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Do different tubes measure different ?
- Thread starter Mackie
- Start date
We have several member that are tube aficionados and there are several threads discussing this topic already.
Suggest you try a title only search on tubes
Suggest you try a title only search on tubes
solderdude
Grand Contributor
Yes tubes measure different just like all transistors, FETs etc.
In a circuit there is usually feedback be it local, overall or both which in essence make the differences between the amplifying components much smaller.
The less open-loop gain and the less amplification you usually get to hear more of the the amplification component's 'properties'.
Usually tubes have a low amplification and especially tube amps with output transformers need a lot of gain.
In this case (transformer output tube amps with just 2 or 3 tubes) usually have little overall feedback and thus there is more 'tube-ness' (combined with the transformer losses).
So with tubes in all tube amps chances are swapping tubes can actually change the overall performance.
Should you build a tube pre-amp with a few times gain (and a few tubes) you basically get none of the 'tube character' and tube swapping is pointless (other than for noise and microphony).
In a circuit there is usually feedback be it local, overall or both which in essence make the differences between the amplifying components much smaller.
The less open-loop gain and the less amplification you usually get to hear more of the the amplification component's 'properties'.
Usually tubes have a low amplification and especially tube amps with output transformers need a lot of gain.
In this case (transformer output tube amps with just 2 or 3 tubes) usually have little overall feedback and thus there is more 'tube-ness' (combined with the transformer losses).
So with tubes in all tube amps chances are swapping tubes can actually change the overall performance.
Should you build a tube pre-amp with a few times gain (and a few tubes) you basically get none of the 'tube character' and tube swapping is pointless (other than for noise and microphony).
- Thread Starter
- #4
Thanks for taking the time to explain.
Regarding a tube integrated amp, do you think the bigger difference in sound comes from the rolling the pre or power section ?
DVDdoug
Master Contributor
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Regarding a tube integrated amp, do you think the bigger difference in sound comes from the rolling the pre or power section ?
It depends on the design.
A good tube amp will simply amplify with no sound of it's own, just like any good solid state amp (or almost ANY solid state amp). With a good design, tube rolling won't make any difference as long as the tube is correct and in-spec. An "unstable" design will change with normal tube variations or when you swap tubes or as the tubes age
solderdude mentioned transformers. Tube power amps and the power-amp section of an integrated amp requires a transformer to drive the speaker. That's another potential source of sound degradation and good ones are expensive. Because of the output transformer, it's easier (and less expensive) to make a good tube preamp than a good tube power amp. Of course you can't easily swap transformers.
If a tube amp does have audible distortion or frequency response variations, etc., it's going to sound different from any other amp. There is no one "tube sound".
solderdude also pointed-out that transistors and MOSFETs vary. But just like a GOOD tube design, the performance of the completed amplifier doesn't vary significantly, and will stay in-spec as long as the transistors/MOSFETs are in-spec. The difference is, transistors/MOSFETs don't age and "wear out" like tubes, and of course they are not easy to swap. Op-amps are sometimes in sockets so some people like to swap those, but it usually only makes imagined differences.
P.S.
This is 2025, not 1955, and there is no advantage to this outdated technology.
It depends on the design.
A good tube amp will simply amplify with no sound of it's own, just like any good solid state amp (or almost ANY solid state amp). With a good design, tube rolling won't make any difference as long as the tube is correct and in-spec. An "unstable" design will change with normal tube variations or when you swap tubes or as the tubes age
solderdude mentioned transformers. Tube power amps and the power-amp section of an integrated amp requires a transformer to drive the speaker. That's another potential source of sound degradation and good ones are expensive. Because of the output transformer, it's easier (and less expensive) to make a good tube preamp than a good tube power amp. Of course you can't easily swap transformers.
If a tube amp does have audible distortion or frequency response variations, etc., it's going to sound different from any other amp. There is no one "tube sound".
solderdude also pointed-out that transistors and MOSFETs vary. But just like a GOOD tube design, the performance of the completed amplifier doesn't vary significantly, and will stay in-spec as long as the transistors/MOSFETs are in-spec. The difference is, transistors/MOSFETs don't age and "wear out" like tubes, and of course they are not easy to swap. Op-amps are sometimes in sockets so some people like to swap those, but it usually only makes imagined differences.
P.S.
This is 2025, not 1955, and there is no advantage to this outdated technology.
- Thread Starter
- #7
Many thanks for that.Regarding a tube integrated amp, do you think the bigger difference in sound comes from the rolling the pre or power section ?
It depends on the design.
A good tube amp will simply amplify with no sound of it's own, just like any good solid state amp (or almost ANY solid state amp). With a good design, tube rolling won't make any difference as long as the tube is correct and in-spec. An "unstable" design will change with normal tube variations or when you swap tubes or as the tubes age
solderdude mentioned transformers. Tube power amps and the power-amp section of an integrated amp requires a transformer to drive the speaker. That's another potential source of sound degradation and good ones are expensive. Because of the output transformer, it's easier (and less expensive) to make a good tube preamp than a good tube power amp. Of course you can't easily swap transformers.
If a tube amp does have audible distortion or frequency response variations, etc., it's going to sound different from any other amp. There is no one "tube sound".
solderdude also pointed-out that transistors and MOSFETs vary. But just like a GOOD tube design, the performance of the completed amplifier doesn't vary significantly, and will stay in-spec as long as the transistors/MOSFETs are in-spec. The difference is, transistors/MOSFETs don't age and "wear out" like tubes, and of course they are not easy to swap. Op-amps are sometimes in sockets so some people like to swap those, but it usually only makes imagined differences.
P.S.
This is 2025, not 1955, and there is no advantage to this outdated technology.
All I can say is I subjectively compared the R8 to a modern class D amp I own and much preferred the R8, just more realistic to my ears. I know it produces distortion etc but when it sounds so good I really don't care when listening.
Some preamp stages are low feedback and many output stages are. In this case you can clearly hear differences between tubes but that includes their defects. For example some preamp tubes are extremely noisy which presents as hiss that may also contain some buzz.
Output tubes that are correctly biased and have proper hum compensation may also produce some noise and even hum. Worn out output tubes sound the most tubey with mushy bass and a lack of extension at the top end.
A properly designed, modern tube amp would/should incorporate gobs of feedback which would minimize differences you can hear or even measure. But if course then it would probably sound indistinguishable from a solid state amp...
Output tubes that are correctly biased and have proper hum compensation may also produce some noise and even hum. Worn out output tubes sound the most tubey with mushy bass and a lack of extension at the top end.
A properly designed, modern tube amp would/should incorporate gobs of feedback which would minimize differences you can hear or even measure. But if course then it would probably sound indistinguishable from a solid state amp...
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