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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: RE: LCR Phono stage posted by Paul Joppa on April 25, 2021 at 22:29:25:
Hey Paul,
Both S&B and Silk made/make 10K modules and while the concept of high impedance is a good one. the use of a 10K number is misguided since it requires obscure cap values. Since the chokes will need to be made custom for any impedance, why not pick something that makes the caps easy values to obtain rather than values that need to be pieced together to adhere to some archaic number? The 600Ω impedance units require 5.04µ and 0.126µ. Simply bumping that number up to 720Ω takes the values to 4µ and 0.1µ much easier values to source. The inductors can be made tapped making the filter easy to trim and a single high quality cap used for each position. I ended up choosing a value of around 7500Ω and the caps were 0.33µ and 8200p which are easy to source values.
As to the low Z tubes driving the 600Ω network, I stared at paralleling the halves of a WE 421A (5998) which would give aµ of 6 and an rP of 150Ω but I discarded that idea since it puts you in the same realm as say a 417A into a 4:1. The 6HV5 / WE 416A were another thought to net a gain of 40-50 and a low enough output impedance to drive 600Î through a step-down but they come with their own baggage and ultimately found that the 6C45/437/triode wired 7788 into a 7.5K LCR gave the best results.
dave
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- RE: LCR Phono stage - dave slagle 06:29:54 04/26/21 (0)
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