[Hebs]

My question is if I mounted two RCA 5963 (12AU7-ECC82) NOS Grey, would I already have an improvement over the stock tubes?

Most definitely yes! Even new production JJs offer an improvement. NOS from the 60ies are awesome. But tube rolling is for fun too. Só don't start paying too much for NOS. Try the cheap stuff too to see how much of a difference you notice. I'm using Phillips Miniwatt 12AU7 and I love them!

 

[stefsant]

Most definitely yes! Even new production JJs offer an improvement. NOS from the 60ies are awesome. But tube rolling is for fun too. Só don't start paying too much for NOS. Try the cheap stuff too to see how much of a difference you notice. I'm using Phillips Miniwatt 12AU7 and I love them!

First of all, I have a black background. Only when switched on are there "frying" noises for a few minutes until the valves heat up. With the original tubes, especially on the right side, every now and then you can hear some slight interference due to the microphonics (like radio tuning), however not evidently perceptible during normal listening. With other 12AU7 tubes the problem is greatly mitigated or disappears completely.
I'm doing some tests with the 12AU7, also giving a "listen" to the amplification stage of the EF400 with equal listening volumes, using the balanced output of the Hifiman amp.
I tried three different pairs of 12Au7s with the Ananda nanos. Fast and "relaxed" tests to have starting references. Notwithstanding the constant greater naturalness and materiality as well as the more visceral impact of the Cayin compared to the EF400, the valve change offers a small difference that I would rate as greater than a signal cable change but less than a cartridge change on the turntable. Small consideration with respect to the declared power: The Cayin would have with the Ananda (selector switch on 8-32 Ohms) 1400 mW vs. 4400mW of the EF400 but the perceived sound pressure levels are equivalent.
First of all, I quickly tried the RCA 5963: airier and more detailed than the tubes supplied. Tonal balance on the clear and feeling of lack of "something in between".
I then moved on to the Siemens 5814A: Dynamic, detailed and equipped with a tight and controlled bass but also "physically" present. Tonally similar to the EF400, and halfway between the RCAs and the Stock tubes. Here, the advantage of the second output of the Cayin with the warmer sound, makes the Siemens almost perfect. Disturbances due to microphonics have become very sporadic.
The last stage of the first lap is the transition to the Brimar 6067: Darker shade with a warmer feeling even compared to the EF400 used as a fixed tonal reference. Slight impact loss compared to Siemens. Almost shared microphony as for Siemens. Tonally, the Brimars seem similar to the stock tubes of the Cayin.
I only have one Gold Lion ECC82 from four or five years ago with a hundred hours and I don't know if it's advisable or feasible to pair it with a new one.
Now, I'm waiting for a pair of Mazda Belvu EL84s to redo a second round of 12AU7 valves with new power valves.

 

[Hebs]

Thanks so much for posting your findings!!! Gold Lion ECC82 is supposed to be very good! I am trying to get a hold on a pair of those, but here in Brazil, it's almost impossible!
Anyways, looking forward to your further exploration of tubes for this beloved amp! I most certainly love mine!
Regards!

 

[jojothewhale]

Guys, has anyone managed to completely get rid of the noise floor of the HA-1A MK2? So far I’ve reduced the initially strong hiss to practically nonexistent, but there’s still a quiet low hum left. Nothing to worry about but can’t help but to think it may be just as solvable as the hiss issue, with the right treatment. I noticed a few posts throughout this tread the amp being referred to the amp as “dead silent” but I couldn’t tell if it was meant literally or as in “pretty quiet for a tube amp of this price range”. Any actually dead silent HA-1A MK2 out there? Your feedback is much appreciated.

I own two of these Ha-1A mkii tube amps and live them! Both of mine are silent. However one had bad tube whine noise sound when I first got
It… i replaced the 2 12au7 tubes with Mullards match pair and it instantly went away and is dead silent now…I have the Mullards in both…fantastic sounding tube amp!

 

[ChristoT]

I own two of these Ha-1A mkii tube amps and live them! Both of mine are silent. However one had bad tube whine noise sound when I first got
It… i replaced the 2 12au7 tubes with Mullards match pair and it instantly went away and is dead silent now…I have the Mullards in both…fantastic sounding tube amp!

Thanks for the reply. Meanwhile I also managed to lower the noise floor of my rig down to negligible. In my experience- the RCA cable grounding the preamp outputs has to be a model with good shielding or else it too adds noise. Feels kinda wrong to waste a good RCA on such a silly thing but it seems there’s no other way. I tried noise caps instead but, while helpful a bit, they didn’t block the noise as completely as a cable connected to a secondary device did.
And the final touch that annihilated the noise were the Goldlions. Now the system just sings.

 

[Hebs]

Hi guys, this amp is 495 on Drop! Very very cheap! It's on pre-order.

 

[stefsant]

Guys, has anyone managed to completely get rid of the noise floor of the HA-1A MK2? So far I’ve reduced the initially strong hiss to practically nonexistent, but there’s still a quiet low hum left. Nothing to worry about but can’t help but to think it may be just as solvable as the hiss issue, with the right treatment. I noticed a few posts throughout this tread the amp being referred to the amp as “dead silent” but I couldn’t tell if it was meant literally or as in “pretty quiet for a tube amp of this price range”. Any actually dead silent HA-1A MK2 out there? Your feedback is much appreciated.

I had heating noises when I turned it on, microphones when I hit it from the side or from above, and random noises, particularly at certain times. I eliminated everything by replacing the tubes, especially the EL84s and connecting the second input to the preamp to have the turntable in headphones. However, I would like to point out that my system is equipped with shielded cables, a filtered power strip for the sources and a linear power supply for the PC.
Now my Cayin is pitch black as if it were a solid state.

 

[stefsant]

I tried several tubes: 12AU7 RCA, Siemens, Brimar, Mullard and Gold Lion as well as EL 84 Gold Lion and Mazda Belvu. I stopped with Mullard ECC82 and Mazda belvu EL84. The Siemens are also beautiful. I also enjoyed the newly produced Gold Lions, but I don't prefer the overly advanced vocals and the slight compressor effect they produce. An interesting pairing is the Mullard ECC82 and Gold Lion EL84. All these considerations with Hifiman EF400 DAC and Ananda Nano Hifiman Headphones.