5f2a-ish build
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stretch2011
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Re: 5f2a-ish build
Yes! You needed to put two 100 ohm resistors to ground to make an artificial center tap
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johnnyreece
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Re: 5f2a-ish build
Yes, that should do it. Good catch!stretch2011 wrote:Yes! You needed to put two 100 ohm resistors to ground to make an artificial center tap
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goldenGeek
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Re: 5f2a-ish build
Yes!! I will try that because the old trafo fits a lot better into the chassis than the one that I put in today. I don't know why this didn't occur to me - I've read about artificial CTs a dozen times the last few years but never had to do it before...
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goldenGeek
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Re: 5f2a-ish build
Can that be done to the secondary high voltage or am I better off with full wave rectification?stretch2011 wrote:Yes! You needed to put two 100 ohm resistors to ground to make an artificial center tap
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martin manning
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Re: 5f2a-ish build
Absolutely not. If the HV secondary doesn't have a CT you have to use a bridge rectifier for full-wave rectification.
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goldenGeek
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Re: 5f2a-ish build
I finally got to try the artificial CT, 100R to ground, and the amp was incredibly quiet and good sounding... for a minute or so. The transformer started to get really hot so I had to shut it down. Can it be that this transformer is not good enough to pull this trick off?
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JazzGuitarGimp
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Re: 5f2a-ish build
You could use an artificial canter tap: use two 100R, 1%, 1W resistors. One resistor goes from one leg of the heater to string to GND and the other resistor goes from the other leg of the heater string to GND.goldenGeek wrote:This brings me back to think about the first transformer... that one had a CT on the secondary, but not on the 5V or 6.3V. Could that be the reason this noise was there? Should I have used rectification and DC-heating?
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goldenGeek
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Re: 5f2a-ish build
Yes, that was what I did (I used 3W resistors though) and the noise was completely gone with that fix, but the transformer got really hot and started to smell burned... so I guess my transformer can not handle this?JazzGuitarGimp wrote:You could use an artificial canter tap: use two 100R, 1%, 1W resistors. One resistor goes from one leg of the heater to string to GND and the other resistor goes from the other leg of the heater string to GND.goldenGeek wrote:This brings me back to think about the first transformer... that one had a CT on the secondary, but not on the 5V or 6.3V. Could that be the reason this noise was there? Should I have used rectification and DC-heating?