|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
141.239.172.61
In Reply to: RE: Sounds like to me you are using a 5K pot posted by Chip647 on October 18, 2016 at 13:27:49
Hi Chip, almost 100% sure that it is 50k Allen Bradley linear. I have the wiper going to the 13K resistor to the grid. Does it matter which leg is going to ground? I did not think it matters.
I will recheck the resistor values. It is not the first time that i have messed up with that. cheers.
Edits: 10/18/16Follow Ups:
a 5K or 10K-pot will give you finer control, in the C- range needed to bias the tubes. Once, you get the set resistors closer to the ideal negative voltage. Play with the circuit-to-ground resistor's value (prolly going to be around 20-30k-ohm), until you get close to nominal C- voltage (prolly around minus 55-60VDC). Then, insert the 5k or 10k-pot.
Good luck!
But, whether or not that is the right value to achieve my parameters, i am not sure as i am pretty much following my other fixed bias amp which had a 50k pot for the voltage adjustment. i admit that the correctly working circuit is not the same as this circuit. This new circuit i chose because it has a fail safe feature. I don't know if it has been vetted by other users. Theoretically, does anyone see why it can not work? I left many of the resistors in the bias circuit unsoldered in anticipation of changes. cheers and thanks for all the suggestions.
solve one problem at a time. Measure voltage at each junction in your fixed bias circuit then draw it out, resistances and voltages. The bias circuit draws almost no current so the voltage out will be the resistance ratio. You may have an unsoldered connection making a poor connection
I just saw this. Isn't the amp cathode-biased, Class "A?"
No, i am doing it with fixed bias. Same thing you just bias the amp up with a meter which measures the current on the cathode. One can dial in the amount of bias you want. Also you can have different power tubes and simply and easily adjust the current to suit the different tube's needs.
Are you in intending to run this SE amp in Class "A?"Thanks!
Edits: 10/19/16
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: