Example: "The resistor should be wired across the entire transformer secondary"
I see this phrasing a lot, but I don't actually know what it means.
I see this phrasing a lot, but I don't actually know what it means.
It's more descriptive imagery than technical. The part (resistor in this case) spans the entirety of the body of the other part or circuit from one pole to the other like the view from one side of the lake to the other.
@Hearinspace So, for an output transformer tap, would that "gap" be between the tap and ground potential?
The resistor across the entire coil stack from the first point to the last. R1 in this picture.
That has to be stated in plain language. If it says across the secondary , it should mean across the secondary - not one part of it to another. If that's not what the author meant, he didn't say it completely. If there's a speaker connected to (or across) the tap and one end of the secondary that is also connected to ground it might be clearer to say the resistor is across the output of the secondary , or across the speaker connections etc.
I can guess that in this case the author might have meant that, but there are other circuits than the one's we usually think of , it's not impossible the author wasn't connecting it to another tap or to the "top" end (ie the opposite end from the grounded one) and how would we know out of context. Electronics itself may be a technical subject but in communicating about it , people are not so precise. There's a lot of poor / incomplete description that ends up relying on the reader's prior knowledge.
Why do you say that? There certainly is a second wire going to the 4 ohm tap, I was just all up in there.
Again, you really lay doubts to rest by posting either a link to the schematic for the circuit you are actually dealing with or an image of the schematic itself, along with whatever text that goes with it that you're trying to decipher.
thisusername is replying like he knows what circuit you are working with, the rest of us don't.
thisusername is replying like he knows what circuit you are working with, the rest of us don't.
See attached schematic. @thisusername actually has the right schematic linked in his post. Might have found it in my other thread.
The 4 ohm tap is certainly grounded. There is no error in the schematic.
This is an essential part of the ARC partial cathode coupling and balanced feedback.
This is an essential part of the ARC partial cathode coupling and balanced feedback.
That's what I thought. So, that would be the tap I would connect me ~150 ohm resistor to, then? 16-4?
The entire transformer secondary is still between 0 ohms to 16 ohms.
The ground connection of the 4 ohm tap changes the absolute signal voltages at all the output taps,
but it does not change the relative signal voltages between the taps.
So connecting a resistor across the secondary still means from the 0 ohms tap to the 16 ohms tap.
The ground connection of the 4 ohm tap changes the absolute signal voltages at all the output taps,
but it does not change the relative signal voltages between the taps.
So connecting a resistor across the secondary still means from the 0 ohms tap to the 16 ohms tap.
Yes.
It happens that the 4 ohm tap, when grounded, creates balanced output signals at the 0 and 16 ohms taps.
These can be used for balanced overall feedback, and for balanced cathode feedback on the output tubes.
What was the original reason for connecting a resistor across the secondary?
Power load testing?
It happens that the 4 ohm tap, when grounded, creates balanced output signals at the 0 and 16 ohms taps.
These can be used for balanced overall feedback, and for balanced cathode feedback on the output tubes.
What was the original reason for connecting a resistor across the secondary?
Power load testing?
I was asking about putting a switch on the output taps, and it was suggested that I shouldn’t operate said which while the amp was on unless I added said resistor to abort high voltage transients
Speaker switches are a problem with tube amplifiers that have output transformers.
The tube amp should always have a load connected when the amp is powered,
but you can't use a shorting switch, which would short two of the secondary winding terminals together.
And you can't use a non-shorting switch, which would open the output connection when powered up.
The tube amp should always have a load connected when the amp is powered,
but you can't use a shorting switch, which would short two of the secondary winding terminals together.
And you can't use a non-shorting switch, which would open the output connection when powered up.
The resistor across the secondary was suggested to solve the issue of opening the output connection on switching.