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Pierre The Bear

Another newbie question, sorry folks. What is "linear"

11 posts in this topic

I'm doing some valve amp research and I read that one of the advantages is that they are linear!
What does that mean?
Sorry if my ignorance bores you all but if you don't ask you don't find out.
Regards,
John.
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A flat frequency response without peaks and troughs. It should be closer to the actual sound being reproduced. Problem is there are also "dynamics" to be considered before you glimse perfection (I deliberately say "glimse").
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Linear to me means that the transfer function i.e. the gain from input to output is linear, i.e. any increase in input translates [B]exactly[/B] to a similar increase in output at any level from zero up to clipping, and at any frequency in the audio range. Any variation in that linearity results in distortion.

I'm surprised that anyone would claim that as a particular property of valves as the necessity of using an output transformer and the lack of linearity of tetrodes and pentodes results in far higher distortion than SS amps. I wonder what they mean.

S.
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Not all valve amps produce significant distortion when operated within their optimum ranges and to all practical purposes, distortion figures are more than perfectly acceptable from a decent valve amp. It bugs me no end when anti-valve enthusiasts gleefully point out spec sheet numbers and fail to recognise the other benefits of valves, namely superior soundstaging and superior tonal timbral qualities over equivalent SS amps. The advertising of valve amps as "linear" or "push-pull" refers simply as to whether feedback is used. When in ultralinear mode, such as SET, no feedback is used and a single valve drives a single channel. In push pull mode, power rating can be increased and twin output driver valves are used employing feedback to control distortion, with each valve operating a phase of the signal. Push-pull are more efficient and more powerful with lower distortion.

Also, there are linear type valves (to complicate matters more) in which the measured output V's distortion graphs are "linear" instead of having the characteristic curve or kink of simple triod operation. Beam pentodes have this characteristic (eg 6L6 types) as do KT type valves (eg KT66, KT77 and KT88). The KT stands for Kinkless Tetrode. These are more commonly associated with higher output amps than the more commonly available EL34 types running in push-pull. Most 6L6/KT types typically produce 25 to 50wpc depending on configuration.

There you have it. Linear refers to several valve characteristics, and take with a large pinch of salt views expressed by anyone who poo-poos valve amps based on distortion values alone, as that is usually taken out of context and doesn't tell the whole picture.
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[quote name='Pac67']Not all valve amps produce significant distortion when operated within their optimum ranges and to all practical purposes, distortion figures are more than perfectly acceptable from a decent valve amp. It bugs me no end when anti-valve enthusiasts gleefully point out spec sheet numbers and fail to recognise the other benefits of valves, [B]namely superior soundstaging and superior tonal timbral qualities over equivalent SS amps.[/B] The advertising of valve amps as "linear" or "push-pull" refers simply as to whether feedback is used. When in ultralinear mode, such as SET, no feedback is used and a single valve drives a single channel. In push pull mode, power rating can be increased and twin output driver valves are used employing feedback to control distortion, with each valve operating a phase of the signal. Push-pull are more efficient and more powerful with lower distortion.

Also, there are linear type valves (to complicate matters more) in which the measured output V's distortion graphs are "linear" instead of having the characteristic curve or kink of simple triod operation. Beam pentodes have this characteristic (eg 6L6 types) as do KT type valves (eg KT66, KT77 and KT88). The KT stands for Kinkless Tetrode. These are more commonly associated with higher output amps than the more commonly available EL34 types running in push-pull. Most 6L6/KT types typically produce 25 to 50wpc depending on configuration.

There you have it. Linear refers to several valve characteristics, and take with a large pinch of salt views expressed by anyone who poo-poos valve amps based on distortion values alone, as that is usually taken out of context and doesn't tell the whole picture.[/QUOTE]


Care to supply some specs for these parameters? Or is it that you just like the sound of valves more?

I completely agree that valves can be quite sufficiently linear if the amplifier is well designed, quite sufficiently meaning that it does not have any more audible distortion than an SS amp. It will certainly have more measureable distortion, but audibly, not so.

The term "linear" has a quite specific meaning in terms of transfer function, if manufacturers want to use the term to mean other things, in marketing-speak rather than engineering-speak, that's up to them. It only serves to confuse rather than enlighten.

S.
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[quote name='Pac67']Not all valve amps produce significant distortion when operated within their optimum ranges and to all practical purposes, distortion figures are more than perfectly acceptable from a decent valve amp. It bugs me no end when anti-valve enthusiasts gleefully point out spec sheet numbers and fail to recognise the other benefits of valves, namely superior soundstaging and superior tonal timbral qualities over equivalent SS amps. The advertising of valve amps as "linear" or "push-pull" refers simply as to whether feedback is used. When in ultralinear mode, such as SET, no feedback is used and a single valve drives a single channel. In push pull mode, power rating can be increased and twin output driver valves are used employing feedback to control distortion, with each valve operating a phase of the signal. Push-pull are more efficient and more powerful with lower distortion.

Also, there are linear type valves (to complicate matters more) in which the measured output V's distortion graphs are "linear" instead of having the characteristic curve or kink of simple triod operation. Beam pentodes have this characteristic (eg 6L6 types) as do KT type valves (eg KT66, KT77 and KT88). The KT stands for Kinkless Tetrode. These are more commonly associated with higher output amps than the more commonly available EL34 types running in push-pull. Most 6L6/KT types typically produce 25 to 50wpc depending on configuration.

There you have it. Linear refers to several valve characteristics, and take with a large pinch of salt views expressed by anyone who poo-poos valve amps based on distortion values alone, as that is usually taken out of context and doesn't tell the whole picture.[/QUOTE]

I have had 2 valve "phases" in my last 40 years and believe that good sound is available from both solid state and valves. The thing which stopped me with valves was variability rather than hating them - I still have a one but it is not connected at the moment.
IMO when listening to a valve amp the overiding influence on the sound is the output transformer...

Also I though ultralinear was a proprietary description of one manufacturer's amp years ago and I am pretty sure it was a push-pull unit.

And linear has always meant linear relationship between input and output, I have -never- heard anybody use the word in relation to distortion. I do believe that most triodes have a more linear characteristic than transistors, in a complete circuit this may not be of benefit, though I have met people who believe it to be so :-)

BTW my current system has the best stereo and instrument timbre I have heard and is all solid state.
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[quote name='SergeAuckland']
The term "linear" has a quite specific meaning in terms of transfer function, if manufacturers want to use the term to mean other things, in marketing-speak rather than engineering-speak, that's up to them. It only serves to confuse rather than enlighten.

S.[/QUOTE]

Quite so!
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[QUOTE]IMO when listening to a valve amp the overiding influence on the sound is the output transformer...[/QUOTE]
Absolutely.

Most of the so called sound quality of valve amps has more to do with the quality of the tranny than anything else, particularly bandwidth.

"Ultralinear" as a term, not necessarily technically correct, is often used these days to describe single ended use which was my point. Push-pull, as I have already pointed out, is quite linear in response.
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[quote name='Pac67']Absolutely.

Most of the so called sound quality of valve amps has more to do with the quality of the tranny than anything else, particularly bandwidth.

"Ultralinear" as a term, not necessarily technically correct, is often used these days to describe single ended use which was my point. Push-pull, as I have already pointed out, is quite linear in response.[/QUOTE]

Ultralinear is an interesting term. My understanding is that it was first applied to push-pull pentode amplifiers, in which some proportion (generally between 20% and 45%) of the output transformer's primary is common to both anode and screen grid. This provides similar linearity as a triode, but with the additional power capability of the pentode. Hence, ultralinear. At the time it was done, single-ended amplifiers had been long considered obsolete, used only in low-fi applications like Dansette record players and some TV audio outputs. There was perhaps one exception, the Pye Mozart integrated amplifier which was single ended, and, I think, ultralinear.

Fast forward some 50 years and the resurgence of Single Ended amplifiers, and some of these are indeed using ultralinear outputs in which some of the transformer's primary is common to anode and grid.

I don't think the term Ultralinear was ever a trade name, but did refer to the specific way the output valve and transformer were connected.

S.
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[quote name='f1eng']I have had 2 valve "phases" in my last 40 years and believe that good sound is available from both solid state and valves. The thing which stopped me with valves was variability rather than hating them - I still have a one but it is not connected at the moment.
IMO when listening to a valve amp the overiding influence on the sound is the output transformer...

Also I though ultralinear was a proprietary description of one manufacturer's amp years ago and I am pretty sure it was a push-pull unit.

And linear has always meant linear relationship between input and output, I have -never- heard anybody use the word in relation to distortion. I do believe that most triodes have a more linear characteristic than transistors, in a complete circuit this may not be of benefit, though I have met people who believe it to be so :-)

BTW my current system has the best stereo and instrument timbre I have heard and is all solid state.[/QUOTE]

I too had my valve phases: Initially in the late 60s, I had a spectacularly unreliable Sinclair Z12, and replaced it with first one, then a pair of Mullard 5-10s. I built several pairs of these for friends, and used it through to my third year at University. At that point, complementary symmetry transistors became available, (2N2955 & 2N3055) and I went back to SS. Then in the late '70s, during a very boring four weeks in Lusaka, I designed a 100w valve amp from first principles, and built it on my return home. I used this up until the late 80s when I went over to active 'speakers. I still have a Leak TL10 and Point One for playing 78s and the odd vintage Jazz CD for the experience.

I too found the variability of valves too inconvenient, and they're rather too tweaky for everyday use but I still find them rather fun.

S.
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