Guys
My brother just dropped off a box full of resistors he got from who knows where! Anyways they are mostly 1watt metal oxide types. From reading here metal oxides should only go in the power supply circuit not the tone path due to noise problems, correct?
Luckily there are some 2-3 and 5 waters too...
Thanks.
Resistors
Moderators: pompeiisneaks, Colossal
Re: Resistors
1W metal oxide resistors can be used in the preamp too: plates, cathodes, grids, etc. Good score!
Re: Resistors
Jelle
Excellent...looks like I gotta build something!
Excellent...looks like I gotta build something!
In theory, theory is the same as practice. In practice it's different.
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Stevem
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Re: Resistors
They are good for anywhere, just note that above 320 TO 350 volts a 1/2 watt resistor should be upped to a 1 watter!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Resistors
Yeah but 1w resistors are easier to handle and usually have longer leads. 
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: Resistors
Yeah, especially as we age and our eyes go to hell....Structo wrote:Yeah but 1w resistors are easier to handle and usually have longer leads.
Re: Resistors
Just note that's an opinion, not a fact or rule. The voltage ratings of resistors is, unless otherwise specified (I'm thinking chassis-mount heatsinked jobbies), the voltage drop through the resistor, not absolute. Check the datasheets of the components you are going to use and respect those ratings.
I don't think that is correct. Resistor voltage drop has to do with it's power rating (watt) voltage rating has to do with the volts applied to the resistor and has to do with the dialectic strength of its construction. Most builder don't take this into consideration in guitar amp building.
I don't think that is correct. Resistor voltage drop has to do with it's power rating (watt) voltage rating has to do with the volts applied to the resistor and has to do with the dialectic strength of its construction. Most builder don't take this into consideration in guitar amp building.
Re: Resistors
...and I have always heard that a higher wattage resistor will be less noisey than it's smaller wattage version. Urban Myth???
In theory, theory is the same as practice. In practice it's different.
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martin manning
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Re: Resistors
Most half-watt MF resistors I use are rated at 350V max working voltage, 700V max overload, and the 1W are rated the same.
In a PI the supply voltage might be as high as 450V, but the peak voltage drop across the plate resistors under signal conditions won't be more than about 2/3 of the supply voltage. Maximum working voltage is therefore more like 275V.
Millions of Amps have been built with 1/2W plate resistors on all the preamp tubes, and they rarely fail from over-voltage.
Edit: The 2/3 fraction of supply voltage quoted above applies for a typical 12AX7 PI. With a higher-current tube, 12AT7 e.g., the max working voltage can be a bit higher, 70-75% of supply. If the supply voltage is high, 450V say, then the max working voltage of the plate resistors will approach the 350V max for typical resistors. In that case resistors with higher ratings might be in order, but simply going to a 1W power rating will not necessarily bring a higher voltage rating.
In a PI the supply voltage might be as high as 450V, but the peak voltage drop across the plate resistors under signal conditions won't be more than about 2/3 of the supply voltage. Maximum working voltage is therefore more like 275V.
Millions of Amps have been built with 1/2W plate resistors on all the preamp tubes, and they rarely fail from over-voltage.
Edit: The 2/3 fraction of supply voltage quoted above applies for a typical 12AX7 PI. With a higher-current tube, 12AT7 e.g., the max working voltage can be a bit higher, 70-75% of supply. If the supply voltage is high, 450V say, then the max working voltage of the plate resistors will approach the 350V max for typical resistors. In that case resistors with higher ratings might be in order, but simply going to a 1W power rating will not necessarily bring a higher voltage rating.