Leopard Single-Ended Triode Class A 12AX7 - 6CK4 Stereo Power Amplifier
Single-Ended Class A topology
5Y3 Rectifier
2x 12AX7 Input Tubes
2x 6CK4 Power Output Tubes
Toroidal Power Transformer
Edcor EI Output Transformers
3W RMS Per Channel into 8 ohms
Input Impedance: 100K Ohms
Frequency Response: (10Hz to 40KHz)
Input Sensitivity: 970mVRMS (for maximum output of 3W)
Hand made in the USA
Front
Rear
A note from the designer/builder:
"This is a design to redefine. The Leopard demonstrates single-ended triode amplification that is very low distortion, wide bandwidth, balanced channel to channel and is noise free. I chose the 6CK4 because it is one of the most spatially vivid power tubes I have listened to music through. Paired with two 12AX7s to provide the voltage drive, this amp achieves channel to channel balance that creates a sonic experience that lets you step into the music. I recommend to match the Leopard with a line stage preamplifier and speakers 90dB and above (1W @ 1 meter) and make this your reference SET amp.
-Jesse
Leopard - 12AX7 - 6CK4 3W Single‑Ended Triode Power Amplifier
Step into the music.
Leopard is a single‑ended Class A triode amplifier built around a completely original circuit that reimagines what a single-ended triode amplification design can be. Delivering 3 watts RMS into 8 Ω, it offers a level of bandwidth, linearity, and quietness that challenges the expectations of traditional single‑ended amplifiers. At 1 watt, the frequency response is –3 dB at 10 Hz and 40 kHz, providing a very wide bandwidth. Channel balance is held to an exceptional 0.2 dB for a stereo image that is wide and deep.
Input sensitivity is 970 mV RMS for full output, making Leopard easy to pair with modern sources and speakers with 90dB sensitivity and above (1W @ 1 meter).
The signal path is elegantly simple:
2x 12AX7 input stage for voltage gain and drive
2x 6CK4 power triodes, each biased for maximum linearity
5Y3 (S or GT) rectifier feeding a dual‑mono power supply
The power supply is one of Leopard’s defining features. The 5Y3 feeds two fully independent high‑voltage rails, one for each channel, giving the amplifier outstanding separation and stability. The result is a noise floor so low that even with your ear pressed against the tweeter or woofer in a silent room, there is no audible noise.
Leopard’s aesthetic reflects its purpose: performance. The powder coated steel chassis is framed by hand‑sanded, oil‑finished solid leopardwood panels with a natural patterning that gives the amplifier its name. A toroidal power transformer and USA‑made Edcor EI output transformers anchor the design with robust magnetic performance and wide bandwidth.
The amplifier’s voice is shaped by the 6CK4, a triode rarely used in audio, yet capable of remarkable linearity when optimized. In Leopard, it becomes the heart of a presentation that feels open, dimensional, and immersive. This is an amplifier that doesn’t just reproduce music, it lets you step into it. Instruments float in real space and the performance venue becomes a place you can sit and listen.
Leopard is a ground‑up, original design built to show what a modern SET can be when distortion is low, bandwidth is wide, and noise is essentially nonexistent.
Leopard: The single‑ended triode amplifier, redefined.
Specifications
Output Power:
3W RMS per channel into 8 Ω (sine‑wave tested)
Frequency Response (1 W):
–3 dB at 10 Hz
–3 dB at 40 kHz
Tube Complement:
5Y3 rectifier
2x 12AX7 input stage
2 ×6CK4 single‑ended output stage
Transformers:
Edcor Output transformers (USA)
Hand‑selected power transformer
Topology:
Single‑ended Class A
All‑tube signal path and power supply
Construction:
100% point‑to‑point wired
Hand‑built and voiced
Weight: 13lbs
Dimensions: 12" W x 8" D x 3" H