"All Tube" - Not Always True

[Tuxedo Kaz]

If you want an 'all tube' amp, buy a Mesa. Nearly all their amps use tube rectification.

 

[Splattle101]

Have you actually read any of the information posted in this thread yet?

 

[Tuxedo Kaz]

Have you actually read any of the information posted in this thread yet?

And this is supposed to be, what, an assault on my valid suggestion that if someone wants tube rectos stock that Mesa is a good idea, or an attempt to undermine my intelligence for unknown reasons?

 

[Splattle101]

It's an attempt to get you examine why you might think you want a valve rectifier anyway. If you interpret that as an attack on you or your intellect, good for you.

And your post wasn't a suggestion. It was written in the imperative, so that'd be an instruction.

 

[Tuxedo Kaz]

Instruction or suggestion, take your choice regardless of semantics.

At any rate, I've heard good amps with tube rectos and without, I don't feel strongly either way. But, you obviously have a point to prove, so I'll go and let you.

Edit: By the way, I do understand the concept of how power sag works. Thanks.

 

[Big John]

Mike Soldano's take on this topic...

Tube vs Solid State Rectifiers

The job of the rectifier is to convert alternating current (AC) which comes out of the wall socket and subsequently the power transformer, into direct current (DC), which is needed to operate all of the circuitry in the amplifier. This process takes place through a device called a diode. Diodes act like a one way valve, allowing current only to flow in one direction.

The diodes in the days of old were vacuum tubes. Today's diodes are made out of silicon.

The tube diode was the first diode ever invented (in fact it was the first tube ever invented). For many years it worked quite dependably, and it was the only choice for rectifying current for high voltage power supplies. When solid state technology was developed in the 1950's, it was found that solid state diodes could do the job of tube diodes, only better.

A tube rectifier has internal resistance. The more current that travels through a tube rectifier, the more the voltage drops. When the voltage drops, the power of the amplifier also drops. The tube rectifier has the drawback of not being able to provide a consistent voltage when it's under load. The other drawback is that the tubes themselves run hot, and can be relatively short lived. Unfortunately, modern day sources for rectifier tubes are not very reliable, and even in their prime these tubes were usually the weak link in most amplifiers.

An amp with a tube rectifier tends to sound much "spongier" in the bottom end. Low frequency notes take more current through the power tubes to reproduce. This increased current causes a voltage drop in the rectifier tube and the amp loses power. So, when more power is actually needed, the amp gives less. Because of this, a tube rectifier amp will sound spongy and more distorted at high volumes. This, probably more than anything, is what gives a vintage amp its sound and color.

A solid state rectifier has no internal resistance whatsoever. It has a very consistent fixed voltage drop that occurs whether there's no current or full current - approximately .7 volts. When an amplifier needs power at low frequencies, there will be no limit to the current that travels through the rectifier. This results in an amp with more headroom that is punchier, more articulate, and able to deliver the goods in the bottom end.

In my opinion, all amps should have solid state rectifiers. I don't believe there are any really good rectifier tubes on today's market and, even if there were, why use them? The technology is obsolete, they are horribly inefficient, and far more expensive and troublesome to build into an amp. These tubes, no matter how good, will routinely need replacing, adding to your maintenance expenses. Besides that, tube rectifiers kill the headroom of an amplifier. If you want that spongy, vintage sound, there are other ways to do it. I have successfully designed and built amps that have replicated that soggy bottom, vintage tube rectifier sound using solid state rectifiers and various circuit modifications.

Of course if you have a vintage amp that uses a tube rectifier, by all means keep it that way! That's what makes it sound the way it does. But if you're contemplating getting a new amp, I recommend avoiding future headaches by staying away from tube rectifiers.

 

[Splattle101]

...At any rate, I've heard good amps with tube rectos and without, I don't feel strongly either way.

Good, neither do I.

But, you obviously have a point to prove, so I'll go and let you.

Whatever . I was trying to cut through the hype. There is a bunch of marketing hype out there about valve rectifiers, class A amplification, AlNiCo magnets in speakers, NOS valves, etc, etc.

They all have an objective basis in fact, but they're all marketed in ways that rely more on enthusiasm and plain old magical thinking than on fact. Mesa, with their 'triple rectifier' amps are as guilty as the next in this. You seemed to be pointing that direction, and thus my rather testy post.

 

[Tuxedo Kaz]

Understandable.

And I agree 100% with everything you've said in this thread so far, so shall we just call it water under the bridge?

I think, bottom line, Mesa makes great amps, and if someone insists on tube rectos, they've got plenty of amps with them. I don't mean to say that makes them better or not.

Besides, didn't you get the memo? The MI is all about hype, nostalgia, and other sh*t that doesn't make one bit of goddamn empirical sense.

 

[Belzeebub]

Mike Soldano's take on this topic...

thanks for posting that. i echo the sentiments of Mr. Soldano.

 

[Deftone]

I used to own a Mesa Heartbreaker, excellent amp. It was a dual rectifier, solid state or tube. I preferred the SS.

This is a great thread.

 

[dwagar]

Soldano: If you want that spongy, vintage sound, there are other ways to do it.

a simple mod to 2203/2204 amps (note: I haven't tried this mod):
Marshall Cream Switch

 

[Texas07R8]

this almost sounds like a PAF tone thread.

Guys, please be civil and don't jump somebody's ass because they have and opinion that may differ from yours. If we all agreed on everything this forum would not exist.

Thanks to BigJohn for posting Mr. Soldano's article, what I take from it is he agrees that there is a vintage tube rectifier sag tone and he's figured out a way to do it in SS mode to "emulate" vintage tube sag. So why is it that some here think a tube rectifier is useless or bad or not in vogue?

I have an all tube amp with a rectifier tube, I can change it to SS or Class A or Class A/B. I love the tone of all the rectifier settings, they are slight differences in attack mostly. Just because your amp has this or that doesn't mean a lot. I really love the warmth of tube driven reverb in my amp and the all tube preamp and 6L6 power section. It's the sum of the parts that make good tone on an amp, vintage valves, good trannies, good circuit design, quality components, etc. You can have a tube rectified amp that sounds like crap if the amp isn't built right and vise/versa.

I've got a modeling system that gets very close to a tube sound, they have really tightened the gap on tube vs emulated tube tone these days but I'll keep my tube amp thank you. Sometimes I run my effects through the clean channel so I can get that full high volume type tube distortion without the volume if I tried to do it with just my amp.

 

[thepacifist20130]

An electronics engineer might be able to explain the differences which us guitarists perceive as better tone in a tube amp.

For starters, any digital amp (like processors, digital amps) will have an A/D converter that samples the input signal with a fixed sampling rate. That puts limitations on the maximum frequencies (harmonics) of the signal. Guitar pickups generate harmonics, which might be killed at the input of the amp/digital processor.
Tubes, because of their physical characteristics, generate harmonics when pushed outside of their operating curves. Since it's all analog circuit, there is no nyquist rate playing a part.
Also, analog components like tubes have their individual capacitances/inductcances/transconductance which change as the tubes heat up. It is near impossible to mimic these on a DSP chip.
Members here will attest to the fact that when you play an amp and the tubes start heating up more, say after half an hour, the amp of the tone changes from what it was when the tubes were cold.

That's ultra lo-fi tube technology for you, my friend
Again, this would be one of the 100 factors that give tube amps the sound that they have.
The important point is we all love them. Though SS amps are becoming more popular as technology advances, those little glass thingies will always have a place in our hearts, and in our amps !

 

[Tuxedo Kaz]

An electronics engineer might be able to explain the differences which us guitarists perceive as better tone in a tube amp.

For starters, any digital amp (like processors, digital amps) will have an A/D converter that samples the input signal with a fixed sampling rate. That puts limitations on the maximum frequencies (harmonics) of the signal. Guitar pickups generate harmonics, which might be killed at the input of the amp/digital processor.
Tubes, because of their physical characteristics, generate harmonics when pushed outside of their operating curves. Since it's all analog circuit, there is no nyquist rate playing a part.
Also, analog components like tubes have their individual capacitances/inductcances/transconductance which change as the tubes heat up. It is near impossible to mimic these on a DSP chip.
Members here will attest to the fact that when you play an amp and the tubes start heating up more, say after half an hour, the amp of the tone changes from what it was when the tubes were cold.

That's ultra lo-fi tube technology for you, my friend
Again, this would be one of the 100 factors that give tube amps the sound that they have.
The important point is we all love them. Though SS amps are becoming more popular as technology advances, those little glass thingies will always have a place in our hearts, and in our amps !

I wonder though if we could improve on the A-D/D-A conversion using the same kind of converters used in high end rack gear that uses digital effects (like digital reverb and such) in these modeling amps. Just a consideration.


Incidentally I know someone who thinks tube amps are going do die out. He's currently jonesing for one of those silly AxeFX things and is deluding himself into thinking it'll cure his GAS for different amps.

 

[hipofutura]

Big John, I stand corrected. I knew SRV was a Fender aficionado, but nothing else beyond that. Thank you, I'm now a bit more knowledgeable than yesterday.

 

[Big John]

You betcha, hipo.
Jimmy Vaughn ended up with all of SRV's gear.
I wonder if he still powers up those old amps.

If he ever puts them on the market, you'll likely see a feeding frenzy beyond words.

 

[st.bede]

I use both tube and SS rectifier for different things.....quick pick attack on the SS and a bit of a bloom with the tube.

 

[Splattle101]

You betcha, hipo.
Jimmy Vaughn ended up with all of SRV's gear.
I wonder if he still powers up those old amps.

If he ever puts them on the market, you'll likely see a feeding frenzy beyond words.

Slightly OT, I've got a vid of SRV somewhere showing one of his early 80s shows. He seems to be using a Vibroverb and some head and 4x12. The amps are never shown clearly. There's a also a Super Reverb behind the Vib, but it doesn't appear to be on. Could be wrong. There's what looks like a small tweed amp on the other side of the 4x12, but doesn't appear to be in use.

Interestingly, even though the Vib is on, the microphone is on the 4x12. There's another mic boom going behind the Vib, and it's either for the Super Reverb (whihc could be on) or it's for the back of the Vib. However, he's got tape on the front of the Vib where the centre of the speaker would be, which suggests he used the front.

Amplifier equivalent of trainspotting.

 

[hbucker]

I don't get caught up in what's "better" than something else before I play it. Too many great tones have been played and recorded through the years on gear that, according to the experts, isn't very good. SS rectified or not, I'm the weakest link in my gear chain.

What I do feel is dishonest with regard to the "all tube" discussion, is when a company advertises that they have an all tube amp for that "pure tone", then they put clipping diodes in for the overdrive channel. I'm aware of at least one company who has done this on a couple of their models. This doesn't sit well with me.

Yet, lots of people love these amps and I'm in no position to tell them they shouldn't love them. And of course, putting an overdrive pedal in front of the amp negates the "all tube" thing anyway. I just have a problem with the concept of misrepresentation that I think is present when the clipping diodes are used in an "all tube" amp.

 

[Angus]

Marshall moved to SS rectifiers in the 1960s. Fender did likewise in the 70s. Most of the Brit manufacturers did, too.

Erm.... Marshall is British.