The LDA ultra low distortion amplifier DiY kits

 

There are 5 different configurations offered as kits, all are based on the LDA17 ultra low distortion audio power amplifier, which is intended for use with high performance home audio loudspeakers, but it can be used as a reference or measurement amplifier as well.

 

LDA MIN

Suitable for building a max. 2x80 Watts per 4 ohms or 8 ohms ultra low distortion STEREO power amplifier with switch-on muting via a mechanical relay. It is intended as home audio power amplifier for high performance, medium 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.

 

LDA MID

Suitable for building a max. 2x120 Watts per 4 ohms (max. 2x75 Watts per 8 ohms) ultra 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, high power, expensive audiophile or high-end loudspeakers.

Click here for the assembly instructions page.

 

LDA DM1

Suitable for building a max. 2x120 Watts per 4 ohms or 8 ohms ultra low distortion DUAL MONO 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, high power, expensive audiophile or high-end loudspeakers. It was designed to be robust and reliable.

Click here for the assembly instructions page.

 

LDA DM2

Suitable for building a max. 2x200 Watts per 4 ohms (max. 2x150 Watts per 8 ohms) ultra low distortion DUAL MONO 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, extra high power, expensive audiophile or high-end loudspeakers. Although the inputs are consumer line level and unbalanced, it might be suitable as a high quality PA amplifier for amplification in small halls, because it was designed to be robust and reliable.

Click here for the assembly instructions page.

 

LDA MON

Suitable for building a max. 200 Watts per 4 ohms (max. 150 Watts per 8 ohms) ultra low distortion MONO power amplifier with full protection via an ultra low distortion solid state relay. It is intended as home audio power amplifier for a single (mono) high performance, extra high power, expensive audiophile or high-end loudspeaker. Although the input is consumer line level and unbalanced, it might be suitable as a high quality PA amplifier for amplification in small halls, because it was designed to be robust and reliable.

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 solder the components yourself, except for the APBMa and APBFa, which are almost fully populated and there are just a few pieces of solder joints to make. (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.

LDA MIN kit

Suitable for building a max. 2x80 Watts per 4 ohms or 8 ohms ultra low distortion STEREO power amplifier with switch-on muting via a mechanical relay.

  + components.

Consists of the following kit subassemblies:

        2x LDA17mc (Ultra low distortion audio power amplifier PCB + medium power component set, except main heatsink)

        1x PS1Sc (Power supply PCB + components, except rail filter capacitors and fuses)

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

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


LDA MID kit

Suitable for building a max. 2x120 Watts per 4 ohms (max. 2x75 Watts per 8 ohms) ultra 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 LDA17hc (Ultra low distortion audio power amplifier PCB + high power component set, except main 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)


LDA DM1 kit

Suitable for building a max. 2x120 Watts per 4 ohms or 8 ohms ultra low distortion DUAL MONO 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 LDA17hc (Ultra low distortion audio power amplifier PCB + high power component set, except main heatsink)

        2x PSS701c (Power supply & solid state relay PCB + components, except main rail filter capacitors and fuses)

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

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


LDA DM2 kit

Suitable for building a max. 2x200 Watts per 4 ohms (max. 2x150 Watts per 8 ohms) ultra low distortion DUAL MONO 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 LDA17xc (Ultra low distortion audio power amplifier PCB + extra high power component set, except main heatsink)

        2x PSS701c (Power supply & solid state relay PCB + components, except main rail filter capacitors and fuses)

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

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


LDA MON kit

Suitable for building a max. 200 Watts per 4 ohms (max. 150 Watts per 8 ohms) ultra low distortion MONO power amplifier with full protection via an ultra low distortion solid state relay.

  + components.

Consists of the following kit subassemblies:

        1x LDA17xc (Ultra low distortion audio power amplifier PCB + extra high power component set, except main heatsink)

        1x PSS701c (Power supply & solid state relay PCB + components, except main rail filter capacitors and fuses)

        1x DPBLEDsc (Protection circuit PCB with SMDs mounted + all unmounted components, except LEDs and fan control components)

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


The LDA 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

LDA17: Ultra low distortion audio power amplifier, PCB

   size: 98x98 mm

Order code: LDA17xc      LDA17 PCB + extra high power component set without main heatsink (max. 200 Watts per 4 ohms)

Order code: LDA17hc     LDA17 PCB + high power component set without main heatsink (max. 120 Watts per 4 ohms)

Order code: LDA17mc     LDA17 PCB + medium power component set without main heatsink (max. 80 Watts per 4 ohms)

Quick specs:

    - suitable for 4-ohms load

    - very low distortion at all power levels (sub 0.0013% 1kHz THD was measured on prototypes at all power levels)

    - low noise (S/N ratio without hum: >114dB at 200 Watts / 4 ohms; >113dB at 120 Watts / 4 ohms)

    - PCB can be ordered with extra high, high, or medium power component set

 

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 APBM or APBF or DPB  protection boards for independent relay control

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

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

 

PSS701: High power mono power supply & a single ultra low distortion, fast acting solid state relay, PCB

   size: 135x73 mm

Order code: PSS701c     PSS701 PCB + all components except main filter capacitors and fuses

Quick specs:

    - max. +/- 70V supply voltage

    - can serve a mono high power amplifier (or two PSS701's can serve a dual mono high power amplifier)

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

    - connects to an APBM or APBF or DPB protection board for the relay control

    - needs +12VDC 35mA regulated supply (with an Euraudio APBF/APBM/DPB connected)

    - usable up to 250 Watts / 4 ohms or 150 Watts / 8 ohms amplifier output power (class B or class AB amplifiers)


Protection circuit

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

Order code: APBFa     APBF PCB almost fully populated + all unmounted components, except for fan control

   size: 67x71 mm

Quick specs:

    - switch-on and switch-off muting

    - loudspeaker (DC offset) protection

    - thermal protection (heatsink overtemperature sensing)

    - overcurrent protection with indicator LED

    - power supplied through PSS(R) module

    - max. 15mA supply current

    - all analog, no need for special preprogrammed chips

    - tested with LDA17 and PSSR350, but may be suitable for other amplifiers and other relay circuits

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

 

APBM:  Single channel (mono) protection circuit without fan control capability, PCB

Order code: APBMa     APBM PCB almost fully populated + all unmounted components

   size: 61x71 mm

Quick specs:

    - same as APBF without fan control capability

 

DPB & LEDS:  Single channel (mono) protection circuit with fan control capability and indicator LEDs, PCBs

Order code: DPBLEDsc     DPB PCB and LEDS PCB with SMD components mounted + all unmounted components, except LEDs

   size: 60x44 mm (DPB), 22x44 mm (LEDS)

Quick specs:

    - same as APBF, but with digital microcontroller control and driver for indicator LEDs for all protections

    - LED panel


 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:

    - same as DPB & LEDS , but without LEDS panel


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 (PSS701/PSSR2S), and via it to the Protection board (APBF/APBM/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 LDA MID kit

    - two auxiliary power supplies, built to handle +12V, min. 40mA each can be used for the LDA DMx kits

    - one auxiliary power supply, built to handle +12V, min. 40mA can be used for the LDA MON kit


Power supply

PS1S: Stereo power supply, PCB

   size: 101x73 mm

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

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 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 min. 110 mA ground independent power supply

    - switches max. 2x 8 A current

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


"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, min. 110 mA ground independent power supply

 

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