I roll this rectifier in the power supply of my phono stage. I had used a Mullard fat base; it sounded good. The GEC u52, which is not an exact equivalent, sounds better, but I have put a fair amount of mileage on the one I bought, which was NIB/NOS. I have a metal base GZ34 en route, also NIB/NOS, which is supposed to be the best sounding among the Mullards (though a made in Holland tube by Philips/Miniwatt as I recall). We shall see. I think part of this is down to the circuit and the voicing of the system. There is a Western Electric tube that is highly acclaimed but hard to find even without regard to price. The other tube that has found favor in this circuit is a military WWII era RCA with a double getter- I have one of those coming as well, also NIB/NOS. Interestingly, with this phono stage, rolling the audio tubes isn't really where the action is-- it is the rectifier. PS: do a Google search for Dubstep Girl's Massive 5AR4 Rectifier Shoot-Out. It's pretty comprehensive, has pictures and commentary for each tube.
Rectifiers can vary a bit in the voltages they deliver, which is what primarily effects the output tubes operation and sound signature.
One of my headphone amps, the DNA Starlett, uses a 5AR4 rectifier. I swapped out the stock tube for a NOS Mullard fat base and found a slight improvement. The sound is a little more open and dynamic, with a nice dead quiet background. The improvement was very subtle in this amp, which apparently isn't known for drastic changes due to tube swapping. During my research I did come across several people who spoke highly of the Mullard's durability. One tube dealer I spoke with over the phone said that they are borderline indestructible. I'm not sure if it was worth the cost, but I'm mostly a "set and forget" guy with tube amps and like the idea of throwing a good one in that spot and living with it for the long term.
when I had my Cornet I used a 1954 vintage Bendix rectifier. It was a big improvement over the Sovtek. Weighed more too.
All of the separate component preamps with tube rectifiers that I've ever owned used either ez81/6ca4, ez80, or 12x4 tubes. I always thought of 5ar4/gz34 rectifiers as reserved for integrated amps or power amps. I like the sound of tube rectifiers. But I think it's important for tube rectified units to have a source of clean and steady AC power that doesn't run or spike above 120v- preferably a few volts under, like 115-118v. A well-made variac is a good investment. I like ones with meter displays. Especially if living somewhere with the potential for a lot of line fluctuations, like a big apartment building.
It's been a while since I did any serious tube rolling but I've also found Mullard GZ34's to be top dog.
I got the Valvo GZ34, it’s a 1962 manufacturer I believe from Brussels. Has a F33 L2J2 code. Is that any good? Not had much experience with rolling rectifier tubes.
Yeah, you can get a pair of IN4007 for a small fraction of that, and that offer better performance. -Bill
On two VTA M-125 tube amplifier monoblocks, it's exactly as Bill from Uptown has stated. I have tested with new old stock Mullard GZ33, Primaluna 5AR4 (China), Gold Lion U77 5AR4 (new production), and of course the Weber WZ68 Copper Cap SS Rectifier (took apart and rebuild with faster diodes just for the hell of it...I was board). The Weber was the clear winner in the bass department, with the GZ33 coming in so close at high listening levels that I stopped and ended my test and kept the Mullard simply for the looks. I think I could have pressed on and made the GZ33 clip (with tubes it's like a sinus congestion sound....nasally) but I never listen at that insane level anyway so why blow things up to prove what, what a dummy I am? I already know that!
My LM210IA experiences significant changes in sound quality when I roll its dual rectifiers. The background noise, the authority and drive, tonal saturation, and clarity. It's remarkable just how large a difference they make in an amp. If I swap NOS RCA 5U4Gs for brand new Psvane 5U4Gs, it sounds like a different amplifier, and certainly not a better one.
So far I have tried 3 5AR4 / GZ34 rectifiers in my Cary preamp. 1) The stock Sovtek, lets the system sound excellent, nice clean highs, smooth bass and good dynamics. Unfortunately one blew after only 4 months and took the main fuses with it. 2) Amperex NOS made for Tektronix, overall smooth, clean but a touch rolled off on top. Also exaggerates the bass in a slightly peaky way that can be annoying. 3) Genelex Gold Lion. Slightly bigger and brighter sound than the stock Sovtek. A little less refined. Pulled in favor of a replacement Sovtek. May try again at a later date. Thinking it could sound better after burn in but somewhat doubtful about this happening to a rectifier, the others did not change sound as they accumulated hours. Waiting for a NOS Mullard to arrive any day.
On that amp avanti I don't think I would feel comfortable trying a GZ33 or GZ37 without getting the green light from the manufacturer. I realize you're not asking that here, just putting that out there in case. The Mullard GZ34 is about the best there is in the 5AR4/GZ34 anyway.
This! Though its my amp that's tube rectified, not my preamp, I run it constantly off a variac set to 115v.
I don't think there's anything unique to tube rectifiers with this statement, but rather all tube gear do better when there isn't huge voltage fluctuations since that will cause tube bias to bounce around. I've never heard an argument that it's better to run a tube rectifier around 115-118V vs 120V. I suppose it could sound slightly different if you're approaching it like Eddie Van Halen who achieved his famous "brown sound" by using a variac setting at 90V. Those older vintage Marshall amps were made for export and probably ran more reliably at 110V but there's no analogy that really applies to modern amps. As @avanti1960 asked...."why?"
About the only thing that I like about tube rectifiers (and I am speaking specifically about indirectly heated rectifiers, such as the 5AR4) is the fact, due to the slow warm-up times, you don't get turn-on thumps in tube-preamps when you use these. Other than that, I think that tube rectifiers just tend to produce soggy bass when compared to SS rectifiers. These also keep you from being table to use large capacitive reservoirs in your power supply, which also is detrimental to your fidelity IMO. But if you like this effect, you only need to put a big resistor in series with a SS rectifier in order to duplicate the current-limiting properties of a tube rectifier. In guitar amps where the voltage sag is considered desirable so that you get more distortion, these can actually make sense. But in hi-fi applications, I have never understood the fascination with tube rectifiers. I say this as somebody who has been running tubes in one form or another continuously inside of my system for the past 40 years.
Cathode based rectifiers such as the GZ34 have very little voltage sag with current changes. Filament rectifiers such as a 5Y3GT is a different story.
Voltage spikes can pop capacitors. I've learned that the hard way. A lot of vintage tube gear was designed to run at 115-118v. And it definitely does not like voltage spiking, which can result from appliances like air conditioner or refrigerator motors cycling on and off. That stability also tends to get more complicated in relation to the number of apartment units drawing on the same supply. The modern world has increased electricity demand in a lot of ways, sometimes producing instability that isn't friendly to tubes (or light bulbs.) As alluded to elsewhere, solid state diode rectifiers provide more stable voltage, and protect against spikes. But they tend to be tougher on tube life, because once they're turned on, they immediately supply full voltage to the tube filaments.
My experience is exclusively with the old stuff. This has made me extremely leery of taking things for granted, or carelessness. I'd never leave that gear turned on at operating voltage, when leaving the house even for ten minutes or so. I'd consider it reasonably safe with a variac turned back to a standby voltage of 10-15v,. But even when an amp is left on with the voltage dialed down, my advice is to always site a tube power amp on a fireproof base, and not near any drapes or other fabric. That may be excessively cautious in the case of modern tube gear, but in my opinion, excessive caution is the side to err on. I feel much the same way about solid state gear that gets hot, like class A amps. If it's too hot to touch, make sure to turn it off when you're away from it for more than a few minutes. A fan helps, but only so much. I once had a Yamaha CA-1000 that had a Class A switch- within a minute or so after engaging it, I could not touch the metal vent on top of the cabinet. I literally could have put a little saucepan on it, melted some butter and (eventually) fried an egg. (An experiment I might have tried, if Instagram had been a thing at the time.) So I left it off. At constant current, the amp just did not have the heat sink required to dissipate the heat safely. I think the fire hazard was minimal, compared to tube gear. But I'm sure it would have shortened the life of the components, increasing the likelihood of amp failure.
With all the talk about solid-state, the common diode will produce a lot of noise vs a quiet tube. Noise on the power supply directly affects the sound. If one ventures into solid-state, the 600 or 1200 volt Cis Cree Schottky or Hexfred diodes are quiet with little to no crossover noise. They are like a solid-state tube. $5 vs 50 cents of the standard diode though.
From this perspective and for gear designed to run closer to 110V then I'd agree that you will improve reliability by dialing voltage back closer to design spec.
Interesting, I live in a 40 unit building and according to my Panamax my voltage only ever varies by a few volts either side of about a steady 122.
Building wiring differs in that respect. AC transmission line step-down transformers differ. Power generation sources differ. Neighbors differ in their power use. fwiw, I've lived in two high rise apartments, and both buildings had around 300 units. Also, for vintage tube gear, 122v can be stressful. A few volts over that, even more so. Vintage Voltage Adapter From a UK source- different AC mains voltage there, but still pertinent: Antique Radio Forums • View topic - EZ80 very high voltage.
