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Rectifier Tube Concerns

FlaCharlie said:
Lots of "tube rollers" have drawers full of tubes, typically expensive ones, that they bought after reading something online. They try them and don't get the results they read about so they go into the drawer. The thing to remember is that tubes don't sound like anything on their own. They are only one element in the system.

Unless someone is using them in the same equipment as you are, with the same speakers and sources, and in a room with similar acoustics, then you shouldn't take specific recommendations that are based on "how they sound" very seriously.

This is especially true when the advice comes from a dealer who has a vested interest in selling you the tube. Typically, the best "holy grail" tubes are always the ones that the "boutique" dealer just happens to have in stock.

People hear things differently too, so even if they're both listening to the same system in the same room together they might not agree.

OTOH, comments about technical differences between tube types can be helpful.


I don't know if specs for your power transformer are available. But the stock 5Z4P rectifier has a 2A heater, so that might be a clue as to what its 5v winding is comfortable with.

A 5AR4 will work fine but it's overkill because a preamp doesn't draw nearly as much current as a 5AR4 is capable of supplying. And even new production ones are not that cheap.

A 5Y3GT will be much cheaper and work just as well. If you want slow start the 6087 variant is also cheaper. Plenty of both on eBay. Even used ones are an option if they are American tubes that test strong and the test results are listed.

As for differences in sound, I would guess that different 6SN7s and coupling caps will have a far greater effect than different types of rectifiers. That's a far deeper rabbit hole.

You should also be aware that there are issues with many Chinese power transformers. Most of them seem to have primaries that are designed for 110v input from the wall. But wall voltage in the U.S. is typically between 120v and 125v. This pushes the secondary voltage and the heater voltages higher. So you should measure the heater voltages to make sure that it isn't too high as this can reduce the life of the tubes significantly, depending on just how high it is.
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Great information! I should have specified that I paid an additional few dollar fee on this preamplifier for an adjustment to 117V. Now I am not exactly sure if they swap out the transformers or what they do, because the fee was all of $3USD.
 
SwedishChef said:
Great information! I should have specified that I paid an additional few dollar fee on this preamplifier for an adjustment to 117V. Now I am not exactly sure if they swap out the transformers or what they do, because the fee was all of $3USD.
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That's interesting. I've never heard of sellers offering PT options.

I would still suggest that you measure the heater voltages, though. Most vintage gear had PTs rated at 117v and the heater voltages are typically a bit high. Sometimes not enough to be concerned about but other times some type of adjustment is a good idea.

Some people will rig up a "bucking transformer" or use a variac to reduce the voltage a bit. I usually just add a couple of resistors to the heater windings to drop the heater voltage and leave the rest alone. In most cases it's just the heaters that are a concern because over-voltage shortens the tube life and tubes can be expensive. Voltage variations elsewhere are not usually too critical.
 
FlaCharlie said:
That's interesting. I've never heard of sellers offering PT options.

I would still suggest that you measure the heater voltages, though. Most vintage gear had PTs rated at 117v and the heater voltages are typically a bit high. Sometimes not enough to be concerned about but other times some type of adjustment is a good idea.

Some people will rig up a "bucking transformer" or use a variac to reduce the voltage a bit. I usually just add a couple of resistors to the heater windings to drop the heater voltage and leave the rest alone. In most cases it's just the heaters that are a concern because over-voltage shortens the tube life and tubes can be expensive. Voltage variations elsewhere are not usually too critical.
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I have actually had great luck with some AliExpress doing modifications on items before they send them. Not just op amp upgrades, but I've paid for toroidal upgrades on some solid state Preamplifiers. I've had them upgrade the knobs even to knurled aluminum and so on. Some stores offer changes, some do not. Some have a major language barrier and rely solely on AliExpress translate to understand what you are trying to ask. I've even gone so far as getting entire chassis changed to something different with more room. I'm hooked on Chi-Fi and will likely end up with a MC-7R and even a Wada Shigeru preamplifier before the end of 2023. The Meixing Mingda MC-7R has been getting great reviews in the Chi-Fi groups that I hang out in. Where no mods whatsoever are even really needed, people just seem to love it. My health says I can no longer ride motorcycles and scooters so I am diving head first into the audio hobby that I already love.

I will definitely measure the heater voltages and find out the true capabilities when it arrives. You have been extremely helpful! All this info is greatly appreciated!!!
 
FlaCharlie said:
That's interesting. I've never heard of sellers offering PT options.

I would still suggest that you measure the heater voltages, though. Most vintage gear had PTs rated at 117v and the heater voltages are typically a bit high. Sometimes not enough to be concerned about but other times some type of adjustment is a good idea.

Some people will rig up a "bucking transformer" or use a variac to reduce the voltage a bit. I usually just add a couple of resistors to the heater windings to drop the heater voltage and leave the rest alone. In most cases it's just the heaters that are a concern because over-voltage shortens the tube life and tubes can be expensive. Voltage variations elsewhere are not usually too critical.
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I've seen a few pieces of Chinese equipment offering transformers with primaries other than 110v and 230v. But not many.
 
FlaCharlie said:
This is especially true when the advice comes from a dealer who has a vested interest in selling you the tube. Typically, the best "holy grail" tubes are always the ones that the "boutique" dealer just happens to have in stock.
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So true, not on-topic but I have seen boutique tube dealers selling NOS tubes from long defunct relabelers of factory seconds.
 
You know how everything happens for a reason? Found an Amazon gift card that I completely forgot about and used it to buy an overpriced Genalex u77/ 5AR4.
So in many ways I suppose my "Rectifier Tube Concerns" are over.

I read all the data sheets and 5AR4 seems to be the most stable rectifier with the least amount of voltage drop. 5Z4 is the second place rectifier choice for stability.

I'm not doubting anyone that says the 5U4G makes their amp sound the best, but I'm not wanting to use a tube that spikes over 600V for 20 to 30 seconds when you first turn it on. I'm still just a tube noob, but this doesn't seem like it would be very good for the other tubes, caps, and components in the circuit.

My one friend insists that 5U3C is where it's at. Claims the 5U3C and WE274 black plates have more punch and attack as he described it. Maybe some day I will try one.

For now I no longer have any "Rectifier Tube Concerns" because I used all the tools available to me to make an educated decision. Reading all the data sheets like somebody suggested was probably the smartest thing I could do. Listening to people here on this forum has been beyond helpful and played a major role in my 5AR4 decision.

It's at the admins discretion of course, my problem and rectifier concerns have been mitigated.
Feel free to close this thread if you like.
Bork! Bork! Bork!
 
I've been playing with a 5V3A in place of a 5AR4. It has a 3A heater draw and a 42v drop. The earlier 5AU4/5V3 has a 3.75A to 3.85A heater draw and 47v drop.
The 5V3A has around a 25v drop over the 5AR4, the Maxpma is 415, and Maxpv is 540v. Compared to the 5AR4 @ 250 Maxpma, 450 Maxpv.
I've been using the 5V3A in my VTA ST-70. The bigger power transformer has a
4 amp 6v winding, so current draw isn't a problem. The power transformer doesn't seem to be running any warmer.
If you can deal with the voltage drop, and the 6v heater winding can handle the higher current draw, it seems like the 5V3A is a cheap sub for a GZ-37? :dunno:
 
SwedishChef said:
You know how everything happens for a reason? Found an Amazon gift card that I completely forgot about and used it to buy an overpriced Genalex u77/ 5AR4.
So in many ways I suppose my "Rectifier Tube Concerns" are over.

I read all the data sheets and 5AR4 seems to be the most stable rectifier with the least amount of voltage drop. 5Z4 is the second place rectifier choice for stability.

I'm not doubting anyone that says the 5U4G makes their amp sound the best, but I'm not wanting to use a tube that spikes over 600V for 20 to 30 seconds when you first turn it on. I'm still just a tube noob, but this doesn't seem like it would be very good for the other tubes, caps, and components in the circuit.

My one friend insists that 5U3C is where it's at. Claims the 5U3C and WE274 black plates have more punch and attack as he described it. Maybe some day I will try one.

For now I no longer have any "Rectifier Tube Concerns" because I used all the tools available to me to make an educated decision. Reading all the data sheets like somebody suggested was probably the smartest thing I could do. Listening to people here on this forum has been beyond helpful and played a major role in my 5AR4 decision.

It's at the admins discretion of course, my problem and rectifier concerns have been mitigated.
Feel free to close this thread if you like.
Bork! Bork! Bork!
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I'm sure the 5AR4 will work fine although it's a bit overkill since its current capabilities are far beyond what is needed for a preamp. Its lower voltage drop may result in higher voltages than the stock tube but probably not a huge difference in a preamp.

While a 5U4 doesn't have a slow start, I'm not sure where the idea that it "spikes over 600V for 20 to 30 seconds when you first turn it on" came from.

Its behavior will depend on the circuit it's being used in but that seems a bit extreme. Is that something that owners of this preamp have measured or just some random statement you found online?

Whatever the peak voltage is at startup it does not stay there for long. It starts dropping as soon as the other tubes start drawing current, although it may take a little while to stabilize. A thermistor can be added to soften it a bit but most vintage gear that used 5U4s didn't bother and voltage spikes don't seem to have resulted in any problems.

Just FYI, moderators don't close a thread to new replies unless it's controversial and the responses get nasty. Long dead threads are often revived. Just looking down the forum page a bit I see one that was started in 2010 and another from 2007.
 
FlaCharlie said:
I'm sure the 5AR4 will work fine although it's a bit overkill since its current capabilities are far beyond what is needed for a preamp. Its lower voltage drop may result in higher voltages than the stock tube but probably not a huge difference in a preamp.

While a 5U4 doesn't have a slow start, I'm not sure where the idea that it "spikes over 600V for 20 to 30 seconds when you first turn it on" came from.

Its behavior will depend on the circuit it's being used in but that seems a bit extreme. Is that something that owners of this preamp have measured or just some random statement you found online?

Whatever the peak voltage is at startup it does not stay there for long. It starts dropping as soon as the other tubes start drawing current, although it may take a little while to stabilize. A thermistor can be added to soften it a bit but most vintage gear that used 5U4s didn't bother and voltage spikes don't seem to have resulted in any problems.

Just FYI, moderators don't close a thread to new replies unless it's controversial and the responses get nasty. Long dead threads are often revived. Just looking down the forum page a bit I see one that was started in 2010 and another from 2007.
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Was just going by what I was told about 5U4G on social media..I do not know what will happen in the circuit until I test. I still need to determine if transformer can even handle 3A draw tubes to experiment.
 
I appreciate looking at a vintage GZ34/5AR4 so let me be clear. But there is a lot of Bovine Scat on the Internet being spewed by armchair experts about Cathode Stripping, instant start up, Cathode Rectifiers etc. Yes, a 5AR4 or 6CA4 etc. are slow starts. But remember that Fisher and HH Scott used silicon rectifiers in their receivers. The 340B/345/380 Scott, and the Fisher 500/800 series receivers. So all of this rubbish about slow start and cathode stripping is just Internet lore. Yes, Cathode Stripping is real... but that would be in high power RF power tubes etc., not our audio equipment.

I will now step down off of the soap box, sorry.
 
nerdorama said:
Maybe something from the 5Y3 family would work. It's a directly heated rectifier like the 5U4 but only needs 2 amps of heater current. It has lower current ratings but for a preamp should be fine. There is also an indirectly heated version known as the 6087.
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The 5V4-GA would be a great sub to consider, it's got the same pinout as the 5Y3, a 2 amp heater VS the 5U4's 3 amp, and has indirectly heated cathodes. The spec sheet has it good for 175 MA.

https://frank.pocnet.net/sheets/093/5/5V4GA.pdf
 
kvflyer said:
I appreciate looking at a vintage GZ34/5AR4 so let me be clear. But there is a lot of Bovine Scat on the Internet being spewed by armchair experts about Cathode Stripping, instant start up, Cathode Rectifiers etc. Yes, a 5AR4 or 6CA4 etc. are slow starts. But remember that Fisher and HH Scott used silicon rectifiers in their receivers. The 340B/345/380 Scott, and the Fisher 500/800 series receivers. So all of this rubbish about slow start and cathode stripping is just Internet lore. Yes, Cathode Stripping is real... but that would be in high power RF power tubes etc., not our audio equipment.

I will now step down off of the soap box, sorry.
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Most of my amplifiers and a couple preamps use SS rectifiers. Faster starts and cathode stripping doesn't keep me up at nights. :no:
 
my big amps are solid state rectifiers and run near 700 volts on the plates. Its not something I spend any time being concerned about either.
 
My latest project is the Kenwood 1100u receiver on the bench. It has silicon diodes in a voltage doubler arrangement. The light on the bench dims ever so slightly when I flip the switch.
 
So I'm curious what people think about a rectifier tube having an impact on sound, especially in an SE amp that has mostly consistent current draw across in. I hear people saying they can now hear angels singing in the background after swapping to XYZ $$$ NOS rectifier, but I have yet to hear any difference in any of my amps swapping these out. Possibly in a PP amp with low value filtering cap where you would see a lot of sag, maybe?
 
I've never heard a difference. Maybe in higher powered amplifiers due to voltage sag at higher volumes? But I would think using the same rectifier type but a different brand there would be very little or no difference. I even recently swapped out a GZ-34 for a 5V3A. The 5V3A has a 25v higher voltage drop compared to the GZ-34. After re-biasing the amplifier I couldn't hear any difference in sound.
 
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