{"id":13418755,"url":"https://github.com/ojg/thatmicpre","last_synced_at":"2025-03-15T04:30:28.633Z","repository":{"id":44405712,"uuid":"257084445","full_name":"ojg/thatmicpre","owner":"ojg","description":"Microphone Pre-amplifier","archived":false,"fork":false,"pushed_at":"2023-10-01T17:27:45.000Z","size":8616,"stargazers_count":129,"open_issues_count":0,"forks_count":8,"subscribers_count":6,"default_branch":"master","last_synced_at":"2024-07-31T22:43:59.337Z","etag":null,"topics":["amplifier","audio","diy","kicad","microphone","open-source-hardware"],"latest_commit_sha":null,"homepage":null,"language":"HTML","has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":"cc-by-sa-4.0","status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/ojg.png","metadata":{"files":{"readme":"README.md","changelog":null,"contributing":null,"funding":null,"license":"LICENSE.txt","code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null,"governance":null}},"created_at":"2020-04-19T19:27:22.000Z","updated_at":"2024-07-20T19:14:14.000Z","dependencies_parsed_at":"2023-10-01T19:43:06.509Z","dependency_job_id":null,"html_url":"https://github.com/ojg/thatmicpre","commit_stats":null,"previous_names":[],"tags_count":0,"template":false,"template_full_name":null,"repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/ojg%2Fthatmicpre","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/ojg%2Fthatmicpre/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/ojg%2Fthatmicpre/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/ojg%2Fthatmicpre/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/ojg","download_url":"https://codeload.github.com/ojg/thatmicpre/tar.gz/refs/heads/master","host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":221536595,"owners_count":16839537,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2022-07-04T15:15:14.044Z","host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["amplifier","audio","diy","kicad","microphone","open-source-hardware"],"created_at":"2024-07-30T22:01:06.641Z","updated_at":"2025-03-15T04:30:28.628Z","avatar_url":"https://github.com/ojg.png","language":"HTML","funding_links":[],"categories":["HTML"],"sub_categories":[],"readme":"ThatMicPre\n=====\nA simple, high-quality DIY microphone pre-amplifier with switched gain.\n\nThe background for this project was that I needed a simple but good microphone preamp for doing acoustic measurements. I needed a switched gain to be able to reproduce the gain setting in a more predictable way than what is possible with a potmeter. I could not find any existing DIY designs, so I decided to make one.\n\nThe design is based on the excellent [THAT1510 or THAT1512](https://thatcorp.com/that-1510-1512-low-noise-high-performance-audio-preamplifiers/) preamp ICs. It is also compatible with [SSM2019](https://www.analog.com/en/products/ssm2019.html) or [INA217](https://www.ti.com/product/INA217). I have followed all THAT's datasheets and app-notes to implement a robust, best-practice design.\n\nA goal was to use simple through-hole parts that I and other DIYers usually have in our parts drawer. So there are no additional IC's or voltage regulators for example, it just uses simple transistors, capacitors and zener diodes for supply filtering and regulation. I selected affordable switches and connectors to keep cost down. Many parts can be substituted without sacrificing performance.\n\nThere are two versions of this design, one suited for a desktop encolsure with gain switch on top, and one suited for a rack-mount enclosure with gain switch on the front.\n\nThere is a separate PCB project in the panels folder that contains PCB layout for front and back panels that fits the 1455K120x case. Since it is copper-clad on the inside, it makes for a nice shielded box.\n\nThis is an open-source project released under CC-BY-SA-4.0 license. It basically means you can use it as you want as long as you share modifications under the same license, and attribute back to this project. See [LICENSE.txt](../blob/master/LICENSE.txt) for details.\n\nSee discussion of this project in this [DIYAudio thread.](https://www.diyaudio.com/forums/equipment-and-tools/356317-thatmicpre-source-mic-preamp.html) If you decide to build this pre-amplifier, please post results of your build there.\n\nSpecifications\n-----\n* Microphone preamplifier with switched gain and 48V phantom power.\n* XLR input and output connectors.\n* Phantom power on/off switch.\n* Phase invert switch.\n* Gains (dB): 0, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60.\n* Gain deviation from nominal: Max +/-0.5dB using R12-series resistors.\n* Frequency response: 0/-3dB from 10Hz to 100kHz for all gain settings.\n* Input impedance: 2.0kohm differential (1kHz)\n* Impedance balanced output, output impedance 200ohm (1kHz)\n* Max output level: 20dBu at 0.1% THD (1kHz).\n* THD+N less than 0.005% at 1kHz at 18dBu output level for all gain settings (20-20kHz BW).\n* 48V DC power supply required, 30mA max. \n  * (Will operate with lower voltage DC power supplies with reduced phantom voltage and max output level).\n* PCB dimensions 75mm x 120mm, fits the [Hammond 1455K120x](https://www.hammfg.com/part/1455K1201) enclosure.\n  * Desktop version has gain switch on top of enclosure for easy access.\n  * Rack version has gain switch on front for easy mounting in a rack enclosure.\n\nPhotos\n-----\n#### Desktop version\n![Photo of desktop](desktop/plots/thatmicpre_v10_frontback_small.jpg \"Desktop with panels\")\n\n![Photo of desktop pcb](desktop/plots/thatmicpre_pcb_v1_1.png \"Desktop PCB photo\")\n(PCBA credit jsenderatx on diyaudio)\n\n#### Rack version\n![Photo of rack](rack/plots/thatmicpre_rack_front_back.jpg \"Rack with panels\")\n\n![Photo of rack pcb](rack/plots/thatmicpre_rack_inside.jpg \"Rack PCB photo\")\n\nThe rack version has a PCB where one part separates. This part contains the gain resistors and switch.\nIt mounts at a right angle to the main PCB with two angled female headers underneath main PCB. See BOM.\n\n## Bill of Materials\nNicely formatted BOM is in the plots folder for [desktop version](https://htmlpreview.github.io/?https://github.com/ojg/thatmicpre/blob/master/desktop/plots/thatmicpre_bom.html)\nand [rack version](https://htmlpreview.github.io/?https://github.com/ojg/thatmicpre/blob/master/rack/plots/thatmicpre_v2_bom.html).\n\nThanks to the [InteractiveHtmlBom project](https://github.com/openscopeproject/InteractiveHtmlBom).\n\nSchematic\n-----\n#### Desktop version\n![Schematic](desktop/plots/thatmicpre_schematic.png \"Schematic\")\n#### Rack version\n![Schematic](rack/plots/thatmicpre_v2.svg \"Schematic\")\n\nMeasurements\n-----\n### Output noise vs gain\n20-22kHz BW un-wtd, 150ohm source impedance.\nNote: Theoretical minimum EIN with 150ohm source impedance is -130.4dBu.\n\n| Gain(dB) | THAT1510\u003cbr /\u003eOutput Noise (dBu) | THAT1510\u003cbr /\u003eEIN (dBu) | THAT1512\u003cbr /\u003eOutput Noise (dBu) | THAT1512\u003cbr /\u003eEIN (dBu) |\n| --- | --- | --- |--- | --- |\n| 0 | -98.5 | -98.5 | -102.4 | -102.4 |\n| 10 | -98.2 | -108.2 | -102.0 | -112.0 |\n| 15 | -97.8 | -112.8 | -101.3 | -116.3 |\n| 20 | -96.8 | -116.8 | -100.0 | -120.0 |\n| 25 | -95.6 | -120.6 | -98.0 | -123.0 |\n| 30 | -93.2 | -123.2 | -95.2 | -125.2 |\n| 35 | -89.8 | -124.8 | -91.5 | -126.5 |\n| 40 | -86.8 | -126.8 | -87.3 | -127.3 |\n| 45 | -82.6 | -127.6 | -82.8 | -127.8 |\n| 50 | -77.8 | -127.8 | -78.1 | -128.1 |\n| 55 | -73.1 | -128.1 | -73.3 | -128.3 |\n| 60 | -68.3 | -128.3 | -68.6 | -128.6 |\n\n### Frequency Response\n#### THAT1510 with 1% R12 resistors\n![alt text](docs/freqresp_vs_gain.png \"Frequency response\")\n#### THAT1512 with 1% R96 resistors\n![alt text](docs/freqresp_vs_gain_1512.png \"Frequency response\")\n\n### THD+N vs Frequency\n#### THAT1510\n![alt text](docs/thdvsfreq_vs_gain.png \"THDN vs frequency\")\n#### THAT1512\n![alt text](docs/thdvsfreq_vs_gain_1512.png \"THDN vs frequency\")\n\n### THD+N vs Amplitude\n#### THAT1510\n![alt text](docs/thdvsamp_vs_gain.png \"THDN vs amplitude\")\n#### THAT1512\n![alt text](docs/thdvsamp_vs_gain_1512.png \"THDN vs amplitude\")\n\n### Common Mode Rejection Ratio\n#### THAT1510\n![alt text](docs/cmrr_vs_gain.png \"CMRR\")\n#### THAT1512\n![alt text](docs/cmrr_vs_gain_1512.png \"CMRR\")\n\n### Bandpass Noise Level\nNote no measureable hum.\n#### THAT1510\n![alt text](docs/bandpassnoise_vs_freq_vs_gain.png \"Bandpass\")\n#### THAT1512\n![alt text](docs/bandpassnoise_vs_freq_vs_gain_1512.png \"Bandpass\")\n\n\n\n---\nOJG 2023\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fojg%2Fthatmicpre","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fojg%2Fthatmicpre","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fojg%2Fthatmicpre/lists"}