Hi:
I am using Toneslut trannies with a Ceriatone kit. I am wondering which of the PT secondary leads need to be grounded and why. I read Paul's page and am wondering about the center tap for the heater browns specifically. Any thoughts would be appreciated.
Thanks:
Gary
Toneslut grounding
Moderators: pompeiisneaks, Colossal
Re: Toneslut grounding
Well to start off the Brown w/white needs to be grounded unless your want to use the two 100k ohm resistors to ground as an artificial ct. Why you would do that I don't know but you could. That's for the heaters. EDIT: let me clarify. The Brown w/white is the center tap for the heaters and needs to be grounded.
The Yellow w/red also needs to be grounded. That is the HT center tap.
If you are not using a recto tube and you don't need the 5v tap for anything just trim the gray leads and shrink wrap the ends. Then tie them back out of the way.
The Yellow w/red also needs to be grounded. That is the HT center tap.
If you are not using a recto tube and you don't need the 5v tap for anything just trim the gray leads and shrink wrap the ends. Then tie them back out of the way.
Re: Toneslut grounding
Thanks for the reply, my question with respect to the heater leads is what does the ground do electrically? One side of the HT winding is used for the bias current but the heater leads are a complete circuit without the center tap grounding. I am a newb so please excuse the stupidity. If there is a good page on theory I would really enjoy the link! I have a basic understanding of the components individually but not as a whole.
Thanks for your patience.
Gary
Thanks for your patience.
Gary
Re: Toneslut grounding
The CT on the heaters is the easiest way cancel some of the hum introduced into the tubes by the AC heater voltage. There are more efficient ways of reducing the hum like DC heaters. A lot of guys don't think they are worth the trouble though. In any case if you do not ground the center tap on the heaters OR provide an artificial CT with the 100 ohm resistors then you will have more noise coming from the heaters.
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peesinstew
- Posts: 45
- Joined: Wed Oct 24, 2007 2:21 pm
- Location: Chicago
Re: Toneslut grounding
well, what's happening is that the two ends of the heater winding are alternating wrt each other at 6.3V AC, but they're isolated from any DC voltage until you attach part of the winding to a voltage reference point.
Remember that ground is always relative. The ground plug in your outlet could be at a different voltage than the ground at my house. Likewise, you won't know what voltage the heater winding is at until you attach part of it to something you do know the voltage of.
By connecting the heater center tap to ground, you are assuring that the point in the middle of the winding is always at zero volts relative to your ground reference. Then when each side of the heater winding alternates, it goes from -3.15V to +3.15V. Sometimes people choose to connect the center tap to a higher reference voltage so that it will have less interaction with the signal sensitive wires in the amp. This just means that, for example let's say the center tap is connected to a 20V source, either side of the winding will alternate between 16.85 and 23.15 volts. Either way, it's just a method of setting the voltage to what you want it to be instead of letting it run wild.
I've also seen some older amps that just tie one end of the heater winding to ground, so instead of having 2 sides both alternating from +/- 3.15V, they had one side always at 0V and the other side varying by the full +/- 6.3V. The heaters will still work like this, but with the larger voltage swing, the wire is more likely to emit noise to the rest of the amp this way, so it's generally better to use a center tap instead.
Remember that ground is always relative. The ground plug in your outlet could be at a different voltage than the ground at my house. Likewise, you won't know what voltage the heater winding is at until you attach part of it to something you do know the voltage of.
By connecting the heater center tap to ground, you are assuring that the point in the middle of the winding is always at zero volts relative to your ground reference. Then when each side of the heater winding alternates, it goes from -3.15V to +3.15V. Sometimes people choose to connect the center tap to a higher reference voltage so that it will have less interaction with the signal sensitive wires in the amp. This just means that, for example let's say the center tap is connected to a 20V source, either side of the winding will alternate between 16.85 and 23.15 volts. Either way, it's just a method of setting the voltage to what you want it to be instead of letting it run wild.
I've also seen some older amps that just tie one end of the heater winding to ground, so instead of having 2 sides both alternating from +/- 3.15V, they had one side always at 0V and the other side varying by the full +/- 6.3V. The heaters will still work like this, but with the larger voltage swing, the wire is more likely to emit noise to the rest of the amp this way, so it's generally better to use a center tap instead.