Cathode resistor in Mrshall 18w (Stout, Hoffman layout)
Moderators: pompeiisneaks, Colossal
Cathode resistor in Mrshall 18w (Stout, Hoffman layout)
I ave this Marshall type 18 w amplifier I built years ago that I thought I'd use for some stuff. Problem is/was that i is very noisy. So I tried to change the cathode resistor from 130R to 2200R and the amp was suddenley almost dead silent. Is this a good to do or is there somewher else I should look also?
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johnnyreece
- Posts: 1061
- Joined: Thu Jan 26, 2012 2:05 am
- Location: New Castle, IN
Re: Cathode resistor in Mrshall 18w (Stout, Hoffman layout)
Can you confirm: You say 2200R? Seems pretty high...
Re: Cathode resistor in Marshall 18w (Stout, Hoffman layout)
Yes. I tried smaller values up till the 2200R, and the noise slowley went away.
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johnnyreece
- Posts: 1061
- Joined: Thu Jan 26, 2012 2:05 am
- Location: New Castle, IN
Re: Cathode resistor in Mrshall 18w (Stout, Hoffman layout)
Sounds like it's biased pretty cold...how does it sound? What's your plate voltage, and what voltage are you getting across the cathode resistor?
Re: Cathode resistor in Mrshall 18w (Stout, Hoffman layout)
Using that method, gain and power output will go down along with the noise.
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Re: Cathode resistor in Mrshall 18w (Stout, Hoffman layout)
noise is related with grounding, lead dress and mechanical layout (positioning of transformers) nothing to do with cathode resistor.