Yulong A100 Class A Headphone Amplifier

General Information

A100 is a class A transistor headphone amplifier, which is carefully designed: The power comes from a high quality, custom made transformer with selected core material, then through a four-way regulating circuit, the voltage and current amplification stage are powered separately. This is to ensure the signal process is not interfered by power supply fluctuation.

The input signal is buffered by an AD827, to reduce the dependence of the signal source as well as the interconnection cable. The low impedance signal from buffer stage feeds into volume control, and then amplified by an OPA627BP (voltage amplification) and a class A transistor buffer constructed with BC557/567+MJE243/253 (current amplification). The output is separated in 2 ways, one for high impedance headphones (direct output) and the other one for low impedance headphones (in serial with 120Ohm resistor).

The designer has been working for years to research the acoustical performance from different circuits, working parameters as well as components. Combining extended listening test with the analysis from dScope Series III digital audio analyzer, A100 has achieved excellent performance – not only in test but also in listening.`

The highlights of A100:
●Lightweight and durable aluminum housing design (Can match perfectly with D100)
●Custom made, high quality toroidal transformer
●Hand matched transistors with digital transistor tester
●High end OPA627 OPAMP
●Analogue UV level display
●110-120V and 220-240V mains voltage (selectable in back plate)
●Input signal impedance convert and buffer
●Dual outputs to fit high and low impedance headphones.

Warning:please adjust the volumn to the minimum before connecting the headphone to the A100 so as to avoid excessive volumn to damage your hearing!
A100 Technical Specification:
●Frequency response:20-20KHz-0.1dB
●output power:
680 ohm: 75mw VPP:20V
300 ohm: 170mw VPP:20V
50 ohm: 343mw VPP:20V
33 ohm: 1W VPP:17V
● Dimensions: 250*180*45mm
● Weight: 2Kg.

Latest reviews


New Head-Fier
Pros: Musical, neutral, detailed, low noise
Cons: UV meters don't add value, low cost potentiometer, plastic volume knob
Previously used the Shanling PH300(0) with my Grado GS1000, which was not a good match. The Grado sounded way too harsh and tiring, already after slightly turning the volume up.
As a result, I purchased the Yulong A100, which was basically another wild guess, despite the positive review on HF. I am very happy with the sound the GS1000 produces when powered by the Yulong A100, which is tight, airy, punchy bass, detailed and musical.
Altogether I can really recommend the Yulong A100.
A few comments to the designer, which could be considered for an I(improved) future version:
- Improve the potentiometer (Alps RK27?)
- Remove the UV meters (too small to add any value)
- Replace the platsic volume know with an aluminium one


100+ Head-Fier
Pros: Crystal clear amp, very low noise (black background), ultra low THD, price
Cons: VU meter channels are switched it's not pratical (right channel is on the left and left channel on the right)
If you want an ideal ss amp, this is the one you need, best bang for the buck.
It is a quality building and revealing sound.
If you need to know about the specs and graphs check the yulong website :


Headphoneus Supremus
Pros: Highly transparent, neutral, well balanced sound, nice build quality and a low price
Cons: Lack of balanced option feels like a missed opportunity since the matching D100 DAC has balanced outs
See above link for my detailed review.
In summary: The A100 is to amps what the D100 is to DACs. Very neutral, accurate, and transparent. It's an excellent value for the price. I docked it a star in the "Design" section because it omits balanced ins/outs, which seems odd given the D100 does balanced.
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