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Old 6th May 2005, 12:14 AM   #1
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Join Date: Apr 2005
Location: AUD
Default Heater voltage circuit change......why please

thank you,
my existing mono block amps have the following 6.3 heater circuit.

[trans]__[rectifier+]____[+4700uf 16v cap]___[heaters]__6SL7/6SN7


[trans]__[rectifier-]____[-4700uf 16v cap]___[heaters]

update to newer model

[trans]__[rect+]__[+4700uf 16v]___[.47R 5w]__[+10,000u 16v]__[heaters]__[47ohm]__[conected to bellow with centre to ground]



[trans]__[rect-]__[-4700uf 16v]______________[-10,000u 16v]__[heaters]__[47 ohm]__[conected to above ]

PLEASE WHY THE CHANGE AND WHAT ADVANTAGE ?

on 10v heater to 211 on original design 10,000u 16v across +- of bridge with .5 ohm resistor in series with + leg to heater
update has .22 ohm on + leg and .33ohm on - leg to heaters with an extra 10,000u 16v across +-

PLEASE WHY THE CHANGE AND WHAT ADVANTAGE ?




Also please, I know there is an AC direction of connection for the primary of the power transformer but is there also the same for conection of the many secondaries to rectifiers and subsequent heaters and circuitry? my circuit has two [10v and 6v]heater taps as well as three other voltage taps for circuitry

Thank you for your help in advance
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Old 6th May 2005, 04:25 AM   #2
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Join Date: Oct 2004
Location: Adelaide South Oz
The 10,000uF cap which has been added has an impedance of 0.16 Ohms at 100Hz. In conjunction with the added 0.47R resistor it will attenuate the ripple voltage by a factor of 4 giving cleaner DC. The 47 Ohm resistors just reference the centre point of the supply to 0V such that the twisted heater wires have one wire of the pair at +3.15V and the other at -3.15V so their electric fields tend to cancel along the length of the twisted heater wires. Also any cathode to heater leakage has a low impedance return path back to 0V.

Should be quite a bit less hum with the new arrangement compared to the original.

Cheers,
Ian
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Old 7th May 2005, 05:28 AM   #3
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Default Thank you for your iformative reply I will now try

thank you I will update my circuit and see if there is a change
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Old 23rd May 2005, 11:40 PM   #4
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Join Date: Apr 2005
Location: anglesey
Default Re: Thank you for your iformative reply I will now try

Quote:
Originally posted by frank2395
thank you I will update my circuit and see if there is a change

Did u try it and if so was there a difference?I'm trying to kill the hum in my preamp.
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Old 24th May 2005, 10:02 PM   #5
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Join Date: Apr 2005
Location: anglesey
Quote:
Originally posted by gingertube
The 10,000uF cap which has been added has an impedance of 0.16 Ohms at 100Hz. In conjunction with the added 0.47R resistor it will attenuate the ripple voltage by a factor of 4 giving cleaner DC. The 47 Ohm resistors just reference the centre point of the supply to 0V such that the twisted heater wires have one wire of the pair at +3.15V and the other at -3.15V so their electric fields tend to cancel along the length of the twisted heater wires. Also any cathode to heater leakage has a low impedance return path back to 0V.

Should be quite a bit less hum with the new arrangement compared to the original.

Cheers,
Ian

Does this apply for all tubes or just one as I have a separate 27000uF cap for each 6sn7 in my preamp.
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Old 25th May 2005, 11:33 AM   #6
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Default huge improvement

huge improvement
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