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STD Op Amp Mixer 2.1 version 1

License: Public Domain

Mode: Editors' pick

Cloned from Op Amp Mixer

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Update time: 2024-06-27 08:21:13
Creation time: 2024-05-05 05:43:21

2.1 mixer preamp board that allows two inputs mixed to a single Stereo output and Subwoofer output. For example, great for computer audio input. Has sub output and bass and treble boost cut. I have now tested the sub output and have added that video to this project and my SqueezLite Rover project here. Based on TI OPA1654 op amp but should work with any good opamp. Overall, I am happy with this project result! However, improvements are always welcome. Oh, and video's may be LOUD so turn down your sound before playing!


Also, I am using PTD902 and PTD901 series potentiometers.

J1 and J2 are 50k such as PTD902-2015K-B503. Also, you can just use PTD902-2015K-B103 if your inputs can tollerate a 10k load and most things are just fine with 10k loads. 

VR1 is 100k PTD902 such as PTD902-2215K-B104 with Detent.

VR2 is 10k PTD902 such as PTD902-2015K-B103 

VR3 is 200k PTD902 such as PTD902-2215K-B204 with Detent.

VR6 is 20k PTD902 such as PTD902-2215K-B203 with Detent.

VR7 is 10k PTK901 as it only has one output such as PTD901-1015K-B103.

VR8 is 50k 4 gang pot PTD904-1215K-B503 with Detent.

I think I have completed this project now.

The good: it works and has really good sound.

The bad: After many attempts to isolate digital noise crated by the ESP32 I have decided that DAC onboard of the pre-amp creates some digital noise that is picked up by the preamp opamps. So, after many attempts to clean this up I have decided to remove the DAC and place it on the ESP32 board directly. I have updated the schematics design to reflect this change. Also, I have found that even powering the DAC via this preamp introduces to much noise into these sensitive preamps.

I would go as far to say do not even attempt to run an ESP32 via the same power supply. I have spent hours of time redesigning the power supply of this board and nothing has been able to prevent the ESP32 from injecting digital noise into the preamp. So, this works great for very small and simple I2S micro controllers. However, if you plan on using with an ESP32 wait until I provide the ESP32 Rover and DAC on my Squeeze Rover DAC project I will be posting by Friday of this week. I have spent much time on both of these already and am waiting for the final boad designs on both of these to give an overall review of a really capable preamp with SqueezeLite cababilities. That project is awsome so go check it out here. Also, check out my blog here there is also a post on this project there and another more simple project based on ESPHome here


Overall, I am almost done with this project. I am proud of how far I have taken it to get to this point. I know I called it a simple preamp but after much testing it has grown into this project. I concider it a well rounded project that delivers excellent sound when you take into concideration about power supplies and isolation of digital from the sensitive analog preamp stage. So, with proper power supply conciderations this delivers very high quality sound with very little background noise or distortion. 


I have also added this project here for the ESP32 SqueezeLite client. This project adds Bluetooth and SquezeLite to this preamp project. I have also added this post to my alshowto.com site.


Added Extra Features

So, this addition allows one to add other outputs that get the same feed as the final output stage. This allows one to do things like add midrange controls as the overall board is as big as I really want to make it. For example, I am working on a center channel element that will allow center midrange speakers to be added. This is also a great spot to add future filtering or further sub woofer outputs tuned to specific amps and speakers. Very much control can be had with this and I will also be adding input 

modules in the future. For now I am testing the center channel concept out and will add that to the project list once I have ironed out all the bugs.

  • GRD - of coarse this is ground for the extra features.
  • 15+ - Positive 15 volts to power extra features.
  • 15- - Negative 15 volts to power extra features.
  • LP - Left Pre Output. This is right before output of final stage that is the final HP filter AKA: LPre in schematic. 
  • RP - Right Pre Output. THis is right before output of final stage that is the final HP filter AKA: RPre in schematic.



Design Drawing
schematic diagram
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ID Name Designator Footprint Quantity Manufacturer Part Manufacturer Supplier JLCPCB Part Class Contributor
1 3.3nF C1,C7,C8,C14 C0603 4 CL10B332KB8NNNC SAMSUNG(三星) LCSC C1613 CL10B332KB8NNNC
2 47nF C2,C3,C9,C10 C0603 4 CL10B473KB8NNNC SAMSUNG(三星) LCSC C1622 CL10B473KB8NNNC
3 10uF C4,C6,C11,C13 C0603 4 CL10A106MA8NRNC SAMSUNG(三星) LCSC C96446 CL10A106MA8NRNC
4 4.7nF C5,C12 C0603 2 0603B472K500NT FH(风华) LCSC C53987 0603B472K500NT
5 4.7uF C15,C16,C32,C33,C36,C41,C44,C45,C46 C0603 9 CL10A475KO8NNNC SAMSUNG(三星) LCSC C19666 CL10A475KO8NNNC
6 100nF C17,C18,C30,C31,C34,C35,C42,C43,C47,C48 C0603 10 CC0603KRX7R9BB104 YAGEO(国巨) LCSC C14663 CC0603KRX7R9BB104
7 WAFER-XH2.54-2PZZ CN1 CONN-TH_XH2.54-2P_1 1 WAFER-XH2.54-2PZZ XUNPU(讯普) LCSC C5359631 WAFER-XH2.54-2PZZ
8 2.54-1*3P CN2,CN3,CN4,CN5 CONN-TH_C722693 4 2.54-1*3P CAX(创都) LCSC C722693 2.54-1*3P
9 10k J1,J2 PTD9022015KA503 2 PTD902-2015F-B103 Bourns Mouser 652-PTD902-2015FB103 Stereo_Potentiometer_50k
10 11kΩ R1,R2,R4,R12,R13,R16 R0603 6 0603WAF1102T5E UNI-ROYAL(厚声) LCSC C25950 0603WAF1102T5E
11 1kΩ R3,R10,R14,R19,R39,R44 R0603 6 0603WAF1001T5E UNI-ROYAL(厚声) LCSC C21190 0603WAF1001T5E
12 18kΩ R5,R7,R15,R17 R0603 4 0603WAF1802T5E UNI-ROYAL(厚声) LCSC C25810 0603WAF1802T5E
13 100Ω R6,R18,R32,R40,R45,R47,R48 R0603 7 0603WAF1000T5E UNI-ROYAL(厚声) LCSC C22775 0603WAF1000T5E
14 3.6kΩ R8,R9,R20,R21 R0603 4 0603WAF3601T5E UNI-ROYAL(厚声) LCSC C22980 0603WAF3601T5E
15 33kΩ R11,R22,R33,R36 R0603 4 0603WAF3302T5E UNI-ROYAL(厚声) LCSC C4216 0603WAF3302T5E
16 OPA1654AIPWR U1,U3,U4 TSSOP-14_L5.0-W4.4-P0.65-LS6.4-BL 3 OPA1654AIPWR TI(德州仪器) LCSC C544430 OPA1654AIPWR
17 220uF C19,C24,C28 CAP-SMD_BD10.0-L10.3-W10.3-LS11.0-FD 3 RVT220UF50V67RV0021 KNSCHA(科尼盛) LCSC C2887271 RVT220UF50V67RV0021
18 4.7uF C20,C25,C27 C1206 3 1206B475K500NT FH(风华) LCSC C29823 1206B475K500NT
19 1uF C21,C26,C29 C0603 3 CL10A105KB8NNNC SAMSUNG(三星) LCSC C15849 CL10A105KB8NNNC
20 47uF C22,C23 CAP-SMD_BD6.3-L6.6-W6.6-LS7.2-FD 2 DV470M050E077ETR CapXon(丰宾) LCSC C83788 DV470M050E077R
21 SS310F D1,D2,D3 SMAF_L3.5-W2.6-LS4.7-RD 3 SS310F 晶导微电子 LCSC C116123 SS310F
22 LESD8D24CT5G D4 SOD-882_L1.0-W0.6-BI 1 LESD8D24CT5G LRC(乐山无线电) LCSC C2912020 LESD8D24CT5G
23 TLC-LSMD050/50 F1 F2920 1 TLC-LSMD050/50 TLC(竞沃) LCSC C506870 TLC-LSMD050/50
24 2.2uH L1,L5 IND-SMD_L3.5-W3.0_SLF0302 2 CD32YP0302-2R2M YJYCOIN(益嘉源) LCSC C492258 CD32YP0302-2R2M
25 33uH L2,L3,L4 IND-SMD_L7.2-W6.6_GPSR0730 3 CYA0650-33UH SHOU HAN(首韩) LCSC C5189937 CYA0650-33UH
26 2.54mm 1*2P P1 HDR-TH_2P-P2.54-V-M 1 2.54mm 1*2P null LCSC C36717 2.54mm 1*2P
27 15kΩ R23,R30 R0603 2 0603WAF1502T5E UNI-ROYAL(厚声) LCSC C22809 0603WAF1502T5E
28 22kΩ R24 R0603 1 0603WAF2202T5E UNI-ROYAL(厚声) LCSC C31850 0603WAF2202T5E
29 2kΩ R25 R0603 1 0603WAF2001T5E UNI-ROYAL(厚声) LCSC C22975 0603WAF2001T5E
30 XL6007E1_C5240411 U2 SOIC-8_L4.9-W3.8-P1.27-LS6.0-BL 1 XL6007E1 XLSEMI(芯龙) LCSC C5240411 XL6007E1_C5240411
31 24v V1 R0805 1 SDV2012E260C800NPTF Sunlord(顺络) LCSC C882642 SDV2012E260C800NPTF
32 560Ω R26,R31 R0603 2 0603WAF5600T5E UNI-ROYAL(厚声) LCSC C23204 0603WAF5600T5E
33 51kΩ R27,R29,R34,R35 R0603 4 0603WAF5102T5E UNI-ROYAL(厚声) LCSC C23196 0603WAF5102T5E
34 57.6kΩ R28 R0603 1 RC0603FR-0757K6L YAGEO(国巨) LCSC C245983 RC0603FR-0757K6L
35 10k VR5 PTD901-1015K-B103 1 PTD901-1015K-B103 Bourns Mouser 652-PTD901-1015KB103 PTD901
36 150nF C37,C38,C39,C40 C0603 4 0603B154K500NT FH(风华) LCSC C1597 0603B154K500NT
37 XH-4A-A CN6 CONN-TH_XH-4A-A 1 XH-4A红色 null LCSC C9900016113 XH-4A-A
38 5.6kΩ R37,R38,R42,R43 R0603 4 0603WAF5601T5E UNI-ROYAL(厚声) LCSC C23189 0603WAF5601T5E
39 1.74kΩ R41,R46 R0603 2 0603WAF1741T5E UNI-ROYAL(厚声) LCSC C22848 0603WAF1741T5E
40 50k VR6 BOURNS_PTD904 1 PTD904-1215K-B503 Bourns Mouser 652-PTD9041215KB503 Bourns_PTD904
41 HX 2.54MM-5P ZZ CN7 CONN-TH_5P-P2.50_HX-2.54MM-5P-ZZ 1 HX 2.54mm-5P ZZ hanxia(韩下) LCSC C7543434 HX 2.54MM-5P ZZ
42 OPA1652AIDR U5 SOIC-8_L5.0-W4.0-P1.27-LS6.0-BL 1 OPA1652AIDR TI(德州仪器) LCSC C30025 OPA1652AIDR http://image.lceda.cn/szlcsc/C30025.jpg


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