[Peter Wieck]

wrote:

The manual that came with this amp is all in Chinse and it does not
seem to explain any about the tubes. My friends and I have no ideas of
the front 4 tubes which are roughly half the size of EL34.
If you google search on Yaqin MC10L, you will get some pics, but still
no info on those smaller tubes.
I wonder whether any of you experts can tell me what they are.

A guess is that they are 12AX7s or some clone thereof. That would be
the most common tube in this application, past times, and assuming that
all four are identical. But, this is a guess. They could also very well
be 6N1 tubes, as they have become popular as drivers. Given that it is
a Chinese product, I lean towards the 6N1 as that would allow a simpler
power-transformer.

You may verify this with great caution by checking the voltage at the
filament pins. If you get ~6.3V, likely that they are 6N1s. 12.6V,
likely 12AX7s.

Peter Wieck
Wyncote, PA