Meng Yue X1 6P1 amp (NOT the mini)

[ksporry]

Hi Guys,
Took the plunge and ordered a Meng Yue X1 6P1 amp on Ebay this weekend. Before that I spoke to the seller (tubestein in my case) extensively about the power supply. He ackowledged that people in teh UK did have issues with the 220-230Vac, although he did insist that it should not cause actual problems (we know better now...). He agreed to provide me a unit with a proper 240Vac PSU, which I will have to check.

However, to do so means i need to have schematics for this particular amp. Has anyone got one for this amp? For info, it is not the mini. It is fitted with 8 6P1's (4 per channel I assume), plus 2 extra tubes (can't remember the type, but I assume they are meant for either driver stage or phase splitter). They quote an output of 24 Watts/channel (might be a bit high I was told).

Now some additional questions:
1) How can I fit a self biassing circuit to this unit (if it isn't already on there)? Does anyone have a schematic for a self biassing circuit that I can learn from?

2) A more general question: I understood there are different caps for different applications. Unfortunately I have not yet bene able to figure out what type of caps go on what part of the amp. I know of the existence of electrolytic caps, metalised polypropylene caps, paper in oil caps, and I'm sure there are a dozen or so more types. My question is: which type of cap do I use when for a tube amp?

I expect many more questions when I get this unit in. I will first want to ensure it is properly set up before I plug it in (meaning, correct Power Supply, correct voltages on heaters, bias correctly set up).

Cheers!
K

[TheGimp]

If it has 8 6P1s, then it is probably running parallel push pull with two tubes in parallel for each side of the output transformers (4 6P1s per channel). IIRC they use 6N1s for input /phase splitters.

I'd be interested in seeing the schematic as I'm working with 6P1P-EVs (Russian tube which the 6P1 is derived from) and just ordered a pair of 5K OPTs to build a similar amp.

As to caps, Electorlytics are normally used for (1) Power supply filtering, and (2) cathode bypass.

Metalized Poly(whatever) caps, Paper in oil, etc are used for coupling caps between stages, and as input caps.

In some cases such as the motor run cap for Air conditioning systems, they may be large enough to use for power supply bypass and cathode bypass.

Various capacitor dilectrics can have an effect on sonic quality. For instance, ceramic capacitors are rarely used for coupling caps as they can be noticably microphonic.

Technically, all caps can be microphonic, but some are worse than others, and some are only microphonic to a degree that very sensitive testing must be done to detect it.

[starne]

Hi,
I've got a Meng X1 6P1, which says it uses (8) "6AQ5/6P1" tubes. They have 9 pins.
But when I look at possible replacement 6AQ5's, they all seem to have 7 pins.
Now, there is the (Russian, I think) 6P1P, which is (I think) a 9 pin:
would this be a "drop-in" replacement for those "6AQ5/6P1" Chinese tubes?
--David

[rotaspec]

Originally Posted by starne

Hi,
I've got a Meng X1 6P1, which says it uses (8) "6AQ5/6P1" tubes. They have 9 pins.
But when I look at possible replacement 6AQ5's, they all seem to have 7 pins.
Now, there is the (Russian, I think) 6P1P, which is (I think) a 9 pin:
would this be a "drop-in" replacement for those "6AQ5/6P1" Chinese tubes?
--David

Yes, they are direct replacements. I have a Meng Mini 6P1, and have tried Russian 6P1P-EV in their place with no problems (or sonic improvement, I might add). The only improvement I noticed was that the Russian tubes were better matched in quiescent currents, and visual appeal of having all their heaters look the same. YMMV

Gary

[starne]

Thanks Gary.
My amp is actually on its way--I'm just trying to figure out in advance what I might want to change.
What about the pre-amp tubes?
Did you keep the originals or try something new?
--David

[rotaspec]

Originally Posted by starne

Thanks Gary.
My amp is actually on its way--I'm just trying to figure out in advance what I might want to change.
What about the pre-amp tubes?
Did you keep the originals or try something new?
--David

If you want the full saga, read my thread here:
Meng Yue Mini schematic?

A few of us looked at different improvements, and yes, the pre-amp section needed improvement. The stock was 6N2 in paraphase arrangement. Changing this to 6N1P in cathodyne arrangement improved the sound a lot. It's more than just changing tubes though, as you will read in that thread.
I didn't go as far as others in that thread, but I am quite happy with mine as it is now. Mine is at about the schematic of Dec 26, 2009.
Two 6N1P-EV tubes, 4 LM317 regulators, and a few resistors were all the parts I put in.

If you are not up to speed on working with tube circuits, I would advise against doing anything underneath unless you have someone experienced looking over your shoulder. Too many exposed lethal voltages.