Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Cree on October 13, 2020, 05:19:33 pm
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Talking about tube amp power supply's here, using SS rectification. I need to understand, charge rate, holding charge, discharge rate. (by rate I mean time to charge, discharge). Which would be best, lower uF caps or higher uF. Say 16uf vs 47uf. Lot of schematics I see now days use 47uF, older schematics used 8's or 16uF's. Then about the higher uF caps, 100uf vs 220uf. Is this a, lower uF is better, for charge up and filtering DC? Is it OK to use 220uF's or 330uF's in a tube amp power supply? Can you get smooth solid DC using the higher uF caps, and still maintain "charge rate"? Looking at physical size does not answer this for me as some 16uF's are about the same size as some 330uF's. :w2:
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the type of PA colors my choice on caps and how i use them
I like solid "stiff" PS, I want my "sound" based on notes n chords, not the sag of my AC
this is my "template" for most of my xSE's, you'll have to do the math :icon_biggrin:
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That is very similar to one I have been studying. One I have been studying uses all 100uF caps. Thank you for sharing your work Shooter.
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bigger capacitance = longer discharge time
Bass frequencies have longer wavelengths than treble frequencies, so for coupling caps, bigger capacitance passes more bandwidth. The smaller the capacitance, the higher the frequencies that pass, because the longer Lower-frequency wavelengths can’t ‘hold on’ where cap discharge time is shorter (so these frequencies don’t make it to the other side of the capacitor).
But for filter caps in power supplies, its better to shunt as-full-a-bandwidth-as-possible to ground to eliminate unwanted noise from the signal path. So longer discharge times mean ‘steadier’ DC. 47uF is better at eliminating ripple in a power supply than 4.7uF, all other things (i.e. reactance, resistance, inductance) being equal.
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... Which would be best, lower uF caps or higher uF. ...
Best for what?
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... Which would be best, lower uF caps or higher uF. ...
Best for what?
Talking about tube amp power supply's here, using SS rectification.
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....Which would be best....
That's like asking: Best computer mouse? Best lover? Best car? Best guitar stand?
Best diving board? In a tube amp, hundreds of uFd improves buzz. But a hard-driven guitar amp may feel like a concrete diving board. A 32uFd may have good "spring". A 8uFd may handle buzz and signal like wet cardboard. (If I may over-stretch a metaphor.)
Best bed?
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Best bed?
All travelers know that answer. Nothing like the feel of my own bed. :icon_biggrin:
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Talking about tube amp power supply's here, using SS rectification.
What PRR said: "Best" depends mostly on how you want the amp to feel, and how loud it's gonna be before it feels that way. Almost anything make the d.c. "clean enough" for a functioning amp.
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I'm thinking that if you're building a tube powered bass amp, you want larger capacitors to keep the low end stiff. For guitar amps, the question is a lot more open to how stiff or saggy you want the amp to be. If I remember correctly, the heavy metal players like their amp to be stiff for the hard edge distortion, but if you're playin the blues, you might want the amp to be more saggy when you're playing loud.
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... if you're building a tube powered bass amp, you want larger capacitors to keep the low end stiff. ...
Agreed. Though it's a difficult philosophical question: If "tight bass" is a goal (and very high power output is needed for bass), why go through the pain of the weight & cost penalty to build a tube bass amp? An SVT head is near-100lbs. But the B-15N is saggy & soft-sounding.
Tight, high-power bass is just so much more easily done with solid-state, with lower weight & less cost.
There are no absolutes, but it's funny how when you keep the end-goal in mind that we all keep learning the same lessons amp-manufacturers figured out years ago. :icon_biggrin:
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"Tight, high-power bass is just so much more easily done with solid-state, with lower weight & less cost."
This is true, of course, but I do prefer the sound of tube driven bass. I played through a silverface Bassman 100 for most of my time playing in a local band. I tried a couple of different solid state amps, but kept going back to the Bassman.
Of course, that's just my personal preference.
And yes, the Ampeg SVT is stupidly heavy...
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"Tight, high-power bass is just so much more easily done with solid-state, with lower weight & less cost."
This is true, of course, but I do prefer the sound of tube driven bass. ...
I'm no bass player, so I don't get a vote. :laugh:
But I liked one friend's B-15N every time I heard him play through it. And I had a different friend that was a gigging player who used a 400w Trace Elliott solid-state head. Now his sound punched your chest while you were still on the sidewalk waiting to get in the club.
Different players, with different applications, choosing different paths to "Good Sound."