Music Angel 300B - "The 300 Bucks amp"
It is a beauty, isn't it?
I mean - 300B tube is a legend. It has probably 10 times more cult status than it deserves.
But someone who was influential - 70 years ago said that 300B is THE TUBE - and the world took this as an 11th commandment.
The amps with 300B which I heard before were all very weak in power,
but paired with "proper" speakers - were all very very good. The sound
is nothing short of magical.
But I almost forgot to mention - they were all VERY expenceive. In the
5000 Euro range. Except the AudioNote 300B KIT which must be one of the
best deals in all highend industry.
So how about our cute little Chinese "Miss Shenzen" ???
Can we peek behind the pretty dress?
Out of the box this amplifier played typical Music Angel sound. Booom
Booom Biiig Bass and muddy everything else. (I think that the boomy
bass in all Angels is a result of cathode bypass capacitor. Removing
cathode capacitors ALWAYS cleans the sound a lot!)
The sound in fact perfectly matches the price tag - 300 bucks. Yes. This is a 300 B from 300 Bucks Sound.
Can we make it sound as GOOD AS IT LOOKS?
At least I tried.
First - I did not like the small septal double triode (3A5) in the
input stage. I know nothing about it, it is rare, it has no easy
replacement, is is very microphonic etc.
Out with it.
I installed a proper noval socket to be able to change different tubes freely.
My sweet 6H6P was too quiet here. I needed more amplification, so i
decided for 6H1P in triode mode - one half is an input stage for every
So far so good.
But the driver tube is wrongly chosen too - the very high amplification
factor plus small current are not optimal here. We need high current.
So I exchanged the 6H9P with 6H8C (In "Chinese language" this is 6N8 replacing 6N9)
This tube is exatc equivalent - 1:1 with 6SN7GT (most popular tube in
the world) and also with my little baby - 6H1P (except it is noval not
After applying the SRPP circuit (lampizator) to the tube - I got just what I needed.
It took me 3 full evenings to find optimal operating points - mostly by trial and error.
First - I drop the power supply voltage from 420 V DC to a more suitable 250 V.
Then I adjust the anode current to be not too big, a conservative 2 mA.
Lastly, I had to rectify the heater circuits. The AC heaters of driver
tubes is humming. Some other variants of this amp have DC heaters (like
on my photos above - from e-shop internet). Also the schematics which is available on the net - ther heaters are DC. But my sample had only the input tube with DC heaters.
Last thing to do would be to at LEAST double all electrolytes in size
and bypass them with a small MKP or better small PIO cap (observing
minimum voltage ratings to be 600 V DC for all applications except 1000
V DC in 300B anode supply).
The caps in this amp are VERY VERY SMALL.
Of course - it goes without saying - that the coupling caps (2 per
channel) must be replaced too, with a 1uF PIO or something like that.
IN THE END - the amp starts resembling areal 300B. It has a midrange
slightly more charming than 845, very very clean and spacy trebles, and
the bass - not too muscular, but rich in colors and vibrations. Nothing
like the stock unit. The difference is really night-day.
If I was doing it again, I would install in the center the octal base
and all 3 tubes would be 6SN7GT from NOS variety (same schematics is
valid as below) - the best there are - "black glass" JAN NOS, maybe
from Kenrad. It is worth
investing 100-200 USD in these three tubes, while I would seriously
hesitate before spending $$$ for the NOS 300B or JJ or any other
exotica. But you may if you wish. In such case - the cheap small
chinese output transformer will be the most serious bottleneck of this
But wait a minute - these transformers can be raplaced too ....;-)
Angel 300B factory circuit (it does not reflect reality !!!)