The CTA low distortion amplifier DiY kits

 

There are 3 configurations offered as kits, based on the CTA12 and CTA14/CTA14A low distortion audio power amplifiers, which are intended for use with audiophile home audio loudspeakers.

 

CTA MINI

Suitable for building a max. 2x50 Watts per 4 ohms or 6 ohms low distortion STEREO power amplifier with switch-on muting via a mechanical relay. It is intended as home audio power amplifier for low power audiophile loudspeakers. This kit doesn't contain the PCB and components for the Mains input/distribution & auxiliary AC power supply, but suggestions for designing this board are provided here.

Click here for the assembly instructions page.

 

CTA MIN+

Suitable for building a max. 2x100 Watts per 4 ohms or 2x90 Watts per 6 ohms low distortion STEREO power amplifier with switch-on muting via a mechanical relay. It is intended as home audio power amplifier for low or medium or high power audiophile loudspeakers. This kit doesn't contain the PCB and components for the Mains input/distribution & auxiliary AC power supply, but suggestions for designing this board are provided here.

Click here for the assembly instructions page.

 

CTA MID

Suitable for building a max. 2x100 Watts per 4 ohms or 2x90 Watts per 6 ohms low distortion STEREO power amplifier with full, independent protection for the two channels via ultra low distortion solid state relays. It is intended as home audio power amplifier for high performance, medium or high power, expensive audiophile loudspeakers.

Click here for the assembly instructions page.

 

The following are included in all the kits: all the PCB's with all components that are specified in the assembly instructions as being part of the kit. This is usually all the components that need to be soldered or mechanically fitted to the PCB's, with a few exceptions. You must populate the PCBs with components yourself. (A few examples of what is NOT in the kits: chassis, main transformer(s), main heatsink(s), most of the cables/wires, on-chassis connectors and switches, main rail filter capacitors.)

If you have questions, please send me an email.


CTA MIN kit

Suitable for building a max. 2x50 Watts per 4 ohms or 6 ohms low distortion STEREO power amplifier with switch-on muting via a mechanical relay.

  + components.

Consists of the following kit subassemblies:

        2x CTA12c (Low distortion, low power audio power amplifier PCB + components, except heatsink)

        1x PS1USc (Power supply PCB + components, except rail filter capacitors and optional heatsink)

        1x SMRS2c or 1x SMRS3c (Switch-on mute circuit with relay + components)

        1x Not supplied with kit: "MIA" Mains input/distribution & auxiliary AC power supply


CTA MIN+ kit

Suitable for building a max. 2x100 Watts per 4 ohms or or 2x90 Watts per 6 ohms low distortion STEREO power amplifier with switch-on muting via a mechanical relay.

  + components.

Consists of the following kit subassemblies:

        2x CTA14Ac (Low distortion, high power audio power amplifier PCB + components, except heatsink)

        1x PS1Snhc (Power supply PCB + components, except rail filter capacitors, heatsink and fuses)

        1x SMRS2c or 1x SMRS3c (Switch-on mute circuit with relay + components)

        1x Not supplied with kit: "MIA" Mains input/distribution & auxiliary AC power supply


CTA MID kit

Suitable for building a max. 2x100 Watts per 4 ohms or 2x90 Watts per 6 ohms low distortion STEREO power amplifier with full, individual protection for the two channels via separate ultra low distortion solid state relays.

  + components.

Consists of the following kit subassemblies:

        2x CTA14Ac (Low distortion, high power audio power amplifier PCB + components, except heatsink)

        1x PSSR2Sc (Power supply & solid state relay PCB + components, except rail filter capacitors and fuses)

        2x DPBsc (Protection circuit PCB with SMDs mounted + all unmounted components, except fan control components)

        1x MID2A (Mains input/distribution & auxiliary DC power supply PCB)


The CTA Kit Subassembly Descriptions

Note: In the images, only the PCB's are shown as they are delivered to you. You'll also get all the components with your order that are specified in the assembly instructions page of the actual kit subassembly.


Audio power amplifier

CTA12: Low distortion audio power amplifier, PCB

   size: 90x48 mm

Order code: CTA12c      CTA12 PCB + all components without main heatsink (max. 50 Watts)

Quick specs:

    - suitable for 4-ohms load

    - low distortion at all power levels (approx. 0.0015% 1kHz THD was measured on prototype at 6 ohms load)

 

CTA14: Low distortion audio power amplifier, PCB

   size: 90x58 mm

Order code: CTA14c      CTA14 PCB + all components without main heatsink (max. 100 Watts)

Quick specs:

    - suitable for 4-ohms load

    - low distortion at all power levels (approx. 0.0015% 1kHz THD was measured on prototype at 4 ohms load)

 

CTA14A: Low distortion audio power amplifier, PCB

   size: 90x59 mm

Order code: CTA14Ac      CTA14A PCB + all components without main heatsink (max. 100 Watts)

Quick specs:

    - same specifications as CTA14, but improved power supply rejection (PSR) ratio

    - suitable for 4-ohms load

    - low distortion at all power levels (approx. 0.0015% 1kHz THD was measured on prototype at 4 ohms load)

 

Power supply & relay

PSSR2S: High power stereo power supply & two ultra low distortion solid state relays, PCB

   size: 205x73 mm

Order code: PSSR2Sc     PSSR2S PCB + all components except main filter capacitors and fuses

Quick specs:

    - max. +/- 45V supply voltage

    - can serve a stereo high power amplifier

    - two pairs of snap-in type electrolytic filter capacitors up to 35mm diameter can be fitted (not supplied with kit)

    - connects to two DPB  protection boards for independent relay control

    - needs +9VDC 70mA regulated supply (with two Euraudio DPBs connected)

    - usable up to 125 Watts / 4 ohms or 75 Watts / 8 ohms amplifier output power (class B or class AB amplifiers)


Protection circuit

DPB:  Single channel (mono) protection circuit with fan control capability, PCB

Order code: DPBsc     DPB PCB with SMD components mounted + all unmounted components

   size: 60x44 mm

Quick specs:

    - switch-on and switch-off muting

    - loudspeaker (DC offset) protection

    - thermal protection (heatsink overtemperature sensing)

    - overcurrent protection

    - +9V or +12V power supplied through PSS(R) module

    - max. 20mA supply current

    - microcontroller controlled

    - indicator LED driver for all protections

    - fan control -> you must make a suitable power supply for the fan, DBP only switches a fan into or out of the ground path


Mains input/distribution & auxiliary DC power supply

MID2A: Mains input/distribution & two auxiliary DC power supplies, PCB

   size: 100x69 mm

Order code: MID2A     MID2A PCB.

Quick specs:

    - use this PCB at your own risk, components are not supplied with the PCB

    - provides supply voltage for the Power supply & relay board (PSSR2S/PSS2S), and via it to the Protection board (DPB)

    - mains input connector, fuse(s), line EMC filter capacitor(s), solder pads for on/off switch(es) and for power transformer primary(s)

    - includes two galvanically isolated auxiliary DC power supplies

    - one auxiliary power supply, built to handle +9V, min. 80mA can be used for the CTA MID kit


PS1US: Stereo power supply, PCB

   size: 90x64 mm

Order code: PS1USc     PS1S PCB + all components except filter capacitors

Quick specs:

    - recommended for up to +/-45V supply voltage, but higher voltage might be used if needed

    - one pair of snap-in type electrolytic filter capacitors up to 30mm diameter can be fitted (not supplied with kit)


Power supply

PS1S: Stereo power supply, PCB

   size: 101x73 mm

Order code: PS1Sc     PS1S PCB + all components except filter capacitors and fuses

Order code: PS1Snhc     PS1S PCB + all components except filter capacitors, fuses, heatsink and heatsink fixing elements

Quick specs:

    - recommended for up to +/-50V supply voltage, but higher voltage might be used if needed

    - one pair of snap-in type electrolytic filter capacitors up to 35mm diameter can be fitted (not supplied with kit)


Switch-on mute circuit with relay

SMRS2:  Stereo switch-on mute circuit with a double-pole mechanical relay, PCB

   size: 72x32 mm

Order code: SMRS2c     SMRS2 PCB + all components

Quick specs:

    - switch-on thump muting

    - suitable for max. 2x100 W / 4 ohms or 8 ohms normal stereo, or max. 1x200 W / 8 ohms bridged amplifier

    - loudspeaker protection, which is not guaranteed, especially at higher amplifier supply rail voltages

    - needs 12...15 VAC, 50 Hz, min. 110 mA ground independent power supply

    - switches max. 2x 8 A current

    - suitable for all amplifiers with symmetric (+/-) power supply


SMRS3:  Stereo switch-on mute circuit with a double-pole mechanical relay, PCB

   size: 72x32 mm

Order code: SMRS3c     SMRS3 PCB + all components

Quick specs:

    - same specifications as SMRS2 with different PCB silkscreen


"MIA" Mains input/distribution & auxiliary AC power supply

Order code:     Not orderable. Not supplied with kit, you make it yourself. Suggestions are provided here.

Quick specs:

    - supplies power to the Switch-on mute circuit with relay (SMRS/SMRS2)

    - to include mains input connector, fuse, line EMC filter capacitor, solder pads for the on/off switch and for the power transformer primary

    - to include 12...15 VAC, 50 Hz, min. 110 mA ground independent power supply (e.g. a small transformer)

 

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