[Zachik]

That's really a rule? I wish there was a translate button after each post

"The language of Head-Fi is English. Please do not post in other languages." - see:
https://www.head-fi.org/articles/posting-guidelines.14048/

 

[IPMano]

Sorry, but just between Gr3... and me, not important message and i've begin
if i speak english like a spanish cow, sorry.

 

[Zachik]

No worries. BTW, you guys can always use PMs (Private Messages) in ANY language you feel like

 

[Gr3g277]

Ok i was not aware of that sorry !
Basically we ordered the ha 6a at almost the same moment, an unfortunately for ipmano, i was the fastest...
It is not very widely available in france yet, it seems !
@Zachik i didn't know about the pm feature thx for the clarification

To get back on the topic, i feel like the hiss issue you guys are talking about, is 50/60hz hum ?

With the hd 650 it is quite noticeable on the high impedance setting... jdut like when you turn on a big ass tube guitar amp with loads of gain !!

I know a bit about tubes , and the choice of the 12 au7 should be silent, as it is a low amplification factor tube.

For instance the 12 au7 amp factor is around 20, where a 12 ax7 in exemple is around 100.

Wondering what is happening here !

Nevertheless, the guitars are soo textured, i love it

 

[Andykong]

hello guys,

Long time reader, not much post here, but I am an avid hifi and headphone enthusiast
I received my HA-6A juste a few days ago, and I am still in the burn-in phase.

What I can say now is that this amp sound really amazing, but as a diva, it is exigeant with the setup...
What a beauty !
pics or it didnt't happen




I have 3 headphones to use it with :
- hifiman ARYA
- sennheiser HD650
- Kennerton Magni

I tested 3 dacs with it:
-marantz hd dac 1
-topping dx3prov2
-schiit bifrost 2 ( retrieved from the main hifi system for testing puposes )

First I will not comment on the sound just yet, because it is still not burned in fully yet, and well, i am not fully decided on the tubes..., but I can already say that the sound quality is very much to my liking...

I read the entire thread, and noticed some of you are experiencing issues with noise and/or hiss.
I would like to share my experience with this beast.
First, I am in france so my unit is 230V/50hz . I planned to use the amplifier for my computer rig, so digital only. First try was with my hd650, connected via RCA to the marantz dac, and usb to the PC....
This was not so good... lots of very loud noise, i could hear blips and high ptiched noise... something was definetely wrong here!
the amp was grounded to the power plug properly, good connection with the rca to the marantz DAC, but it was really unlistenable at first, I was puzzled ! I tried switching dac, with the topping, same problem ! then I scavenged the bifrost 2 from the living room to try a balanced connection.

Strange pc Noise was gone ! and the unit was silent ! ( almost... more on that later )

I understood from my testing that this amp, with all the power available, is very sensitive to grounding...

The bifrost 2 is grounded to the mains...not the other two dacs, so they were connected to the ground via the USB plug on the pc, which is connected to the ground. So there was a ground loop with the PC Usb cable and the rca connector... I confirmed this by connecting an optical cable between the marantz dac and the noisy pc, thus eliminating the shared ground from those two = bingo ! silence !

Now we can talk about the hiss issues you guys are talking about.
I tested with the arya, no problems whatsoever, regardless of the impedance settings, sounds gorgeous
with the hd650 however, on the high impedance setting, I don't get hiss, but I get HUM, very noticeable. on the low impedance, hum is almost non existent.

I think it is related to the very high power the amplifier gives to a 300ohm load.... or maybe to much gain ? with xlr IN in can turn the volume 3 cliks and i have loud music already !

The preamp part is very sensitive to the quality of your tubes as well, I tried NOS 5814a RCA blackplates, JJ ECC802S and the 12au7 from my primaluna main amp , and the quietest one is actualy the original EH that comes with it.
I get hiss and microphonics with the NOS 5814a and low hum, no hiss or microphonics with JJecc802s but louder HUM ! so my advice is check your preamp tubes !

I have some 6189 and 6L6 on the way, i'll report back when I get them !

Also i have a question, how hot does the power transformer get on your devices ? on mine After 2h of playing, I can barely touch it ! I know it is Class A but it feels really hot ! much hotter than my primaluna for exemple.


here is my first experience, I think it is a great amp but It need some work to give the best.

regards

Thank you for your sharing, your experience is very helpful to fellow HA-6A users and tube headphone amplifier users in general.

USB Audio cable is a known source of interference, it can be a ground loop problem as you have encountered, or it can be a back cable design that doesn't provide proper insulation between the power wire and the data wires.

Some tubes are more sensitive to RF interference than other, its is not necessarily a bad tube, just a design issue that make is less suitable for high end audio application.

 

[Little Bear]

Does anyone think the HA-6A would be able to drive the Hifiman Susvara or HE6se without any issue? Both are low impedance planars with about 83 dB/mW sensitivity.

 

[Andykong]

Does anyone think the HA-6A would be able to drive the Hifiman Susvara or HE6se without any issue? Both are low impedance planars with about 83 dB/mW sensitivity.

According to @GU1DO, HA-6A can power HE6se easily (HERE)

 

[Gr3g277]

Hey guys,

just a quick update to let you know that I received some Jan 6189, and that i'm loving those tubes

Still enjoying the amp a lot with my arya, and i'll give my listening impressions in a while, when I will be more used to the unit. ( I have quite some tubes to test lol )

I was wondering about the resistor change that @Relaxasaurus was talking about , any news about that ? I can help as well, if needed as i am an engineer.

I also have some questions for @Andykong :

-we already know that changing the impedance switch affects the ouptut power of the amp , but how does it affect the output impedance ? do you have numbers for output impedance for all the modes ? for example, if listening to a 300ohm can on L impedance switch, is it bad for the amp ? what about the other way round ?

-The VU meters , how are they calibrated ? do they monitor the input signal only ? or are they related to the output power as well ? I can tell that they do not behave similarly when using different headphones ( I had them maxed with the arya already, not with the hd650 unless unconfortably loud ).

best regards

 

[Andykong]

Hey guys,

just a quick update to let you know that I received some Jan 6189, and that i'm loving those tubes

Still enjoying the amp a lot with my arya, and i'll give my listening impressions in a while, when I will be more used to the unit. ( I have quite some tubes to test lol )

I was wondering about the resistor change that @Relaxasaurus was talking about , any news about that ? I can help as well, if needed as i am an engineer.

I also have some questions for @Andykong :

-we already know that changing the impedance switch affects the ouptut power of the amp , but how does it affect the output impedance ? do you have numbers for output impedance for all the modes ? for example, if listening to a 300ohm can on L impedance switch, is it bad for the amp ? what about the other way round ?

-The VU meters , how are they calibrated ? do they monitor the input signal only ? or are they related to the output power as well ? I can tell that they do not behave similarly when using different headphones ( I had them maxed with the arya already, not with the hd650 unless unconfortably loud ).

best regards

The output transformers of HA-6A were specially winded to provide three set of impedance matched outputs at 8-64Ω, 65-250Ω, and 251-600Ω respectively, the exact impedance might vary but basically they are somewhere around the mid-value of these ranges.

The VU meter is reporting the current output power, it is a linear proportion of the output in Vrms (not watt per channel).

The HiFiman Arya has a much lower sensitivity then HD650, so despite the HD650 is rated at 300ohm impedance, the actual power required to drive the Arya at your regular sound level is HIGHER then the power required to drive the HD650 at the same sound level, so the VU meter will swing closer tot he red area when driving the Arya.

 

[Relaxasaurus]

I was wondering about the resistor change that @Relaxasaurus was talking about , any news about that ? I can help as well, if needed as i am an engineer.

I mailed the HA-6A to a repair center in Arizona on Cayin's dime, on May 29. It's been almost a month but AFAIK it's still at the repair shop.

I luckily have the WA22 to keep me company but that's about all the news I have.

 

[wazzupi]

I'm torn between this unit and the pendant!!

 

[Celty]

I mailed the HA-6A to a repair center in Arizona on Cayin's dime, on May 29. It's been almost a month but AFAIK it's still at the repair shop.

I luckily have the WA22 to keep me company but that's about all the news I have.

What is the problem with such a new amp?

 

[Relaxasaurus]

What is the problem with such a new amp?

I was getting hiss and the repair guy is checking it out. It may involve a simple resistor change but not sure exactly.

 

[wazzupi]

I was getting hiss and the repair guy is checking it out. It may involve a simple resistor change but not sure exactly.

Did the the hiss ever turn to ppppsssstttttt hehe

 

[wazzupi]

I think I'll be waiting til this issue has been resolved to purchase my next tube amp. But this amp is a strong contender.