I recently reviewed the Nobsound Douk 6N3 tube preamp. Owner was kind enough to also send me a pair of matched 6N3P-E matched vintage NOS Russian tubes bought from Amazon which cost US $47.50.
Let's roll them in and see if they make a difference.
6N3P-E Tube Measurements
I let the tubes warm up and was pleasantly surprised how fast they did so:
I then ran our desktop measurement:
Note that I could not perfectly match the volume as it is very sensitive in this range. And there are variability in this type of device that is unavoidable. With those disclaimers aside, mains hum was sharply reduced. To make sure this was not run to run variation, I quickly put the old tubes back in and noise floor went way up as in the original review.
On the other hand, distortion is worse in one channel with the new tubes. With the original both channels clocked at SINAD of 53 dB and we are down to 50 dB now.
In the last tube rolling test people kept asking for frequency response measurements. I explained that I did not expect the frequency response to change in the audible band. There are likely differences in capacitance and such but that affects much higher frequencies. I ran the test this time:
I have left the gain slightly different so the two curves weren't on top of each other. As you see, over the audio band there is no difference at all. Above 50 kHz, the 6N3P-E slopes down a hair faster. That is not consequential in any manner.
I also ran the IMD distortion test which also confirmed what we already know about lower noise floor but slightly higher distortion in one channel:
Conclusions
Within the vagaries of products in this class and tube designs in general, it does seem like the replacement 6N3P-E tubes provide much lower mains hum. If hum is an audible concern, then replacing tubes can get you there assuming you have measurements such as this. Without it, we don't have enough data to know if there is a reliable conclusion regarding any specific brand or type of 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 roll them in and see if they make a difference.
6N3P-E Tube Measurements
I let the tubes warm up and was pleasantly surprised how fast they did so:
I then ran our desktop measurement:
Note that I could not perfectly match the volume as it is very sensitive in this range. And there are variability in this type of device that is unavoidable. With those disclaimers aside, mains hum was sharply reduced. To make sure this was not run to run variation, I quickly put the old tubes back in and noise floor went way up as in the original review.
On the other hand, distortion is worse in one channel with the new tubes. With the original both channels clocked at SINAD of 53 dB and we are down to 50 dB now.
In the last tube rolling test people kept asking for frequency response measurements. I explained that I did not expect the frequency response to change in the audible band. There are likely differences in capacitance and such but that affects much higher frequencies. I ran the test this time:
I have left the gain slightly different so the two curves weren't on top of each other. As you see, over the audio band there is no difference at all. Above 50 kHz, the 6N3P-E slopes down a hair faster. That is not consequential in any manner.
I also ran the IMD distortion test which also confirmed what we already know about lower noise floor but slightly higher distortion in one channel:
Conclusions
Within the vagaries of products in this class and tube designs in general, it does seem like the replacement 6N3P-E tubes provide much lower mains hum. If hum is an audible concern, then replacing tubes can get you there assuming you have measurements such as this. Without it, we don't have enough data to know if there is a reliable conclusion regarding any specific brand or type of 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/