Tube sound terminology

I am a retired EE who has just recently gotten into tube amplifiers. I have a 1967 ST-70. As I read the various forums on tube rolling, I constantly encounter terms like Bright, Dark, Tight, Loose, Tubey, Muddy, Full, Crisp, etc. What do these terms mean, and how do they relate to the electrical characteristics of the tube? Thanks,

Mike
1967 ST-70

.

Hi Mike --- well, as a retired physicist who has been into Dynaco tube stuff since the
mid-1960's, no two people hear the same way and the terms that you ask about don't really correlate to the electrical characteristics of a vacuum tube. (They may correlate to the materials or fabrication techniques used to make the modern vacuum tubes since modern production tubes are normally not as durable as the Old Stock made in the 1950's or 60's or 70's --- IMHO)

A lot of listeners agree that the stock ST70 sounds "muddy", but that is because the ST70's original power supply was not very good and can now be improved with modern capacitors and/or an upgraded PA60 Power Transformer.

The improved power supply component also gets rid of the "LOOSE" quality of the sound, everything tightens up soundwise.

As far as the term "tubey", there is a difference in sound between a solid state amp and a tube amp.  For instance, MOSFETs as opposed to BIPOLARs have that "tubey" sound.

Room dynamics and the actual tube used and the ear can change how listeners perceive the other terms you mentioned: Bright, Dark, Tight, Full, and Crisp.

Since some tubes sound better than others, I am afraid that tube rolling is an individual art and not a science.

Hope that I have not confused.
Stew

Thanks for the excellent replies. It will take me a little time to develop my hearing, in order to distinguish the subtle differences between different tube options.

You forgot "sharp" in your list ...   



It's all just a feeble attempt to describe the sound. Much easier if you're able to hear it yourself, which is why a lot of folk have a whole bunch of tubes over time. I'm a bit of a tube-aholic myself, but it's well worth the effort, and you can always "roll" what you don't want to someone else.

I'm still comparing sets here, and enjoying every minute of it, as it's a combination of tube "flavors" that can affect what comes out of the speakers. Drivers, especially the center driver on the ST series amps, have the most impact, but the power tubes also can have major differences. You also need to consider your preferences in genre, as jazz and orchestral tend to benefit from a darker overall effect, while with progressive and wango de tango, you want to hear every shrill note and make your ears bleed ... Which reminds me, your average listening level enters into the mix also, as different tubes have "sweet" levels where they really shine.

So ... the current set in my ST120 is a quad of TungSol KT120's, which tend to be full bottomed as well as precise in the lower registers, with exceptional definition in the mids. They do tend to be a bit dark at the top, so I compensate for that with brighter drivers, as in a matched set of 12AU7a RCA cleartops in the channels, and a circa 1940's triode balanced 12AU7 RCA foil getter in the center position. That combination results in a fluid high end with no sibilance or ringing, and an exceptionally wide and deep stage. A Mullard GZ37 bottle rectifier rounds out the set - much more robust than the more common GZ34 or 5AR4, allowing the amp to achieve it's full potential without browning or pinching on impact.

(Hey, I even impressed myself with that one! That's right up there with some of the drivel you see in Absolute Sound!)

stewdan wrote:as a retired physicist who has been into Dynaco tube stuff since the
mid-1960's, no two people hear the same way and the terms that you ask about don't really correlate to the electrical characteristics of a vacuum tube.

I'm surprised they let you have a stereo ...

@mazeeff let your own ears be your guide what sounds best to you Is, like sKIZo I like to experiment with different combinations for my ears right now with an ST-120 I am enjoying two matched Sylvania 12BH7 in the outboard positions and a Panasonic 12BH7 in the center
Have fun with it.

This has been quite helpful. If I understand correctly, a "muddy" sound describes the effect of power supply sag. Is that correct? When you use the term "dark", are you referring to an attenuation of low/high frequencies?

Mike

Hi Mike -- Yes, I equate "muddy" with the Power Suppy not properly functionioning.

I can't awswer about "dark", because I really don't know what it relates too.  But, I would imagine it has something to do with frequency as you suggest.  Maybe someone else has a more definitive answer.

Stew

I see the term "tubey" used a lot when talking about running the EL34's in Tetrode mode. Is the term "Tubey" associated with an increase in harmonic distortion, which many folks see as desirable?

Mike

Tooby!

Smoother, warmer, as in not harsh. Solid state tends to have a more "technical" feel to it. Comes with the signal having to pound it's way thru sand to get to the speakers. A tube's magic happens as the electrons float majestically through vacuum ...

Tubes watts also tend to be bigger, relatively speaking, mostly because you can push a tube amp harder without them getting raspy or hard clipping. A hard clip is one that distorts the wave to the point where you get all sorts of harsh nastiness that can actually damage speakers. We've all heard the result of that. Tubes DO clip, but they do it gracefully - it's certainly noticeable in an extreme case, but won't rip your ears off doing it.

That tooby sound is even more important in instrument amplification, where the goal IS controlled distortion. Synthetic grunge with a dirty lick from a humbucker pushed to overdrive will never compare to the real deal from a tube amp.

sKiZo wrote:Tooby!

A tube's magic happens as the electrons float majestically through vacuum ...

Very good!!! And I thought we were only cooking the electrons in a frying pan, where they fly off screaming, to be herded like cattle for slaughter! When I first got my St-70, I brought it to audio tech friend who has a audio generator and spectrum analyzer. We ran the ST-70 and a Onkyo SS amp side by side. The ST-70 had much more harmonic content than the Onkyo. The 2nd harmonic was especially predominate on the ST-70. Harmony can be pleasing to the ears, and bands like The Byrds, Crosby Stills Nash & Young, Simon & Garfunkel, etc., took advantage of this. I even like to listen to a good barbershop quartet! Are terms like Tooby, Wamer, and Smoother simply describing subtle changes in the harmonic content? If operating the EL34 in triode mode makes the amp sound more tooby, what exactly is the mod doing to the tubes characteristics? Based on what I am hearing here, I may be looking for a bit more more Tooby sound. If I can get this with the Triode mode, then I may try that prior to investing in multiple tube sets.

Mike

Like describing a great wine, describing the tube sound is tough. Once you've had a great wine, you just know it. I recently built an ST70 and I'm enjoying it immensely. I've stopped trying to describe what I'm hearing, but will suffice it to say that I just enjoy listening to music a whole lot more, my speakers now sound like a much better set of speakers without the harshness when driven by my usual Sunfire Cinema Grand amp, but most of all the music is all more enjoyable and even after hours I just don't get that listeners fatigue I used to get. The dealer who sold me my first system many years ago gave me a piece of advice: "Listening is a skill that has to be used continuously and your ear will continue to develop- let your ears guide you. Forget terms and descriptions, when something isn't working you'll either turn it down or turn it off. If it's truly nice, you'll leave it on all day without complaints." I'm almost there now, and building a SP14 will hopefully help further.

Laminarman wrote:Forget terms and descriptions, when something isn't working you'll either turn it down or turn it off.  If it's truly nice, you'll leave it on all day without complaints."

Thanks. This is very true. Last fall, I restored a 1962 RCA stereo console. It has a small 8W single-ended class a amp. I can listen to that all day long. The 8W output was a little low, so I got the st-70. I can not listen to the st-70 for more than a couple of hours, before I end up switching back. I have tried different speakers, DAC's, and preamps on the ST-70. Nothing sounds perfect yet! The engineer in me wants to find a direct fix for the problem, but I need to accept that it will be an process of trial and error.

Mike

mazeeff wrote:

Laminarman wrote:Forget terms and descriptions, when something isn't working you'll either turn it down or turn it off.  If it's truly nice, you'll leave it on all day without complaints."

Thanks. This is very true. Last fall, I restored a 1962 RCA stereo console. It has a small 8W single-ended class a amp. I can listen to that all day long. The 8W output was a little low, so I got the st-70. I can not listen to the st-70 for more than a couple of hours, before I end up switching back. I have tried different speakers, DAC's, and preamps on the ST-70. Nothing sounds perfect yet! The engineer in me wants to find a direct fix for the problem, but I need to accept that it will be an process of trial and error.

Mike

See, I haven't listened to an older, original ST70 amp, only Bob's from Tubes4Hifi and it's been fantastic. But I know what you mean by comparison with a solid state experience I had recently. In my basement I had a Yamaha integrated amplifier which I fed a CD player into (workout music, woodworking..etc.) I took our office music receiver which we've had forever, a McIntosh MAC1900, and hooked that up, and I just seemed to enjoy it so much more. Was it purely objective? I don't think so. The MAC looked cooler, was "retro", the knobs were better feeling, but somehow it sounded better to me and I played music louder. The guys who are servicing it now (FM board went on it) said I should put a turntable on it, I'd be surprised how well the old phono stage sounds.