Purchased my 1st valve amp and can only get one channel working, please help!

[moon158]

Hi guys, I've just purchased my first valve amplifier (first decent amplifier of any sort to be honest) it's a Yaqin MC-100b Chinese tubey beast.

I have also purchased a pair of Mission m32i's, some decent grade cable, reasonable valves, and am saving for a nice DAC. BIG BIG smiles as I love my friends audiophilesque setup and am very excited to finally get something better than my logitech computer speakers . However when I decided to connect my speakers to the amp (I single wired them as the amp is only single wireable and couldn't afford 2) but only the right channel seems to be working.

As I am only testing the amp at this stage because I don't have a multimeter to bias the valves or a DAC and my pc is playing up I have simply connected my Ipod using a Monster Ipod to RCA cable to give it a test drive. I am certain that both speakers work as when either is plugged into the right channel they play wonderfully. However a strange thing occurs when I connect the Ipod to either of the several input connections at the back of the amp (for DVD/CD etc), as sound does start coming out of the left channel speaker but extremely quietly.

Does anyone have any idea why this is happening or if there is anything I can do to remedy this? The fact that no sound comes from the left channel when connected to the front but some sound comes when connected to the back seems to me to suggest dodgey wiring but as I say I'm completely new to this so would love to hear what more experience audio lovers think. I have tried it in ultra linear and tri linear modes and this doesn't seem to make a difference. I would take it to a hifi repair shop but I live near Stoke-on-Trent and have an eye condition which means I'm not legally allowed to drive, and the nearest hifi repair shop according to yell.com is a 50 minute drive away.

Any help or suggestions would be greatly appreciated

Cheers

[Arnulf]

Have it replaced under warranty. I mean, you bought a new piece of equipment and you want to fix manufacturer's mistakes despite your eye condition ... would you attempt to fix new car where steering only worked in one direction ?

[kevinkr]

Make sure your iPod cable is ok by swapping the left and right channel rca plugs. If the amp still only plays on the right channel the problem is in the amplifier - if it now plays on the left channel it is the cable from your iPod.

You'll need to get the amplifier repaired/replaced if that does not demonstrate that the cable is the issue.

[Globulator]

Shame you live so far from me - almost the other side of the country!! In the absence of a local diyaudio-er you will need I think to consider the cost of sending it back versus fixing it here.

I would stick to low volumes as OPTs (OutPutTransformers) do NOT like an open connection - you must have a speaker connected and your fault condition is unknown..

You need to buy a multimeter, a cheap one is about £5, spend a little time online and order one. Then you can start unplugging your tubes and measuring voltages from the top - the safest place to do it. You can set the range to 1000V and compare each side and that will be a very useful report here to track the error down.

You need to look at DC conditions first with a multimeter - nothing will work if these are wrong. The only really biggie problem would be a faulty OPT, nothing else is expensive to fix.

[Mr. Zenith]

Make sure your iPod cable is ok by swapping the left and right channel rca plugs. If the amp still only plays on the right channel the problem is in the amplifier - if it now plays on the left channel it is the cable from your iPod.

I would also suggest the audio equivalent of jiggling the toilet handle: Gently jiggle the input plugs and see if that makes a difference. I have an old Studer A725 that has a loose center connection on one of the rear RCA Jacks. The music is severely attenuated unless I jostle the plug until it gets just right.

Fortunately, I have another A725 for parts...

it's a Yaqin MC-100b Chinese tubey beast

BTW, I Think I saw the "Tubey Beast" here.

[moon158]

Thanks very much for the replies everyone, sorry it took me so long to get back to you but I've been on my hols in Cape Verde (nice place but me + all inclusive = chronic liver failure...). I'll try all the suggestions here to hopefully find out what the problem is then try and decide whether to send it back, but I foolishly purchased it from a Chinese store rather than a UK retailer so it looks like I might need to try and send bribe a friend to drive me to a far out DIY guy :-( . Good likeness on the picture though Zenith, but knowing my luck it'll be as difficult to fix my tubey beast as it would be to seduce that one.

Cheers for the help guys

[morisleilei]

Hi,

where did you buy it? I'm really want to buy one of this but I can not find it anywhere except ebay, but all of them are post from Hongkong, not really sure if I can buy from them, not only the high postage but also the customer service after sales. Thanks.

[morisleilei]

I finally choose the fatman itube valve amplifier with wharfedale diamond 10.1 speakers. It makes a very good sounds when I play it with TEAC cd player. The only one thing I noticed that is I can hear mmmmm from the speakers when I don't play anything. not sure what is that from, any idea? Should I
check the tube? Thanks guys.

[Rockmore]

Again, another post and need for a separate, specific Yaqin forum for Yaqin (Yaoin) tube audio products...

[vinylkid58]

Originally Posted by Rockmore

Again, another post and need for a separate, specific Yaqin forum for Yaqin (Yaoin) tube audio products...

Isn't it up to the manufacturer to initiate a forum within the commercial section? Or, at least give the ok?

jeff