The LDA (low distortion amplifier) non-profit DiY kits

 

Recently I'd like to sell a few low distortion amplifier (LDA) DiY kits without any profit and without any wage for work (I sell the kits at the price that I buy the components for, with no any additional fee for the cost of my labor.) With this, I'd like to support the first people who will build this amplifier, and so make this DIY design more popular, besides I hope to get some feedback about the completeness and quality of the building instructions.

There are 4 different configurations offered as kits, all are based on the LDA172mc or LDA172hc low distortion power amplifier.

 

LDA MIN_np

Suitable for building a max. 2x100 Watts per 4 ohms low distortion STEREO power amplifier with minimalist protection via a mechanical relay. It is intended as home audio power amplifier for high performance, medium power audiophile loudspeakers. This configuration has only loudspeaker protection and doesn't have amplifier overcurrent and heatsink overtemperature protections. This kit doesn't contain the PCB and components for mains input/distribution and you yourself must also make a 12...17 VAC 50mA power supply for the protection circuit board.

Click here for the assembly instructions page.

 

LDA 43S_np

Suitable for building a max. 2x110 Watts per 4 ohms low distortion STEREO power amplifier with full, individual protection for the two channels via separate mechanical relays. It is intended as home audio power amplifier for high performance, medium power audiophile loudspeakers.

Click here for the assembly instructions page.

 

LDA 53DM_np

Suitable for building a max. 2x200 Watts per 4 ohms low distortion DUAL MONO power amplifier with full, individual 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. 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 53M_np

Suitable for building a max. 200 Watts per 4 ohms 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, 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's 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, on-chassis connectors and switches, main rail filter capacitors.)

If you have questions, please send me an email.


LDA MIN_np (non-profit) kit

Suitable for building a max. 2x100 Watts per 4 ohms low distortion STEREO power amplifier with minimalist protection via a mechanical relay.

Non-profit price on ebay: 75 EUR + postage.

Consists of the following kit components:

        2x LDA172mc (Low distortion power amplifier PCB + medium power component set, except main heatsink)

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

        1x SPRSc (Protection circuit and mechanical relay PCB + components)


LDA 43S_np (non-profit) kit

Suitable for building a max. 2x110 Watts per 4 ohms low distortion STEREO power amplifier with full, individual channel protection via separate mechanical relays.

Non-profit price on ebay: 125 EUR + postage.

Consists of the following kit components:

        2x LDA172mc (Low distortion power amplifier PCB + medium power component set, except main heatsink)

        1x PSMR101Sc (Power supply & mechanical relay PCB + components, except main rail filter capacitors)

        2x APBFa or 2x APBMa (Protection circuit PCB almost fully populated + all unmounted components, except for fan control)

        1x MIB12sc (Mains input/distribution & auxiliary power supply PCB + stereo component set)


LDA 53DM_np (non-profit) kit

Suitable for building a max. 2x200 Watts per 4 ohms low distortion DUAL MONO power amplifier with full, individual channel protection via separate ultra low distortion solid state relays.

Non-profit price on ebay: 192 EUR + postage.

Consists of the following kit components:

        2x LDA172hc (Low distortion power amplifier PCB + high power component set, except main heatsink)

        2x PSSR350c (Power supply & solid state relay PCB + components, except main rail filter capacitors)

        2x APBFa or 2x APBMa (Protection circuit PCB almost fully populated + all unmounted components, except for fan control)

        1x MIB12dc (Mains input/distribution & auxiliary power supply PCB + dual mono component set)


LDA 53M_np (non-profit) kit

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

Non-profit price on ebay: 100 EUR + postage.

Consists of the following kit components:

        1x LDA172hc (Low distortion power amplifier PCB + high power component set, except main heatsink)

        1x PSSR350c (Power supply & solid state relay PCB + components, except main rail filter capacitors)

        1x APBFa or 2x APBMa (Protection circuit PCB almost fully populated + all unmounted components, except for fan control)

        1x MIB12mc (Mains input/distribution & auxiliary power supply PCB + mono component set)


The LDA Kit Component Descriptions

Note: Only the PCB's are shown in the images 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 component. With a few necessary exceptions this means all the electronic parts that need to be soldered and all the mechanical parts that need to be mounted onto the PCB.


Power amplifier boards

LDA172: low distortion power amplifier, PCB

   size: 98x98 mm

Order code: LDA172hc     LDA172 PCB + high power component set (max. 200 watts per 4 ohms)

Order code: LDA172mc     LDA172 PCB + medium power component set (max. 110 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 or >113dB at 110 watts / 4 ohms)

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

 

Power supply & relay boards

PSSR350: high power mono power supply & a single ultra low distortion, fast acting solid state relay with its control circuit, PCB

   size: 175x73 mm

Order code: PSSR350c     PSSR350 PCB + all components except main filter capacitors

Quick specs:

    - max. +/- 70V supply voltage

    - PSSR350 can serve a mono high power amplifier (or two PSSR350's can serve a dual mono high power amplifier)

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

    - needs +12V 40mA regulated supply, when an APBM or APBF board is also connected (MIB12dc or MIB12mc is a suitable supply)

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

    - usable up to about 250 Watt amplifiers (class B or class AB amplifiers)

 

PSMR101S: stereo power supply & two independent SPST mechanical relays with their control circuits, PCB

   size: 159x73 mm

Order code: PSMR101Sc     PSMR101S PCB + all components except main filter capacitors

Quick specs:

    - recommended for up to +/-50V supply voltage, but higher voltage might be used for 8 ohm amplifiers if needed

    - max. 10A output current per relay

    - independent fuses and relays for two (i.e. stereo) channels

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

    - needs +12V 100mA regulated supply, when two APBM or two APBF boards are also connected (MIB12sc is a suitable supply)

    - connects to two APBM or two APBF protection boards for the relay control


Protection circuit boards

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

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

   size: 71x67 mm

Quick specs:

    - loudspeaker (DC offset) protection

    - overcurrent protection

    - switch-on and switch-off muting

    - thermal protection (heatsink overtemperature sensing)

    - 12V power supplied through PSSR or PSMR module

    - all analog, no need for special preprogrammed chips

    - tested with LDA172 and PSSR350 / PSMR101S, 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 board, PCB (without fan control capability)

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

   size: 71x61 mm

Quick specs:

    - See APBF without fan control capability


Mains input/distribution & auxiliary power supply board

MIB12: Mains input/distribution board and two galvanically isolated +12 VDC power supplies, PCB

  size: 98x73 mm

Order code: MIB12dc     2x 12VDC 50mA with isolated grounds -- MIB12 PCB + dual mono component set (e.g. for two PSSR350's)

Order code: MIB12mc     12VDC 50mA -- MIB12 PCB + mono component set (e.g. for a single PSSR350)

Order code: MIB12sc     12VDC 100mA -- MIB12 PCB + stereo component set (e.g. for the PSMR101S)

Quick specs:

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

    - supplies +12 VDC to the Power supply & relay board(s), and through them to Protection board(s)

    - PCB can be ordered with dual mono, stereo or mono component set


Power supply board

PS1S: stereo power supply, PCB

   size: 101x73 mm

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

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)


Protection circuit board with relay

SPRS: simple dual channel (stereo) protection circuit board with a mechanical relay, PCB

   size: 71x32 mm

Order code: SPRSc     SPRS PCB + all components

Quick specs:

    - loudspeaker (DC offset) protection

    - switch-on muting

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

    - needs 12...17 VAC min. 50mA power supply

    - max. 2x 8 A output current (independent channels) or 1x 8 A output current (bridged channels)

    - simple and all analog, no need for special preprogrammed chips

    - suitable for all amplifiers with dual (+-) power supply


 

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