#1
Not exactly, obviously...

but is it a similar principle as far as circuit design is concerned? neglecting heaters etc
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#2
Tube triodes, i.e., a 12AX7, are more or less the same as solid-state triodes when you're talking about circuit design. The only differences are that, obviously, tubes need to be heated, and they require much higher voltage to sound right, they're big and tube-shaped, and they rely on current instead of voltage. I think, it may be the other way round.
#3
Quote by cokeisbetter
Tube triodes, i.e., a 12AX7, are more or less the same as solid-state triodes when you're talking about circuit design. The only differences are that, obviously, tubes need to be heated, and they require much higher voltage to sound right, they're big and tube-shaped, and they rely on current instead of voltage. I think, it may be the other way round.

Yeah, i getcha, just wanted conformation
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#4
Quote by cokeisbetter
Tube triodes, i.e., a 12AX7, are more or less the same as solid-state triodes when you're talking about circuit design. The only differences are that, obviously, tubes need to be heated, and they require much higher voltage to sound right, they're big and tube-shaped, and they rely on current instead of voltage. I think, it may be the other way round.


Tubes operate off voltage, while MOSFET's/transistors in general operate off current. And yeah, apart from that you're spot on.
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#5
^ ive read that article... but to from the point of view of the electronic buffs, thats just the 1,000,000,001st attempt that failed to replicate the triode.

there are lots of tube amp simulations that use almost the same schematic of the amp theyre after and replace the triodes with JFETs [low-power devices similar to the mosfet]
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#6
Quote by the_random_hero
Tubes operate off voltage, while MOSFET's/transistors in general operate off current. And yeah, apart from that you're spot on.
If you can find somebody that can translate this page for you, I'm sure you'll find some very helpful things.


Not exactly, Drew.

Bipolar transistors are current controlled current sources.
(or current sinks, depending on how you want to view them.)

MosFETs, jFETs, and Vacuum Tubes (Valves) are voltage controlled current sources.

So, the design for the latter group does follow a similar pattern. Obviously the lack of heaters and the lower voltages in the FETs make things easier. The fact that you can have opposite polarity devices also makes transformers unnecessary in the output stages using FETs. Not using an Output Transformer is one of MANY reasons why Solid State amps sound different from Tube amps. Also, there are many ways you can employ solid-state devices that you simply can't with tubes.

Some of the "flaws" of Tube amps are exactly why they have a characteristic tonality that many of us have grown to love. With great difficulty and care, you can emulate (but not quite duplicate) these flaws.

...
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#7
Quote by SomeoneYouKnew
Not exactly, Drew.

Bipolar transistors are current controlled current sources.
(or current sinks, depending on how you want to view them.)

MosFETs, jFETs, and Vacuum Tubes (Valves) are voltage controlled current sources.

So, the design for the latter group does follow a similar pattern. Obviously the lack of heaters and the lower voltages in the FETs make things easier. The fact that you can have opposite polarity devices also makes transformers unnecessary in the output stages using FETs. Not using an Output Transformer is one of MANY reasons why Solid State amps sound different from Tube amps. Also, there are many ways you can employ solid-state devices that you simply can't with tubes.

Some of the "flaws" of Tube amps are exactly why they have a characteristic tonality that many of us have grown to love. With great difficulty and care, you can emulate (but not quite duplicate) these flaws.

...


I think you mean that these devices can be used as current sources, not that they are current sources.
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#8
Quote by ljplum12
I think you mean that these devices can be used as current sources, not that they are current sources.


No, actually I meant the latter. It has to do with mathematical modeling of devices. Of course in the real world they, by themselves, are not sources of current, but rather are only capable of controlling current. Calling them voltage controlled current controllers would be more accurate ... and also look ridiculous. Whether they used as current sources or current sinks is dependent on configuration. If you're uncomfortable with the terminology, just call them current sinks. It's a somewhat accepted accepted form. I alluded to that in my reference to bipolars.
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#9
Cheers, just I wanted to know - building an overdrive pedal sometime soon, and only REALLY have a knowlegde of MOSFETs, but I understand the basics of tubes etc.

Also, would you be able to tell me the open loop gain of the 12AX7?

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#10
Gain (Amplification Factor) is dependent on the circuit as well as the tube itself.

They claim the amplification factor for a 12ax7 in a typical circuit to be 100.

Here's a link you can use to look up tube data:

http://www.nj7p.org/Tube.php
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#11
Quote by SomeoneYouKnew
Gain (Amplification Factor) is dependent on the circuit as well as the tube itself.

They claim the amplification factor for a 12ax7 in a typical circuit to be 100.

Here's a link you can use to look up tube data:

http://www.nj7p.org/Tube.php

Which is why I said open loop gain

and cheers for the link
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