Decided to spark some controversy today..... The question of 'hearing the difference in tube rectifiers' is one that I often shunned away from, however I adamantly affirmed that I could 'hear' the difference in moving from a Tube Rectifier to a Solid State rectifier. And, now that I'm just a bit older and wiser...... I have a pretty good feeling of knowing 'why' I could hear that difference. And, while I have not yet really graduated to hearing the difference in Tube Rectifiers...... I have it on pretty good authority from trusted friends and fellow 'audio buffs' that THEY claim to hear the difference....and I no longer question them. However, the 'what' they are hearing is, I believe' the real issue.....and perhaps even further, is what they are hearing actually an 'improvement' or a 'detriment' to the function of the audio device.
When one considers the world of 'tube rectifiers'...... there is really quite a deviance in their performance level.....even when operating at the same basic 'filament' voltage. Considering 'just' the family of 5 volt rectifiers out there, the 'range' of both 'current' capability AND 'voltage drop' is really quite dramatic. And, when applying this to 'some' amplifiers, clearly those changes can make a difference in how they act, or 'sound'; particularly if all you do is pull a rectifier from it's socket and substitute another one. I would take the example of moving from a 5U4 to a 5AR4....with the voltage drop difference being perhaps the biggest difference in that family of 5 volt rectifiers. Removing the 5U4 and installing a 5AR4 can significantly increase B+...which can clearly affect sound! BUT..... is it 'good' for the amp? In many cases, that increase in B+ can push the amp beyond it's original design intentions, and even take the voltage levels beyond the tolerance limits of some of the components there in; specifically power supply filters, but not limited to that. Tube plate voltage levels can also fall into this category, as can other parts.
So....is swapping rectifiers necessarily a 'good' thing? Maybe? But, the REAL test is, to me, a question of answering two questions with 'yes'. The first question is: Can the amp 'take it'? In other words, will the increase in B+ cause damage or failure....... and the second question is: Does the change cause the amp to generate a cleaner signal with increased output? This second question is really the heart of the issue to me....assuming the amp can 'take' the VR increase in B+ without blowing a filter cap or eating tubes. In reality, I believe these original designers were NOT all that dumb! So, changing a rectifier tube is NOT necessarily going to benefit the amp in any discernible way. But, not all tubes were 'available' during the production of some of these amps, so the popular 5U4 may have been used just because there were gajillions of them back when the amps were designed and built. However, just maybe, the installation of a 5AR4 WILL make the amp work better.
To answer this question, I believe you really need some sophisticated test equipment. Putting your tone controls at 'flat' and your volume control at 1/2 and then changing rectifiers is NOT the way to test this, but sadly, I believe it's what a lot of people who have reported being able to 'hear' the difference have done. When you take this kind approach, then 'yes' you'll probably hear a difference. BUT, you'll NOT know what the changes are in B+, AND, you'll not know if you're putting your amp 'at risk' of failure from being operated at too high a voltage level. So, then how do you really know? Well, as I see it, you have to see where the amp is performing with one rectifier, KNOW for a fact that the change in rectifier will NOT damage the amp, then you have to see how the amp performs with the second rectifier....and all of this has to be done while measuring power output, distortion levels, AND watching for visible distortions on a scope while looking at the wave pattern.
Let me wrap up my comments here by saying that I understand there is a LOT to this subject. I guess I'm just trying to address the issue of popping in rectifier tubes and listening for changes...while NOT knowing if the amp might be damaged down the road. So, to all those who read this...'thanks'! To those who comment..... I'm looking forward to it! WC
When one considers the world of 'tube rectifiers'...... there is really quite a deviance in their performance level.....even when operating at the same basic 'filament' voltage. Considering 'just' the family of 5 volt rectifiers out there, the 'range' of both 'current' capability AND 'voltage drop' is really quite dramatic. And, when applying this to 'some' amplifiers, clearly those changes can make a difference in how they act, or 'sound'; particularly if all you do is pull a rectifier from it's socket and substitute another one. I would take the example of moving from a 5U4 to a 5AR4....with the voltage drop difference being perhaps the biggest difference in that family of 5 volt rectifiers. Removing the 5U4 and installing a 5AR4 can significantly increase B+...which can clearly affect sound! BUT..... is it 'good' for the amp? In many cases, that increase in B+ can push the amp beyond it's original design intentions, and even take the voltage levels beyond the tolerance limits of some of the components there in; specifically power supply filters, but not limited to that. Tube plate voltage levels can also fall into this category, as can other parts.
So....is swapping rectifiers necessarily a 'good' thing? Maybe? But, the REAL test is, to me, a question of answering two questions with 'yes'. The first question is: Can the amp 'take it'? In other words, will the increase in B+ cause damage or failure....... and the second question is: Does the change cause the amp to generate a cleaner signal with increased output? This second question is really the heart of the issue to me....assuming the amp can 'take' the VR increase in B+ without blowing a filter cap or eating tubes. In reality, I believe these original designers were NOT all that dumb! So, changing a rectifier tube is NOT necessarily going to benefit the amp in any discernible way. But, not all tubes were 'available' during the production of some of these amps, so the popular 5U4 may have been used just because there were gajillions of them back when the amps were designed and built. However, just maybe, the installation of a 5AR4 WILL make the amp work better.
To answer this question, I believe you really need some sophisticated test equipment. Putting your tone controls at 'flat' and your volume control at 1/2 and then changing rectifiers is NOT the way to test this, but sadly, I believe it's what a lot of people who have reported being able to 'hear' the difference have done. When you take this kind approach, then 'yes' you'll probably hear a difference. BUT, you'll NOT know what the changes are in B+, AND, you'll not know if you're putting your amp 'at risk' of failure from being operated at too high a voltage level. So, then how do you really know? Well, as I see it, you have to see where the amp is performing with one rectifier, KNOW for a fact that the change in rectifier will NOT damage the amp, then you have to see how the amp performs with the second rectifier....and all of this has to be done while measuring power output, distortion levels, AND watching for visible distortions on a scope while looking at the wave pattern.
Let me wrap up my comments here by saying that I understand there is a LOT to this subject. I guess I'm just trying to address the issue of popping in rectifier tubes and listening for changes...while NOT knowing if the amp might be damaged down the road. So, to all those who read this...'thanks'! To those who comment..... I'm looking forward to it! WC
