Does tube make a difference in the sound?

[Alan0354]

I read a lot about people think one brand of tubes sounds better and the other sound worse.

1) Does different brands of 12AX7 really make any difference in the sound? Why?

2) Does different brands of the same power tubes make a difference in sound? ie, different brands of 6L6.

3) Does 6L6 sounds different from 6V6 different from EL84? Why are they different?

[km6xz]

Tubes are a matter of faith and belief for most people so you have opened the same can of worms that a question about whether there was a difference between various religions.
Yes, a random tube put into a amp can change the sound from another random tube of the same general type. Not because the tube has an inherent sound but because it interacts with the rest of the circuit differently. Imagine the question about tires. Someone will swear that you should only use Goodyear xxx model because it handles better. They truly believe that based on their sample of one. But you buy a set and it does not work well at all. Why? Because handling is a complex interaction between many factors that any changes results in less than expected results. His car might be a VW and yours, a Ferrari and he will always remain convinced he was right and you will always know he is dead wrong. Both are part right.

Answer to # 2 is the same as #1, depends on the circuit<>tube interaction. Keep in mind that there is no standards committee defining what a 6L6 is so any tube with the same pin outs and general specs plus or minus 50% gets labeled as a 6L6. At one time, when they were subject to licensing from the patent holder, other manufacturers made the same style tube and had to maintain close similarities so they could be named second sources for manufacturers of finished products. RCA, which had the patents on several distinct features of the 6L6, would not sell any to manufacturers of radios or amplifiers if they were the only source for them. They could not sell them to the government for the same reason. RCA cross licensed manufacturer of the 6L6 to other companies as a way of assuring product manufacturers that there would always be a second source available so the price would be competitive and so there would be no single source able to control the end product if they stopped making them or bumped the prices up 300%. As a result, if you bought a 6L6, you could replace an old one and be confident that the unit would work essentially the same, no matter who made the tube. Now, tubes are wildly mis-spec'ed and there is no one monitoring makers of tubes to see what they really label as anything. If you try a bunch of different tubes, because they are not the same electrically, you would expect them to interact with the circuit differently than the one the designer intended. That does change the tone and system characteristics. While a random new tube might not work to your satisfaction in your amp, another owner of a different amp might feel it is the only perfect one because his amp has different demands on the tube.
#3 is a subset of answers 1 and 2. El84 is a 6BQ5 in the US which was designed as a lower cost to make, low power tube for table radios and TV audio output where were using the larger octal base 6V6. In that respect, they work well in most circuits designed for the 6V6. Some say the 6V6 is a baby 6L6 and there are similarities in transfer function but not in values.
If you were designing for a specific transfer function, most tubes available could deliver it if the circuit it was in was optimized for it. For new builds it is certainly possible to get a 6BQ5/EL84 to sound very much like any other amp that was designed for 6L6 but if comparing previously designed and existing stock of amps out in the market, that were built around the 6L6, a lower voltage version that used EL84 would sound different. Just as two different El84s sound different from different manufacturers of tubes.
One complication for all this is there are many many brands of tubes, some are claimed to be great by internet gurus and other are panned.....that came off the exact same assembly line on the same day, with the only difference being the logo ink stating it was a different model. The reason is there are only a small handful of manufacturers of tubes supplying the hundred or so brands.

So your questions are good and will generate heat but not much fact. The simple fact is tubes do not have inherent sound properties any more than tires have inherent handling properties. Further complicating the discussion is that "sound" is purely subjective and not related to any natural superiority of one over another and a preference of a tone characteristic is almost always traced to origins in the listener associating that tone to a song that meant a lot to them some time in the past. The song and the playing style drives the search for certain tones, not something inherent in the tone. If you heard a song with a totally different tone signature but the song really instilled strong emotional connection to you, that tone would suddenly because associated with special meaning and you might search for years trying to duplicate the feeling. Generally strong song writers and stylists care very little about a specific tone, that is more of the domain of amateurs and beginners. Style and song dominate in fashioning genre shifts, not tone. Tone never sold one more record or cause one more bad review. If you are not wildly popular with your audience, it is NOT tone, any more than tone making a label want to sign you. In fact a tone style that has been done before will work against you unless working in a cover band on a cruise ship or prom nights.

[soundmasterg]

Nice post Stan!

I wonder though about something you said?

If you were designing for a specific transfer function, most tubes available could deliver it if the circuit it was in was optimized for it. For new builds it is certainly possible to get a 6BQ5/EL84 to sound very much like any other amp that was designed for 6L6 but if comparing previously designed and existing stock of amps out in the market, that were built around the 6L6, a lower voltage version that used EL84 would sound different. Just as two different El84s sound different from different manufacturers of tubes.

Typically in comparison, EL84/6BQ5 amps tend to have less bass and a more high frequency emphasis than 6L6 amps, but the overall sound is very harmonically rich and balanced, whereas the 6L6 tends to sound more bass heavy with a mid scoop and a bright top end. So given that typical behavior, how would you redesign an EL84 amp to have the bigger bass like a 6L6 amp or even the higher bass emphasis of a 6V6 amp? I always assumed it was the nature of the specific tubes themselves that sounded that way...I have a 1964 RCA console stereo here that sounds great but is a little lacking on the bass....and of course it is using EL84's. I assumed it was just the nature of the tubes that caused that....

Greg

[km6xz]

The natural frequency response of tubes is from DC up to the frequency were internal capacitances limit it. So, if a amp seems to have lower low frequency output, it is not the but because most tubes are flatter in response than any other device in the amp, including carbon comp resistors. A 12AX7 has flat response from DC to 50,000,000hz. A power tube, a bit narrower. There are many reasons for an apparent lack of lows...output transformer with not enough iron is a good place to look and the preamplifier where lows are attenuated in guitar amps and usually flat in hi-fi amps(one being a distortion generator emphasising upper order harmonics as a "production" device and the other is intended as a "reproduction" device, to not impart harmonic alteration). So plot the response of the preamp at low level for frequency response. Then drive the tube harder and measure the harmonic production. Is it second harmonic or upper order odd harmonics? That really impacts the perception of fundamental content. A pure sine wave not over driven compared to the spectral output of a overdriven amp will produce a very different frequency domain output. Again, it is not the tube itself that has a frequency selective effect on the sound. As a result, you can get any tube to "sound" just about any way you want.

Regarding the 1965 console stero: Remember the times, any low frequencies coming from records or radio was noise so an amp that intentionally cut the lowest frequencies sounded better. Records had restrictions in modulation of low frequencies, since they were wider tracks and introduced tracking distortion when mixed with upper mids and highs. Broadcast, was restricted in bandwidth. Concerts did not reproduce lows because there was not enough power since every octave below 100 hz required a logarithmic increase in power. A typical concert sound system was sound re-inforcement, mostly for vocals, and not the full spectrum from stage. A loud concert hall like Fillmore West with their high efficiency Altec horns, filled the space with ear numbing sound with less than 200 watts total because they were not expected to reproduce low bass. So the RCA was purposely limiting bass response for the listener's benefit, besides it saved about half the production cost difference between a 15 watt amp and speakers which were flat down to 100hz compared to 50hz.
Our ears did not care if the deep bass was there or not, we heard the second harmonic and higher harmonic sequence and our brains filled in the rest, we had no problem locking in to the kick drum in a dance song, the bottom notes were inferred by their harmonic sequence. If anything it was easier to hear the rhythm, say on the old MoTown hits when the fundamentals were missing, when played on the 6x9 oval speakers in the back deck of the car with the 2.5 watts from the car radio. Deep bass is a fairly recent cultural preference and not naturally part of music in most cultures.

[nashvillebill]

...I have a 1964 RCA console stereo here that sounds great but is a little lacking on the bass....and of course it is using EL84's. I assumed it was just the nature of the tubes that caused that....

Greg

I have a RCA "console pull" amp, it's a RCA RS177J with EL84's in push-pull. I totally refurbished it: completely recapped it (including coupling caps) and replaced all the resistors. Hooked to real speakers (ancient Radio Shack Mach Ones) and driven with a SS preamp, it's got very good bass response. In fact when I first fired it up I was surprised at the "oomph" that little amp produces. I'm certain that if it were back in the console, with the open-back original speakers, and if had not been refurbished, and if it were still being driven by the original tube preamp, I would not have been impressed. It's not the use of EL84's that limits bass response but rather everything else.

[Jazz P Bass]

I agree totally.

I also have a RCA 'pull' unit in my shop.

What a wonderfull amp.
2 EL84's per channel.
18 watts of stereo joy.

I use the complete system.
Preamp, AM/ FM radio.
My signal source for CD's is a boom box utilizing the headphone out jack.

When I was fixing her up, I ran a test signal dirrectly into the power amp.
The coupling caps in this setup where way too bassy.

With the preamp installed, it is matched very well.

[Mick Bailey]

I built a little console amp years ago and it's fantastic - just a pair of ECL82s. The transformers are tiny, improved to some extent by NFB.

My thoughts these days are that those older designs found in radiograms, TVs and whatever else, were only let down by speaker limitations.

As far as the OP's question about tubes making a difference to sound? Here lies the road to madness. I can imagine Zeus punishing Prometheus, but instead of having his liver eternally torn out by an eagle, he's forced to A-B different tubes until he can convince the whole of mankind which one is best.

There are people who claim to hear a difference if a tube comes in a printed or plain box. Or if it has a brown or black base, or if it's a Wednesday or Friday. You can't win, because once every aspect of physics and science have been debated to the point of complete exhaustion, you're still left with subjective human opinion.

[Alan0354]

I pretty much know the answer. I just want to hear from others that is more electronics inclined.

I frequent Strat Talk Forum what people are mostly end users rather than lab rats like us. They have a totally different believes and they claim they can hear the difference. Could it be we lab rats keep looking at the circuit and we are desensitized but days of starring at the circuit and the knowledge of the circuits?

There are definitely a lot to do with perception also. Funny CTS pots are much preferred for guitar volume and tone pots. It's only a resistor element but people swear by it. It turn out the 1250K CTS pots measure about 220K or so. Because of the high impedance nature of the pickup and increase with frequency. That make the sound of the thin strat pickup fuller sounding compare with a true 250K pot because as the frequency increase, a voltage divider formed between the impedance of the pup and the pot and the high frequency get attenuated.

Also they claim the orange drop caps are better. I measure the capacitor when I use for tone and coupling, I am stunned how much the value varies. I think it's the difference in value that change the tone. Particularly if one brand tends to bias lower or higher than the stated value. then the carbon comp resistors!!! But if you want to sell amps, you have to deal with this.

[nashvillebill]

There's even audio enthusiasts who swear they hear a difference between different brands of rectifier tubes. "The RCA 5AR4 is more musical while the GE 5AR4 has more midrange clarity" for example.

[Alan0354]

One thing kind of puzzling. I did experiment what different power tubes in my Pro Reverb. It has a pair of 6L6. I use zener diode and a switch to get either 440V or 400V so I can test both 6L6 and 6V6. The switch also adjust the bias for the tubes also. I tested the original 6L6, Ruby 6V6GT and JJ 6V6S. They do sound slightly different to me. I did a video and people said they are day and night different. The Ruby 6V6 seems darker of the three.

But then I work on the Bassman 100 platform with a Classic Tone output transformer for Pro Reverb and Vibrolux. I put in the same circuit that lower the voltage. The power transformer is still 100W exactly the same as Twin Reverb and the amp is SS rectifier. I use a 100 ohm resistor in series with the +B to get some sag to simulate the tube rectifier. This time the 6L6 sounded muddy and the Ruby 6V6 actually has the most clarity and sounded the best!!! The rest of the circuit in the power amp and PI stage is exactly the same as the Pro Reverb.

So this verify what we believe that tube is only part of it, it needs to work with the rest of the circuit to make the sound. But I am surprised how big a difference between the two amps!!!! The only difference is the output transformer and SS rectifier. I still wonder what make such a drastic difference.

[Alan0354]

There's even audio enthusiasts who swear they hear a difference between different brands of rectifier tubes. "The RCA 5AR4 is more musical while the GE 5AR4 has more midrange clarity" for example.

So are they psychosomatic or are we too desensitized?

Do you know how many people buy a new amp and spend $100 buying a set of new tubes!!! When they buy a used amp, they immediately change the tubes. I kept telling them wait, test the sound, does it sounds good, does it seems to distort at lower volume first. Don't just waste $100 automatically. But I was told many times I was wrong!!!!

[Mick Bailey]

So are they psychosomatic or are we too desensitized?

I don't consider anyone in the repair business is desensitized. Rather like I don't consider an aircraft engineer to be desensitized because he doesn't believe that invisible angels are responsible for flight.

[Alan0354]

I don't consider anyone in the repair business is desensitized. Rather like I don't consider an aircraft engineer to be desensitized because he doesn't believe that invisible angels are responsible for flight.

What I means is we studied electronics and there are theory about components. Like the variable of a capacitor is the loss tangent, carbon resistor has a tiny voltage coef only compare to the plate characteristics. These are physics and you learn it, it's in your mind. We are programmed to question these.

Like you guys just talk about frequency response of tubes. Tubes goes from low frequency governed by the coupling to high frequency into MHz. How can you blame one tube has more bottom?? Instead, we question the circuit around the tube rather than the tube.

In that sense, we are kind of desensitized about there opinions as we discount a lot of them!!!

[Jazz P Bass]

Then what you should do is 'plot' the response of each tube, on both OPT's.

Therein, within the data, is the answer to what is different.

The 'why' may be elusive.

[tedmich]

tubes do sound different! My old Amperex bugle boy in the V1 slot of my modded Ultra+ sounded sublime until it died and the NOS GE 12AX7A took about a week before I deemed is acceptable. The JJ 6L6s sounded like ass right off the bat compared to the Winged C SEDs that I now use... Its all about preference, expectation and natural human caprice...no science there...