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What Determines Voltage at the Speaker terminals:Tube Amp
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Author:  tomp [ October 14th, 2015, 2:16 pm ]
Post subject:  Re: What Determines Voltage at the Speaker terminals:Tube Am
SoundMods wrote:
Hey Tom!

What you just described is the hole theory for transistors. Just saying. :character-oldtimer:


Actually it is more a description of a capacitor. Increasing current flow through a transistor does not increase the voltage (pressure) in a linear fashion but rather a log fashion until you reach a point beyond it's rated current at which point it becomes linear but usually damages the transistor. Also if you reverse the direction of flow in a transistor bad things happen. Except for polarized capacitors that is not a problem with caps.
Author:  Stuart Polansky [ October 14th, 2015, 2:21 pm ]
Post subject:  Re: What Determines Voltage at the Speaker terminals:Tube Am
If the real Roscoe or Tomp were here they'd probably tell you, like they told me, to take it to a new thread, quit hijacking Chris' thread. None of this B.S. benefits him.
Author:  SoundMods [ October 14th, 2015, 2:27 pm ]
Post subject:  Re: What Determines Voltage at the Speaker terminals:Tube Am
Why the negative Kharma? :angry-tappingfoot:
Author:  Roscoe Primrose [ October 14th, 2015, 2:31 pm ]
Post subject:  Re: What Determines Voltage at the Speaker terminals:Tube Am
SoundMods wrote:
Why the negative Kharma? :angry-tappingfoot:


Why the condescending attitude that's been in essentially every post you've made on this forum? You'll find that routinely talking down to people won't get you very far around here. Especially when you're factually incorrect.

And, Stuart is correct. If you wish to push this discussion further, please start another thread, probably in General Discussion.

Roscoe
Author:  chris1973 [ October 14th, 2015, 7:22 pm ]
Post subject:  Re: What Determines Voltage at the Speaker terminals:Tube Am
I liked Tom's people in the room post!

I'm going to try to memorize that.

Thanks!
Author:  chris1973 [ October 14th, 2015, 7:55 pm ]
Post subject:  Re: What Determines Voltage at the Speaker terminals:Tube Am
tomp wrote:
You should compare a capacitor to a compressed air cylinder not a water tank. WIth a capacitor as you increase the voltage (pressure) you add more charge(cubic feet of air) to the capacitor. Water is not compressible. With hydraulics you can transfer energy but cannot store it. WIth pneumatics you can both transfer and store energy. The stored energy in a compressed air cylinder is dependent on both the pressure and voume of air inside. WIth a capacitor the stored energy is dependent on the voltage and quantity of charge.

Tom

So this might sound ignorant, or repetitive, but the quantity of the charge is the volume of air, and the voltage is the pressure?

Can other electrical circuits be explained pneumatically better than they are hydraulically?

I'm a SCUBA technician, so I have a little bit of practical knowledge with compressed air.

thanks,

Chris
Author:  tomp [ October 14th, 2015, 8:01 pm ]
Post subject:  Re: What Determines Voltage at the Speaker terminals:Tube Am
chris1973 wrote:
tomp wrote:
You should compare a capacitor to a compressed air cylinder not a water tank. WIth a capacitor as you increase the voltage (pressure) you add more charge(cubic feet of air) to the capacitor. Water is not compressible. With hydraulics you can transfer energy but cannot store it. WIth pneumatics you can both transfer and store energy. The stored energy in a compressed air cylinder is dependent on both the pressure and voume of air inside. WIth a capacitor the stored energy is dependent on the voltage and quantity of charge.

Tom

So this might sound ignorant, or repetitive, but the quantity of the charge is the volume of air, and the voltage is the pressure?

Can other electrical circuits be explained pneumatically better than they are hydraulically?

I'm a SCUBA technician, so I have a little bit of practical knowledge with compressed air.

thanks,

Chris


You are correct.

Tom
Author:  SoundMods [ October 15th, 2015, 6:10 am ]
Post subject:  Re: What Determines Voltage at the Speaker terminals:Tube Am
I was only trying to help. :sad-roulette:
Author:  Guy [ October 15th, 2015, 9:35 am ]
Post subject:  Re: What Determines Voltage at the Speaker terminals:Tube Am
Hi, Walt, my two cents:
I wasn't offended by your posts (just my personality?), but I think the discussion of simple circuit theory for Chris1973 got too complicated by the theoretical discussion of Why things work. I felt that he needed to understand some of the fundamental things like current flow, voltage dividers, and such before getting into more complicated things. So I am pushing the approach of How things work instead of Why things work.

I noticed that Chris1973 kind of fell by the wayside in terms of postings compared to arguments about air and water (earth, fire, and something else and we can do Witchcraft! :) ) I think we've swamped him with too much detail (Chris can verify if he likes.)

A big problem with textual postings is that we get only 7% of the original information this way - we can't easily tell sarcasm, anger, confusion, and such from the typed words. At this point, we start writing our own stories about what the author really meant. :crazy:

And I've been guilty of redirecting the original theme of a thread, especially as it gets older and longer: at that point, someone usually suggests we should start another thread on my new topic. Like this thread: I think we dug too deep into theories compared to the original fundamental theme of the initial postings, and I may have started it by the comparison of electric current and water. Analogies and how thing work would make interesting General Discussions.

I think Chris is learning about electrical circuits, and we have trouble thinking about it without considering the things we've already learned with experience but understand now without considering it and vocalizing.

There are good pointers in this thread about Ohm's Law [ Voltage (E, Volts) = Current (I, Amps) x Resistance (R, Ohms), or substitute Impedance (Z) for Resistance, & Power (P, Watt) = Voltage (E, Volts) x Current (I, Amps)]. So as commented earlier, if you are putting 50 watts into your 8-Ohm speaker, we substitute I = E/R into P = EI to get P = E^2/R (that's E squared divided by R.) You want the voltage, which is the square root of PxR, or sqrt(50 x 8) = sqrt(400) = 20 Volts. Alternating Current (AC) theory rears its head: the 20 volts is an average over time so it can be compered to Direct Current (DC). As Stuart pointed out, that averaging process is called Root-Mean-Squared (RMS), and go get to the peak value of AC voltage, we have to multiply the 20 Volts RMS by sqrt(2), which gives us 28 Volts positive from zero. Because there is the same voltage below zero (for AC), the voltage from the positive peak to the negative peak is twice that, or 57 Volts. The next standard voltage about that is 63 Volts, but I'd like a safety factor for spikes and such, so I'd go higher to maybe 100-Volt capacitors.

This thread pointed out that, beyond just the theory, capacitors with higher voltage ratings sound better (not something that is in the specifications) so we like to use even higher-voltage ones.

For future consideration: the more you play and experiment, the more you see that Everything has an affect on the sound - not saying it's good or bad, but different parts make the sound different.

I'll stop rambling now - is there a theme to what I've written? I'll have to read it over. :shock:
Author:  J-ROB [ October 15th, 2015, 11:33 am ]
Post subject:  Re: What Determines Voltage at the Speaker terminals:Tube Am
Hey Walt...All circuits form a complete circle relative to ground...that is why they call em "circuits."

Yours, truly,
Mr. Obvious.

-----------------------

And, Chris, to make the water analogy a bit more useful, think of ground as a tank full of electron water and the power supply is sucking it in via B+ rather than squirting it out.

Direction of electron flow is the reverse of current flow. Think of electrons and it makes a bit more intuitive sense.
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