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Best 7025/12AX7 mic tube?
Old 4 weeks ago
  #31
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Quote:
Originally Posted by Radardoug View Post
OK, how can I take you up on that 100% guarantee? Thats a very bold statement. I've been around sound for 50 years, and done electronics all that time as well. I like the way the golden ear brigade insist that measurements dont quantify audio accurately, and so they dont bother to measure anything.

So what specific metrics as applied to an audio system can we not measure accurately enough?

The defining characteristics of an audio system are:
1/ Frequency response
2/ Noise
3/ Distortion

Which of these metrics can we not measure accurately enough?
Or have I missed one?
Sure those are three qualities which you have tools to measure. It’s not that the “ear test” isn’t measurable, I just don’t think you (we) have the tools that are capable. Example. We have telescopes, yet we can’t detect dark matter. Doesn’t mean it isn’t real or that it’s immeasurable, we just don’t have the equipment or knowledge to measure it directly.

Perhaps the tools were never developed a cause back in the day having a human do a listening test was commonplace? I don’t think much has changed. I’ll repeat, just because you cannot measure the differences does not mean the differences aren’t there.

Honestly Doug, to me this is like saying the sky isn’t blue. You can tell me all day, tell me that You can’t measure it or whatever, and tell all us “golden ears” that tubes from different manufacturers, brands, eras, even batches don’t sound different from one another, but everyone else knows the sky is still blue even if you can’t see it and don’t have the ability to measure it with your three electric properties.

What about tambre? That is an audible quality that I would be curious how your testing equipment would measure.

Imagine guitars. You are implying that if you can’t measure a difference in the output of two instruments then they must sound the same. Any one who had played guitars for a bit knows some guitars sound better than others. A 60s vintage strat sounds different than a modern reissue. Same (Relatively) materials, design, manufacturer, etc. I’m pretty sure the output would not be too different on measuring equipment (at least on my dmm). Yet they sound clearly different. To me. To a lot of people I know.

Point of all this is that the human ear is very sensitive. More sensitive to a lot of differences that test equipment doesn’t show. Perhaps it’s how we read the test equipment? Perhaps there is a lack of sensitivity. Test equipment tells us a lot of things we can’t hear, but doesn’t do a good job at telling us what “sounds good” to our human ears.
Old 4 weeks ago
  #32
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Radardoug's Avatar
 

Of course guitars sound different. There are a multitude of differences between guitars. And you would be able to observe that in the waveform from them. You talk about tambre. Thats timbre by the way. Part of that will be the different overtones produced by the strings. Yes, new strings sound different from old strings. All measurable. But the point is the ECC83 or any tube is manufactured to a specification, that specifies the range of a number of important tube parameters. If two tubes have those same parameters within a reasonable margin, then they will sound the same.
I have asked you to quantify the differences that would make a major difference to the sound of a tube. If the gain was vastly different it would sound different, but it would not be within specification for that tube. So that would sound different. But if you have two ECC83s with gain within 5%, and other parameters similar, they will sound the same. However I guess I'm never going to win an argument with someone who thinks his hearing is an absolute precision standard that does not vary from day to day, and is not affected by body chemistry and drugs. I wish my hearing was that good! It isn't, I accept my failings.
Old 4 weeks ago
  #33
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Doug I think you are deliberately missing the point I am making in order to dismiss the whole thing. You (our) measurement tools are limited in the characteristics they measure, and perhaps (!) there is more going on inside a tube or audio in general that is not measured by frequency response, noise, and distortion.

You act like every tube has the same physics structure and exact same materials. This is what I was trying to highlight using the guitars. Two Very different 12ax7s in the same circuit sound different, just like two guitars in the hands of the same musician with the same signal chain etc sound different (I’m assuming controls like strings cable length, I won’t even get into cable material, there is snake oil out there, are the same etc). Like one tube made in the 60s and another from a current production.

The question is not if they sound different, but why and if you need to quantify it beyond this one sounds better to the listeners ear, how can it be measured? If you ever team up with someone who can hear the which tube sounds better, why not investigate it scientifically?
Old 4 weeks ago
  #34
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chipss36's Avatar
 

Show me a pre amp tube that has matched gain half’s, is not microphonic, and is that way consistently...Lol

They are all different, they measure different.
Many were manufactured differently...

Say a gz34 of Millard or a new what ever gz34...
longevity plays a roll, due to different construction
And quality of construction ..Even if they measure the same , yet usually do not! Especially over time.



Only consistency in a vacuum tube is that they are inconsistent...
Same with transistors, a curve tracer shows this clearly.
And One reason negative feedback is used.

The hypothetical of the same gain in a tube, consistently is just not happening...
This all reminds me of a lecture Rupert neve gave..
About how much in audio we don’t know...
And that some things considered absolutely, could in fact be wrong.

Last edited by chipss36; 4 weeks ago at 08:07 PM..
Old 4 weeks ago
  #35
Gear Addict
 

Quote:
Originally Posted by Radardoug View Post
OK, how can I take you up on that 100% guarantee? Thats a very bold statement. I've been around sound for 50 years, and done electronics all that time as well. I like the way the golden ear brigade insist that measurements dont quantify audio accurately, and so they dont bother to measure anything.

So what specific metrics as applied to an audio system can we not measure accurately enough?

The defining characteristics of an audio system are:
1/ Frequency response
2/ Noise
3/ Distortion

Which of these metrics can we not measure accurately enough?
Or have I missed one?
no,you are not right...
many mics have the same freq,response,noise ...but the sound is so different!every mic has its sound and they are so many with alsmost similar responses.the difference is sound is huge.transients play a great role.the way that transients are handled in similar systems ,change a lot.
Old 4 weeks ago
  #36
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Radardoug's Avatar
 

no,you are not right...
many mics have the same freq,response,noise ...but the sound is so different!every mic has its sound and they are so many with alsmost similar responses.the difference is sound is huge.transients play a great role.the way that transients are handled in similar systems ,change a lot.

I've never seen two mikes that have the same frequency response, let alone noise and distortion. So they will be different. Measurable.
Old 4 weeks ago
  #37
Gear Addict
 

Quote:
Originally Posted by Radardoug View Post
no,you are not right...
many mics have the same freq,response,noise ...but the sound is so different!every mic has its sound and they are so many with alsmost similar responses.the difference is sound is huge.transients play a great role.the way that transients are handled in similar systems ,change a lot.

I've never seen two mikes that have the same frequency response, let alone noise and distortion. So they will be different. Measurable.
Many mics have similart response.They are so close.maybe in some frequencies the differencies are =/- 1 db.The final sound difference is much more different.howe can you explain this?
for example ,some mics with ''bright '' freq response sound smooth and open.Other mics with very similar response sound bad,harsh,with resonanses etc....
the test/measurements are taken under very specific parameters and situations...only under very specific distance ,freq,power pressure etc some mics have the response that they were measured.
Old 4 weeks ago
  #38
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Radardoug's Avatar
 

I think you will find the curves you are looking at are smoothed by the manufacturer. Try doing some measurements yourself. +/- 1 dB is extremely unlikely.
Old 4 weeks ago
  #39
"Compute Smooth" is a function on the Audio Precison analyzer. It can make a picket fence look like a smooth frown.
Old 4 weeks ago
  #40
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lame pseudonym's Avatar
 

You experts don't need to hear anything from a spud like me, but when I was selecting a 12ax7 for my phono preamp there were tubes that I liked and there were tubes that I didn't like, and I could write down why.

I don't listen for more treble or less treble or more bass or less bass. That's not what I'm after.

If it's all just a dream, really, that's okay with me. It works.
Old 4 weeks ago
  #41
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ruffrecords's Avatar
Quote:
Originally Posted by Jim Williams View Post
A 16 bit system will not offer the analog resolution of the Audio Precision. FFT's are usually used to detect distortion products. The AP's noise vs amplitude test does an excellent job. Load the noise vs frequency sweeps and then you can see exactly where the noise resides. That is paramount for removing it as you need to understand the noise spectrum as well as the amount.
I think you need to read up on FFTs Jim

Cheers

Ian
Old 4 weeks ago
  #42
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Doug I think I’m starting to understand what you are saying. If I understand you correctly, you are saying that you feel the difference people hear in different tubes are caused by the wide variance between tube performance? Not construction materials and design? That if you had two tubes with the same gain from different eras and manufacturers, they would sound identical as they would measure identically, if tested in the same circuit?
I’m not sure if I agree but I think I am starting to see the nuance of your position.
Old 4 weeks ago
  #43
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ruffrecords's Avatar
Quote:
Originally Posted by lame pseudonym View Post
You experts don't need to hear anything from a spud like me, but when I was selecting a 12ax7 for my phono preamp there were tubes that I liked and there were tubes that I didn't like, and I could write down why.
This is perfectly reasonable. There are plenty of tube designs around that are sensitive to the particular characteristics of the tube used and many of these circuits are phono preamps. The reason you can hear a difference is the designs are poor. A well designed phono amp will sound good/the same no matter which brand of tube is used although some will most likely be noisier than others.

Cheers

Ian
Old 4 weeks ago
  #44
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Radardoug's Avatar
 

Quote:
Originally Posted by enginefire View Post
Doug I think I’m starting to understand what you are saying. If I understand you correctly, you are saying that you feel the difference people hear in different tubes are caused by the wide variance between tube performance? Not construction materials and design? That if you had two tubes with the same gain from different eras and manufacturers, they would sound identical as they would measure identically, if tested in the same circuit?
I’m not sure if I agree but I think I am starting to see the nuance of your position.
Correct. For a given tube from a given manufacturer, you would expect the tubes to be very similar. For a given tube type from two different manufacturers, still similar but with maybe greater tolerance. Using the number 12AX7 or whatever means those tubes are made to the specification for that tube type.
Putting a 12AU7 where a 12AX7 was will be wildly different.
Old 4 weeks ago
  #45
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Quote:
Originally Posted by Radardoug View Post
Correct. For a given tube from a given manufacturer, you would expect the tubes to be very similar. For a given tube type from two different manufacturers, still similar but with maybe greater tolerance. Using the number 12AX7 or whatever means those tubes are made to the specification for that tube type.
Putting a 12AU7 where a 12AX7 was will be wildly different.
Yes this is clear, changing tube types will greatly affect the performance of the circuit. However, I was referring to the differences heard between two tubes of the same designation, say 12at7, in a circuit that calls for that tube. Eliminate variables such as one can make with a tube tester (tests good, “matched” for gain). All that remains as obvious differences is that they are from different manufacturers and time periods.

I have tried this, same piece of equipment, only changing the tubes, recording sounds from tube A and then tube B (Even tube C and D sometimes) and have found that the differences in sound has been from subtle to huge. I would even wait a few days and then listen again. Have friends come over and rate each selection, describe characteristics etc, to be sure it wasn’t just me.

How do you account for this? More importantly, how can this difference be quantified using test equipment?
Old 4 weeks ago
  #46
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Radardoug's Avatar
 

Well you dont quantify the differences you are hearing. Is it duller? Brighter? That would be frequency response. Warmer? Maybe distortion. Did you have a beer with your friends when they came over? That would be alcohol distortion hehe.
Old 4 weeks ago
  #47
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None of that here when it’s science time. I put the engine in engineer!

I would describe a better tube sound as “more musical” ... not very helpful.

“Less brittle” any better?

Smoother upper mids
Warmer bass
More transparency in the highs
Clearer, more like real life.
Old 4 weeks ago
  #48
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Radardoug's Avatar
 

I presume you do realise that a difference of 2 dB in gain will make things sound different to most listeners? Thats why double blind testing is so necessary, to eliminate expectation bias and other biases.
Old 4 weeks ago
  #49
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lame pseudonym's Avatar
 

Quote:
Originally Posted by ruffrecords View Post
The reason you can hear a difference is the designs are poor. A well designed phono amp will sound good/the same no matter which brand of tube is used although some will most likely be noisier than others.

Cheers

Ian

A reasonable person might suggest that it is the transparent circuit that reveals the differences in tubes and the crummy one that obscures them.
Old 4 weeks ago
  #50
Quote:
Originally Posted by ruffrecords View Post
I think you need to read up on FFTs Jim

Cheers

Ian
You may want to read the Audio Precision user manual.
Old 3 weeks ago
  #51
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ruffrecords's Avatar
Quote:
Originally Posted by Jim Williams View Post
You may want to read the Audio Precision user manual.
I have done better than that - I have spoken to someone who worked there. He confirmed they use typical top of the range 24 bit converters. Once you are in the digital domain AP can do nothing that someone else cannot do in software. The only place they can be better is in the analogue front end that feeds the converter. I checked the specs of the best 24 bit converter AP uses and it can achieve a S/N of 120dB. The specs for the 24 bit Focus rite 2i2 I use with REW show it achieves a S/N of 110dB.

This means in a 1 root Hz bandwidth the AP can 'see' down to -163dBu and the 2i2 can see down to -153dBu. I can live with that and I certainly would not pay ten grand for the extra 10dB.

Cheers

Ian
Old 3 weeks ago
  #52
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ruffrecords's Avatar
Quote:
Originally Posted by lame pseudonym View Post
A reasonable person might suggest that it is the transparent circuit that reveals the differences in tubes and the crummy one that obscures them.
That makes no sense. What do you mean by "the transparent circuit"? Is this the passive parts surrounding the tube or does it include the tube itself?

What counts is the topology.

Cheers

Ian
Old 3 weeks ago
  #53
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audiospecific's Avatar
 

I have to agree with Ruff, but it's not absolutely that either. Because it follows a ranking order when it comes to design and building. 1. Topology 2. Layout 3. Passive parts choices (resistors, caps, and wire). There isn't really a transparent circuit, and what you described is a circuit is one that has greater miller capacitance sensitivity, or to say that a different way, a circuit that it's performance depended on the Miller capacitance of the tube selected
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