[drphoto]

I know the Mapletree thread has been inactive, but I pulled my old 4SE Ultra out of the closet. I looked at the old thread and based on that I upgraded the stock Sylvania preamp tubes to RCA NOS. Plus the biggie.....a NOS Mullard EZ35 rectifier. OMG. This little inexpensive preamp now sounds amazing. Big and open sound. Great detail. Tight and controlled. Huge improvement over the stock GE tube.

How the hell is this possible?? the rectifier just converts AC to DC.  I might be losing my mind. 

Even if placebo effect, combined w/ the wonderful Audiolab transport I just got, I'm finally listening to music instead of nitpicking my rig.

I've saving my pennies for a Denefrips DAC down the road. Now using my Stan Warren modded 1st gen DacMagic.

[S Clark]

Interesting.  I've never had any gear with that rectifier.  I run the big bottle Sylvania 5AR4 and like them over the Mullards.  I also find that what works in one doesn't necessarily mean it well transfer over to another amp/preamp. 

[JackD]

In the couple of pieces of gear I've owned that used the 6X5GT (GZ35) tube I've found that the NOS Blackburn Mullards were the best of the bunch followed by the NOS Tung Sol's.  In the not so distant past you could pick up most of the brands of NOS 6X5's for under $20 so not too expensive to test which one worked best in a particular piece. No the case anymore. 

[drphoto]

But tube brand aside, I'm can not figure out why changing the rectifier would be audible. I know some rock guitarist like tube rectified preamp sections because it can add what is called 'sag' which I take adds a bit of compression to get those nice creamy lead tones.

But why would it matter in a hi-fi rig? I'm going to take a guess and say the Mullard has a faster 'recovery' than the GE, so the exact opposite of the sag effect......it's letting more of the detail come through. Seems plausible , but I don't much about.....well anything to tell the truth.

So if that theory is correct......why a tube rectified version at all.....that was more expensive than the SS version? There has to be a sonic reason. 

($42 for the tube shipped NOS in original box)

[JackD]

Never really delved into the why just know that it makes a difference. The most likely cause just like in signal tubes is the differences in manufacturing processes and materials used. Once I heard how bad the new production stuff sounded I always picked up NOS spares when the prices were still reasonable.

[Early B.]

But why would it matter in a hi-fi rig? I'm going to take a guess and say the Mullard has a faster 'recovery' than the GE, so the exact opposite of the sag effect......it's letting more of the detail come through. Seems plausible , but I don't much about.....well anything to tell the truth.

Don't look for a logical reason. Tube amp designers can't explain it, either. Everyone simply accepts the fact that tubes often sound different.

[JakeJ]

But tube brand aside, I'm can not figure out why changing the rectifier would be audible. I know some rock guitarist like tube rectified preamp sections because it can add what is called 'sag' which I take adds a bit of compression to get those nice creamy lead tones.

But why would it matter in a hi-fi rig? I'm going to take a guess and say the Mullard has a faster 'recovery' than the GE, so the exact opposite of the sag effect......it's letting more of the detail come through. Seems plausible , but I don't much about.....well anything to tell the truth.

So if that theory is correct......why a tube rectified version at all.....that was more expensive than the SS version? There has to be a sonic reason. 

($42 for the tube shipped NOS in original box)

Welcome to the world, no galaxy, wait, it's actually the Universe of tube rolling.

It may well be the Mullard recovers faster.  That may simply be a function of the tube's ability to handle voltage and current swings better than the previous one in that circuit.  It is interesting, eh?

[FullRangeMan]

How the hell is this possible?? the rectifier just converts AC to DC.  I might be losing my mind. 
Tube engineers know well why rec tubes sound different and what tube are more suited to an audio equip, otherwise they would not be engineers.

The EZ35 is a small rec with low output tension 325V and even lower current 70mA, so its suited to a small pre-amp or DAC not a powerful power amp, big rec as Russian 5C8S(used in the Lampizator GM70) and 6D22 delivery hi V as 1700V to supply military equip.
5C8S
Peak anode current 1.2 A
Anode current powering on 5 A
Anode Peak negative anode voltage 1700V
Power dissipated by the anode Anode power dissipation 30 W
Rectified current 420 mA

6D22 half wave
Maximum ratings anode voltage 6000 V
Peak anode current 1 A
Anode current, continuous 300 mA
Anode dissipation 11 W
Envelope temperature 200 Cº
6D22S is a glass-envelope power diode for use as a half-wave
B+ rectifier in high-quality audio amplifiers. Originally intended for colorTV damper-diode service, the 6D22S is similar to the 6DL3 except for base connections and some ratings. The 6D22S features very slow warmup (30 seconds typical), making it an excellent, rugged power-on delay device for audio amplifiers.
Its warm-up time is longer than that of common rectifier tubes (such as the 5AR4, GZ34) and it is lower in cost than electronic delay relays.
Its heater may be operated from the same supply as other tubes in amplifier, up to Vb=600 volts. Its high pulse current capability gives sound quality which is superior to commonly-used rectifier tubes.
Other factors that influence the sound are the shape of the internal elements and the treatments of the metals that was done at that time, these treatments was banned today by the eco agenda because the products are toxic but there are many others Iam unaware as Iam not tube engineer.

[charmerci]

But tube brand aside, I'm can not figure out why changing the rectifier would be audible.

And you're sure that the old tube wasn't going bad and functioning properly?

[Jaytor]

I think there are two ways that the rectifier tube can change the sound. Tube rectifiers have a considerable voltage drop compared to silicon diodes, and this voltage drop can vary considerably from one tube to the next. This difference subtly changes the operating points of the tubes in the audio circuit (assuming no active voltage regulation). In addition, the voltage drop changes with load, so some tubes will have more or less sag as the audio signal changes.

EDIT: After thinking about it, there are a couple of other factors that vary from tube to tube. The reverse leakage current (the current that flows when the cathode voltage is higher than the anode) will vary subtly; and the speed at which the tube turns on and off as the AC voltage swings will also vary. These additional factors will also be affected somewhat by the current draw.

[doggie]

I think there are two ways that the rectifier tube can change the sound. Tube rectifiers have a considerable voltage drop compared to silicon diodes, and this voltage drop can vary considerably from one tube to the next. This difference subtly changes the operating points of the tubes in the audio circuit (assuming no active voltage regulation). In addition, the voltage drop changes with load, so some tubes will have more or less sag as the audio signal changes.

This is my understanding also.

For those who want to really go down the rectifier rabbit hole go to Head-Fi and allow a week or so to read all of the posts in the years long rectifier thread there: "Dubstep Girl's Massive 5AR4/5R4/5U4G Rectifier Review/Comparison!"

[FullRangeMan]

I have learned much with Dubstep Girl, recommended.