Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: EKDENTON on April 15, 2016, 12:07:21 pm

Title: cathode resistor
Post by: EKDENTON on April 15, 2016, 12:07:21 pm
On the schematic below it has the cathodes on V2 tied together. This would create twice the current on the cathode....right?  Should that 1k2 be changed to a 750 ohm resistor?  The capacitor symbols seem to be drawn odd also.....
Title: Re: cathode resistor
Post by: HotBluePlates on April 15, 2016, 12:20:53 pm
On the schematic below it has the cathodes on V2 tied together. This would create twice the current on the cathode....right?  Should that 1k2 be changed to a 750 ohm resistor?  ...

Did you mean 1.5kΩ? The only 1.2kΩ resistor I see is in the long-tail inverter.

If you mean one of the 1.5kΩ resistors, they shouldn't share a cathode connection because they're amplifying opposite-phase signals. The cathode connection would be positive feedback...

...  The capacitor symbols seem to be drawn odd also.....

Whoever drew the schematic used a symbol for a polarized cap everywhere, likely without understanding what it implied. They also drew the curved plate (usually the - plate) on the wrong side for all the e'lytic caps. Oh well...
Title: Re: cathode resistor
Post by: EKDENTON on April 15, 2016, 01:57:28 pm
opps! I was looking at the wrong schemtic. That is the phase inverter not the second valve. Sorry, I should have looked at that closer before asking that.