On December 17, 2016 at 10:23, highfigh said...
All rectifiers have forward voltage drop, but some drop a lot more. Subbing diodes when a piece of equipment originally used a 4AR4/GZ34, 5Y3, etc can cause problems with component reliability AND sonic performance. For that matter, changing a bias resistor can kill the power supply's filter caps.
That's all true. Previously you said there MAY be voltage drop. In truth there is always, as you now correctly put it, forward voltage drop.
Never said anything about DC from the transformer.
See the italics:
On December 16, 2016 at 10:21, highfigh said...
If the plate voltage is higher, how is the transformer NOT increasing the line voltage, whether it's DC or AC?
Previously you referred to the output of the transformer as increased line voltage. Here you refer to the line voltage as "whether DC or AC." Since you have not separated the concepts of transformer input and secondary output, you have here said that a transformer can output DC.
| In order for the B+ to be in the 300VDC+ range, the output from the power transformer's secondary must be increased before it reaches the rectifier, where it may/may not pass through without voltage drop.I missed a whole other thing here: The output from the power transformer's secondary is already higher than the line voltage by the factor of the windings ratio and "output... must be increased" is not true.
There is NOTHING between the output from the transformer's secondary and the rectifier except a piece of copper wire. And this wire somehow increases that voltage?
Here you are very clearly saying that after going through the transformer, the transformer's the voltage must be increased in order to get to the 300VDC+ range. After the transformer, what device or occurrence increases the voltage further?
[There is an apparent increase after the rectifier because a sine wave, rectified and filtered, tends to increase from the RMS value of the sine wave up toward the peak voltage of the sine wave, minus, of course, the forward voltage drop of the rectifier. In tube equipment, that voltage drop can be substantial, way more than the drift from RMS voltage to peak voltage. I just looked up the 5U4 and its voltage drop at 275 mA per plate is 50 volts.]
See, you did say something about DC from the transformer, because at that point you were conflating the concept of "line voltage" with "secondary" and not mentioning that there's an entire circuit between the transformer secondary and the DC measurement point.
Your facts are right but they're expressed in a way that they can clearly mean something you did not intend. It's also hard to tell exactly what you do mean because of the way you put things together. I can't believe you actually intended to say that "the output from the power transformer's secondary must be increased before it reaches the rectifier." But it's what you wrote.
