| 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: 148
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 #99123 is a reply to message #86356] |
Wed, 03 December 2025 06:54 |
positron
Messages: 148
Registered: May 2020
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Master |
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In general, I have found all tube/solid state designs are
quite inaccurate (specs mean virtually nothing except channel
separation high frequency response, damping factor etc within reason.
However, in my lab/audio company, retired for over a decade,
I was able to create a line pre-amplifier that listening
tested perceptually perfect to the source. Many musical selections
were used because of differing quality.
The amplifier was different as I used a constant load. When connecting
a reactive load, one has to match more carefully, both the correct total
gauge speaker wire for bass control, and parallel wires to minimize
reactance at higher frequencies. The wire type, Jenalabs 6N all copper,
worked nicely, and is quite superior sounding to 3N wire sold locally.
One caveat is that every component used, sources, line pre-amplifier,
monoblock amps use polypropylene capacitors in the place of electrolytic
capacitors in decoupling applications (except high voltage amplifier
power supply with electrolytics bypassed by a large polypropylene capacitor,
and multiple cathode bypass capacitors). As such, the system is extremely
transparent, perceived sonic differences down to 1 part in
4,000,000 reliably.
I would guess most audio systems would not be as sensitive, so
sonic differences may not be as noticeable.
cheers
pos
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