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Old 8th June 2012, 05:01 PM   #2551
Salas is offline Salas  Greece
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The speakers would not be in dc danger when transformer coupled. If a tube amp has no inter stage ac coupling though, it could kick its power stage to latch at B+ when strong DC will drive it and overload it, also overloading its transformer primary. That could take out expensive active and passive components depending on their power handling. By large majority they have a series capacitor at least on the grids of their output tubes, but better investigate the schematic of the intended power amp.
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Old 9th June 2012, 04:23 PM   #2552
Mihan is offline Mihan  New Zealand
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Thanks for your response Salas.
My power amp is a modern version of a classic tube amp design with SRPP input, a driver stage, then capacitor coupling to a push pull output stage.
Do you think it would be okay if DC got through or would the standard B1 be a better choice here?
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Old 9th June 2012, 06:16 PM   #2553
Salas is offline Salas  Greece
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Very slim chance a DC breakdown feed could take out any serious components. The all important power stage and OPT are DC blocked.
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Old 26th July 2012, 03:02 PM   #2554
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My two DCB1 are all build and tested. They all have ~1mV DC offset which is really good.

Now I'm ordering the transfos from Antek and will get two 100VA but should I aim for 15Vac or 18Vac per secondaries? Please keep in mind that since the primary are 115Vac and that in my sector I have 120Vac the secondaries will be a bit higher than stated.

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Old 26th July 2012, 03:09 PM   #2555
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100VA for the DCB1 x 2 seems a little excessive, considering at 200mA and +/-20V they only require 8VA.

I'm running mine at 150mA and using a 50VA toroidal.
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Old 26th July 2012, 03:10 PM   #2556
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Quote:
Originally Posted by KatieandDad View Post
100VA for the DCB1 x 2 seems a little excessive, considering at 200mA and +/-20V they only require 8VA.

I'm running mine at 150mA and using a 50VA toroidal.
I will run them both at 600mA

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Do
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Old 26th July 2012, 03:55 PM   #2557
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From AndrewT (post #2260)

A DCB1 draws continuous current from the PSU.

That continuous DC current is ~=your CCS current, i.e. 600mA per polarity.
I recommend that the transformer be rated to >=~twice this AC current, i.e. 1.2Aac

15-0-15Vac 1.2Aac centre tapped transformer or 0-15, 0-15Vac 1.2Aac dual secondary transformer is suitable for a 600mA DCB1. 50VA should run a little cooler than a 36VA transformer. For cooler long term running, I would double the current rating again to 2.4Aac, i.e. ~72VA.
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Old 26th July 2012, 04:03 PM   #2558
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I couldn't hear any difference with running the SALAS Shunt Reg at currents above 300mA. In the end I opted for 160mA (ish), the MOS-FETs run cool and there is no danger of component cooking.

Irrelevant of the current the PSU is consuming, the B1's run at about 7-10mA each (determined by the Idss of the 2SK170BLs).

The 2E heatsinks run at a nice cool 30 degrees at 200mA but start to heat up rapidly above 300mA.
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Last edited by KatieandDad; 26th July 2012 at 04:09 PM.
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Old 26th July 2012, 04:18 PM   #2559
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Thanks to all.

I will be testing at different current. I've just ordered 2x 100VA from Antek since they only have 50VA and 100VA. The price was about the same. This will enable me to test various scenarios. I have some HeatsinkUSA 10.080 profile in stock so heat should be under control.

My goal is to have a good balance of sound and heat. I might end up doing 300mA in the end but will make my own tests.

Do
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Old 26th July 2012, 04:45 PM   #2560
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Quote:
Originally Posted by pinnocchio View Post
Thanks to all.

I will be testing at different current. I've just ordered 2x 100VA from Antek since they only have 50VA and 100VA. The price was about the same. This will enable me to test various scenarios. I have some HeatsinkUSA 10.080 profile in stock so heat should be under control.

My goal is to have a good balance of sound and heat. I might end up doing 300mA in the end but will make my own tests.

Do
You wont go wrong with either 50VA or 100VA. Usually it comes down to size or cost.
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