New rectifier tubes

These rectifiers dwarf my previous 5AR4's! No comparing!

Pretty much bulletproof under normal use too ... I've got a couple years on this one, and a spare just in case.



Stands tall amongst the other big bottles.

Mmmmm. The GZ 37 is a sexy seductress among rectifiers.

To me, it resembles nothing so much as a falcon at rest. Sleek, and ready to dive at near-supersonic speed into my tunage. Which it does nicely.

But Real Men need GZ-33s. Tall as that DC-6B's tail. Now we're talkin'.

You guys are tempting me to take the GZ-33s out of the storage (aka drawer).

Pedro, be happy to take them off your hands if they're a burden to you . . .

I originally wanted GZ33's, but wasn't able to find any.

LeGrace wrote:I originally wanted GZ33's, but wasn't able to find any.

They're around. I know a guy in Ankara, Turkey who's got a few.

deepee99 wrote:Pedro, be happy to take them off your hands if they're a burden to you . . .

You kind of scared me there for a second so I ran to my storage and they are still there...

pedrocols wrote:

deepee99 wrote:Pedro, be happy to take them off your hands if they're a burden to you . . .

You kind of scared me there for a second so I ran to my storage and they are still there...

Quit showing off, Pedrocols or I'll find out where you live and where you've stashed those tubes.

deepee99 wrote:

LeGrace wrote:I originally wanted GZ33's, but wasn't able to find any.

They're around. I know a guy in Ankara, Turkey who's got a few.

I tried out your guy. My wife deleted the email confirmation because she thought it was Russian spam mail. But turns out they are totally legit. Surprising bit I received the tubes in just 6 days. From Turkey! That's faster then service I commonly get from Amazon!!

The Mullard GZ-33 is available from Upscale Audio:

Mullard GZ-33

I got one a couple of weeks ago; sounds good in my Latino VTA-70.

But to do it justice, you need to feature it center-stage, like sKiZo in his custom VTA-120, where it stands proud and erect.

Oh Gregg, go to your room and stay there until your father gets home!

Gregg R. wrote:The Mullard GZ-33 is available from Upscale Audio:

Mullard GZ-33

I got one a couple of weeks ago; sounds good in my Latino VTA-70.

But to do it justice, you need to feature it center-stage, like sKiZo in his custom VTA-120, where it stands proud and erect.

We VTA owners all stand proud and erect, no matter where the rectifier is positioned . . .

Seriously, I've got a logic question on SS vs. tube rectifiers.
I've long preferred the sound of tube rectifiers. I'm beginning to understand that it likely has to do with the voltage drop which all tubes provide, more or less, compared to the SS, which provides little or none.
How does this impact the ability of the amp to handle peaks - i.e. headroom? It seems to me that a tube rectifier might change the way the output stage reacts to huge peaks in a way that is more forgiving, yet at the same time more realistic. Anyone?

The GZ-33 in my VTA-70 replaced a JJ 5AR4. I didn't need to adjust the bias at all, so I presume the voltage drop was about the same. Yet, the two tube rectifiers did sound different: the Mullard was richer sounding, the JJ thinner, but a little more detailed. I think there is more involved than simply a voltage drop.

In the overall scheme of the amplifier, the differences are small. But we are audiophiles, so any change assumes epic proportions.

I ordered some UF5408 diodes for the yellow sheet modification. When installed, does the amplifier retain the sonic signature of a tube rectifier, or does it now sound like solid-state rectification?

I chose the fancy Vishay branded diodes, but looking at the invoice I noticed that the country of origin is China; kind of a bummer: I was hoping for some sultry French-speaking diodes: Ooh-la-la!!

I gotta a pair!

Blue: I ass-u-me you meant "I gotta GET a pair"? Or maybe, "I gotta pair"??? {I hope you mean GZ-33s and not..... }

Gregg, you hit a nerve with your statement about "small changes". and I totally agree, though some cynics would attribute the perception of change to wishful thinking. There's perhaps no logical, or empirical, reason for such discrepancies, yet that certainly seem very real. As I'm {too} fond of saying, there are things that can be measured but not heard and there are things that can be heard yet not measured.
That said, I believe the import of the yellow-sheet diode mod is that you retain the SQ of the tube, while protecting same by "pre-rectification" with diodes. Thus spake tubes4hifi.

Hi Kent,

There is some wishful thinking on my part. I paid $18 delivered for the JJ 5AR4, and about $108 for the GZ-33; if the Mullard does not sound better, I'd be kicking myself. To double-check, I put the JJ back in last night; that confirmed my initial reactions: the Mullard is richer, the JJ thinner; I prefer the Mullard. The JJ looks plain and ordinary, the GZ-33 is tall and shapely. You have a hi-fi system and listen to music because it makes you feel good. It's difficult to measure that! Music can be reduced to mathematics, but it's the overall "gestalt" that you're after. Vacuum tubes help.

I'm glad that the "yellow sheet" modification retains the sonic flavor of the vacuum tube rectifier; I probably will be installing the diodes within the next week. I'll use the JJ 5AR4 first to test the new circuit, then if all is well, install the Mullard.

Thanks for your help.

Kentley wrote:Blue: I ass-u-me you meant "I gotta GET a pair"? Or maybe, "I gotta pair"??? {I hope you mean GZ-33s and not..... }

Gregg, you hit a nerve with your statement about "small changes". and I totally agree, though some cynics would attribute the perception of change to wishful thinking. There's perhaps no logical, or empirical, reason for such discrepancies, yet that certainly seem very real. As I'm {too} fond of saying, there are things that can be measured but not heard and there are things that can be heard yet not measured.
That said, I believe the import of the yellow-sheet diode mod is that you retain the SQ of the tube, while protecting same by "pre-rectification" with diodes. Thus spake tubes4hifi.

GZ-33's....if you were as old at Kently and myself I would call you a "DIRTY OLD MAN"

Is it possible a GZ-33 or any rectifier tube cause hum? With all things being equal, that is my construction was the same, solder joints good, four KT-88's in each amp. I still have a hum in both channels. Tried different speaker, eliminated the ground with 3>2 adapter, relocated one amp, shorted out the input. All I can think of is the rectifier tube. Mullard GZ-33, your thoughts. I may order a pair of JJ GZ-34 from Amazon since they have everything and then some.

Steve G wrote:Is it possible a GZ-33 or any rectifier tube cause hum?  With all things being equal, that is my construction was the same, solder joints good, four KT-88's in each amp.  I still have a hum in both channels.  Tried different speaker, eliminated the ground with 3>2 adapter, relocated one amp, shorted out the input.  All I can think of is the rectifier tube.  Mullard GZ-33, your thoughts.  I may order a pair of JJ GZ-34 from Amazon since they have everything and then some.

I'd be checking my inter-connects before blaming a single rectifier for a two-channel hum. If your RCA cords are too close to the AC power lines, you're gonna get hum on both sides. If they *must* be close together, cross them at a 90-degree angle. A parallel run almost guarantees hum.

Kentley wrote:Blue: I ass-u-me you meant "I gotta GET a pair"? Or maybe, "I gotta pair"??? {I hope you mean GZ-33s and not..... }

Gregg, you hit a nerve with your statement about "small changes". and I totally agree, though some cynics would attribute the perception of change to wishful thinking. There's perhaps no logical, or empirical, reason for such discrepancies, yet that certainly seem very real. As I'm {too} fond of saying, there are things that can be measured but not heard and there are things that can be heard yet not measured.
That said, I believe the import of the yellow-sheet diode mod is that you retain the SQ of the tube, while protecting same by "pre-rectification" with diodes. Thus spake tubes4hifi.

"pre-rectification with diodes"...I did the diode mod this week and 30 minutes ago just popped out the Webers and replaced with U77s. To my ears it sounds about the same so far...just a little jazz in ultra-linear mode. Does the diode mod actually allow the U77 put out more current than the stated current spec for this rectifier toob?

deepee99 wrote:

Steve G wrote:Is it possible a GZ-33 or any rectifier tube cause hum?  With all things being equal, that is my construction was the same, solder joints good, four KT-88's in each amp.  I still have a hum in both channels.  Tried different speaker, eliminated the ground with 3>2 adapter, relocated one amp, shorted out the input.  All I can think of is the rectifier tube.  Mullard GZ-33, your thoughts.  I may order a pair of JJ GZ-34 from Amazon since they have everything and then some.

I'd be checking my inter-connects before blaming a single rectifier for a two-channel hum. If your RCA cords are too close to the AC power lines, you're gonna get hum on both sides. If they *must* be close together, cross them at a 90-degree angle. A parallel run almost guarantees hum.

I completely re-located one amp with no input and the other amp was off, the input was shorted and no inter-connect cables were in the mix. Also used a different speaker. The only thing I did isolate causing a "buzz" not a "hum" was my cordless phone and when I unplugged it the buzz went away, so that's not it.