[povidlo]

A Pristine, Compact Sound Amplifier You Build Yourself​

The HA-S is a Nutube-equipped DIY Headphone amp kit that will let you enjoy the highest quality audio anywhere. No soldering is required, so even if you are new to the world of DIY, you will be able to assemble the HA-S to add a warm, analog tube-driven signal boost to any sound source in no time!

Built-in Nutube​

Nutube is a new and revolutionary fully analog vacuum tube developed by KORG INC. and Noritake Itron Corporation. The same as a conventional vacuum tube, Nutube is constructed with an anode, grid and filament, and operates as a complete triode tube, effectively generating the response and same rich harmonic characteristics of conventional vacuum tubes in a more compact, stable and energy-efficient way.
The transparent case of the HA-S delivers a glimpse into this technology; allowing the glow of the tube to be visible at all times.

Energy efficiency​

The filament of the Nutube is powered by a DC to DC converter, which consumes less electric current and thus allows for a longer battery life than other vacuum tube equipped amplifiers. The design is so efficient that the HA-S can drive the Nutube with a line voltage of 26 V using only two A4 batteries., for a rich and authentic vacuum tube sound.

Sound possibilities​

The HA-S has a special NFB (Negative Feedback) switch, that allows you to choose from a high fidelity clean and pristine sound, or a warmer, more harmonically rich sound as expected from a vacuum tube.

When the NFB switch is OFF, the harmonics present in the Nutube (triode tube) will be amplified to create a sound rich in harmonics, warmth and textures. When the NFB switch is ON, the distortion ratio and frequency characteristics will be modified, creating a really detailed and clean sound.

For further sound modification, we have included two OP amp options for the output: the premium audio oriented "MUSES01" and the industry-standard “NJM4580”, both from JRC. These can be easily replaced so even the most purist audiophiles will be able to customize and adapt the sound of their HA-S to their heart’s content.

For advanced users who want to customize their amplifier, even more, the circuit diagrams are readily available, making it really easy to change discrete components and make your own and unique headphone amp matching your desired tone and performance -, the possibilities are endless!

Specifications
Vacuum Tube: Nutube 6P1
Connections: INPUT/OUTPUT stereo minijack
Controls: volume, internal NFB (Negative Feedback) switch
Output impedance: 10Ω, recommended load：15Ω or more
Power: 2 alkaline AAA batteries
Autonomy: approx. 9 hours
Dimensions (W x D x H): 111 65 29mm
Weight：110g（without batteries

 

[povidlo]

Korg HA-S - Unboxing and Assembly tutorial​

In this tutorial you will learn how to to build your HA-S Nutube Headphone Amplifier Kit.

 

[captblaze]

Picked one of these up and am pleased with the purchase. Always like assembling non complicated electronic projects since I was kid, and this was no different. Put it together from the instructions included although the video tutorial would have helped.
Was pleasantly surprised that there were 2 different OP amps included (NJHM 4580/Muses01). One thing I will recommend is using an IC puller to remove the Op amp that is installed and carefully realign it when reinstalling. All in all thumbs up for making this kit and having it be non complicated to assemble. Bigger thumbs up for including the Muses01 ($45 to purchase at a reputable supplier)

Will start doing some listening this weekend with The HA-S connected via lineout to a VE Megatron. DT1990 Pro will get the sound to my ears. I am curious for both a good long listen and to see how long the battery lasts.

 

[povidlo]

Regarding assembly, I had an issue whereas there was constantly noise in one channel when amp is touched/moved. I troubleshooted a few basics (re-inserting op amp, loosened/tightened knob, etc.). What ended up happening, the tube circuit board was making contact with VR5 adjuster. I tucked the harness wires under the tube to prevent it from moving. That stopped it from making contact with VR5 adjuster. All good since then.

 

[povidlo]

Picked one of these up and am pleased with the purchase. Always like assembling non complicated electronic projects since I was kid, and this was no different. Put it together from the instructions included although the video tutorial would have helped.
Was pleasantly surprised that there were 2 different OP amps included (NJHM 4580/Muses01). One thing I will recommend is using an IC puller to remove the Op amp that is installed and carefully realign it when reinstalling. All in all thumbs up for making this kit and having it be non complicated to assemble. Bigger thumbs up for including the Muses01 ($45 to purchase at a reputable supplier)

Will start doing some listening this weekend with The HA-S connected via lineout to a VE Megatron. DT1990 Pro will get the sound to my ears. I am curious for both a good long listen and to see how long the battery lasts.

It's freakin awesome HA-S comes with MUSES01, very high quality op amp. Unfortunately (for me) HA-S works with single version op amps. All other op amps and amplifiers I have use dual version op amps. So for now I stuck with MUSES01 and haven't done any op amp rolling. The other cheap stock op amp included with HA-S is pretty bad in my opinion, I've heard it before in other units.

Regarding batteries, it's mentioned on the unit to use 1.5V AA batteries. 1.5V AA is only available in non-rechargeable version. This is what I have been using. Rechargeable AAs come with 1.2V voltage only. So technically, rechargeable will only provide 2.4V, while non-rechargeable provide 3V of voltage. Apparently, non-rechargeable will go dead as soon as it drops to 1.35V. So although more expensive to use non-rechargeable, it seems like they're able to provide proper, higher voltage to HA-S.

 

[captblaze]

It's freakin awesome HA-S comes with MUSES01, very high quality op amp. Unfortunately (for me) HA-S works with single version op amps. All other op amps and amplifiers I have use dual version op amps. So for now I stuck with MUSES01 and haven't done any op amp rolling. The other cheap stock op amp included with HA-S is pretty bad in my opinion, I've heard it before in other units.

Regarding batteries, it's mentioned on the unit to use 1.5V AA batteries. 1.5V AA is only available in non-rechargeable version. This is what I have been using. Rechargeable AAs come with 1.2V voltage only. So technically, rechargeable will only provide 2.4V, while non-rechargeable provide 3V of voltage. Apparently, non-rechargeable will go dead as soon as it drops to 1.35V. So although more expensive to use non-rechargeable, it seems like they're able to provide proper, higher voltage to HA-S.

Reading the data sheets for both models they are listed as dual op amps. I was looking at a BB as a potential future roll, but I want to make 100% sure that this board can handle dual op amps before I needlessly make with the magic audio smoke

 

[ClieOS]

...

Regarding batteries, it's mentioned on the unit to use 1.5V AA batteries. 1.5V AA is only available in non-rechargeable version. This is what I have been using. Rechargeable AAs come with 1.2V voltage only. So technically, rechargeable will only provide 2.4V, while non-rechargeable provide 3V of voltage. Apparently, non-rechargeable will go dead as soon as it drops to 1.35V. So although more expensive to use non-rechargeable, it seems like they're able to provide proper, higher voltage to HA-S.

Not entirely true.

Yes, rechargeable NiMH AA battery only comes in 1.2V. However, some rechargeable Li-ion / Li-polymer AA sized battery actually is 1.5V (it has a 3.7V battery cell inside with built-in a constant voltage converter to output 1.5V). I used them on my Stax SR-002 (which also takes 2 AA sized batteries) all the time.

 

[povidlo]

Not entirely true.

Yes, rechargeable NiMH AA battery only comes in 1.2V. However, some rechargeable Li-ion / Li-polymer AA sized battery actually is 1.5V (it has a 3.7V battery cell inside with built-in a constant voltage converter to output 1.5V). I used them on my Stax SR-002 (which also takes 2 AA sized batteries) all the time.

i've never seen rechargeable 1.5v AA. please share the link to the ones you're using.

 

[povidlo]

Reading the data sheets for both models they are listed as dual op amps. I was looking at a BB as a potential future roll, but I want to make 100% sure that this board can handle dual op amps before I needlessly make with the magic audio smoke

I understood this is a single op amp based on this note in the manual. I could be reading it incorrectly? I wonder if there's a way to visually tell a difference between MUSES01 single and dual versions?

 

[captblaze]

I understood this is a single op amp based on this note in the manual. I could be reading it incorrectly? I wonder if there's a way to visually tell a difference between MUSES01 single and dual versions?

I’ll be contacting KORG tomorrow for clarification. Both Op amps are listed as dual on their data sheets and from everything I’ve researched so far

 

[captblaze]

i've never seen rechargeable 1.5v AA. please share the link to the ones you're using.

Amazon has them, but the reviews aren’t too encouraging. Lots of failures

 

[ClieOS]

i've never seen rechargeable 1.5v AA. please share the link to the ones you're using.

The brand I used is KentLi. I used this particular brand because it is actually one of the first Chinese company that makes 1.5V AA style Li-ion battery at the time and has a fairly decent reputation as battery manufacturer, but the downside is that it needs its own special charger to charge its battery. I have seen other newer brand that can be charged via Type-C, though I have no idea how those fair. These days Li-ion 1.5V AA is much more common in China then when I bought mine so there should be bigger brand to buy.

 

[captblaze]

Received a reply from KORG, not much more than what is in the manual

Thank you for contacting Korg USA Product Support.

As specified in the manual, you can replace the op amp with a DIP8 style type with the voltage rating of 24-28 V single power.



my best advice is read the data sheet for the op amp you want to try. some are both single and dual power and that information should be on the data sheet

 

[povidlo]

Received a reply from KORG, not much more than what is in the manual

Thank you for contacting Korg USA Product Support.

As specified in the manual, you can replace the op amp with a DIP8 style type with the voltage rating of 24-28 V single power.



my best advice is read the data sheet for the op amp you want to try. some are both single and dual power and that information should be on the data sheet

Thanks for sharing. Too bad Korg can provide a clear answer. I'm probably just going to stick with stock muses01 for now. Keep the thread posted if you end up doing any op amp rolling.

 

[captblaze]

Burr Brown OPA2137P works with this amp. Thankfully it works with single and dual power supply. No ability to A/B, so all I can say is that it works and there is no hiss or static of any kind.

VE Megatron LO to HA-S
HD700 / DT1990 Pro are the headphones used