The LDA (low distortion amplifier) DiY kits

 

There are 3 different configurations offered as kits, all are based on the LDA17mc or LDA17hc low distortion audio power amplifier.

 

LDA MIN

Suitable for building a max. 2x100 Watts per 4 ohms low distortion STEREO power amplifier with only switch-on muting. 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 DMON

Suitable for building a max. 2x200 Watts per 4 ohms low distortion DUAL MONO power amplifier with 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. This kit doesn't contain the PCB and components for the Mains input/distribution & +12V power supply, but suggestions for designing this board are provided here.

Click here for the assembly instructions page.

 

LDA MON

Suitable for building a max. 200 Watts per 4 ohms low distortion MONO power amplifier with 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. This kit doesn't contain the PCB and components for the Mains input/distribution & +12V power supply, but suggestions for designing this board are provided here.

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. 2x100 Watts per 4 ohms low distortion STEREO power amplifier with only switch-on muting via a mechanical relay.

  + components.

Consists of the following kit components:

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

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

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

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


LDA DMON kit

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

  + components.

Consists of the following kit components:

        2x LDA17hc (Low distortion audio power amplifier PCB + high power component set, except main heatsink)

        2x PSSR350c or 2x PSS701c (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 fan control components)

        1x Not supplied with kit: "MI12" Mains input/distribution & +12V power supply


LDA MON kit

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

  + components.

Consists of the following kit components:

        1x LDA17hc (Low distortion audio power amplifier PCB + high power component set, except main heatsink)

        1x PSSR350c or 1x PSS701c (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 fan control components)

        1x Not supplied with kit: "MI12" Mains input/distribution & +12V power supply


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.


Audio power amplifier board

LDA17: low distortion audio power amplifier, PCB

   size: 98x98 mm

Order code: LDA17hc     LDA17 PCB + high power component set (max. 200 watts per 4 ohms)

Order code: LDA17mc     LDA17 PCB + medium power component set (max. 100 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 100 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

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

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

 

PSS701: high power mono power supply & a single ultra low distortion, fast acting solid state relay with its control circuit, PCB

   size: 135x73 mm

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

Quick specs:

    - see PSSR350, except that one pair of snap-in type electrolytic filter capacitors up to 35mm diameter can be fitted


Protection circuit boards

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

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

    - thermal protection (heatsink overtemperature sensing)

    - switch-on and switch-off muting

    - 12V power supplied through PSS(R) module

    - max. 15mA current consumption

    - 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 board, PCB (without fan control capability)

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

   size: 71x61 mm

Quick specs:

    - Same as APBF without fan control capability


"MI12" Mains input/distribution & +12V power supply board

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

Quick specs:

    - supplies +12 VDC to the Power supply & relay board (PSS701/PSSR350), and via it to the Protection board (APBF/APBM)

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

    - to include two galvanically isolated +12V, min. 40mA power supplies for LDA DMON

    - to include one +12V, min. 40mA power supply for LDA MON


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)


Switch-on mute circuit with relay

SPRS:  stereo switch-on mute circuit with a double-pole mechanical relay, PCB

   size: 71x32 mm

Order code: SPRSc     SPRS 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

    - needs 12...15 VAC min. 125 mA ground independent power supply (e.g. a small transformer)

    - max. 2x 8 A output current

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


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

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 (SPRS)

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

    - to include 12...15 VAC, min. 125 mA ground independent power supply (e.g. a small transformer)

 

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