Tube Rectifiers do sound different

[Original Burnedfingers]

Up until just recently if anyone had told me that rectifiers sound differently I would have responded with something to the effect that they were crazy. But, I swear they do have different sonic qualities and no I haven't been drinking. I first thought I heard a difference when I experimented with different rectifiers in my 6SN7/6SN7 Aikido P-to-P line stage. I started off with a home made SS plug in rectifier and then progressed to a 5Y3. I thought the
SS sounded a little punchy. I then tried a 5AR4 a JJ that I had handy and then a Japaneese Mullard 5AR4. The Mullard sounded better. Then I tried a Chinese 5Z4P and it sounded really smooth. Then I tried a #80 in a octal to 4 pin adapter and it sounded the best of all.

I ordered (2) #83's to try.

So, the question is am I right? Do rectifiers really sound different. Even the wife admitted she heard some difference after telling me just play the damn thing.

I also tried different rectifiers in my Stereo 70. The Japaneese Mullard first followed by the JJ followed by the SS plug in followed by a 5U4. To my ears the Mullard sounded really good followed by the 5U4. The 5U4 has a really nice smooth midrange and this is after setting the bias to the correct setting because it was lower with the 5U4 than the 5AR4.

Am I totally nuts?

[SY]

Maybe. But maybe not.

First thing I would check is the actual delivered voltages. Second thing would be what the ripple waveforms look like. Third, I'd check the amplifier output for noise differences. If all of those look about the same, I'd consider doing a more controlled listening test- susceptibility to unconscious preconception is an attribute of normal human brains. So if there isn't anything there, you're not nuts (or you might be, but this has nothing to do with it), but if there is, you've got some interesting experiments to do.

[Evenharmonics]

Also, slight change in ear location can cause audible difference even when all the gears remain the same. It's referred to as "room mode". Microphone mounted on a stand would alleviate this issue.

[Original Burnedfingers]

I had already looked at B+ differences and written them down.

Location for listening is exactly the same. One easy chair positioned 10 ft away from the speaker arrays.

Even had others switch the rectifiers with me not knowing which was which and they recorded the results.

SS rectifiers highest B+ highest ripple.

5AR4's within 5 volts of each other ripple roughly the same.

5U4 lowest B+ ripple slightly lower.

#80 B+ same as 5Y3 ripple same.

Don't know if pink noise as source and calibrated microphone with output to plotter would show any differences.

[SY]

You don't need to get that fancy. Measurement of voltage waveforms at the speaker terminals is enough. That's what the amplifier delivers.

[jrenkin]

So each rectifier produced different B+ and ripple, so of course they would make the amp sound different. Control for these things so that all rectifiers produce the same and then test. Somewhat difficult as it would require each rectifier be in a different circuit, which may then sound different.
Probable virtually possible to make a controlled experiment, so we will always be uncertain o the differences.
Or said more simply: they sound different cuz they are different.

[DF96]

In the case of a PSU containing chokes, the different rectifier resistances will offer different amounts of damping of subsonic resonances.

My guess is that the main effect will be changes in harmonic structure of the ripple. How much effect this has will depend on PSRR of the amplifier, and its supply IMD performance.

[Lazybutt]

Originally Posted by jrenkin

Control for these things so that all rectifiers produce the same and then test.

Well then you're not comparing those rectifiers anymore..... you're comparing different circuits altogether

Originally Posted by jrenkin

So each rectifier produced different B+ and ripple, so of course they would make the amp sound different.

YES, as you say, I guess the outcome is they ARE different, but simply because of voltage drop and internal resistance, which makes the supply different (and is no surprise by the way!).... but it's not because of magical properties of such or such tube or rectifier... with good engineering most types or rectifiers should be able to produce an acceptable output!

[Original Burnedfingers]

I have mentioned two individual tests. Power supply in the line stage contains no chokes.

The stereo 70 has a choke in the power supply.

The power supply on the Aikido is extremely clean. The Dynaco is cleaner than stock form will measure if desired.

Haven't put my head in a vice to prevent movement yet but have used the same distance from the equipment and same relaxed seating.

As mentioned possibility of different internal resistances internal to the rectifier tubes. Power supply difference due to resistance changes between tubes resulting in a 5 volt or so difference between the same model number of tube. Don't know if 5 volt B+ difference is enough to hear.

Could there be any capacitence difference between the tubes that might result in a apparent sonic difference?

[analog_sa]

Originally Posted by Original Burnedfingers

Am I totally nuts?

This is such an old hat that i find it incredible it's even worth discussing. Of course rectifiers sound different. Even if followed with the fanciest shunt reg, they still sound distinctly different. Anyone with ears knows this. And no, it cannot be explained with Ohm's law or gross simplifications.