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Guest crashie

Misunderstand sijosae schematic! help urgent

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Guest crashie

Hi, i got a problem with the schematic. why do we need 2 heater supply to operate one filament? thanks

 

post-4525-1273046806_thumb.jpg

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It is correct. The 2 LM317's are not configured as voltage regulators. They are configured as Constant Current sources.

 

Hence, by calculation, each of them are sinking 1.25v/( (15*20)/(15+20) ) = 0.146A.

 

Therefore, instead of driving the filament with a fixed voltage and obtaining the current flow by the resistance of the filament, both current sources sink nearly 0.3A together through the filament.

This negates the need for a separate voltage source/ regulation for the filament.

A regulated supply connected across the filaments would stabilized at a fixed current after warming up but this design allows for regulated current through the filament regardless of the voltage supply.

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Guest jacj6049

Should be correct, in this case, the voltage is split between the 2 filaments. Check out this, similar design, http://diyaudioprojects.com/Solid/12AU7-IR...-LM317-Headamp/.

The filament wiring is explained in the article.

 

 

hi,but if i use this diy project to build 2 amps,but one of the amp jus use for ground channel,it is sound better than jus use 1 unit?should be able get al the parts from koba rite?thanks

 

regards,

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It is not recommended. For starters, the amp is not in unity gain, which is what you need for the ground channel.

Secondly, even if you had the 12AU7 in a cathode follower configuration, that design does not have global feedback, which is what you need to ensure that the currents on the ground channel are always balanced.

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