[Joe Lau]

Quote:

Originally posted by Orpheus k... apprently you are not aware of the current problems. my tech was told by Divergent that on one of your latest batches the pot was screwed up. one channel is almost 2x as loud as the other at moderate to low volumes. that is a huge difference. if you want, i can give you the tech's number so you can talk to him. my first mg head did not have this problem, but both my current one and born2b's do have this problem. Divergent is aware of this problem. and i know you ain't using an Alps pot... or at least a quality one. the tech said the pot in your unit had to have cost lest than a couple bucks. do you know what is mean 3db ? Yes ! We can still use Alps as before but most of the user don't like it had click. acceptable hum level?--well, that's pretty easy... buy some headphones, plug it in... if the hum distracts you, well, then it's too loud. and on headphones, almost ANY hum is too loud. besides, i don't think any unit should have any noticeable self-hum... none of my other amplifiers do. i listened to my bro's Corda headphone amp... and it is DEAD SILENT with the volume turned all the way up. No ! It is not easy to judge ! Do you know some Headphone can have 110 db /1mW sensitive but AKG1000 just 74db /1mW. You can heard huge hum in 110db Cans but completely silent in AKG1000 due to it sensitive is so far away. I only have Cans 102db/mW. It is most common. polarity?--well, i know others here have reported changing polarity helps. but in my house, i bought a cheater plug and changed polarity. no difference. a company with no problems?--no of course not. ...you wanna know what happens to car companies in the US with quality issues? they are sued for billions of dollars... even AFTER issuing a recall! make a 100% problem free product?--of course you can't. there will always be a problem. but the point is to offer a warrantee, not the ******** policy Divergent has. i couldn't even get my amp fixed under warrantee.... Divergent turned me down. but your products have many more problems than any other piece of equipment i have ever had. and that says something. I had no comment on this point. your solution?--find out why your cases are crooked. why holes for the switches/pots/plugs are drilled wrong. clearly your design is not bad... but consistency is. if you have to personally check every unit before it's shipped, then that's what you should do... or hire someone to do it for you. Yes ! We can made very high precicion Chassis if : 1. I can order thousand Pcs of Chassis from sub-contractor and pay expensive tooling. 2. Use CNC machine to do it. Both of these will increase the cost to double. i think you can easily check for some simple problems fairly quickly: 1. crooked faceplates 2. uneven feet 3. hum/buzz it'll only take you a minute or two just to quickly give the unit a glance, and measure self-hum. Point 1 & 2 may be more easy. Point 3 - May be you can give be a standard ! What Hum level or S/N is acceptable ? you know, if Sony had this problem, it wouldn't have been any problem for me to just return my amp.... and again, Divergent said no way. tell them to get with the program. No ! Sure you can return the amplifiers if you have problem. You even can send it to "Divergent" but claim for me. I can send you a new one from Hong Kong within 2 weeks. why don't you try out some of your competitor's headphone amps... then you can see what an "acceptable" level of hum is. No ! I had try many but some of them have problem but I don't like tell you the brand. Or may be you can search in Head-Fi. Is other completitors products 100% no hum ? No any quality problem. Anyway many thanks for your comment on our products. I will try my best to improve it.

 

[Orpheus]

i think you missed the point man.

i am trying to tell you that Divergent is screwed up. they DID refuse my amp. the fact that you are going to force them to take MY amp doesn't help... they need to provide quality support to ALL customers. that is what i'm trying to tell you. i am not just speaking for myself... there are many that are fed-up with Divergent. if you don't believe me... you can watch your business go down the drain. Headroom is just the first.... more will follow. and it's not just end-users like me... Mr. Dealy and other technicians are pissed off at Divergent too... cause they simply are LIARS.

anyway... what i want to see is an effort to fix the existing problems: your quality control, and Divergent's bad attitude.

...and you know, there's no point in returning my amp now to Divergent. come on.... I just spent $500 on one. you think i'm gonna give it up to make a point!?

you know, there are some out there that probably think i have a big mouth... and i bitch too much. but i know there are others that will benefit from my experiences. i'm not a complainer at heart... i only open my big mouth if i really have something to say... and after 6 months without a working amp, $200, and all the hassle along with returning this stuff and making calls.... is really not good for me. k?

so for your benefit and ours, do something. and it would be nice to be compensated for all my money and trouble.

 

[evilcthul]

Dear Joseph,

I can see your point about the hum and how much is acceptable but why don't you buy the most commonly used headphones and test your designs? This method would probably be the easiest.

For example:
You could buy the Sennheiser HD 600, Grado RS1 and Etymotic ER4S. They're probably the three most popular headphones and cover a range of impedances.

Your amps should have no audible hum, buzz or crackling with any of those headphones even at high volume levels say with the pot turned about 3/4 of the way up. Basically you want no hum at any listening levels including very quiet and moderately loud. You should maybe design your own test cd to verify this. The best method for hum management is a real world listening test...

As for QC problems, you should maybe give every amp 48 hours burn in and maybe a stress test (outside specifications (maybe a dummy load)) then check for physical defects like crooked face plates etc. Then after the 48 hours is up, perhaps give them a listen. If the unit has passed this then it should be shipped.

In addition to this, perhaps you should have people test batches of signal path components which are prone to problems (like the potentiometer) before they're put into amps. Perhaps you should also have people inspect boards and test for cold solder joints on signal path components or identify where cold joints normally occur and test the crucial points.

Sure, this all costs time and money but I'm sure a lot of people would be very happy to pay a bit extra to save themselves months and months of trouble with Divergent and others. In the long run, this saves you time because you're not dealing with returns and it lets you have more time to design better products and handle less customer complaints.

Basically, what I'm saying is each amplifier should be burnt in for 48 hours + stress tested outside of specification and receive at least 30 minutes of individual attention INCLUDING a full listening test with a range of headphones to make sure everything works. Maybe, your QC staff should also stamp a certificate to ship with the amp so that if any problems arise you can identify batches etc and stop them from being shipped to people.

You also now have a lot of friends in Hong Kong like Gino and Ze-Ant etc. You should maybe beta test your new designs with them as customer feedback is often the best way to improve!

I think personally with your MG Head OTL (although I've never had problems) you should go for:

Higher Quality Potentiometer
Larger Chassis
Better Quality Coupling Caps (if possible)
More careful routing of wire (twist it, use shielded wire for noise rejection)
Polarity Switches
Ground Lift Switch

More personal attention!

Sorry if this seems like offering you too much advice but I love ASL products and it pains me to see so many people unhappy with the current state of affairs. You're a man obviously dedicated to your work and short of Headroom and Jan Meier you're the most enthusiastic manufacturer in our headphone community. You also make the biggest range of headphone tube amplifiers out of any manufacturer and whatsmore you actually pay attention to our requests! No other non-headphone company supports our hobby as much as you do and for that I commend you.

The question now isn't whether the products themselves are good or not because on paper they're fine. The designs are great we love them when they're WORKING. It's purely an issue of QC and consistency. You certainly are going the right way about it by addressing the issue but endless discussion amounts to nothing so it's time to act and take the advice to heart.

 

[evilcthul]

Orpheus,

I'm not sticking up for Divergent as their actions are in no way laudable by all accounts but if Joseph did manage to fix the root of the problem then Divergent would inevitably have less claims and (hopefully) be able to deal with returned units in a more civilised fashion. Divergent no matter how bad their customer service may be, can't remedy the issue at the grass roots level so getting them up to speed would purely be a temporary fix and would not address the cause of the problem. I however do agree with you that you shouldn't have to endure endless service calls etc before the unit is returned. Divergent shouldn't be giving you the run-around and I hope that their performance does improve.

Joseph perhaps you should consider appointing an NA distributor? Or at least get Divergent to employ an NA service centre/repair centre as a temporary measure until the number of complaints lowers? This would be a good fix as I'm sure some people like Headroom would find it easier to ship within North America than having to get a unit to Canada.

Joseph: I propose that you get the units back from Divergent and see what the most common problems are. If you browse the forums the symptoms are always similar so I'm sure there are some common problems with the units out there. I'm also sure Divergent is well aware of the problem. If someone is unhappy the issue should be addressed they shouldn't be told "the unit is like that" because it reflects badly on you and Divergent. Your products aren't as bad as Divergent makes them out to be. They shouldn't hum have crooked face plates and uneven feet and consumers shouldn't have to put up with it. If it happens it should be dealt with and not shrugged off as a minor defect that is small in comparison to channels not working etc... Cosmetic problems should be the easiest to fix.

Maybe you could improve the components in the signal path to all brand name units (doesn't have to be most expensive brand name) to save on QC/checking etc and raise the prices a bit. I'm sure if you pay for some brand name parts it'll eventually save on QC/Returns/Customer service and may improve the sound.

Also I personally suspect that sum hum comes from the fact that your tubes don't have cages over them and as such the tubes are picking up RF like the EMP does. Maybe you should make the tube cage standard?

How much would you guys be willing to pay for an MG Head that say has had at least 72 hours of attention in the factory and has midrange parts like say Panasonic Caps/Alps Pot/Neutrik Jacks/Vishay Dale Resistors/Auricap Coupling Caps (or something similar)?

Would something say like $450-475USD sound like too much? Alternatively, you could sell the upgraded unit with no tubes (to bring down the price) as most people like to roll their own anyway.

Update:
ASL Problems/Solutions & Experiences with Divergent Thread

Register your experiences so we have a catalogue of all peoples concerns in one place.

 

[Orpheus]

i agree with you man. i think we're at least on the same page.

but i am starting to get irritated that Joe Lau doesn't seem to really believe he is at fault (he's the president isn't he?) he does seem to think that such problems exist in all components in this price range... which we all know just ain't true.

...and i still don't hear anything about my expenses... not that i'm selfish or anything... but it wasn't fair to me to have to put up with so much crap and have to spend so much money to get a good unit.

i want to see an apology from Divergent. and i want some kind of REAL warrantee here. if he wants, i can email him a copy of my receipt for all the repair work and shipping charges i have incurred during the last 6 months.

so far the bullcrap 1 year? warrantee has been worthless. i want proof that ASL is willing to honor their words.

 

[Joe Lau]

No ! I never say my products don't have problem. I'm only want to sure the standard and solve the problem in next shipment.

1. Do you think unbalance within 1db or 1.5db is acceptable. It is impossible to sure even Alps Audio grade Pot but I can selected it. So I really want to sure the standard.

2. Hum - I don't have much money to buy too much Headphone. It is not cheap. It will higher our cost if I do that. I had limited resource and limited profite. Why I'm not direct sell ? It will higher the profite if I can selling in same price but I'm only worry the after sales service. So I only sell my amplifiers by our distributors.

To Tuberoller :

REAL warrantee - I really so sorry on Twin Head. It is my wrong ! not "Divergent". You can return it to Divergent and I will send a new units of which tested by me and may be other Head-Fi Member in Hong Kong before ship. That Waht I can do ! or do you have any suggestion ?

I really many thanks for all comment even positive or negative to our products. It will help us to improve our products.

 

[evilcthul]

Joseph,

As for channel unbalance, I don't think the unbalancing is the problem rather the fact that the unbalancing has been a LOT bigger when the potentiometer is on the quieter settings.

I suggest you hand check your pots for intermittent channels and balancing on the quieter listening levels.

 

[Kevin P]

Quote:

As for channel unbalance, I don't think the unbalancing is the problem rather the fact that the unbalancing has been a LOT bigger when the potentiometer is on the quieter settings.

Perhaps the problem is that the MG Head is used at very low levels on the volume pot more so than other amps, due to its sensitivity (especially when used with higher gain tubes like the 12AX7). One suggestion would be to add an attenuator switch, that reduces the gain 6 db or so, then using that the volume can be turned up higher and into a more "balanced" range on the pot.

For those who have had balance issues at low volume levels, have you tried a lower gain tube, such as a 5751 or 12AU7?

KJP

 

[Born2bwire]

I use 5751 tubes and still had the imbalance problem. With the pot, the difference in the positions of the settings between using a 5751 and a 12AX7 is not that big of a difference in my opinion.

 

[braillediver]

How many different tubes are you basing your conclusions on?

Do you know if the tubes are any good to start with?

How well balanced are the sections of the driver tube?

Have you tried swapping the power tubes?

Where are you using the amp? Is the power clean there? Is it near any fluorescent lights? Is there a dimmer switch connected to the power circuit anywhere?


I’m surprised people modify things before they get the basic functionality ironed out.

How do you know the upgrades will actually improve the sound when a solid baseline hasn’t been established?

 

[Born2bwire]

I don't have any 12AU7 tubes and I really like the sound of my 5751 tubes. Either way, it's a moot point now seeing as the pot has been replaced. Just got a hold of a cheater plug and it didn't seem to make a difference with the Ei 12AX7 stock tube.

 

[Orpheus]

this is what Divergent told Mr. Dealy... that on one batch of the new MG Heads, defective pots were used. they were sending him a new cheap-o pot to replace mine with, but i told him to go ahead and upgrade to a good Alps model.

--it's not specific to born2b's amp... mine too. the tubes are fine....

the pots ARE defective. there ARE NOT within spec, not even for the cheapest of pots.

I am not talking a couple dB difference here... at low volumes, one channel almost dissapears. that is BAD. at "normal" listening levels, one channel is still noticeably louder than the other. again... you shouldn't be able to hear a couple dB difference..... and this is a significant volume difference between sides.

"I don't have much money to buy too much Headphone. It is not cheap. It will higher our cost if I do that." -- um, dude.... you cannot make amps without at least trying them out with proper equipment right? i don't understand how you could possibly make headphone amps without having some headphones yourself. if what you meant was buying a bunch so that your assembly team could test out your products.... just one would probably do... one guy could test for the bigger problems fairly quickly, if he knows what to look for.

...and again, what about my $200 and 6 months of time, Joe?

 

[RGA]

I'm just curious but I have the MG head DT(non OTL version for about a year and 1/2 now.

The thing is dead quiet all the way up to full volume...the feet are fine and the face is fine...I have rolled only the preamp tube but all tubes are quiet...in fact I use the Head as a preamp for my Arcam Delta 290 BECAUSE IT GOT RID OF THE HUM in the Arcam.

Assuming nothing has changed over the last year and a half I doubt it can be a parts problem. There may be some assembly issues that need to be addressed. Also I have lived in two different places in that period of time.

My curent apartment had a horrible problem with amplifier Hum(on both my Arcam Delta 290 and Sugden A48B) that was related to tv cable not being grounded. I phoned the cable company and it turned out that they did not isolate the line coming into the building. The Hum - which was AS LOUD as the music was totally gone.

The interesting thing was that the ONLY amp I own that didn't have this problem was the MG Head????

Strange

 

[Orpheus]

yeah... that happens. it isn't all mg heads that are bad... and that's why it's a quality control issue, not the inherent design.

heh he... but wouldn't it be funny that both your Arcam and Sugden were made fine... but the bad stuff in your MG Head actually reacted to it's environment in a weird way and resulted in good performance, while your properly made equipment reacted the way it should and hummed? you know what i mean? just a thought....

(you might have a reveresed electrical polarity situation in your apartment. an engineer suggested that to me for another situation.... but he said you would have to buy some fancy equipment to know for sure.)

but yes, there are plenty of mg heads that are perfectly fine. but then again there are plenty of mg heads that are all screwed up.

 

[Born2bwire]

The DT model is a great model. It rarely has any hum because it has the feedback circuit in it. But on the OTL models, you can easily remove the feedback or use the OTL modes, both of which can introduce an audible hum in the left channel. Personally, I prefer the OTL mode and thus the whole reason of trying to remove the hum, otherwise, I would just be using trans w/ feedback.


Orpheus- Oh, you're gonna love this. The channels on my amp are switched around, Dealy must have wired them in reverse on the pot

. Yeah, just my good fortune, I made sure by using a speaker test off of my soundcard. So I guess I'm going to have to open it up and switch the wires on the pot, I don't think that's out of my range of skill. Either way, if he was consistent, you may want to double check the channels on your amp.