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Old 10th November 2005, 08:25 PM   #1
Bryan is offline Bryan  United States
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Default 3 stages... Two Power Supplies

Hey Guys,

Just wondering here...

Lets say I have a 3 stage power amp. The current power transformer cant handle the power requirements of all three stages. Would it be better to buy a new power transforemer and use one power supply for all three stages, or could I build another PS with a differnet tranny (which I have on hand) and use this for the input and driver.

The driver and output are IT coupled.

Thoughts?

Bryan
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Old 11th November 2005, 12:22 AM   #2
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I would personnelly recommend if you can power the input and driver separately on its own dedicate ps. It just sound much better. I suspect that the high current draw of the power tube effects the input and driver in sonics i.e. ripple. Imaging becomes better also bass n highs also improves. WIth good power supply i tend to notice the effects are always in the highs and the bass the extremes

ANyway those were my thoughts on this matter

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Old 11th November 2005, 01:06 AM   #3
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Hi neighbor!

IMO, separating the "finals" from the small signal circuitry is a good thing. You are talking about a 3 stage design and decoupling is pretty much mandatory. With separate PSUs, decoupling between the 2 small signal stages MIGHT not be necessary.

There's more than 1 way to get the separate rails. Obviously, 2 power trafos will work. A slick "trick" from Pete Millett is to use a CT rectifier winding, of appropriate VA rating, whose end to end voltage meets the higher rail requirements. The entire winding is bridge rectified and an additional rectifier's anode is connected to the CT. A rail of approx. 1/2 the end to end rail is taken from the "extra" rectifier's cathode. Both rails are full wave rectified, as the path to ground in both cases is the same. PM used SS diodes to ground and vacuum rectifiers elsewhere.
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Old 11th November 2005, 01:21 PM   #4
Bryan is offline Bryan  United States
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Thanks for the advice guys...

This is the situation I am speaking of specifically. I've been running DIY 845 monoblocks with a power tranny that makes enough power to run the amp, but it is being pushed to its limits.

What I want to do is keep the current PS and just feed the 845 plate from PS 1. I would then build up another PS to feed the input and driver stage, which are cap couple. I will use proper decoupling here, and I may feed the input tube with a CCS. The driver will use an IT to feed the grid of the 845.

I was worried that this set-up may increase the possibility of ground loops, having two PS's and all. If I am careful with my ground returns, use good single point star grounding, I should be ok, right?
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