New article on weibo about the EA4:
http://weibo.com/5819639917/5078082...trans=5819639917_5078082007075645&s_channel=4
EA4 "Evolution of Design" — 4 Practical Improvements for the User
As a flagship tube amp, the EA4 sticks to our philosophy of “good things take time”. After several adjustments and improvements over different versions, the final EA4 now combines top-grade sound quality with the best user experience. We'll break this down into two parts: exterior design and internal design. This first part is giving you an in-depth look at this new product.
(Note: In the images referenced in the article, the higher the position of the EA4 version, the newer it is, meaning the EA4 in the top image is the final release version.)
Improvement#1:Larger Heatsinks for Better Cooling
The case design is where you’ll notice the most obvious changes. Compared to the early flat-surfaced prototypes, the final version introduces several grooves. We know that the final version of the EA4 can output a maximum power of 6500mW@32Ω, which generates a lot of internal heat. If this heat is not transferred from the inside to the case, it will cause the internal temperature to rise and affect the lifespan of the components.
For a high-powered tube amp like this, the large surface area equals better heat dissipation. That's why we added cooling fins to the case —it’s the most effective way to increase the area that transfers heat.
Improvement 2: Clear Volume Display to Prevent Sudden Loud Volume
Volume scale design ：During exhibition and our internal tests, we noticed many users preferred pairing the EA4 with IEMs, most of which are low-impedance. With the EA4’s high power output, there’s a real risk of "ear-blast" volume without some kind of volume display. If you had to adjust the volume to the lowest setting every time before using it, and then slowly raise it after putting on the IEMs, it would be too troublesome. Therefore, we considered adding a visible volume scale.
Custom Potentiometer: Standard analog potentiometer don’t show volume levels, so we had to specially design a potentiometer with visible markings. We had to get it right — the scale range had to be evenly distributed, the size of the potentiometer had to fit inside the case, and the performance deviation between each potentiometer had to be minimized. We also needed to consider the impact of the potentiometer on sound quality. After a lot of tweaking, the potentiometer delivers great sound, a smooth and accurate markings, and minimal channel imbalance at low volumes.
Power/Preamp-amp status indicator light:Additionally, this potentiometer also includes a power status indicator. Since the power button was moved to the rear panel, checking the status would otherwise be a pain. Plus, the LED changes color to show whether you’re in preamp mode or amp mode, making it super easy to know what’s going on.
Improvement #3: Optimized Front Panel Layout for More Tuning Options
Replaced Toggle Switches for Push Buttons to Prevent Accidental Power On: In the early prototypes (see the bottom pics), notice the four toggle switches on the lower part of the front panel. The leftmost switch changed from an on/off power switch to an ILH/ILA switch (Input Level Hold/Attenuation). the power switch，which was too easy to hit by accident, especially when placing in a bag. If triggered, it could leave the EA4 running, draining the battery. To fix that, we moved the power button to the back and switched it to a push button that requires a long press to turn on. We also added a MCU to enable this long-press feature, along with a double-tap option for switching between pure preamp and amp modes.
New ILH/ILA Mode Toggle:The four toggle switches on the front are all for sound tuning, and with the new ILH/ILA switch, doubles the number of tuning combinations. The toggle originally named 0dB/-6dB, but we changed it to ILH/ILA since the -6dB option was too much of a attenuation, making it hard for the preamp to compensate. This also avoids confusion about whether it controls the gain for the amp section.The actual attenuation value for the ILA mode is less than -6dB.
Lowering the amp’s supply voltage for higher current output: Another change is in the second toggle from the left, where the ±12.8/±16V switch was changed to ±13/±15V. Lowering 16V to 15V balances the current output. As everyone knows, when the power remains the same, increasing the voltage will reduce the current, which affects the amp's ability to drive low-impedance headphones. Considering this, we decided to limit the voltage swing to ±15V.
Improvement #4: Power Indicators for a More User-Friendly Experience
Power Button Update: In the earlier versions, the rear panel didn’t have a power button at all. Later versions moved the power button and charging port to the rear. Now, it’s a long-press for on/off and a double-tap for switching modes, all designed to prevent accidental power on.
Adjustment of the charging port location: We also moved the charging port to a better spot, ensuring the charge indicator is always easy to see when a USB cable is plugged in.
the images of each version are actual samples. Every adjustment was made based on our tests and feedback from users. features like the new ILH/ILA button and power switch relocation also require changes to the internal circuitry. Therefore, every external modification also implies significant changes to the circuit board.
Through these revisions, we’ve worked to fine-tune the EA4 into something that truly enhances your listening experience. We hope you can feel these improvements when you get your hands on the final version and enjoy the music even more. Thanks for your support!
