• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Yaqin MS 34 D

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#5
vinylkid58 said:
Appears to be one of the many push pull EL34 variants coming out China. Some are happy with them, some like to tweek them, and some sell them on. What speakers are you going to be using with this amp?

Here's a short review FWIW: AudiogoN Forums: Review: Yaqin (China) MS-34D Tube amp

jeff
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Thanks for reply jeff im going to be useing mission m74 speakers for now. Allways fancied a tube amp but im a bit confused about something called biasing
 
#6
Well, it's not really "Highend" as they say... and no, you should not run it directly on 240v: the heater voltage would be higher than normal (6.9v instead of 6.3). The difference may seem small, but it would seriously shorten the tubes' lives.

What to do? Have it modded by a pro, or run it on a Variac... Or buy another amp.
 
#9
One question - do you know what your mains voltage really is? In the UK, it is nominally 230 volts with a tolerance of +10% to -6% (the official 240 value was quite a long time ago). It will vary quite a lot from one location to another. In my home I see around 235V, at work I often see about 244V. For historic reasons in many places it is more likely to be above 230 than below.
 
#10
Desppain not, If you kindly ask them for a schematic, they ll likely send you one, and the nice ppl here will tell you what to do and how,

But first, the million euro question: Are you handy with a soldering iron?

About the Audiogon Review: "Pure Class A" yeah riiiiight...
 
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#11
costis_n said:
Desppain not, If you kindly ask them for a schematic, they ll likely send you one, and the nice ppl here will tell you what to do and how,

But first, the million euro question: Are you handy with a soldering iron?

About the Audiogon Review: "Pure Class A" yeah riiiiight...
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Hi costis yes i can solder neatly but i dont understand wireing diagrams. Ican change caps and opamps stuff like that its just the wireing diagrams i dont understang
 
#12
12E1 said:
One question - do you know what your mains voltage really is? In the UK, it is nominally 230 volts with a tolerance of +10% to -6% (the official 240 value was quite a long time ago). It will vary quite a lot from one location to another. In my home I see around 235V, at work I often see about 244V. For historic reasons in many places it is more likely to be above 230 than below.
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Good point lol i assumed 240v.Idont really want to spend loads of money on some variac or exspensive reg as im skint now i have bought the amp. Im a bit peed off as i thought i could just run it off the british voltage with no problems
 
#15
bull041161 said:
Good point lol i assumed 240v.Idont really want to spend loads of money on some variac or exspensive reg as im skint now i have bought the amp. Im a bit peed off as i thought i could just run it off the british voltage with no problems
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So long as you can measure the heater voltage, I would just plug it in with a load connected to the speaker terminals - let the amp warm up for 2 or 3 minutes and then measure the heater voltage on all of the valves - there may be one, two or even three heater supplies from the mains transformer. If you measure 6.3 to 6.6 volts AC I would be inclined not to worry. If I saw 6.7 or higher then I would see what I could do to lower the voltage into the amplifier since prolonged running at excessive heater voltage is not a good thing. Short term for testing it will do no real harm, however.
 
#16
Yes, I would only be worried about the heaters really. I believe the operating points of the valves etc are not that scientifically designed by the experts in Yaquin 😛

I m sure the logic circuits are powered by a regulator, so no worries there either.
 
#17
12E1 said:
So long as you can measure the heater voltage, I would just plug it in with a load connected to the speaker terminals - let the amp warm up for 2 or 3 minutes and then measure the heater voltage on all of the valves - there may be one, two or even three heater supplies from the mains transformer. If you measure 6.3 to 6.6 volts AC I would be inclined not to worry. If I saw 6.7 or higher then I would see what I could do to lower the voltage into the amplifier since prolonged running at excessive heater voltage is not a good thing. Short term for testing it will do no real harm, however.
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Hi thanks for the help. Sorry to sound thick but what would i use to load the the amp a resistor or some thing. Im not very good at this sort of stuff. I just wanted something i could plug in and use if i had know about the biasing and voltage problems dont think i would have bothered lol. I was going to upgrade the tubes later. I do have a volt meter though
 
#18
bull041161 said:
Hi thanks for the help. Sorry to sound thick but what would i use to load the the amp a resistor or some thing. Im not very good at this sort of stuff. I just wanted something i could plug in and use if i had know about the biasing and voltage problems dont think i would have bothered lol. I was going to upgrade the tubes later. I do have a volt meter though
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The key thing is that there should always be a load connected to each channel of the amplifier when it is powered up. These can be simple resistors in the range of 8 ohms to 16 ohms and rated to a few watts at least. Unless you are running significant output power for testing you do not need to have very high power resistors.

Or you can use some speakers. If testing a new amplifier I would not use my best speakers just in case something is not right, but using speakers will of course allow you to hear if there are any big problems such as excessive hum on the outputs.
 
#19
12E1 said:
The key thing is that there should always be a load connected to each channel of the amplifier when it is powered up. These can be simple resistors in the range of 8 ohms to 16 ohms and rated to a few watts at least. Unless you are running significant output power for testing you do not need to have very high power resistors.

Or you can use some speakers. If testing a new amplifier I would not use my best speakers just in case something is not right, but using speakers will of course allow you to hear if there are any big problems such as excessive hum on the outputs.
Click to expand...

Hi would some small surround sound speakers be ok from a panasonic surround sound
 
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