DIY Headphone Amp Funk LPA-2a

Recently I built myself a High-End DIY headphone amplifier, which is based on modules from german manufacturer Funk Tonstudio Technik. The amp has balanced XLR input sockets and a standard unbalanced stereo headphone output. DIY means: the headphone amp, the unbalancing amplifier and the power supply modules are from Funk, the rest: case, inputs, outputs, connections, soldering, etc. is all DIY.

Pictures

LPA-2a side view
Funk LPA-2a
internals
internals
bottom
bottom
rear
rear

Specifications And Price

The LPA-2a has excellent specifications. Regarding specs it’s one of the best, if not the best, headphone amp available. Soundwise it’s optimized for purest transparency, so no colorful analogue sound here. Since a stepped ALPS attenuator is used, the stereo-balance is very good. The unbalancing board and the power supply module also have execellent specs. And the best thing: in relation to the quality the modules are relatively cheap (round about 250 €, the price for the case and other DIY stuff is round about 150€. That said: there are much cheaper cases available).

Module specifications:

The Case

The case was designed using Frontplatten Designer by Schaeffer AG. Means: the aluminium front plate was milled by Schaeffer AG, also the corner aluminium profiles are from Schaeffer AG. The rest of the case was made from various pieces of sheet metal from blechscout.de. That was much cheaper than ordering directly from Schaeffer AG. Top, bottom and side sheets are 2mm stainless steel. The back plate is a 3mm aluminium sheet. I drilled all holes of the back plate by myself (cheaper). For mounting I used stainless steel hexagon socket screws.

case parts
case parts
front plate
front plate

Electrical Components

Electrical components are the already described Funk modules, various Neutrik signal I/O sockets, power socket, on/off switch, power led, cables and stuff. Finally there’s a DIY connector board that connects everything together (see details below). To assemble the cables some special tools / crimping tools are needed, or at least it’s helpfull to use them.

electric components
electrical components
needed tools
needed tools

Connector Board

In order to connect the power supply, amp and I/Os, I soldered a slightly modified version of Peter Rill’s LPA-2 connector board. Thanks to Peter for the scheme ! Peter’s design also includes a relay which switches on/off the output signal. The relay is controlled by the Funk power supply. Means: 5 seconds after switching on the power supply, the relay closes, and as soon as the power supply is switched off, the relay opens. This protects your headphones and ears from nasty pops and clicks.

connector board top
connector board top
connector board rear
connector board rear

Adjustable Amplification

Depending on the used headphones the LPA-2a and the SIA-5 support various amplification settings ranging from -6 dB … + 18 dB. For more details see specifications.

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5 Responses to DIY Headphone Amp Funk LPA-2a

  1. Frank Kreutz says:

    Hallo airmann,

    ich gehe mal davon aus, dass ich deutsch schreiben kann aufgrund der .DE – Adresse.
    Habe mir letzte Woche ebenfalls einen Funk LPA-2a mit dem Netzteil PWS04a_V2-1 bestellt.
    Also momentan noch nicht das SIA-5. Nun habe ich Deinen Blog gefunden und die Teile auf dem Bild gesehen, die Du verbaut hast. Hättest Du mir evtl. Deine Einkaufliste für die ganzen Zubehöre ? Bei wem hast Du diese gekauft – Reichelt, Conrad ? Momentan traue ich mir die Bastelei noch gar nicht so richtig zu, aber vielleicht kannst Di mir ja noch ein paar weitere Tipps und Infos geben ? Aber diese Teileliste würde mir schon sehr helfen.

    Vielen Dank im Voraus !

    Gruß
    Frank

  2. Philip says:

    Würde mich auch interessieren! 🙂 Danke!

  3. Michael says:

    Tolles DIY-Projekt! Ich würde mir auch sehr gerne einen LPA KHV von Funk basteln. Großes Interesse habe ich an Deinem Connectorboard. Wäre es möglich, mir den Schaltplan und die Teileliste dafür zu schicken? Das wäre wirklich prima! Vielen Dank im Voraus!

  4. Michael says:

    Hallo airmann,

    mich interessiert auch die Teileliste sowie der Schaltplan für Dein Connector-Board 🙂

    Vielen Dank im Voraus!

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