What really are the philosophical differences between triodes and Pentodes? What are the effects on sonics of each?
Is another *ode term, diode, in any way related?
Are there other *odes?
What are the pros & cons of each. In my limited experience, triodes sound better than pentodes but I imagine it's system and music dependent.
Is there also such a thing in solid state?
Triode vs. Pentode vs. Other *odes: Pros & Cons?
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Triode vs. Pentode vs. Other *odes: Pros & Cons?
by rtsyrtsy » Thu Jan 30, 2003 8:03 am
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odes of ode
by johnmarc0 » Thu Jan 30, 2003 2:39 pm
actually the "ode" came from the term electrode so a diode is a vacuum tube device (wala pa SS when they coined the term in the turn of the last century) with two electrodes or di-electrode or simply diode same with tri-electrode for triode, tetra-electrode (4) for tetrodes and penta-electrodes for pentodes.
Huge difference between the two, triodes and other multigrid amplifying device (barest amplifying device is a triode, a diode do not amplify) like tetrodes and pentodes have non linear characteristics but can handle more gain, very efficient and more power the triode on the other hand triode is inefficient, small gain but highly linear.
Linearity dictates amount of distortion, a pentode without feedback will generate 15% distortion (because of it's non-linear response), with feedback will go as low as 8% distortion pero panget tunog even with low distortion (due to phase shift, which is an imaging killer).
Triode naman usually have 5% distortion but only 10 to 15% efficient so a 30 Watt triode tube can only spew 2 to 8 watts the rest is converted to heat. But can reproduce near exact tones and thousandfold better than pentodes.
JM
Huge difference between the two, triodes and other multigrid amplifying device (barest amplifying device is a triode, a diode do not amplify) like tetrodes and pentodes have non linear characteristics but can handle more gain, very efficient and more power the triode on the other hand triode is inefficient, small gain but highly linear.
Linearity dictates amount of distortion, a pentode without feedback will generate 15% distortion (because of it's non-linear response), with feedback will go as low as 8% distortion pero panget tunog even with low distortion (due to phase shift, which is an imaging killer).
Triode naman usually have 5% distortion but only 10 to 15% efficient so a 30 Watt triode tube can only spew 2 to 8 watts the rest is converted to heat. But can reproduce near exact tones and thousandfold better than pentodes.
JM
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by rtsyrtsy » Thu Jan 30, 2003 3:41 pm
More electronics-empty questions.
I don't hear so much about tetrode amps? Do they sound worse than pentodes so no one makes them?
Another term I hear is "directly heated triode." Valves are by themselves hot, why heat 'em up some more?
Don't worry, you may call me anytime for restaurant recommendations, working with complex business plans on Excel, and some video editting stuff.
I don't hear so much about tetrode amps? Do they sound worse than pentodes so no one makes them?
Another term I hear is "directly heated triode." Valves are by themselves hot, why heat 'em up some more?
Don't worry, you may call me anytime for restaurant recommendations, working with complex business plans on Excel, and some video editting stuff.
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by arnoldc » Thu Jan 30, 2003 3:47 pm
ang natutunan ko kay prof. jm
Tubes such the 2A3 and 300B, do not have heaters: their cathode and filament are one. He he he, kaya kailangan ng heater.
In such tubes, the filament can be heated by DC or AC voltage...
tapos nakatulog na ko...
Tubes such the 2A3 and 300B, do not have heaters: their cathode and filament are one. He he he, kaya kailangan ng heater.
In such tubes, the filament can be heated by DC or AC voltage...
tapos nakatulog na ko...
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by johnmarc0 » Thu Jan 30, 2003 3:51 pm
tetrode amps are actually used for TV and Radio Station transmitters. They sound the same as pentodes but current production KV and rating.
Directly heated triodes on the other is a long story, tubes have an electrode called cathodes, for cathodes to emit ions and conduct current they have to be heated (the glow that you can see) so there is two methods to heat it up. directly and indirectly, indirectly, a heating filament is placed behind the cathode and it heats up, since it's proximity to the cathode, eventually the cathode also heats up that is indirect heating but when tubes started, they have no technology to build indirectly heated cathodes, they actually use the filament as the cathode so the filament is "directly heating" the cathode.
DHT for me sounds better than IDHT
JM
Directly heated triodes on the other is a long story, tubes have an electrode called cathodes, for cathodes to emit ions and conduct current they have to be heated (the glow that you can see) so there is two methods to heat it up. directly and indirectly, indirectly, a heating filament is placed behind the cathode and it heats up, since it's proximity to the cathode, eventually the cathode also heats up that is indirect heating but when tubes started, they have no technology to build indirectly heated cathodes, they actually use the filament as the cathode so the filament is "directly heating" the cathode.
DHT for me sounds better than IDHT
JM
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by Killer Mike » Thu Jul 15, 2004 1:58 pm
Hey Fastback!
Nice illustration bro! Man! you are everywhere in this forum! I'm happy for you learning a lot and keep it up. 
Nice illustration bro! Man! you are everywhere in this forum!
I'm happy for you learning a lot and keep it up. -
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by FASTBACK » Fri Jul 16, 2004 12:48 am
Mike wrote:Hey Fastback!
Nice illustration bro! Man! you are everywhere in this forum!
Mike
Thanks I'm just catching on the threads I missed before.
Too bad I haven't found an illustration of the pentode etc..
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by Quiel » Fri Sep 03, 2004 4:00 pm
from DADEV.COM. (abridged)
**************************8
The Vacuum Tube FAQ
by Henry Pasternack
--------------------------------------------------------------------------------
Q: What is "ultralinear" operation?
A: In ultralinear operation, the screen grid is connected to a tap on the output transformer primary such that the screen voltage varies in proportion to the plate signal voltage. The constant of proportion- ality typically ranges from 30-50%, although other ratios will also work. The resulting tube characteristic has properties intermediate between those of the triode and the pentode. In essence, the ultra- linear connection forms a local negative feedback loop around the output stage. This may be advantageous depending on circuit topology and gain distribution. Advocates of ultralinear operation claim this connection combines the best features of triode and pentode mode, while detractors claim it lack the virtues of either.
Q: Compare the general properties of triode, pentode, and ultralinear power amplifiers.
A: It is probably misleading to characterize the various types of output stage connections in terms of sound quality. Many factors contribute to the sound of an amplifier, and a good designer will blend these elements in order to achieve a particular goal. On the other hand, certain sonic qualities are associated with each type of output stage frequently enough that they deserve repeating here. In addition, there are objective differences that are worth mentioning.
The triode amplifier is characterized by low efficiency and low power output. This is because a smaller voltage swing is available from the triode for a given DC plate voltage. Consequently, the triode amplifier burns up more power at idle relative to its peak output. The sound of the triode amplifier is often described as "rich" or "sweet", conveying in a natural and realistic way the harmonic structure of musical instruments and voices.
The pentode amplifier is often described as having a more analytical sound than comparable triode units. Others may accuse it of sounding harsh. Objectively, the pentode output stage tends to produce more high-order distortion products than a comparable triode. In addition, the pentode is more sensitive to load impedance variations and may clip more sharply than the triode.
The ultralinear amplifier combines the benefits (or flaws, depending on your point of view) of the triode and pentode connections. The ultralinear characteristic curves resemble those of the triode in some ways, those of the pentode in others, and have unique characteristics as well (regretably, they are hard to render in ASCII). While the general concensus favors triode mode above all, there seems to be no strong trend supporting ultralinear over pentode mode, or vice-versa. Perusing the high-end magazines, one can find examples of well-regarded amplifiers ueing either type of output connection.
The one certainty is that the ultralinear connection is the cheapest way to get good performance and high power out of a pentode. Whereas a quality pentode design requires a stiffly regulated screen grid supply, all that is needed to implement an ultralinear output stage is a pair of transformer primary taps. Perhaps the economic argument leads the sound quality argument in this case.
Q: Can I convert my amplifier back and forth between pentode, triode and ultralinear modes in order to hear the difference for myself?
A: In general, the answer to this question is "No." Under some circumstances, it may be possible to perform such experiments, but subject to limitations.
If the amplifier is an ultralinear design, it is possible to convert it to pentode operation by connecting the screens to a fixed voltage source. The correct screen voltage depends on the type of output tube, the B+ supply voltage, and the output transformer primary impedance. For audiophile performance, a regulated screen supply may be required. This makes the pentode conversion a major modification.
The most common conversion is to modify an ultralinear or pentode mode amplifier for triode operation. In many cases, this modification can be made successfuly and with little effort, but some caveats apply. One would like to be sure that the maximum triode-connected plate potential is not exceeded. For many EL-34/6L6/KT-66/5881 amplifiers running B+ supplies on the order of 400V, there is no problem converting to triode operation. On the other hand, a 6550 amplifier with 550V on the plates is probably not a candidate for triode conversion without a reduction in B+ voltage. When the conversion is made, a 100 Ohm non-inductive resistor is usually specified, connected directly between the screen and plate pins on the tube socket, to suppress RF instability.
Changing the output stage connection from pentode to triode mode typically lowers the open-loop gain of the amplifier. As a result, the closed-loop global feedback factor also goes down. The output impedance of the amplifier, its sensitivity, the total harmonic distortion and the distortion spectrum will all change. Overload behavior and stability will likely be improved. Typical comments are that the triode-connected amplifier sounds "more relaxed", "warmer", and "sweeter" after the conversion. Whether this is due to an inherent quality of triode-strapped pentodes, or is a consequence of modifying a topology that was not designed with triode output in mind, is open for debate.
Q: What about "pure-triode" amplifiers?
A: The vintage triode power tubes, such as the 845, 2A3, and 300B, are classic devices from the earlier days of vacuum tube technology. They are still available in limited supply and at high cost (although there are now Chinese copies on the market that offer a reasonable, lower- price alternative). A significant structural difference between these tubes and more modern units is the use of a directly-heated cathode. In this design, the cathode heater also serves as the emissive element. In contrast, newer tubes employ a separate heater that is electrically and mechanically isolated from the cathode.
These tubes are "pure triodes", meaning that there is no screen grid to be strapped to the plate in order to achieve triode operation. The classic triodes have very low plate resistance and low voltage gain. Many require significantly higher plate supply voltages than ordinary pentodes. In exchange for these limitations, these tubes offer very linear characteristic curves, making possible the design of low- distortion amplifiers that use little or no local or global feedback. The sound of a pure-triode amplifier is reputed to be exceedingly musical, with a natural harmonic structure, very low grain or noise, and a realistic, inviting nature. Triode adherents claim that the pure-triode output stage is sonically superior to one constructed with strapped screen grid pentodes. Other listeners will find the pure-triode amplifier to be colored, restricted in bandwidth, inefficient, and overpriced.
Single-ended triode amplifiers have been very popular in Japan for some time, and are making a limited comeback in North America.
Q: What is the difference between a single-ended and push-pull amplifier?
A: A push-pull output stage uses one or more pairs of output devices connected in a symmetrical arrangement such that output current flows to the load first through one half of the circuit and then through the other half. The advantages of the push-pull topology are higher efficiency, higher power output, much lower even-order distortions, immunity from power supply ripple, and zero DC current in the output transformer primary.
In contrast, the single-ended output stage employs only one set of output devices which conduct continuously throughout the output current cycle. This forces the stage to be operated in class A mode, limiting the available power output and greatly lowering efficiency. Total harmonic distortion is higher because there is no cancellation of even-order harmonics. Power supply ripple is not rejected by the single-ended output.
The most significant difficulty of the single-ended output stage is that the output transformer is required to carry a large DC current in its primary. Due to magnetic saturation and nonlinearity effects, a very special output transformer design is required. Such a transformer is large, heavy, expensive, and has a low power rating. The resulting amplifier is restricted in bandwidth at both extremes of the audio spectrum and produces a great deal of distortion. To minimize distortion (and to add to the single-ended mystique), it has become fashionable to design single-ended amplifiers with pure-triode output stages.
While no one claims the pure-triode, single-ended amplifier is "neutral" or "accurate", devotees of the genre describe in almost mystical terms the sonic attributes of these amplifiers. The word "magic" is often used. Listeners will have to judge for themselves.
--------------------------------------------------------------------------------
Henry A. Pasternack
Member Scientific Staff
Bell Northern Research, Montreal
E-mail: hap@bnr.ca
**************************8
The Vacuum Tube FAQ
by Henry Pasternack
--------------------------------------------------------------------------------
Q: What is "ultralinear" operation?
A: In ultralinear operation, the screen grid is connected to a tap on the output transformer primary such that the screen voltage varies in proportion to the plate signal voltage. The constant of proportion- ality typically ranges from 30-50%, although other ratios will also work. The resulting tube characteristic has properties intermediate between those of the triode and the pentode. In essence, the ultra- linear connection forms a local negative feedback loop around the output stage. This may be advantageous depending on circuit topology and gain distribution. Advocates of ultralinear operation claim this connection combines the best features of triode and pentode mode, while detractors claim it lack the virtues of either.
Q: Compare the general properties of triode, pentode, and ultralinear power amplifiers.
A: It is probably misleading to characterize the various types of output stage connections in terms of sound quality. Many factors contribute to the sound of an amplifier, and a good designer will blend these elements in order to achieve a particular goal. On the other hand, certain sonic qualities are associated with each type of output stage frequently enough that they deserve repeating here. In addition, there are objective differences that are worth mentioning.
The triode amplifier is characterized by low efficiency and low power output. This is because a smaller voltage swing is available from the triode for a given DC plate voltage. Consequently, the triode amplifier burns up more power at idle relative to its peak output. The sound of the triode amplifier is often described as "rich" or "sweet", conveying in a natural and realistic way the harmonic structure of musical instruments and voices.
The pentode amplifier is often described as having a more analytical sound than comparable triode units. Others may accuse it of sounding harsh. Objectively, the pentode output stage tends to produce more high-order distortion products than a comparable triode. In addition, the pentode is more sensitive to load impedance variations and may clip more sharply than the triode.
The ultralinear amplifier combines the benefits (or flaws, depending on your point of view) of the triode and pentode connections. The ultralinear characteristic curves resemble those of the triode in some ways, those of the pentode in others, and have unique characteristics as well (regretably, they are hard to render in ASCII). While the general concensus favors triode mode above all, there seems to be no strong trend supporting ultralinear over pentode mode, or vice-versa. Perusing the high-end magazines, one can find examples of well-regarded amplifiers ueing either type of output connection.
The one certainty is that the ultralinear connection is the cheapest way to get good performance and high power out of a pentode. Whereas a quality pentode design requires a stiffly regulated screen grid supply, all that is needed to implement an ultralinear output stage is a pair of transformer primary taps. Perhaps the economic argument leads the sound quality argument in this case.
Q: Can I convert my amplifier back and forth between pentode, triode and ultralinear modes in order to hear the difference for myself?
A: In general, the answer to this question is "No." Under some circumstances, it may be possible to perform such experiments, but subject to limitations.
If the amplifier is an ultralinear design, it is possible to convert it to pentode operation by connecting the screens to a fixed voltage source. The correct screen voltage depends on the type of output tube, the B+ supply voltage, and the output transformer primary impedance. For audiophile performance, a regulated screen supply may be required. This makes the pentode conversion a major modification.
The most common conversion is to modify an ultralinear or pentode mode amplifier for triode operation. In many cases, this modification can be made successfuly and with little effort, but some caveats apply. One would like to be sure that the maximum triode-connected plate potential is not exceeded. For many EL-34/6L6/KT-66/5881 amplifiers running B+ supplies on the order of 400V, there is no problem converting to triode operation. On the other hand, a 6550 amplifier with 550V on the plates is probably not a candidate for triode conversion without a reduction in B+ voltage. When the conversion is made, a 100 Ohm non-inductive resistor is usually specified, connected directly between the screen and plate pins on the tube socket, to suppress RF instability.
Changing the output stage connection from pentode to triode mode typically lowers the open-loop gain of the amplifier. As a result, the closed-loop global feedback factor also goes down. The output impedance of the amplifier, its sensitivity, the total harmonic distortion and the distortion spectrum will all change. Overload behavior and stability will likely be improved. Typical comments are that the triode-connected amplifier sounds "more relaxed", "warmer", and "sweeter" after the conversion. Whether this is due to an inherent quality of triode-strapped pentodes, or is a consequence of modifying a topology that was not designed with triode output in mind, is open for debate.
Q: What about "pure-triode" amplifiers?
A: The vintage triode power tubes, such as the 845, 2A3, and 300B, are classic devices from the earlier days of vacuum tube technology. They are still available in limited supply and at high cost (although there are now Chinese copies on the market that offer a reasonable, lower- price alternative). A significant structural difference between these tubes and more modern units is the use of a directly-heated cathode. In this design, the cathode heater also serves as the emissive element. In contrast, newer tubes employ a separate heater that is electrically and mechanically isolated from the cathode.
These tubes are "pure triodes", meaning that there is no screen grid to be strapped to the plate in order to achieve triode operation. The classic triodes have very low plate resistance and low voltage gain. Many require significantly higher plate supply voltages than ordinary pentodes. In exchange for these limitations, these tubes offer very linear characteristic curves, making possible the design of low- distortion amplifiers that use little or no local or global feedback. The sound of a pure-triode amplifier is reputed to be exceedingly musical, with a natural harmonic structure, very low grain or noise, and a realistic, inviting nature. Triode adherents claim that the pure-triode output stage is sonically superior to one constructed with strapped screen grid pentodes. Other listeners will find the pure-triode amplifier to be colored, restricted in bandwidth, inefficient, and overpriced.
Single-ended triode amplifiers have been very popular in Japan for some time, and are making a limited comeback in North America.
Q: What is the difference between a single-ended and push-pull amplifier?
A: A push-pull output stage uses one or more pairs of output devices connected in a symmetrical arrangement such that output current flows to the load first through one half of the circuit and then through the other half. The advantages of the push-pull topology are higher efficiency, higher power output, much lower even-order distortions, immunity from power supply ripple, and zero DC current in the output transformer primary.
In contrast, the single-ended output stage employs only one set of output devices which conduct continuously throughout the output current cycle. This forces the stage to be operated in class A mode, limiting the available power output and greatly lowering efficiency. Total harmonic distortion is higher because there is no cancellation of even-order harmonics. Power supply ripple is not rejected by the single-ended output.
The most significant difficulty of the single-ended output stage is that the output transformer is required to carry a large DC current in its primary. Due to magnetic saturation and nonlinearity effects, a very special output transformer design is required. Such a transformer is large, heavy, expensive, and has a low power rating. The resulting amplifier is restricted in bandwidth at both extremes of the audio spectrum and produces a great deal of distortion. To minimize distortion (and to add to the single-ended mystique), it has become fashionable to design single-ended amplifiers with pure-triode output stages.
While no one claims the pure-triode, single-ended amplifier is "neutral" or "accurate", devotees of the genre describe in almost mystical terms the sonic attributes of these amplifiers. The word "magic" is often used. Listeners will have to judge for themselves.
--------------------------------------------------------------------------------
Henry A. Pasternack
Member Scientific Staff
Bell Northern Research, Montreal
E-mail: hap@bnr.ca
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by caruzo » Mon Oct 18, 2004 9:57 am
FASTBACK,
You are very resourceful to present the graphics to differentiate a diode vs a triode.
I can still recall my college days in 1961 in my Electrical Engineering Course.
What you uploaded to this website is really an educational material for others.
CONTRATULATIONS!
Thanks,
Caruzo
You are very resourceful to present the graphics to differentiate a diode vs a triode.
I can still recall my college days in 1961 in my Electrical Engineering Course.
What you uploaded to this website is really an educational material for others.
CONTRATULATIONS!
Thanks,
Caruzo
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by mozilla » Mon Oct 18, 2004 12:02 pm
The accompanying write-up to the images posted by Fastback can be found here:
http://www.angelfire.com/electronic/funwithtubes/
http://www.angelfire.com/electronic/funwithtubes/
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