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Old 30th May 2005, 01:24 PM   #1
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Default CCS fed shunt regulators

I would like to try a shunt regulator with a CCS feeding a series of 0A2+0B2 to obtain 255V. I'd like to use an ccs even in the driver stage. In this case could I have problems with the maximum current in the power supply? This kind of power supply can handle 40/50mA for the stage that it feeds?

I mean...if the driver stage is a long tailed pair of 6h30 with a ccs on its cathode ( idle current 30mA for example) and if I'd set the ccs current in the power supply as 50mA (30mA+20mA for the 0A2+0B2), than could the shunt regulator works quite happy?

If the absorbed current is stable then the current in the diode valve does not depend on the variations of the main voltage and it could handle the 40mA that I need.

I've never tried this kind of reg. and maybe I'm wrong. What do you think about this issue?


Mark
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Old 30th May 2005, 02:33 PM   #2
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The CCS current for the regulator is simply the sum of the current requirements for the amplification stage and the current through the regulator valves. Should the amplification stage draw less current, the regulator valves will draw more, and vice versa. The trick is to choose it such that at the highest and lowest current draws from the amplification stage, the regulators aren't starved of current, or sent over the maximum rating.

Since you are thinking of using this to regulate the supply of a differential pair with a CCS tail, the current draw from the amplification stage will be constant. So, say you're going for 15mA through the regulators and 30mA through the amp stage, set the CCS for 45mA.
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Old 30th May 2005, 02:43 PM   #3
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Hi Mark,

CCS fed shunt regulators work (and sound) very nice. In class A stages where the DC current from the power supply is fixed you won't have any problems with the active devices drawing more current than the VR tube stack.

The largest difference in operating current vs. regulator current I have done personally was in Lynn Olson's Karna amplifiers. In the driver stage we were running a total of 120ma through the CCS feeding the driver stage with 100ma for the 2A3's and 20ma through the VR tubes.

A nice touch for the VR tubes is to add a small bypass cap across the VR tube stack. The key is small or you will build youself a nice relaxation oscillator. The max capacitance spec for caps directly across most VR tubes is .1uf. The .056 Soviet TEFLON caps work very nicely for this duty.

Also, when stacking VR tubes a high value shunt resistor across one of the tubes will decrease the required strike voltage to get the VR tubes to light off as the tubes will strike in sequence rather that all at once.

Gary
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Old 30th May 2005, 03:14 PM   #4
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Thankyou for the answers.
These are the answers that I've needed.
For the cap across the VR tubes, a polipropilene cap works good enough?

X Gary: hi Gary, I'm the italian student that wrote to you in the past weeks. I've sent you two emails asking about the ccs self bias. I've sent you the schematics of the small el84 push pull. Now I'm going to redrawing the driver stage to use a 6H30 and I'm designing a -50V psu for the css in the long tailed pair.
Look here:

-50V negative supply


I'll send you an email in the weekend for the paypal details that I need to buy your boards
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