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

[MattHooper]

Hard to imagine if your amps are and speakers are working properly. I have old tube amps (MC-30 for instance), and I don't perceive any difference as they warm up. I don't have any gear that changes sound like you describe.

Regarding the mic. If you have a computer and $30 spare dollars, you could get a Dayton mic and answer your question. $100 for a UMIK-1. The $30 Dayton would answer this question in 20 mins... No way any of us can answer though, unless we came over to your place with a mic! And, if you suspect your amp is misbehaving (it is after all 20 years old, and it's tube, etc...), you could set up the mic to a laptop, open up REW, do a sweep, crank tunes for 20 mins, do another sweep, compare. You would learn so much about your system. You would also get huge support from the ASR community, as well as the usual odd comments from people like me! And you would answer this question, and move on to better things. I actually don't enjoy measuring, it is tedious. I am motivated by the result. My enjoyment or not of the measurement totally beside the point. I say because this is ASR and you do post lots of questions that beg a simple measurement. And, we never quite get to a solution. You could just get your answer with a cheap mic.

It could be worn out tweeters. I don't know how old your speakers are, but old ferro-fluid tweeters can age (for instance). I don't think this is your case, but I did wear out a pair of the same Seas Excel tweeters you have in your Joseph Audio, but with a lower crossover than they use... A mic would tell you if the tweeters were (for instance) heating up, or you had a crossover component degraded, etc.

I think it's likely perception. Especially if you tend to adjust volume as you listen. If I make a significant volume adjustment, I perceive for a bit of time a new tonal balance which I believe is Fletcher-Munson combined with our mutable perception of hearing. It could be tinnitus.

This is the era of easily available measurement. And you are a member of one of the only measurement-based communities on the web. We also talk about hearing and perception all the time here so you probably already know we can't provide much help with a problem where perception and sound reproduction intersect. You have some interesting classic gear that naturally seems to cause you to question, and has even given you some odd results.

Thanks very much for your detailed response!

You have a good point about the measuring. I'll re-visit this info if I feel that there's something sounding not right or impinging on my enjoying the system. Then perhaps it will be best to trace it down with measurements. Over the years any issues have been very rare, and when something has popped up I drop the amps down to a local electronics place who restore and fix old gear. If there's an issue they fix it. (But I think the only things have been a fuse going, a tube dying...)

 

[SIY]

Engineered by who? Yeah, it's possible to design around the problems in classic tube amps like the Stereo 70, but why bother?

Whoever designed the ST-70 (since you mentioned it, less than 0.5dB down at 20kHz, 0.1 db at 20Hz), the Eico HF-86 and HF-87, Citation, Marantz, Williamson, Mullard, RCA... not to mention contemporary engineers.

 

[Doodski]

Whoever designed the ST-70 (since you mentioned it, less than 0.5dB down at 20kHz, 0.1 db at 20Hz), the Eico HF-86 and HF-87, Citation, Marantz, Williamson, Mullard, RCA... not to mention contemporary engineers.

This looks like a bargain for those kind of tube amp specs. The amp looks veryyy nice too.

Dynakit (Dynaco) Audiophile Series ST-70 Tube Amplifier

Dynaco ST-70 Dynaco ST-35 Dynakit Stereo 70 Dynakit Stereo 35 Dynaco PAS PAS2 PAS 3X Tube Amplifiers Preamplifiers Vintage Classic Modern Components Updated Features New Used Rebuilt Serviced. For Sale Shop and Buy Online Home Delivery. Audiophile Sound and Top Performance. Best Deal on a Tube...

getdynaco.com

 

[Ron Texas]

Whoever designed the ST-70 (since you mentioned it, less than 0.5dB down at 20kHz, 0.1 db at 20Hz), the Eico HF-86 and HF-87, Citation, Marantz, Williamson, Mullard, RCA... not to mention contemporary engineers.

I don't know where you are getting these measurements, but the bass from the two ST-70's I owned was nothing like that. That might be for a new and recently adjusted unit, but not reality in my non expert lifetime.

Besides, why spend a bunch of money on engineering a tube amp for low distortion when solid state is available for a lower cost, no tube replacements, heat or electric bills.

Mr. expert, please stop leading me off the trail over some detail or other you can contest when the point is about something else. To go back to the point, it's possible to engineer tube amps all kinds of ways, but why bother if the result sounds like a solid state amp which costs a lot less?

 

[SIY]

I don't know where you are getting these measurements

Amir measured it and posted it here.

As for the "why," I answered that in detail early in this thread.

 

[Ron Texas]

Amir measured it and posted it here.

As for the "why," I answered that in detail early in this thread.

This thread is 79 pages long making it unreasonable to refer to an earlier post without quoting it. I continue to see no reason to make a tube amp sound like solid state. It makes as much sense as trying to photoshop a film image to look like it came out of a digital camera.

 

[Doodski]

no reason to make a tube amp sound like solid state.

I think if it can be done then let it be done. Flat frequency response, low impedance drive, low output impedance etc all are handy to have even in a tube amp. Frankly I didn't know it could be done until @SIY advised it can be done and gave a model for reference.

 

[pseudoid]

I continue to see no reason to make a tube amp sound like solid state.

Wait one second, please.
Wasn't that a Bob Carver challenge, once upon an era?

This thread is 79 pages long making it unreasonable to refer to an earlier post without quoting it.

I agree with you about 79 pages... but has the answer - to the initial question of @watchnerd - been agreed upon yet?
If so; could someone brief me.
I have 'need-to-know' qualifications; as I co-habitated with a McIntosh MC275 for a few decades.

 

[Ron Texas]

I agree with you about 79 pages... but has the answer - to the initial question of @watchnerd - been agreed upon yet?
If so; could someone brief me.
I have 'need-to-know' qualifications; as I co-habitated with a McIntosh MC275 for a few decades.

If the thread is 79 pages and the question was answered why does this keep going on?

 

[Angsty]

Interesting measurements from a "highly engineered" tube amp. That price is pretty well-engineered, too.

Audio Research Reference 160S power amplifier Measurements

Sidebar 3: Measurements

www.stereophile.com

 

[pseudoid]

I was really looking for an answer to my first question.
Yet, you chose to answer the latter question... but with another question.

Wasn't that a Bob Carver challenge, once upon an era?

"The Carver/Stereophile Magazine Challenge".

 

[GXAlan]

There is a tube sound. Frequency response is rolled off at the extremes of the audio range and there is a lot of 2nd order harmonic distortion.

Not from actual speaker measurements (even though the roll off occurs with resistors) — at least with my 300B SET.

Resistors vs. Speakers
Ignore the SPL numbers in the legend for all of these. You just want to look at the "shape of the curve". I took these REW sweeps at different dbFS.

In a resistor, you don't see any surprises with different volume content. Lower volumes reveal the 60 Hz AC mains noise.

Now look at the JBL XPL90 which has been measured here and look at the different results depending on the dBFS sweep.

 

[Ron Texas]

Not from actual speaker measurements (even though the roll off occurs with resistors) — at least with my 300B SET.

Resistors vs. Speakers
Ignore the SPL numbers in the legend for all of these. You just want to look at the "shape of the curve". I took these REW sweeps at different dbFS.

In a resistor, you don't see any surprises with different volume content. Lower volumes reveal the 60 Hz AC mains noise.

Now look at the JBL XPL90 which has been measured here and look at the different results depending on the dBFS sweep.

However, frequency response is not the same thing as the prized 2nd order harmonic distortion that tube amps have. Look, whatever I say here means nothing if you are enjoying music on your tube gear. It can get pretty crazy.

 

[roog]

The industry couldn't wait to get rig of valves. High cost, heavy assemblies, fragile, they got hot, used loads of power, they wore out and the 'transistor' had the marketing edge. I sense the guitar amp industry despite also jumping on the 'transistor' band wagon were perhaps the first to realise a down side, but I suspect that was largely because they were genuinely exploiting the characteristics of the valve technology when used incorrectly!

The HiFi industry is always looking for an angle, and right now nostalgia sells.

 

[computer-audiophile]

... The amp looks veryyy nice too.

A small aside: you and I often agree, it seems to me, but not in this case. The Dynaco amplifier is a classic, I also had one, but even in this dressed up form as in the picture I do not find it beautiful, because the circuit board sticks out of the top of the chassis. In general, I also find a proper hand wiring better, as with the old LEAK amplifiers.

 

[roog]

One things for sure, they had to work hard for just a few Watts back in the day. If they could have seen us using modern IC amps it would have looked impossible, like cheating or witchcraft!

 

[computer-audiophile]

Like a nice warm fireplace crackling away. Same shade of orange to the coals.

The color spectrum of fire, what man has long loved. Blue LEDs virtually represent the opposite, the coolness of the modern.

 

[roog]

Blue LEDs might have been the 'big break through', but when used alone they can be piercingly bright, I have a guitar pedal which uses blue LEDs that are just too distracting, I am sorely tempted to swap them for amber, green or red, in fact anything but blue.

Sorry, I've been meaning to get that off my chest for sometime!

 

[fpitas]

Blue LEDs might have been the 'big break through', but when used alone they can be piercingly bright, I have a guitar pedal with blue LEDs that are just too distracting, I am sorely tempted to swap them for amber, green or red, in fact anything but blue.

Sorry, I've been meaning to get that off my chest for sometime!

Engineers always drive LEDs too bright. When no one is looking here at work I increase the dropping resistors so the light is more reasonable.

 

[computer-audiophile]

I find it particularly distasteful when the glass bulbs of electron tubes are illuminated from below with LEDs. No matter what color. McIntosh, for example, makes such a kitschy light show.