If "Tube Sound" Is a Myth, Why Tubes?

[watchnerd]

Mono with or without tube ??

Here is the question !!

Triode or no triode?

 

[orangejello]

This overload problem had to do with the NAB equalization curve used on American tape machines. NAB had a 5-6dB pre emphasis boost in the bass region, and the metering on the machines did not reflect anything but the flat response of the input signal. So if the program material had anything with bass (like a fff bass drum whack), the tape would saturate with no warning from the meters. European machines use the CCIR (IEC 1; as do most all tape machines now) curve which does not have this bass pre emphasis so this is much less of a problem for instance on current 15ips tape releases.

So overload distortion has nothing to do with tube vs solid state electronics. It has to do with analog tape saturation? Still it is pretty amazing the level of recording quality that was produced with these superseded analogue and tube technologies.

Once again what are the sonic characteristics of low level IM distortion, and is it more likely to occur in tube electronics? It seems that feedback should reduce that to almost inaudible levels. I would have to think that decent tube recording electronics used a fair amount of feedback, unlike some consumer tube amplifiers which were designed with a specific tube sound in mind.

 

[MakeMineVinyl]

So overload distortion has nothing to do with tube vs solid state electronics. It has to do with analog tape saturation? Still it is pretty amazing the level of recording quality that was produced with these superseded analogue and tube technologies.

Once again what are the sonic characteristics of low level IM distortion, and is it more likely to occur in tube electronics? It seems that feedback should reduce that to almost inaudible levels. I would have to think that decent tube recording electronics used a fair amount of feedback, unlike some consumer tube amplifiers which were designed with a specific tube sound in mind.

Overload in tape at higher than normal operating levels is due to tape saturation - this is separate and distinct from tube distortion. The VU meters on tape machines don't reflect the pre emphasis either in the bass or high frequencies, so it is up to the engineer to 'know' how to set levels to accommodate this. Also, VU meters were average responding devices and would be rather blind to transient peaks. If there was for instance a flute solo and during it a big bass drum hit, the flute could take on a very audible 'fluttery' quality from saturation.

Tape playback preamplifiers have, due to the reproduce EQ, up to 40dB or so of feedback from that source alone. RIAA phono EQ is similar. These EQ curves don't have to be implemented in feedback, but in tape machines that is the way it was mostly accomplished. Due to the nature of the EQ curves, the low frequencies have the least feedback, and the high frequencies the most.

IM distortion is usually not spec'd for tape machines, probably because it would look pretty ugly. Tape, by its nature suppresses even order harmonic distortion so what remains is almost totally odd order distortion (in a 'perfect' machine this would be totally the case). The typical harmonic distortion of tape at normal operating levels is about 0.6%.

Since the distortion products are mostly low-order, the ear doesn't hear the distortion as such, at least at levels below saturation. On direct comparison, tape verses digital is totally obvious but that doesn't keep tape or vinyl from sounding very, very good.

This is a graph I made awhile back which compares the 1kHz harmonic distortion at normal operating levels between tape and vinyl. The tape machine was vacuum tube.

https://drive.google.com/file/d/1FoPWw0pe_5L6rZk8qBSa0rLDQtDv8fOz/view?usp=sharing

 

[watchnerd]

Still it is pretty amazing the level of recording quality that was produced with these superseded analogue and tube technologies.

15 IPS can sound very very good.

Better than LP by quite a bit.

Most consumers have never heard high speed reel to reel.

 

[Julf]

Most consumers have never heard high speed reel to reel.

No, but they have heard digital...

 

[watchnerd]

No, but they have heard digital...

Well, yes.

But how does that relate?

 

[orangejello]

15 IPS can sound very very good.

Better than LP by quite a bit.

Most consumers have never heard high speed reel to reel.

I had the opportunity to hear 30 IPS copies of some of some 30 IPS masters. You are right. They are phenomenal.

 

[orangejello]

Overload in tape at higher than normal operating levels is due to tape saturation - this is separate and distinct from tube distortion. The VU meters on tape machines don't reflect the pre emphasis either in the bass or high frequencies, so it is up to the engineer to 'know' how to set levels to accommodate this. Also, VU meters were average responding devices and would be rather blind to transient peaks. If there was for instance a flute solo and during it a big bass drum hit, the flute could take on a very audible 'fluttery' quality from saturation.

Tape playback preamplifiers have, due to the reproduce EQ, up to 40dB or so of feedback from that source alone. RIAA phono EQ is similar. These EQ curves don't have to be implemented in feedback, but in tape machines that is the way it was mostly accomplished. Due to the nature of the EQ curves, the low frequencies have the least feedback, and the high frequencies the most.

IM distortion is usually not spec'd for tape machines, probably because it would look pretty ugly. Tape, by its nature suppresses even order harmonic distortion so what remains is almost totally odd order distortion (in a 'perfect' machine this would be totally the case). The typical harmonic distortion of tape at normal operating levels is about 0.6%.

Since the distortion products are mostly low-order, the ear doesn't hear the distortion as such, at least at levels below saturation. On direct comparison, tape verses digital is totally obvious but that doesn't keep tape or vinyl from sounding very, very good.

This is a graph I made awhile back which compares the 1kHz harmonic distortion at normal operating levels between tape and vinyl. The tape machine was vacuum tube.

https://drive.google.com/file/d/1FoPWw0pe_5L6rZk8qBSa0rLDQtDv8fOz/view?usp=sharing

Thanks. That what I figured. You would need to do a direct comparison between tape and digital to appreciate the difference in IM distortion. It would otherwise just be added into the harmonics and not likely to be noticed.

 

[Robin L]

So overload distortion has nothing to do with tube vs solid state electronics. It has to do with analog tape saturation? Still it is pretty amazing the level of recording quality that was produced with these superseded analogue and tube technologies.

Once again what are the sonic characteristics of low level IM distortion, and is it more likely to occur in tube electronics? It seems that feedback should reduce that to almost inaudible levels. I would have to think that decent tube recording electronics used a fair amount of feedback, unlike some consumer tube amplifiers which were designed with a specific tube sound in mind.

Not quite. I don't know all the intricate details of the tape recorders, but for whatever reason, tube microphones would overload sooner than the Solid State microphones I've used. It might be that one can find a tubed microphone with the same overload margin as a solid state design, but that is not something I've experienced first-hand.

 

[Julf]

Well, yes.

But how does that relate?

Reel to reel tape, at sufficient tape speed and with well-managed levels, gets audibly close to digital.

 

[Robin L]

15 IPS can sound very very good.

Better than LP by quite a bit.

Most consumers have never heard high speed reel to reel.

I have. Being as it was a Tascam 32, it sounded worse than my best cassette recorder. But I've heard better decks, 15ips can sound very good.

 

[watchnerd]

I have. Being as it was a Tascam 32, it sounded worse than my best cassette recorder. But I've heard better decks, 15ips can sound very good.

I was thinking more along the lines of this:

Among the 3 RTR decks I have, this is the reference standard I use to compare and calibrate the others.

 

[watchnerd]

Reel to reel tape, at sufficient tape speed and with well-managed levels, gets audibly close to digital.

Yes, exactly.

What I think can surprise people is just how close that can be.

It's not like listening to 8 track.

I've had guests say "it sounds like a CD".

 

[Robin L]

I was thinking more along the lines of this:

View attachment 100100


Among the 3 RTR decks I have, this is the reference standard I use to compare and calibrate the others.

The old KPFA building had this model scattered throughout the various rooms, some installed in the wall. They also had an Otari that I never got to use in the new building, on account of having progressed to DAT by then. The old Ampex machines had the most '50's sound I've encountered, nice and predictably "Phat":

 

[egellings]

I enjoy tubes simply because they are fun and I like the look. I in no way think that they are better than S.S. devices for use in audio applications, especially power amplifiers with their problematic OPT's. If used carefully, they can generate low distortion sound, or if a looser attitude is taken with design, they can be made to have a euphonic, if inaccurate, sound. It's in the ear and the eye of the beholder. If it's about low output impedance, then the vacuum triode beholder will have to bow to the crystal triode beholder on that one.

 

[MakeMineVinyl]

Not quite. I don't know all the intricate details of the tape recorders, but for whatever reason, tube microphones would overload sooner than the Solid State microphones I've used. It might be that one can find a tubed microphone with the same overload margin as a solid state design, but that is not something I've experienced first-hand.

The tube mic overload might have something to do with its output transformer going into saturation. Solid state microphones can have electronic balancing on their outputs, something which is difficult if not impossible to do on a practical tube mic. Likewise, solid state mixers can have electronically balanced inputs which don't have the saturation problems, especially at low frequencies, of input transformers likely used in tube mixers. The Ampex rack mount mixers used tiny Beyer 'peanut' input transformers which would have lousy overload margins.

 

[watchnerd]

The old KPFA building had this model scattered throughout the various rooms, some installed in the wall. They also had an Otari that I never got to use in the new building, on account of having progressed to DAT by then. The old Ampex machines had the most '50's sound I've encountered, nice and predictably "Phat":

View attachment 100103

Yeah, that crosses a line for domestic acceptability in our house.

 

[Robin L]

The tube mic overload might have something to do with its output transformer going into saturation. Solid state microphones can have electronic balancing on their outputs, something which is difficult if not impossible to do on a practical tube mic. Likewise, solid state mixers can have electronically balanced inputs which don't have the saturation problems, especially at low frequencies, of input transformers likely used in tube mixers. The Ampex rack mount mixers used tiny Beyer 'peanut' input transformers which would have lousy overload margins.

Makes sense. The one piece of tube gear I really liked was the Stax energizer/Amp, SRM T-1:

Stax SRM-T1 Review (kenrockwell.com)

It was a hybrid amp, also OTL. My sense when I hooked up my Marantz 8b via an energizer into my Stax Signature Pros, was I was hearing the transformer in the Marantz amp. Things were much more open and clear via the SRM T-1.

 

[orangejello]

I have. Being as it was a Tascam 32, it sounded worse than my best cassette recorder. But I've heard better decks, 15ips can sound very good.

BTW I like your avatar (if that is what it is called). Sri Yantra. Try drawing one with Euclidean geometry. Turns it you have to trisect angles (at least) to get the intersections right. Some Russian mathematician wrote a paper on it and concluded that it must have been “imagined” some 3 to 4 thousand years ago because the mathematical prowess to actually draw it was not there. I work on it for several months and wound up making approximation (cheating) before I got a huge drawing of it in India ink. It played tricks with the eyes with different patterns emerging and receding before the next pattern emerged.

 

[Robin L]

BTW I like your avatar (if that is what it is called). Sri Yantra. Try drawing one with Euclidean geometry. Turns it you have to trisect angles (at least) to get the intersections right. Some Russian mathematician wrote a paper on it and concluded that it must have been “imagined” some 3 to 4 thousand years ago because the mathematical prowess to actually draw it was not there. I work on it for several months and wound up making approximation (cheating) before I got a huge drawing of it in India ink. It played tricks with the eyes with different patterns emerging and receding before the next pattern emerged.

Thanks, took me well over a year to complete this one. I draw the intersecting triangles off a computer print-out available online. I use a brush known as a liner to apply acrylic paint, most of the hues metalized. It's all cross-hatched like an ink drawing.