Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: SnickSound on February 09, 2021, 03:20:35 pm
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I was gonna use 32uF.
It's a push-pull 2x6L6GC power amp. The preamp is mostly from a JCM800 2204 (which has 50uF on the screens and PI). But it also has bits of Mesa DNAs infused in it (like a NFB defeat switch that also reconfigures the Presence circuit). The Single Rectifier has 33uF on the screens, and 10uF on the PI.
I was gonna use 32uF.
But then, reading Valvewizard's article on PSUs, he mentions how the choke and capacitor can resonate and you want to keep that resonance frequency to 10Hz at most. My choke is 4H... do the math and I'd need 64uF!
But wait a minute, that set of transformers is technically for a Tweed Bassman... which has a mere 20uF on the screens.
So yeah... overthinking.
50... 32... 50... 32... does it even matter? I want a stout power section, but I do like an amp that's not too stiff and sterile.
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Cap value is also ( more ) a matter of rectifier
Solid State like the Marshall can use higher caps value.
Tubes rectifier, lower caps value.
Power Transformer do not matter
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... Tweed Bassman... which has a mere 20uF on the screens.
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50... 32... 50... 32... does it even matter? I want a stout power section, but I do like an amp that's not too stiff and sterile.
Unless you dime the amp a lot, the higher capacitance will only ever make the amp stiffer.
If you truly dime the amp (like playing into an attenuator or load box for recording), you may experience ghost-noting with an "under-filtered" supply.
The correct balance between "filtered enough" and "feels right" cannot be known without blasting the amp & using your judgment. Different players have differing opinions about which is the better sound.