DAC - Elvee's Circlophone Power Amplifier - PCB

Price: 200.00INR
Ex Tax: 200.00INR
Brand:  diyaudiocart (DAC)
Product Code:  ELV-CP-35W-PCB
Availability:  In Stock
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DAC - Elvee's Circlophone© Power Amplifier - PCB


Circlophone© is a new topology (a more efficient Class A, dynamic Class AA), with a live sound character and an easy build. This design is reference to the Elvee's Circlophone© amplifier. It is capable of delivering 35W into 8 ohms. This is a very well designed audio power amplifier that will give you true Hi-Fi quality suitable for the most demanding HiFi Power Amplifier build. It provides high input sensitivity, low distortion, good frequency response and operating stability. Two of these kits can be used together to make a modern high quality Stereo amplifier.

The following features makes it unique from other power amplifiers. It combines a circlo output topology with an active bias servo. The servo stabilizes the quiescent current, but it goes further: it actively controls the output stage so that both sides always remain active in a "warm" class AB, having most of the attributes of the full class A, including a complete absence of crossover artifacts.

It is extremely easy to build, offers excellent performance even with 2N3055's, requires no adjustment, no matching, no thermal compensation and yet has a rock-solid thermal stability. It is also incredibly healthy, and behaves gracefully, even with loads lower than 2R. In short, a nice little amplifier, not in the top-class, but with excellent all round performances.

Meet the Circlophone©!!!

Technical Specifications:

Power: 35W RMS @ 8 ohms impedance, 70W RMS @ 4 Ohms impedance

Supply Voltage: +/- 25V DC

Output impedance: <3mΩ @1KHz

THD @1KHz and 0.9*Vmax: <0.005%

Full power bandwidth: >100KHz

Slew rate: Positive ~24V/µs, Negative ~20V/µs


  • More efficient Class A amplification (Warm Class AB)
  • Robust ON semi output devices (MJL21194) with excellent SOA and gain linearity
  • Same-sex output transistors
  • Fully tested and pre-assembled 
  • Crystal clear fatigue free sound quality
  • High quality components (OnSemi, Visha, WIMA, Fairchild, Panasonic and Nichicon)
  • Excellent value for money
  • With minor modification output power can be increased to 75W (See Sizing Chart in the Schematic)


  • Best for Bookshelf speaker's
  • Mono block amplifier
  • Instrument amplifier
  • Stereo amplifier
  • Active Speakers

Useful link for reference from DIY Audio Forum:

Building Elvee's Circlophone: Documentation, Parts, Accessories, & beginner friendly, Please Click Here.

Schematic, Please Click Here.


I. The output voltage together with the collectors currents of the output transistors: one can see that Ic never falls below ~75mA, and that the crossing current (Iq) is ~150mA (warm class AB).

II. The Circlophone© has its THD practically unchanged on a strongly inductive load.


III. Clipping behaviour, It is shown with 20V supplies, the clipping occurs to within <1.5V of either rail.

Please note that the above images of measurements are taken from diyAudio forum which are posted by Elvee.

Usage notes:

  1. This listing is for PCB only and hence users who are well versed in electrical/audio field should buy the product. It’s not a responsibility of the seller for any accidents/hazards arising out of improper /inexperienced usage.
  2. Connections are clearly marked on PCB and also in image. Do not interchange the wiring connections.
  3. Always use a Mains Bulb Tester (MBT) before powering on for the first time.
  4. Do not touch any part of the circuit unless the AC mains are unplugged and PSU is completely discharged.
  5. Never operate the amplifier without a heat sink - even for testing, even for a short period. The output transistors will overheat and will be damaged.
  6. Price listed is for single PCB. 

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