Item nr.

Gerard Simson Amplifier

Digital amp deluxe

Data for Gerard Simson
ProductionThe Netherlands, 2019.
Price was 1.51 €; chassis 60ct, 2x 3.5mm jack 20ct, power jack 13ct, 2x LS jack 40ct, bolts 10ct, knop 8ct.
PAM8403 Amplifier IC.
CabinetTire repair kit box (steel). Size 12.5x2x6cm. Weight 72gr.
PowerDC 3-6V.
DocumentsSchema of PAM module.

The Design

After building a small amplifier I got the suggestion to use a metal box to reduce hum. Instead of dismantling the amp and reboxing it in metal, I built a next amp from fresh parts. The Simson amp improves over my previous amp, the Pam Amp, in four ways. (1) Extra shielding by metal box as following the suggestion; (2) Audio cable not fixed but plugged; (3) Headphone output available; (4) Hum-suppressing circuit.

As for (2): some of my earlier amps had the audio cable attached. But I got some 3.5mm jacks to make the cable pluggable, and I liked this so much better that I also modified the PamAmp to have a pluggable cable. As for (3): In the office I sometimes use headphones so as not to disturb the collegues, but headphones are close to impossible to feed from a bridge amp. Indeed, the two ears of the headphone have a common ground, while outputs of a bridge amplifier may never be conected. So I made a headphone connector in the input circuit of the amplifier. Plugging the headphone will feed the headphone directly from the input (PC of MP3 player can drive headphone), will cut the sound from the amp, and will disable the volume control of the amp. As for (4): Though the metal box shields the amp effectively, hum and noise could still enter the amp through the feed cable. A special hum suppressing circuit almost completely eliminates hum! (So it's not possible to test the amplifier by putting your finger on the audio cable, you'll hear nothing!)

The amp uses so little energy that it can be fed from a USB charger (old Ipad chargers work fine). A rewired cable is needed, because the DC jack is not a USB connector but a 5.1mm power jack. Feeding it from the USB port of the laptop that plays the music gives audible noise in the speakers.

The name

The text Simson was already printed on the bottom of the box. It refers to the biblical character Simson, see book of Judges chapter 13 and beyond. Simson was very powerful, like my amp (and the repair material originally sold in the box), so I found no problem in keeping the name.

Obtained7/2019 from Home built.

This Object

The amplifier chassis measures only 20x28mm, so the amplifier cabinet contains air mostly. Even the amplifier PCB is mostly empty, it contains the volume pot as the largest component, and all amplification happens in the PM8403 IC which is only something like 4x12mm. You can see the power wires (yellow and black) connecting the power jack (3-6V, center positive) and shielded cable connecting the input, running via the headphone jack.

Part of Gerard's Radio Corner.
Generated by SiteBuilder on 4/6/2020 by Gerard (g.tel@uu.nl)