According to pictures of the inside (easily found by a search with Google), the ms-10d mkii is a hybrid amplifier. The power stage is a chip amp (LM1875) and the voltage amplification is done by an operational amplifier (4558). Tubes should be on the signal path between the 4558 and the LM1875. Filaments are feed by one of the 16V secondary windings of the power transformer, with a silicon diode in series to chop half of the wave. According to the pictures the filaments are very bright, because the filament voltage is not 6.3v as required. If this behaviour is true on your specimen, don't use expensive tubes because they may have a short life.
On the MS-10D MKII the tubes seems to be in the audio path, but I've been unable to find a schematic. It is basically a standard low-cost chip amp plus a low voltage tube buffer combined togheter, with a price markup due to the cool retro-look. Definitely not a true tube amplifier and not something I would buy, but according to the reviewers it does the primary function of driving a speaker in a pleasent way (like most chip amps). Some pictures shows a bipolar transistor output board instead of a chip amp board. Because is not a classic tube circuit and the schematic is not known, it is unclear if the sound will change by changing the tubes. By the way, with the same amount of money, it is possible to build a low-power tube stereo amplifier that will sound better than the MS-10D MKII on most instances.
Very enlightening!
Apparently the circuit doesn't do much with the tubes except light the heaters.....
Reference to tube rollers who heard differences between tubes = priceless.
Thanks!
Do you mean GAVNO?
Chinese guano, Russian Говно, or whatever. It's dung and highly malodorous.
Remember, this site's software s out certain words, including *.
Last edited by a moderator:
If I remember right, the 6N1 tubes I have run fairly bright at 6.3V. They run 600mA at 6.3V.
Hi, I have requested to reopen this thread in the hope to have someone accustomed to the MS-10MKii to give their opinion::
suddenly experiencing distorted audio signal last week - I figured it was the tubes. Then I bypassed the tubes with connecting the signal cables in the header towards the valve board, the sound was exactly the same! But still distortion issues, checked the cables and speakers.. I'm guessing it's an issue in the solid state circuitry, any idea what it could be?
suddenly experiencing distorted audio signal last week - I figured it was the tubes. Then I bypassed the tubes with connecting the signal cables in the header towards the valve board, the sound was exactly the same! But still distortion issues, checked the cables and speakers.. I'm guessing it's an issue in the solid state circuitry, any idea what it could be?
If distortion is on both channel, check the power supply voltages. Measure the voltage on both main filter capacitors on the solid state power amplifier mainboard, and the output voltage on the 3-terminal regulators on the mainboard. The power stage is a basic discrete amplifier based on TIP41C/TIP42C. Also try a different source, just to be sure that the fault is the amplifier.