PDF for a Zener 100 W mono amplifier with a quasi-complementary output stage, as indicated by the Spanish word cuasi, 569 KB in size.

Mirrored PCB artwork for a Zener amplifier board, a 237 KB PDF; espejo is Spanish for mirror.

Document numbered UM10155, a 179 KB PDF. The UM prefix is used by NXP for user manuals, but the name does not reveal which product it describes, so open it to identify…

Spanish-language PDF for a Tonante stereo unit, labelled as a legend sheet for thermal transfer, meaning a component-side print layout meant to be ironed onto…

Schematic in PDF form for a stereo preamplifier with a loudness control, a common DIY audio circuit that boosts bass and treble at low listening volume.

PDF schematic named only Ramsés, with no device type, brand or board number given, so its contents can only be confirmed by opening it.

Schematic PDF with a generic messaging-app export name built from a date stamp, 13 April 2023, and a sequence number.

Cross-reference sheet listing equivalents for diodes, bridge rectifiers and transistors, originally prepared as an Excel table and saved to PDF, despite being filed here…

Small 26.2 KB PDF, filed as a datasheet, holding a schematic of a Class D amplifier rated around 200 W RMS that uses two MOSFETs in its output stage.

Merged PDF of application circuits for the STK41XX series, the Sanyo thick-film hybrid power amplifier modules used in many audio systems and mini components.

Service schematic for the Bose AM15P, as named in the file, likely an amplifier or powered bass module from an Acoustimass-type speaker system.

PDF bundle of Bose schematics, 1.53 MB in size, whose name lists no particular model, so the covered products must be confirmed by opening it.

Power-section schematic, going by the pwr-sch suffix, for equipment identified only as BFI, an abbreviation the name does not explain.

Service manual PDF for the Audio Pro TA150 receiver, matching the rec and sm tags in the name.

Service manual for the Audio Pro B1.35 MK2 subwoofer, read from the B1_35MK2, sub and sm tokens in the name.

Power-supply service schematic for the Audio Pro AP3000, based on the pwr and sm tags in the name.

Audio Pro Ace Bass B4-200 subwoofer service manual, going by the AceBassB4_200, sub and sm tokens.

Schematic, per the sch suffix, for the Audio Pro Ace Bass B2-70 subwoofer. The 546 KB PDF covers the built-in amplifier, likely including the ACE-Bass circuitry, Audio…

Service manual PDF for the Audio Pro Ace Bass B2-50 subwoofer, named with the sub and sm tags.

Audio Pro Ace Bass B2-40 subwoofer service manual in PDF form, about 1.96 MB, as indicated by the sub and sm tags.

Service documentation for the Audio Pro Ace Bass B1-45 subwoofer, going by the sub and sm tags.

Service manual for the Audio Pro Ace Bass B1-39 subwoofer, a compact 272 KB PDF that likely holds the core amplifier schematic and perhaps a parts list.

Audio Pro Ace Bass A101 service manual, with the int tag suggesting an integrated amplifier, though the name does not state this firmly.

Second part of the service manual for the Audio Pro A4-14 speaker, going by the spk and sm2 tokens.

First part of the service manual for the Audio Pro A4-14 speaker, a 6.15 MB PDF identified by the spk and sm1 tokens and paired with a second volume.

Service schematic for the Audio Pro A2, supplied as a 542 KB PDF; the int-sm suffix most likely marks an international service manual edition.

Audio Pro A101 service documentation in PDF form, about 3 MB, with the int-sm tag pointing to an international service manual version.

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.