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Solid State vs. Vacuum Amps [message #86356] Fri, 20 October 2017 13:35 Go to next message
frankieg is currently offline  frankieg
Messages: 10
Registered: September 2017
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?
Re: Solid State vs. Vacuum Amps [message #86358 is a reply to message #86356] Fri, 20 October 2017 16:05 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18009
Registered: January 2001
Illuminati (33rd Degree)

There's a lot to consider, and it's more than just the active elements. You want to also consider the topology: Single-Ended, Push-Pull, Ultralinear, Parafeed, etc. Also consider where feedback is used and how much. Do some searches here or just peruse this forum and you'll find a lot of discussions on these topics.

But to get you started, check out this booklet:
Re: Solid State vs. Vacuum Amps [message #92478 is a reply to message #86356] Thu, 22 October 2020 20:18 Go to previous messageGo to next message
The Noise is currently offline  The Noise
Messages: 134
Registered: October 2012
It is interesting that Edison was able to patent something, part of the filament I believe, without knowing exactly HOW it worked. Could that even happen these days?
Re: Solid State vs. Vacuum Amps [message #92500 is a reply to message #92478] Sat, 24 October 2020 21:24 Go to previous messageGo to next message
gofar99 is currently offline  gofar99
Messages: 1589
Registered: May 2010
Location: Southern Arizona
Illuminati (4th Degree)
Hi, there are a number of differences. Start with cost, power consumption and efficiency and heat generation. Add in amount of output power available and finally the one that is controversial is sound qualities. All of the first 4 mentioned tend to favor solid state amps. The last one is where the discussion gets murky. In theory any well designed amp should reproduce the source material well. If response figures, noise levels and distortion are equal the sound would logically be the same for either type. However, all things are seldom equal and the results are that they usually sound differently. Not bad or good, just different. So my suggestion is to listen to a few of each type and decide on what you like best. I personally prefer tube ones, but have a number of high end solid state ones as well. Often you will hear that folks say that tube amps have a "warmer" sound and solid state ones more detail sometimes to the point of being analytical. I don't personally share those thoughts (YMMV). I suspect that those comments probably made sense in the early days of solid state amps as the components and designs were not always as good as they are now. To be fair there were a lot of poor tube amps as well. Now both technologies are greatly refined and either type can fit most uses.

Good Listening
Re: Solid State vs. Vacuum Amps [message #92527 is a reply to message #86356] Mon, 26 October 2020 23:23 Go to previous messageGo to next message
hurdy_gurdyman is currently offline  hurdy_gurdyman
Messages: 416
Registered: May 2009
Illuminati (1st Degree)
Are we talking guitar amps or stereo amps?

Re: Solid State vs. Vacuum Amps [message #92868 is a reply to message #92527] Sun, 27 December 2020 20:11 Go to previous message
positron is currently offline  positron
Messages: 11
Registered: May 2020
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.


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