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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: RE: Interstages and grid load resistors??? posted by TomWh on December 8, 2014 at 06:56:36:
Are you talking about "grid leak" resistors? They help set the input impedance of the tube they are connected to. While high input impedance is a good thing, !M can be a problem. When tubes age they can get gassy and experience grid emissions (current). This flows through the grid leak resistor to ground and drives the grid positive (Ohms law). That drives the tube harder (more plate current). Not a stable condition. One of the benefits of ITs is that they provide a low DCR to ground for the tube's grid. Grid chokes can do the same thing. It would be really helpful if you could post a schematic of what you are trying to do. In phono pre's RIAA considerations come into play. My phono pre is 3 stage differential with the 1st/2nd stage direct coupled, 2nd/3rd IT coupled with a line out transformer. All RIAA resistors and caps are shunt. Getting the RIAA response correct is a bit tricky as Miller capacitance etc. come into play. I'm sure if you can post a schematic you'll be able to get some help and advise.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
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Follow Ups
- RE: Interstages and grid load resistors??? - JKT 12/8/1413:01:09 12/8/14 (1)
- RE: Interstages and grid load resistors??? - TomWh 17:08:51 12/8/14 (0)
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