[gr8soundz]

 
An interesting detail to notice but yes it does.

 
Oh boy.... I thought Cayin would've fixed this by now. The mk2 has a design flaw (imo) which I'll try to explain. I'm no expert but I do have a mechanical engineering background. Plus the problem is easy to see.
 
Had hoped my issue was unique and, since (til now) no one else mentioned having the same problem, I didn't post too many details (didn't want my experience to have an overly negative impact). But now, here goes.....
 
 
Here's a pic inside the original HA-1A:

Notice the dual transformers up top and the supports along the bottom.
 
 
Now here's an internal pic of the defective mk2 I had:
 

 
The braces are gone and at least one of the transformers has been relocated to the bottom under two large metal shields (basically, more mass below). The lower portion of the amp has caved inward from the extra weight. Probably happened during shipping where the structure wasn't strong enough to prevent permanent flexing and the L-shaped bottom rails are more prone to bending inward than outward (especially if the amp/box is upside down when the package is 'bouncing' in transit).
 
The mk2 weighs 22 pounds (compared to the original's 15) so it makes no sense why it has even less structural support.
 
I went back and forth with several emails between myself, the manufacturer, and dealer. Seems those covered transformers along the bottom are now too close to the circuitry above. Hence the hiss/hum that I heard and you are now hearing.
 
I advised them that their engineers needed to restore the supports or other amps could have the same problem. Unfortunately, seems my words were ignored.
 
To anyone else thinking about the mk2, I recommend immediately flipping the amp over and taking a look. If it looks anything like below, walk away. I'm guessing the bottom was perfectly flat when it left the factory with the QC sticker on it (at least I hope it was).
 

 

[abvolt]

Much appreciated for this..

 

[Andykong]

I'm hearing hum even when power cord is plugged in only. It is strange that hum and hiss gets amplified when you turn impedance selector knob.

I didn't have any problems with my iha-6 and lyr 2 so i don't think it is a grounding problem. When i switch off the amp while playing a song hum disappears and amp keeps playing and until capacitors get discharged. Could it be a bad tube? Since i am hearing hum from both channels i am planning to replace 12dt5 power regulator tube.

An interesting detail to notice but yes it does.

Sorry to know that your friend is running into some unsual hissing problem with his HA-1Amk2, can you tell me more detail about the condition of the unit? The hissing problem appeared in the first date of open-box? When a headphone hiss with a tube amplifier, it probably will not be affected by the impedance selection but the impedance of the headphone will make a different. So have you tried other headphones? What are the headphone that you have testing and confirmed the hissing problem? The hissing is at the same level in both left and right channel? Besides curved bottom panel, is there any physical damage to the machine and the package noticed during the initial unbox process?

Hissing can be a tube problem, a transformer leaking, grounding issue, and sensitive headphone, and of course it can also include a structural damage as indicated by another HA-1Amk2 user.

When and where did the unit purchased? Can I help out by contacting the dealer and ask him they can provide local support to your friend?

 

[Andykong]

Oh boy.... I thought Cayin would've fixed this by now. The mk2 has a design flaw (imo) which I'll try to explain. I'm no expert but I do have a mechanical engineering background. Plus the problem is easy to see.

Had hoped my issue was unique and, since (til now) no one else mentioned having the same problem, I didn't post too many details (didn't want my experience to have an overly negative impact). But now, here goes.....

Spoiler: Warning: Spoiler!

Here's a pic inside the original HA-1A:


Notice the dual transformers up top and the supports along the bottom.


Now here's an internal pic of the defective mk2 I had:




The braces are gone and at least one of the transformers has been relocated to the bottom under two large metal shields (basically, more mass below). The lower portion of the amp has caved inward from the extra weight. Probably happened during shipping where the structure wasn't strong enough to prevent permanent flexing and the L-shaped bottom rails are more prone to bending inward than outward (especially if the amp/box is upside down when the package is 'bouncing' in transit).

The mk2 weighs 22 pounds (compared to the original's 15) so it makes no sense why it has even less structural support.

I went back and forth with several emails between myself, the manufacturer, and dealer. Seems those covered transformers along the bottom are now too close to the circuitry above. Hence the hiss/hum that I heard and you are now hearing.

I advised them that their engineers needed to restore the supports or other amps could have the same problem. Unfortunately, seems my words were ignored.

To anyone else thinking about the mk2, I recommend immediately flipping the amp over and taking a look. If it looks anything like below, walk away. I'm guessing the bottom was perfectly flat when it left the factory with the QC sticker on it (at least I hope it was).

Well, we didn't know if the unit that was in question is having the same structural problem or were it acquired before your unit. Do you happen to know the date of purchase for sure when you pointing finger to Cayin?

Thanks for your detail report with photo, we have been extremely careful in handling every HA-1Amk2 dispatch ever since, offering extra protection and padding/double box depends on the logistic arrangement.

Sine you have raised the issue, maybe I can share a bit more on what Cayin has done after we received the case.

HA-1Amk2 was launched in China at 2015-12-4, it is a fairly popular units and we sold hundreds of them at domestic market. The HA-1Amk2 is less popular in oversee market because of the high logistic course and care-taking requirements. Most retailer will prefer iHA-6 over HA-1Amk2, especially when they are selling at the same price (i.e., similar cost before shipping and logistic). Since the logistic cost in China Domestic market is fairly low when compare to the international market, the availability and popularity of both headphone amplifier are more less at the same level.

The structural damage as exhibited in your case is the first of its kind out of our HA-1Amk2 track record, we have had exterior damage on corners and bad tubes but in most cases the boxes shows sign of damage. We finally can replicate similar damage after a series of drop test, several units of HA-1Amk2 were written off in due course, and we believe logistic is the cause of the damage in your particular case. For this reason, we have step up our logistic handling for oversee transactions. Domestic market is not affected because we have not receive similar instance report after 1 years of sales history. Long term solution will involve reinforcement of structural design as this is cheaper then extra logistic cost in the long run. However our new structural design will involve revising some of the components in the framework and this will take several months before we can roll out the revised design in our production line. Yes, it takes that long when we have to go through the proper design modification procedures, ISO process and related supply chain, and we only have one production batch of HA-1Amk2 in every 2-3 calendar months.

 

[wadi]

Does anyone know how impedance selector works? I guess it doesn't change the output impedance of headphone output. Does just increase/decrease gain or adjust the voltage accordingly?

 

[project86]

It actually does change the output impedance, tapping different windings on the output transformers.

 

[polarbear9988]

Hi Andy,
 
My HA-1A MK2 also hisses and hums.
 
Having said that, I wonder what amount of hiss and hum are considered to be a problem.
 
With my less sensitive headphones, the hiss and hum are barely noticeable.  
 
BTW, does the HA-1A MK2 has relay mute at start up?
 
The Chinese manual seems to suggest that the power light will blink at start up but mine does not, it just lights up without blinking.  
 
Thanks! 

 

[project86]

My review is finally live - click HERE to check it out and feel free to leave comments! 

 

[Andykong]

Hi Andy,

My HA-1A MK2 also hisses and hums.

Having said that, I wonder what amount of hiss and hum are considered to be a problem.

With my less sensitive headphones, the hiss and hum are barely noticeable.  

BTW, does the HA-1A MK2 has relay mute at start up?

The Chinese manual seems to suggest that the power light will blink at start up but mine does not, it just lights up without blinking.  

Thanks! 

If you are experiencing hissing problem with low-impedance high sensitive headphones, and the issue is significantly reduced at less sensitive headphone, it will be different from the previous two reports which are likely caused by magnetic leaking of the transformer at lower deck.

The HA-1Amk2 is a very powerful tube amplifier, so it is indeed not a good match with the highly sensitive headphones, in fact John Grandberg has reported similar problem with his AKT5P. High impedance and planar should be a better match with HA-1Amk2.

Changing the small driver tube (12AU7) to a better tube will also reduce the noise floor of the tube amplifier, You don't necessary go for the very expensive NOS tubes if noise floor is your main concern. I have changed my personal set of HA-1Amk2 with Gold Lion reissued and the improvement is very significant, much quieter and improved sense of 3D because of darker background.

My unit has the same problem, audio will delay for around 20 seconds and then comes in gradually, and the LED is always on instead of blinking.

 

[Andykong]

My review is finally live - click HERE to check it out and feel free to leave comments! 

A very detail review with lots of headphone matching and tube rolling suggestion. This is a good starter guide for HA-1Amk2 owners as well as an informative reference for HeadFier who are interested in the HA-1Amk2 tube headphone amplifier.

So your picks of 12Au7 are Amperex Bugle Boy 12AU7 and NOS Tung-Sol ECC82 black glass, I have find the following photo and eBay links for our reader's reference, I hope I find the correct tube as suggested:


http://www.ebay.com/itm/Very-Strong-Balanced-Matched-Pair-Amperex-Bugle-Boy12au7-Ecc82-Vacuum-Tubes-/162350071025?hash=item25ccd17cf1:g:QDIAAOSwgmJX0P0N


http://www.ebay.com/itm/NOS-Matched-Pair-Tung-Sol-USA-12AU7-ECC82-Black-Glass-Vacuum-Tubes-/152385955283?_trksid=p2349526.m2548.l4275

(The eBay links are provided for reference only, Cayin are not affliated with these tube sellers and is in no position to recommend tube stores in US or locations outside mainland China.)

I do agree that changing the driver tube (12AU7) is the first and probably most effective tweaking with HA-1Amk2. I have shared an printed review in Hong Kong (written in Chinese, sorry) few months back and the reviewer has raised exactly the same recommendation. There are loads of choice in the market, some of them are good for low noise (Telefunkens Smooth Plate, Mullard M8136. Amperex 7316, ...) which is a good option for users with sensitive headphones. There are others provides more detail and extension (JJ ECC82，Sylvania 6189, Tungsram 12AU7, ...). So I don't recommend our customers to rush into exotic tubes immediately, they do offer significant improvement over the stock tubes, but you have to understand the need of your system before you can shortlisted appropriate tubes for your setup.

If you are completely new to the tube domain, you probably need to read up some background information about 12AU7 and its variants:

https://en.wikipedia.org/wiki/12AU7
http://www.effectrode.com/signal-tubes/the-12au7-tube/
http://www.jacmusic.com/nos/ECC82.htm


There are also some discussion on 12AU7 tube rolling on the original HA1A here in HeadFi:

http://www.head-fi.org/t/392713/12au7-comparison
http://www.head-fi.org/t/183771/what-kind-of-tubes-are-compatible-with-12au7
http://www.head-fi.org/t/448505/12au7-aficionados-please-reply

 

[Andykong]

Cayin will attend the CanJam NYC next week and we'll taking up the private room Uris, this is Cayin's first attempt to run a private room in CanJam, the ample space has enabled a lot of possibility for us including setup a special tube-rolling demo for HA-1Amk2.

Cayin @ Canjam NYC Preview and Sneak Peaks Starting at [COLOR=FF00AA]30m44s [/COLOR]

​

We shall setup TWO HA-1Amk2 side by side, driving by the same DAC (iDAC-6) and using the same headphone (HD800 and Dharma D1000). One of the HA-1Amk2 will run on stock tubes, while the other HA-1Amk2 will have the EL84 (x2) and 12AU7 (x2) replaced by Gold Lion reissued tubes. These are one of the better tubes that are readily available at an affordable price. We hope by offering first-hand experience to show visitors, they can understand and appreciate the effect of tube rolling in Cayin HA-1Amk2.

This is an unique opportunity to AB test the HA-1Amk2 using different tubes, if you will attend Canjam NYC, please stop by our room and check out the HA-1Amk2 tube rolling demo.

 

[polarbear9988]

Has anyone tried 5963 with the HA-1A MK2?
 
My understanding is that the 5963 has lower maximum plate voltage than the 12AU7 but it is otherwise very similar.

 

[project86]

  Has anyone tried 5963 with the HA-1A MK2?
 
My understanding is that the 5963 has lower maximum plate voltage than the 12AU7 but it is otherwise very similar.

 
I did not try those unfortunately... I suspect it would likely work, as I've never had any problem using the 5963 in place of 12AU7. But that only represents a sample size of maybe 3 or 4, so not particularly definitive. Perhaps Cayin can chime in after they finish with the CanJam event taking place right now.

 

[zzzmonster]

Has anyone used this amp with the AQ Nighthawk or the ZMF Atticus? Thanks

 

[project86]

  Has anyone used this amp with the AQ Nighthawk or the ZMF Atticus? Thanks

 
 
Closest I have come is with several of the T50RP-based mods - Alpha Dogs, old Thunderpants, etc. It does a very good job, better than most tube amps out there likely due to stout current delivery. Tube choice will determine your final results of course.