I recently reviewed the Mhdt Pagoda tube DAC. Owner was kind enough to send me three other tubes to test with it. Here are the set of tubes I received:
Let's start again with the tube supplied with the unit (GE 5670)
Now let's switch to Tesla 6CC42 (GA):
Other than slightly more mains hum at 60 Hz, I see no other difference. Gain is reduced negligible amount.
Next up is the Western Electric JW2C51:
Distortion is 0.7 dB lower. So nothing significant there.
Finally I tested the Western Electric 396A tube which produced a surprising result:
Channel 1 is the same but channel 2 has 6 dB lower distortion. Is half the tube better or is there some asymmetry in the design?
That's all I have for you.
Conclusions
It is clear that by far the source of distortion is the design and not choice of tube. In three cases the difference is negligible and inaudible. In the forth example, the WE 396A, there is reduction of distortion in one channel. In the larger picture, there is so much distortion here that reducing it with this tube is not going to make a difference one way or the other.
Notice the level of instrumentation it takes to see the impact of the tube. You need to measure to see if there is a difference and not just assume there is.
Personally even if I signed up for a tube product, I would not waste time "rolling tubes." You are likely to suffer more from "rolling placebo" by your brain than any variation in such tubes.
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As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Let's start again with the tube supplied with the unit (GE 5670)
Now let's switch to Tesla 6CC42 (GA):
Other than slightly more mains hum at 60 Hz, I see no other difference. Gain is reduced negligible amount.
Next up is the Western Electric JW2C51:
Distortion is 0.7 dB lower. So nothing significant there.
Finally I tested the Western Electric 396A tube which produced a surprising result:
Channel 1 is the same but channel 2 has 6 dB lower distortion. Is half the tube better or is there some asymmetry in the design?
That's all I have for you.
Conclusions
It is clear that by far the source of distortion is the design and not choice of tube. In three cases the difference is negligible and inaudible. In the forth example, the WE 396A, there is reduction of distortion in one channel. In the larger picture, there is so much distortion here that reducing it with this tube is not going to make a difference one way or the other.
Notice the level of instrumentation it takes to see the impact of the tube. You need to measure to see if there is a difference and not just assume there is.
Personally even if I signed up for a tube product, I would not waste time "rolling tubes." You are likely to suffer more from "rolling placebo" by your brain than any variation in such tubes.
----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/