Copper-side PCB artwork for the Apex AX 20 amplifier project, a 208 KB PDF showing the track pattern rather than a circuit diagram.

Mirrored version of the Apex AX 20 copper-side layout, a small 62.3 KB PDF. The reversed image is meant for toner-transfer or photoresist methods, where the pattern must…

Component placement drawing for the Apex AX 20 amplifier board, a 61 KB PDF. It shows where each resistor, capacitor, transistor and connector sits on the PCB, which…

Top silkscreen layer for the Apex AA9 board, marked as MD revision 2, in a 58.7 KB PDF.

Component layout for the Apex Class A shunt design; raspored elemenata is Serbo-Croatian for parts placement.

Copper pattern of the Apex Class A shunt board, viewed through the PCB from the component side, according to the Serbo-Croatian title.

Spanish-language schematic for a stereo amplifier titled Zener, rated at 1000 W, in a 1.15 MB PDF.

Reference design document for an adjustable-output 200 W SEPIC power supply, a 3.26 MB PDF.

Michaels International diode equivalents guide, a large 8.42 MB PDF catalogued here as a schematic but actually a cross-reference book.

Schematic for the 60 W NDFL amplifier published by ETI in 1983, combined with a regulated power supply, in a 6.74 MB PDF.

Tone control circuit intended for a 2.1 channel audio system, in a 159 KB PDF. It shows the bass and treble adjustment network that sits between the source or preamp and…

Speaker protection circuit for a 2.1 audio setup, a user-drawn design in a 139 KB PDF. Such boards normally delay relay engagement at power-up to stop thumps and…

Diagram of a 2.1 preamplifier joined to an audio power amplifier, taken from a YouTube project; the doubled pdf extension is just a naming slip.

Hi-fi 2.1 amplifier schematic credited to SeahorseDIY, in a 688 KB PDF. It covers a stereo-plus-subwoofer layout, likely with the crossover or filter stage feeding the…

Schematic of a 2.1 channel amplifier based on the TDA2030A, from Technical Mriganka, in a 416 KB PDF.

2.1 channel hi-fi audio amplifier circuit by Technical Mriganka, a 164 KB PDF. The title does not name the amplifier ICs or output devices, so identify them from the…

2.1 amplifier schematic attributed to Amiru, a compact 98.7 KB PDF. The name gives no details about the ICs or power level, so the diagram itself must be read for…

Technical Mriganka 2.1 amplifier design using the TDA7379 and TDA7377 power amplifier ICs, a 206 KB PDF.

2.1 amplifier schematic built around the TDA7294, by Technical Mriganka, in a 219 KB PDF.

2.1 amplifier schematic using the 2SC5200 and 2SA1943 complementary power transistor pair, in a 184 KB PDF.

Class H power supply schematic, version 0.2, fuse type, marked final, in a 1.39 MB PDF.

Schematic of a 1000 W audio power amplifier rated into 2 ohms, marked R2, RLVA SE1, 2012 revision 1, in a 110 KB PDF.

Modified 2.1 channel amplifier schematic, a 90.6 KB PDF; the title does not say which original design was altered or which ICs are used.

Schematic of a 5-band graphic equalizer in a small 16 KB PDF, with a YMYA tag in the name that may refer to the source or the designer.

An 8.63 MB PDF schematic whose name refers to a kd43x7 F series. That appears to be a TV or display chassis model designation, though the name does not confirm the…

Service manual for the Fluke 87V digital multimeter, a 1.18 MB PDF. Manuals of this kind normally cover specifications, performance verification, calibration adjustment…

Issue of Silicon Chip magazine dated February 2005, scanned to a 24.7 MB PDF. Silicon Chip is an Australian electronics magazine that publishes construction projects…

Silicon Chip magazine, November 2005 issue, in PDF form at 15.4 MB; the trailing number in the name suggests a duplicate copy.

October 2005 edition of Silicon Chip, the Australian electronics magazine, as a 19.9 MB PDF scan.

Audio Power Amplifier Design by Douglas Self, a 13.7 MB PDF book. The title is a well-known engineering reference on solid-state amplifier topologies, distortion…

PDF of 6.86 MB titled for an XTi series, with no brand given in the name. Crown sells a power amplifier line called XTi, so the document may relate to it, but contents…

Book in PDF form, about 7.88 MB, covering valve and transistor audio amplifiers; the tag in the name only reflects where the copy was sourced.

Schematic PDF of 2.29 MB for a tone control circuit with low, mid and high adjustment plus a sub-woofer section, according to the name.

Studiomaster Logic-12 schematic, a compact 552 KB PDF. Studiomaster is a British maker of mixing consoles and powered mixers, and the Logic name refers to one of its…

Soft start circuit schematic, saved as a 1.78 MB PDF; the note in the name indicates it was converted from another format.

SMD marking code reference in PDF form, 11.4 MB. Books of this type list the short codes printed on surface-mount transistors, diodes, regulators and other small…

Simple preamplifier schematic built around the NE5532 dual low-noise op-amp, a 405 KB PDF; the extra tag in the name only marks the source site.

Sallen-Key subwoofer filter schematic as a 389 KB PDF, with a source tag in the file name.

Regulated power supply for a preamplifier, drawn in a 601 KB PDF schematic with a source tag in the name.

Modified schematic for the Yamaha PA-2400 power amplifier, an 83 KB PDF marked as version 1 and apparently a copy of an earlier file.