JD SERENADE

                                                                              JD SERENADE

                            HIFI Bluetooth 5.0 Integrate Tube Amplifier

1. The Serenade panels are made of aluminum and treated with wire drawing oxidation to create an even and fine texture. On the panel, from left to right, there are power switch buttons, volume and channel switching knobs, and Bluetooth indicators. The volume and channel switching knobs have a retro design with a flat single-handle knob featuring a round bottom - not so much nostalgic as they are a tribute.
2. The upper end of the machine features three large transformer housings. A total of eight tubes are arranged in a sequential manner, with alternating heights. Each of the three transformers is individually packaged and separated by aluminum plates on both sides for stable structure and insulation from electromagnetic interference. The entire machine is equipped with a removable black hollow metal mesh cover, adorned with delicate round holes, resulting in an extremely refined and precise appearance.
3. The simplicity of the panel is echoed by the Serenade. The back of the Serenade is equally simple, with a red power switch in the center and a closely connected US standard power input port on the right. Below, there is a dedicated ground terminal provided. On both sides of the power switch, two groups of three large custom pure copper gold-plated terminals are arranged, totaling six terminals. These terminals correspond to the connection of 4Ω and 8Ω different impedance speakers for left and right channels. Additionally, there are two sets of signal input RCA gold plated sockets located on the far left side of the backplane for connecting different audio sources. Next to these RCA gold-plated sockets, there is also a gold-plated SMA port placed for Bluetooth antenna connection.
4. The Serenade is equipped with a Bluetooth 5.0 module that meets industry-high specifications, providing dynamics of up to 120 DB-A. It supports Apt-X HD for high-quality audio transmission decoding and has been specially adjusted for optimal compatibility. Even with ordinary Bluetooth audio signal sources, it delivers excellent playback effects. When used with an HD format signal source, it offers a listening experience surpassing that of CD soundtracks.
5. The Serenade power tubes are all Russian Electro-Harmonix tubes. Each channel is equipped with one ECC83-S built with an improved SRPP circuit as the front stage and an optimally designed long tail inverter amplifier circuit using ECC81. These circuits drive a pair of EL34EH parallel outputs for each channel, resulting in sine-wave undistorted output power up to 30W/8Ω. The amplifier also has abundant power reserve.
6. Serenade has made several design improvements in internal circuitry and component selection. It starts with the most basic PCB board, which is made of epoxy resin material with a high glass transition temperature point. This material has excellent moisture resistance and high temperature stability. The PCB board is wired with copper foil weighing up to 2 ounces thick, reducing the skin effect across the full band. As a result, the current density of electric load is greatly improved, overcoming the difference in transmission impedance between high and low frequency signals and providing a solid physical foundation for sound reproduction. To overcome the low-frequency roll-off that occurs when output transformers are used with large signals, a specially designed low-frequency correction circuit based on equal loudness curve is implemented. This circuit allows for enhanced low-frequency density when listening at lower volumes while minimizing low-frequency drop during louder playback.
7. Serenade circuits are designed to provide an authentic listening experience, with strict pipe matching at a reasonable cost. The traditional large loop negative feedback of the machine is abandoned, and instead independent feedback windings are incorporated into a newly built output transformer for improved feedback stability and reduced transient distortion. The high voltage power supply utilizes a specially designed Kelvin wire film capacitor, resulting in reduced output impedance of the full frequency power supply and providing high density transient energy. This also stabilizes the sound floor and creates sharp dynamics.
8. Serenade bias adjustment is still done in a way that allows guests to participate. Use a flat-head screwdriver to adjust the adjustable resistance set in the countersunk hole at the end of the fuselage. The bias of the four tubes can be easily adjusted to enhance sound accuracy.
9. The design of Serenade is fully optimized, making the circuit more reasonable and smooth. The frequency response index has been significantly improved, resulting in excellent sound performance based on superior parameters. In particular, it excels in the "first watt of gold" performance. It achieves a flat amplitude response across the full frequency range of 20Hz to 100kHz, ensuring low in-band distortion and noise levels. This lays a solid foundation for transparent, deep, and broad sound performance. Since its victory in Las Vegas in 1996, this is the seventh round of upgrades to this classic product, making it the pinnacle of excellence that is worth listening to and owning.

Amplifier technical specification

Rated Output Power: 30 W per channel at 8 ohms, 18Hz to 60KHz

Maximum Power Output : 60 W per channel at 8 ohms, 1KHz

Frequency Response:  (at 1 watt into 8 ohms)10Hz to 60KHz±3dB;0dB at 1KHz

Bandwidth: 12Hz to 65KHz （-3dB）; 0dB=30 W 1KHz, 8 ohms

Distortion THD: Less than 1% at 15W output, 50Hz to 20KHz, 8 ohms

Circuit Type: Ultra Linear, Class AB1

Input impedance: Less than 100K ohms

Input sensitivity: Max. 320mVrms at 1KHz for 30 watt output

Output Impedance:4 ohms and 8 ohms

Negative Feedback:Less than 9 dB

Noise and Hum: 85dB at rated output

L/R Isolation:  78dB at 1KHz

Channel Isolation:  82dB at 1KHz

Tube Complement:4 matched pairs(4) of 6CA7/EL34 power output；2pcs. 12AX7A(ECC83-S) pre-amplifier；2pcs. 12AT7(ECC81)power drivers.

Dimensions:11.81 inches(30 cm)wide by 12.2 inches(31 cm)deep by 8.27 inches(21 cm) high

Weight: 33 pounds(15 kg) net, approximately 50 pounds(23 kg)  Packaged

Bias adjustment: 180 mV

Fuse: 100-120 VAC, 6.3 fast blo; 200-240 VAC, 3.15 fast blo,5mm x 20mm

Warranty :One years limited parts and labor. Six months or 500 hours whichever comes first on Jolida Tubes.