Nobsound NS-02E mod (with octal 6Н8С/6Н9С tube and other)
Pros: Very compact, unusual design, ability to influence the sound (two op amps plus tube), two op amps can be easily replaced without soldering iron
Cons: According to the manufacturer, it has already been removed from production
Hello, maybe it will be someone interesting. This is my experience of easy modification the Nobsound NS-02E amplifier.
When I first saw Nobsound NS-02E in 2016 I immediately liked it. The chinese goods in general very similar, but this baby is stand out on general background. I mean design.
In 2021 I bought it. Contrary to the opinion that the chinese use a tube in amplifiers as a garland, in Nobsound NS-02E this tube really works. Firstly, without tube there is no sound. Secondly, the sound appears gradually as the lamp warms - first in one channel, then in the second.
Of course, I bought Nobsound NS-02E with a view to make mod. I wanted to replace condensers and resistors, but don't know which one. Unfortunately, I don't understand in the electronics. Therefore, I went the standart way - changed the OpAmps NE5532. I tried many variants - AD826, AD827, AD8620, OP42, OPA627, OPA2134, LT1498, Mitsubishi M5216/M5218, JRC4559D, JRC4580D. Now my choice stopped at vintage M5216 (or vintage AD827 with white paint, or vintage JRC4580D).
After this I replaced the chinese 6N3 stock tube on the Soviet 6Н3П. It gave a small effect, it became a little "warmer" (softer) and denser.
Then I decided to go for radical measures - ordered adapters (made for me by my request) for experiments with various tubes, including octal.
So, I tried the Soviet 6Н1П, 6Н2П, 6Н5П, 6Н6П (analogue of 6N2) and the octal 6Н8С/6Н9С (analogue of 6SN7GT(A), B65, ECC32, 6CC10 "Tesla", 13D2, 5692, 6180, 6N9P, 6SL7, 1579).
With lamp 6Н8С/6Н9С (6N9P, 6SL7 and 1579) I get the most correct/natural, clear and smooth sound. Attached few images below.
P.S. I think, the potential of the Nobsound NS-02E can be revealed even more with a help of soldering iron, but without tips of professionals I can't do it self-resting.