Letter to Little Dot -- LDII+ owners, PLEASE read - Page 3

[QUOTE=PYROphonez]The folks over at LD say that if you see no signs of arching within the first 100 hours of use, the tubes are fine. I suspect they had a batch of bad tubes.

the tubes in my 2+ started arcing way after 100 hours, the funny thing is that only the tube in the left channel position arcs in my amp, it is the same even if the tubes are switched around. i would expect the arcing to move with the tube if the tube was faulty, but that wasn't the case with my amp.

i have a 12Ax7 that has a arcing problem and it arcs averytime power is applied to it, not selectively like the tube in the 2+. a bad tube is a bad tube, a bad tube will be bad all the time no matter what socket it is in.

i am not try ing to make the 2+ look bad, it is a good little amp that perform above it's price point, but my concern is with the premature death of the tubes, and the possibility of damaging whatever phones are hooked up to it when power is applied.

[QUOTE=jamdigga] Wow, the arching thing is extremely weird with you. I'm not the original owner of my amplifier, but he had tubes replaced once due to minor arching. The replacements had no issues whatsoever after I think he said 100-200 hours. I received it, and saw no arching. Then a tube blew on me later. You may want to email little tube about that one, because that really shouldn't be happening.

[QUOTE=PYROphonez] Actually, I dun think jamdigga is the only person who experienced the arcing issue. I've got the replacement tube set from Mr. Yang about 2 weeks ago (which was due to the arcing in the first set of tube, and suprisingly, it's the tube at the left channel!) and after about 100 hrs of burn in, there were some even bigger arcing at the left channel of the new set of tube. I did not turn the amp off and on in about 10 minutes, I waited for a day before I do so and the tube still arc. Most interesting thing is, when I swap the sides of the tubes, a large arc was seen in the left one (which was on the right channel originally and didn't arc before).

Just found it in a chinese website, erji.net (which is a headphone forum similar to head-fi), there was a discussion thread from Yang announcing the availability of the new LDII++(http://www.erji.net/read.php?tid=298020&keyword=). I'll try to translate his post with my limited chinese.

Little Dot II++

The prototype unit of new LDII++, that uses British made NOS EF92(CV131) for the driver stage and 6C19 for the power stage, had finished all testing. The 6C19 triode has a very low impedance (less than 300ohm, which is even lower than the famous 2A3), which makes it particularly suitable for the negative output stage. I have been considering making head-amps with 6C19 for a long time, but due to frequent business trip, I hadn't been able do it until the national day holiday, when I finished all the testings at the prototype unit.

When testing the prototype, music material was more detailed and focused compared to the 4P1S. Bass became more solid, mid-range became much brighter and the hi-frequency became more detailed and smooth. We no longer need to use the 4P1S pentode as a triode, because the 6C19 is a triode itself, which results in better reliability and the elimination of arcing in the power tube.

Because the power rating of 6C19 is much higher than 4P1S, a toroidal transfromer is used in LDII++ (also reducing the working temperature); capacitance of the capacitors was also doubled, resulting in an increase in production costs. The estimated RRP of the LDII++ will be $688 (translator's note: roughly about USD$100).

However, compared to the increase in production costs, the improvement in sound quality is well worth it.


Now as you can see in the highlighted line. It seems like Yang DOES know about the fact that using the 4P1S as triode is the cause of the arcing that we are experiencing and he even mentioned that in the post. Yang also mentioned that the driver stage remained similar, if not identical, to the LDII+ (Post #32).

ok guys, don't be so excited first, I've got some pretty bad news here. As one of the member at that forum, radman, asked yang about whether there will be upgrade available for LDII+ user or not (post #14). Yang's refused to do so (post #16), saying that "the tubes, transformer, pcb.......every parts different (from the old model)".

If the arcing is really caused by using the 4P1S pentode as triode, then, IMHO (based on what I know about tubes, may be wrong), the responsibility should be at the manufactuer not the owner of the LDII+. I am suspecting that the circuit around the screen grid and the suppressor grid has a design or manufacturing flaw, which lead to the excessive electron discharge at the starting up of the amplifier. If that's a design flaw, I believe that the manufacturer should take up the responsibility to replace the faulty unit, may be not a LDII++ but at least a LDII+ with the problem fixed.

However, personally I'm quite disappointed when I saw the response that no upgrade or exchange is available even if you pay Yang the differences and I am worrying that it will be the same for us, the overseas customers, as well. Let's keep out fingers crossed that we'll be able to work out something with Yang here at head-fi.

Well since just about everything about it is different, I would say then this is actually the Little Dot II ++ not a "LDII+ That Works" or "LDII(3/2)+"

Yes I think maybe at some point they thought about the arc problem, but it was probably high time for a new big update too. Think about it, the update is way more drastic than the II -> II+

All the stuff says before sounds more like it applied to the II -> II+. Better parts and new power tube. The II+ -> II++ is like.. same driver tube.. same enclosures.

As of now I am more optimistic than mad. I feel they have done a lot to help me, replying quickly, and sending tubes, and actually paying attention to the problem. Whatever mistake they probably made was they release it so soon after the arch crises. They should just delay the II++, test it for months, maybe send a few to customers (like me ) to try out and do a "real" quality test. Maybe around christmas time release it, after protos have been properly gone through its cycle of test, customer proto test, etc..

Thank you, that contains a lot of info!

This topic makes me feel bad about my LDII+.

According to your quote, you said it would cost approximately $100 USD. I don't think that's correct. I read in the other LDII++ thread that it would be $199+shipping.

@vcoheda: I previously emailed Dave, and he informed me he was out of town for a bit, and was working on a laptop, limiting his time to answer emails and so on.

Profit++

I love the new world of capitalism.... where you can fix your faulty designs and at the same time increase the profit by 40%...

Man!!! I feel so stupid....

xe.com Universal Currency Converter ® Results
Live mid-market rates as of 2006.11.05 05:17:28 UTC.
688.00 CNY = 87.4073 USD
China Yuan Renminbi United States Dollars
1 CNY = 0.127045 USD 1 USD = 7.87120 CNY

Of course you realize they've already read all versions as they read this board.

I was thinking the same thing.