Chinese amp discussion

HI
This is my first post here.

I own an unmodified Ming Da MC34-B Valve amp with Sovtec 5881 output tubes. Ive owned this unit for just over a year now and love it..but there are some limitations and I wondered if I should bother with upgrading this unit or just buy another on ebay

Here are a couple of links:

http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWA%3AIT&rd=1

http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWA%3AIT&rd=1

http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWA%3AIT&rd=1

My amp seems much better suited to Chamber Classical / jazz and acoustic music and hardens up noticably (gets confused) with loud rock music etc ...is there anything that could be done about that (changing capacitors / resistors etc or rolling the tubes? Also there is quite noticable sibilence with some cd's (again Rock music etc is more noticable) although this improved dramatically when I bought Qed speaker cable.

I assume the problems are down to the transformers being too small and stock chinese (cheap) components being used. A couple of the amps mentioned above are more than double the weight of my Ming-da and weigh in at 27kg!

Im using a Sony DVD player whose signal is fed into a Bel Canto Dac2 using Ixos digital cable (1m) and van den hul Hybrid cable from the Dac into the amp (0.5m x2). my speakers are Wharfedale pacific evolution 30's (89db sensitivity), Bi wired with QED silver anniversary cable. and I have a simple mains filter.

Unfortunately I cant afford esoterica with a young family and mortgage etc but after owning a mission Cyrus two for 18 years i can safely say that this little chinese valve amp soundly trashed the mission in every area apart from the ones mentioned above.

So I have much hope that my listening problems can be solved with minimum layout.

Any help would be much appreciated.

Best Regards.

Jack.

[NealG]

Sounds like the amp is running out of puff when you crank it up?

Don't think any amout of exotic components will change that.

Wharfedales...... Perhaps you need an easier load for the amp.

Or go with the Kit88 PP amps you linked to on FeeBay for a bit more power and headroom. The 300B SET won't cut it with those 'speakers and loud rock music.

The danger in buying from FeeBay/Hong Kong is if you aren't capable of soldering/understanding valve ccts you will be faced with a headache if something goes wrong or if there is a fundemental fault with the amp and or design in the first place. However peoples mileage varies.

Many can help here but do you want the hassle?

[petercom]

When buying chinese made amps from Hong Kong you also need to watch out for the cheap chinese valves they sometimes use.

[Richard]

Welcome Jack,

I agree with Neal that you need a decent push-pull of 20W+ for rock into those speakers.

Can you scope the Chinese amp? Look particularly at power bandwidth. They don't usually do what they say on the label.

Best value would be a secondhand Kel34, Kit34, Kit88 or Kit6550 off FeePay, or put a wants on here. You'd then have a good basis for improvement and hobby interest.

Rich

Thank you Neil, Petercom and Richard.

My Amp is 22W per channel btw.

Yor right Neil, ordering from China is a worry on loads of levels. Petercom, I planned to buy better valves after a month or so, but there is the problem of biasing (I dont have a clue how to).
Richard, I would love a WAD amp but..the expense!?

If I can find a picture of the insides of this amp, would you have a look at it for me and check for quality etc?.

Perhaps i should change my speakers to a higher sensitivity pair? these ones are 89db into 6ohms.

Anyway its all good fun.

Jack.

[Richard]

Some thoughts, have you tried 4R and 8R outputs into your speakers to see which sounds best and have you tried adjusting bias?

Component wise it probably uses polyprop coupling caps which could be replaced with polyester for a more natural sound.

Rich

[Global]

While one experience does not prove anything, I bought a Chinese single-ended 20W+ (maybe) 845 amp. Service and delivery were great. It took longer to get from E. Midlands airport to Glasgow than it took to come from China.

I was unconcerned about warranty 'cos I knew I would tear it to bits anyway.

The supplied Chinese valves are actually quieter than NOS valves I have tried and the build standard and other component quality is very good.

My only real concern with it is the fact that the transformers are clearly meant for 220v and, probably, 60Hz and they get too hot for comfort. Most of this can be cured with a variac.

I can buy this amp + carriage +VAT + variac for MUCH less than a UK product and it can be refined and modded.

My experience was positive and represented excellent service and I would buy from these guys again without too much worry.

Mark

Richard, if you mean the 4 and 8 ohm taps on the amp, it sounds much better on 8ohm.
I dont have a clue about bias adjusting, would that go some way to reducing the level of 'muddle' in the loud bits.
bought the amp from Edenlake here in England and it was upgraded with Sovtek tubes and rebiased for me.

Global, Its very heartening to read your experience what did the amp sound like before you went to work on it?
They certainly look well made from a laymans perspective and Ive had no problems so far (touch wood) with this little Mc34-B amp. The Transformers do get hot though!

[Richard]

Jack, It's easy enough to bias if you have a multimeter, for hundreds of v and mV, and can measure the HT at pin 3 of the 5881s (clockwise from the keyway looking from underneath)

Rich

[Global]

Originally Posted by Jack Hawthorne

Global, Its very heartening to read your experience what did the amp sound like before you went to work on it?

Hi Jack

I have to be careful not to rave about something just because I bought one! This amp was my first exposure to a single-ended design, having been a long-time user of a modded KiT88. I immediately found the sound of this amp significantly different from what I was used to. The only word I can think of is 'exciting'. I had expected bass weakness but heard no sign of it. The sound was open, fluid and sparkling. The only major weakness was poor imaging. This problem was rectified by swapping the volume pot for something decent.

I have concerns about the suitability of this amp for the non-enthusiast however. The transformer issue could be a long-term problem with all Chinese kit and the volume pot mod has to be considered essential. If, however, you ARE an enthusiast and are competent and confident with solder fumes and high voltages then you get a great experience for relatively little money.

Mark