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In Reply to: RE: We have discussed this before, posted by gusser on February 25, 2015 at 10:42:30
Here is a Stromberg Carlson ASR-444 integrated amp with that setup.They sound very good but I still put a grid stopper in. Why do you think SC did this?
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Follow Ups:
He's talking about the grid leak, not grid stopper. There is no resistor to ground after the cap coupling the 300B. A big error on the schematic.
Dan Santoni
Wow!
I just looked at that circuit and how can that amp operate with no potential on G1? It if were direct coupled to a cathode follower that may work but I don't see where the 300b would be stable at all if it did work.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Grid stopper or Grid resistor?
dave
Grid stopper,the one that goes to the control grid.It basically acts as a high frequency low pass filter to help keep RF out causing parasitic oscillation.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
The typically 1K series resistor to the grids of PP output tubes was not historically there to prevent oscillation but to prevent blocking distortion from periodic overload. Crowhurst covers this in the link below.
The grid stopper is very often optional.The grid leak is typically not optional.
Edits: 02/25/15
Yes
I see that now..I just noticed it had no grid stopper and it also has no grid leak which is far more important.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
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