| Solid State vs. Vacuum Amps [message #86356] |
Fri, 20 October 2017 13:35  |
frankieg
Messages: 10
Registered: September 2017
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Chancellor |
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What are the differences between solid state amps and vacuum amps? My roommate just started playing the guitar (and already thinks they are a rockstar) and is thinking about getting an amp. I told him I would ask the experts, ie you all. Is one better than the other, or do they just offer different things? Are there other kinds?
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| Re: Solid State vs. Vacuum Amps [message #92868 is a reply to message #92527] |
Sun, 27 December 2020 20:11  |
positron
Messages: 146
Registered: May 2020
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Master |
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Off the top of my head, there are inherent differences between SS and Tube amplifiers due to the amplifying devices themselves. This may seem inconsequential, but I thought it would be beneficial for some.
1. Capacitance within the amplifying device. Vacuum tubes have a vacuum as a dielectric between the elements, hence virtually no DA or ESR/DA characteristics. SS devices, of course, have solid, semi conductor material with high DA and ESR/DF characteristics.
2. Miller Capacitance. The plate to no. 1 grid forms a capacitance, and that capacitance times the ~gain of the stage is called the Miller Capacitance, which the preceding stage "sees".
3. The internal junction capacitance in a FET varies with voltages across the junctions until ~25 volts and higher. Thus the Miller Capacitance varies as the signal varies in amplitude. Fortunately, the Miller Capacitance is low in some phase splitters and in output stages operated as source followers.
4. The power supply is quite different between Tube and SS. Where as vacuum tubes usually use a combination of chokes and small/medium size filter capacitors, SS generally uses vastly larger filter capacitors. The article "Picking Capacitors", by Walter Jung/Richard Marsh, shows that capacitors can have resonance in low khz. (See Below Attachment.)
In typical SS amplifiers, capacitances of 5 fold or more are often used.
This generally has a negative effect on sonics even though a typical sine wave may show low HD distortion. High DA and ESR/DF won't show up on a distortion analyzer.
Hope this helps in general understanding.
pos
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| Re: Solid State vs. Vacuum Amps [message #99078 is a reply to message #92868] |
Thu, 06 November 2025 11:22 |
Helen
Messages: 57
Registered: September 2025
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Baron |
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Oh, that’s fun! My husband actually talked about this once when he was looking at amps. From what I understand, solid-state amps use electronic circuits, so they’re usually lighter, cheaper and more reliable.
Vacuum tube amps (or valve amps) use old-style glass tubes and give that warmer, more “classic” sound that a lot of guitarists love. They just need a bit more care and can be costlier.
I don’t think one is exactly better because it depends on what sound your roommate likes. Tube amps sound smoother and more natural, while solid-state ones are cleaner and easier to maintain. There are also hybrid amps that try to give you the best of both. It might be fun for them to try a few in person to see what feels right.
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