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What is DC or heater elevation in tube amps


blindopher

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Hi,

 

My amp has developed a buzz and i'm trying to trouble shoot it.

 

My amp is using DC elevation in order to reduce heater noise.

 

I fail to understand how this scheme works and the concept of floating voltages which is apparently involved in this process.

 

This method of noise reduction is briefly explained here:

 

http://www.valvewizard.co.uk/heater.html

 

and specifically pertaining to the my amp - the Mod 102, here:

 

http://guitarkitbuilder.com/kit-review-mod-102-diy-guitar-amplifier-kit/

 

This link also includes the schematics for my amp.

 

thanx!

 

 

 

 

 

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  • 3 weeks later...
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Normal AC is a sine wave that goes from zero to a positive, back to zero, then goes to a negative voltage, and back to zero.

 

If its a 6V heater it goes 0v > +3v > 0v > -3v >0v in one complete cycle. The difference between +3v and -3v = 6vac

 

When you add the DC voltage you shift the zero voltage mark to a positive voltage. Instead of the heater voltage beginning at zero volts, it may begin at say +4V, increases to +7V comes back to +4V, goes down to +1V then back to +4V In a single cycle.

 

You still have 6 volts AC with a +3 and -3 volt voltage change but the AC always remains positive during the ac cycle. This eliminates at least half of the heater ripple noise by preventing the heater voltage going negative (below zero)

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