	#880
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Add two windings giving an extra 2 to 3Vac to add on to the 12Vac.