New tube amp: the Cayin HA-1A MK2

[project86]

Yes, 12AU7 is the input or preamp tube stage.
 
While you can physically fit a 6922 in place of a 12AU7, I wouldn't recommend it. They have differences which in most amps will lead to sub-par performance or even flat out failure. Exceptions exist but I don't know if the Cayin amp is one of them, and I wouldn't take the chance. 

 

[Andykong]

So the two 12AU7 are the input tubes (sometimes referred to as ECC82 or E82CC)? Correct me if this is wrong.

Searched online but can't confirm: will a matched pair of 6922 (E88CC or ECC88) tubes work as replacements for them?

 

Yes, 12AU7 is the input or preamp tube stage.

While you can physically fit a 6922 in place of a 12AU7, I wouldn't recommend it. They have differences which in most amps will lead to sub-par performance or even flat out failure. Exceptions exist but I don't know if the Cayin amp is one of them, and I wouldn't take the chance. 

Please do not use 6922 as input tubes of HA-1Amk2, they are not direct replacement and cannot be used in our tube headphone amplifier without certain level of modification.

 

[gr8soundz]

I won't be rolling the tubes on the amp too soon. First want to hear how it sounds stock which means many hours of burn-in.
 
Only asked since I'm familiar with the sound signature of a particular set of 6922s. The 12AU7s are new to me so I'll need to research which are most recommended. They appear to be fairly inexpensive but I'm trying to avoid ending up with a giant showcase of spare valves.
 

 

[abvolt]

very tempted to get one of these for my other place also really love it's look..

 

[MisterPC]

I wonder how the tubes are prevented from getting everything around them hot.

 

[project86]

  I wonder how the tubes are prevented from getting everything around them hot.

 
Good question. There's a few things at play here:
 
1) There's significant ventilation on the top panel above the tubes, which seems to be effective.
 
2) I was initially worried about the wood on the sides but there's actually a layer of metal underneath the wood portion. The wood itself gets only slightly warm, not enough to where I think it would be a problem. The metal structure underneath feels like it soaks up a good amount of heat.
 
3) The area where the tubes are located is fairly well separated from other components. There's several inches between the tubes and the nearest capacitors. 
 
4) There's also a mirror-finish metal piece isolating the tube section.  So not only is there distance between the tubes and those capacitors, but also a metal wall. 
 
The original HA-1A had a similar design and I don't think there were any reliability issues there. 

 

[gr8soundz]

One of the reasons I went ahead with the mk2 was because of how everything appears to be sectioned off internally. Really clean looking design.
 
I'll know for sure in a couple of days but (in pics) I thought I saw several horizontal vent slots along the wooden sides. Good to know there's metal underneath them though.
 
Btw, is the wood removable so the sides can be all metal like the original amp?
 

 

[project86]

No the wood is attached to the metal "shell" underneath. There's no separating them.
 
I had a hard time removing the outer case at first. As with many enclosures or covers, once you figure out the right way to angle as you pull, it's not so hard. I was really worried it would be super delicate but it seems pretty tough. Still not as easy as swapping tubes on a more "traditional" open-tube design though.  

 

[gr8soundz]

 
I had a hard time removing the outer case at first. As with many enclosures or covers, once you figure out the right way to angle as you pull, it's not so hard. I was really worried it would be super delicate but it seems pretty tough. Still not as easy as swapping tubes on a more "traditional" open-tube design though.  

 
That's another reason I ordered the mk2. I'm not much of a tube roller (yet) and shy away from exposed tubes. No concerns about accidentally hitting them or being burned because they're all enclosed. I know most tubes are tougher than they look though.
 

 

[gr8soundz]

Received the mk2 yesterday. All around, a very impressive amp so far. Will post impressions soon but thinking I may do my first full review (on head-fi at least) to help others who want more complete details (as best I can provide). Lord knows we need more info out there about this amp; (as of today, PTA is still posting stuff from RMAF......... 

 ).
 

 

[abvolt]

  Received the mk2 yesterday. All around, a very impressive amp so far. Will post impressions soon but thinking I may do my first full review (on head-fi at least) to help others who want more complete details (as best I can provide). Lord knows we need more info out there about this amp; (as of today, PTA is still posting stuff from RMAF......... 

 ).
 

cool, include some pics if you would & congrats on your new amp..

 

[gr8soundz]

Thanks. Still listening and burning it in a bit (maybe 10-12 hours so far; giving tubes a long rest between sessions; rather not keep them running 24/7).
 
The sound is impressive but I'll need more time to properly describe further details. More to come......
 
I will say this though: Build quality is exceptional.
 
Here's a quick (rough) pic with the Vali on top for size reference.
 

 

[gr8soundz]

Here's a few listening impressions after about 45 hours burn-in (trying to give the amp 100-200 hours before making any final conclusions):
 
The mk2 sounds more neutral than I expected. Closer to a laid-back hybrid with a ton of power rather than an all-out euphonic tube amp. It does have that smoother, fuller sound with a (very) beefy low-end, extra-wide soundstage, and an overall hint of warmth. Vocals sound intoxicating and instruments hit with tons of impact yet the sound is never fatiguing.
 
At times the Cayin might be too powerful. I rarely get past 9 o'clock on the volume dial before things get too loud. There is some hiss even with my 600 ohm T1.2 on all but the lowest impedance setting but its faint and doesn't really intrude on the music.
 
Obviously I'm still on the stock tubes. With such a (relatively) neutral sound, I don't doubt that the amp's character changes with different tubes (just as @project86 mentioned). Guess I'll be seeking out some 12AU7s that might run quieter, further widen the soundstage (to feed my addiction), and add a bit more musicality. I hear the Mullards and RCA Clear Tops are good candidates.

 

[gr8soundz]

Turns out the hiss I was hearing was caused by a defect.
 
I'll be shipping the mk2 back and am currently in communication with the dealer and manufacturer.
 

 

[project86]

I must have missed your initial post about hiss - you definitely should not have any using the 600 ohm T1. Glad to hear the dealer is taking care of you, as they should.