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Do you like tube distortion? - listening test
Do you like tube distortion? - listening test
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View Poll Results: Which of the files you prefer by listening?
I prefer ella1 but I do not have an ABX result 7 53.85%
I prefer ella2 but I do not have an ABX result 5 38.46%
I prefer ella1 and I do have an ABX result 1 7.69%
I prefer ella2 and I do have an ABX result 0 0%
Voters: 13. You may not vote on this poll

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Old 1st November 2018, 06:47 PM   #1
PMA is offline PMA  Europe
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Default Do you like tube distortion? - listening test

Another of my series of listening tests. This time, we have 2 files, and it is a comparison of a "wire sound" and a "tube sound". One of the files is recorded just through the link cable and the second one is recorded through the tube preamp with distortion spectrum shown in the attachment. The distortion is almost independent on frequency, but depends on level.

The test files are at

http://pmacura.cz/ella.zip

Please vote in the poll which of the files sound you prefer and please also leave some comment here.
It would be nice if you could post a foobar ABX protocol or screenshot to verify you were able to verify the sound difference.

Thank you and have fun!
--------------------------------------

The poll expires today, so here is a bonus, same test setup and same music but another take, now in 24-bit resolution saved as 32-bit PCM floating point wav

http://pmacura.cz/trees.zip

Please do not mix these new files in a test with original ones, they have different volume level.
---------------------------------------------
Nov 15, 8:05 pm

The poll has just expired. As you could read in another thread, the files were:
- ella1 recorded through a tube preamplifier
- ella2 recorded through a link cable
The soundcard was playing a mono file. Left channel of the DAC was connected to the tube preamp input, tube preamp output was connected to left channel ADC input. Right channel of the DAC was connected directly to the right channel ADC input.

A stereo file was recorded, simultaneously tube channel and wire channel. A stereo file was then split into two mono files. Levels were equalized within 0.1dB order. Two mono files were posted as test files.
===================================
November 16
I was asked, by my colleagues at our local forum, to prepare a new test with more contemporary recording that would in 24-bit resolution. So I took their recommendation and prepared the same test chain with new files, that may be downloaded from

Dropbox - skot.zip

This time, I am not indicating which file is which, it is up to you, dear listeners. And tell me which one you prefer and please attach an ABX protocol, in case you have any.
Attached Images
File Type: png spectrum3.png (54.0 KB, 885 views)

Last edited by PMA; 16th November 2018 at 11:58 AM.
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Old 5th November 2018, 12:35 PM   #2
traderbam is offline traderbam  Europe
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Hi PMA,
I don't know whether this is a useful result? I could not tell the difference between the wav files using foobar ABX and I do not have a preference. But I did compare them with what I think is the same recording on TIDAL and the latter is easy to identify and sounds better to me. By better I mean less brittle, more natural voice, more space between instruments. On the other hand, I didn't ABX with TIDAL so I may be delusional. Or the recording may be different. Or the software processing between foobar and TIDAL may be different.
I am curious how you are digitizing the tracks...how good is your recording process?
Also, I imagine the track was originally recording using valves; would this affect the comparison?
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File Type: png Ella Tidal.PNG (246.4 KB, 585 views)
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Old 5th November 2018, 01:16 PM   #3
gabdx is offline gabdx  Canada
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.5% 2n harmonics can be hard to detect especially if the original sound has lot of 2n content already, might be impossible.

However I am starting to have a totally different interpretation.

I can clearly hear differences when AB components between 0 feedback, moderate and high feedback, I can hear differences in 5 ,10, 50 and 100 watt tube amps.

However this whole power rating is not the explanation I think.

I put the scope yesterday on very low sensitivity speakers and they played quite loud with a vinyl. 6 ohm impedance at worst with at maximum Peak to peak 6 Volt is maybe 1 watt at a given time.

I know that waves are summed at different frequencies.

SO the next test is to place a resistor in water bucket with isolation at a temperature and measure T elevation vs time to calculate the real power dissipated by the amplifier into a load.

I will use a 8 ohm load
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Old 5th November 2018, 01:36 PM   #4
scott wurcer is online now scott wurcer  United States
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Quote:
Originally Posted by gabdx View Post

SO the next test is to place a resistor in water bucket with isolation at a temperature and measure T elevation vs time to calculate the real power dissipated by the amplifier into a load.

I will use a 8 ohm load
This experiment has many error sources, calorimetry is very difficult to do accurately. If you have a purely resistive load computed true rms voltage would be easier.
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Old 5th November 2018, 02:45 PM   #5
gabdx is offline gabdx  Canada
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Hi Scott I did the experiment and blast the power into a 6ohm into a bucket of 1kg of water, after 4 minutes not even 1 Celcius of change which confirm the low power of audio.

I think the rise and fall time and how the amplifier can control that is the main factor. This could explain the 'distortion' we hear in lower power amps.

At the same time low level signal loss would explain why also simpler amps with less feedback as well as low loss output transformers are praised.

I would never do a 50watt single wave test such as I do for THD purpose with a speaker connected by fear of damaging the drivers.
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Old 6th November 2018, 02:43 PM   #6
DF96 is offline DF96  England
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Quote:
Originally Posted by gabdx
I can clearly hear differences when AB components between 0 feedback, moderate and high feedback, I can hear differences in 5 ,10, 50 and 100 watt tube amps.
Given that varying feedback varies frequency response and our ears are quite sensitive to frequency response variations it is hardly surprising that you can hear differences as feedback is varied. To hear the difference between amplifier A with feedback and amplifier B without feedback is similarly unsurprising. I am not clear exactly what you are saying.

Quote:
SO the next test is to place a resistor in water bucket with isolation at a temperature and measure T elevation vs time to calculate the real power dissipated by the amplifier into a load.
The next test of what? What was the first test?

Quote:
I think the rise and fall time and how the amplifier can control that is the main factor. This could explain the 'distortion' we hear in lower power amps.
??

Quote:
At the same time low level signal loss would explain why also simpler amps with less feedback as well as low loss output transformers are praised.
Low feedback amps are praised because some people like a little distortion and lumpy frequency response. Put those things right with well-designed feedback and those people complain of 'clinical boring' sound i.e. sound which faithfully reproduces the input signal.

PS what has this to do with this thread?
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Old 6th November 2018, 02:51 PM   #7
gabdx is offline gabdx  Canada
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This has to do that adding 2nd harmonics to a song doesn't represent tube sound.

I also think that you need a sound sample which has low 2nd harmonics in the first place and an audio system which has less 2nd harmonics than is added to one sample.
-------------------
Low feedback amps are praised because some people like a little distortion and lumpy frequency response. Put those things right with well-designed feedback and those people complain of 'clinical boring' sound i.e. sound which faithfully reproduces the input signal.

I don't think this argument holds anymore, the average listening level is at 0.5 Watt at maximum, at which any decent output transformer will have a broad frequency response and low THD. At 0.5 Watt maximum there should be no differences between a 300B (8 watts) and a 100Watt solid state.

To me it is the rise and fall time which you hear, what they call slew rate or something.
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Last edited by gabdx; 6th November 2018 at 02:57 PM.
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Old 6th November 2018, 03:03 PM   #8
scott wurcer is online now scott wurcer  United States
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Quote:
Originally Posted by gabdx View Post
To me it is the rise and fall time which you hear, what they call slew rate or something.
But now you describe small signal conditions where rise time is solely determined by bandwidth.
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Old 6th November 2018, 03:10 PM   #9
gabdx is offline gabdx  Canada
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I know it makes no sense
In the condition that both amplifiers have the same bandwidth at the relevant listening power, how could the determined maximum power bandwidth affect the perceived resolution and tone, everything being almost equal?

We already know that amplifiers which are un-able to play square waves can excel with music and vice-versa.

I think the answer will be with analyzing arbitrary wave forms with speakers connected to the output, but this test will be arbitrary...
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Old 6th November 2018, 06:16 PM   #10
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Nothing can "play" a perfect square wave as this would take infinite BW. What's your point?
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