Favourite NOS Carbon and Metal resistors for balckface

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Bombacaototal
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Favourite NOS Carbon and Metal resistors for balckface

Post by Bombacaototal »

As the title says I am wondering what is everyone's favourite NOS resistors both Metal and Carbon for Blackface builts

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Stevem
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Post by Stevem »

It depends, comps make added hiss especially as they age, but they do add there own small degree of good distortion when used as plate loads.
Eithere way plate loads in the preamp section should be up rated to 1 watt types, and plate loads in the PI section should go to 2 watt types due to the voltage across them, heck even the 5 watt Ciramic types used as screen resistors are not rated for the voltage they have across them!
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martin manning
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Re: Favourite NOS Carbon and Metal resistors for balckface

Post by martin manning »

Steve! Read the spec sheets! Wattage rating does not determine voltage rating!!
Bombacaototal
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Re: Favourite NOS Carbon and Metal resistors for balckface

Post by Bombacaototal »

On caps, For the treble cap and bright switch what is everyone's preference: silver mica or ceramic
pdf64
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Re: Favourite NOS Carbon and Metal resistors for balckface

Post by pdf64 »

In case you're not already aware of it, here's the article explaining how CCs may be used to benefit tone http://www.geofex.com/Article_Folders/c ... oncomp.htm
Stevem wrote:...plate loads in the PI section should go to 2 watt types due to the voltage across them, heck even the 5 watt Ciramic types used as screen resistors are not rated for the voltage they have across them!
I don't think any LTP plate resistors of regular tube amps tend to dissipate over ~0.5W, so 1 watt resistors should be sufficiently derated for good life?

5W ceramics are usually at least 200V rated, so should be fine for most regular screen grid resistors, eg overdriven EL34 screen grids pulling 50mA via 1k screen grid current limiting resistors, which would drop ~50Vdc average, so maybe a Vpeak of 100V.
HT droppers need a voltage rating around the VHT, as they may be exposed to high surge voltage at power up, before the cap they supply has charged up.
keewee
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Re: Favourite NOS Carbon and Metal resistors for balckface

Post by keewee »

Bright cap I like polystyrene seems a little smoother to me, some people even mix two, this is highly subjective and a personal preference.
BetterOffShred
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Re: Favourite NOS Carbon and Metal resistors for balckface

Post by BetterOffShred »

I'm not by any means a professional amp builder but I play a lot and I feel I'm fairly discerning with tone. That being said, I pretty much replace everything with 1/2 watt metal films for being quieter and higher tolerance. Sure there is mojo hidden in component variation between circuits etc but I'd rather have it like the schematic and go from there. I get all my stuff from Hoffman, and his resistors are top notch.

I 'Blackfaced' my '68 AB165 with carbon comps and it sounds good, and refreshed the bass channel with metal films, and I do agree it's quieter. Not a whole lot, but noticeable to my ear.
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TUBEDUDE
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Re: Favourite NOS Carbon and Metal resistors for balckface

Post by TUBEDUDE »

If using carbon comps for plates, I use 2 watt units if I can find them in the value I need. I've found the physically larger units have lower noise.
That said, I prefer not to use carbon comps as plate resistors
Tube junkie that aspires to become a tri-state bidirectional buss driver.
keewee
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Re: Favourite NOS Carbon and Metal resistors for balckface

Post by keewee »

use carbon comps only where you have a large voltage swing, to generate even harmonics, this is usually the second or third stage plate resistor, keeping power rating close to its working range also increases the 2ND harmonic. This to me gives good tone while lowering the noise floor. Physics
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