Friday, November 18, 2011

2 input headphone amplifier with TPA6120

I already designed circuit and 3 versions of PCB with TPA6120. I heard only good reviews about this circuit, this is the reason why I made new version again. In this board I want to use all features of this circuit with 2 inputs and one outputs placed to the PCB, with transformer. I want to use this device for my computer sound-card what is EMU1212m, this card shipped without headphone output (and without microphone input). But have very good sound quality, therefore I need this headphone amp.

Because I would like to use all possible features with all-in-one PCB:
  • Small transformer placed to the PCB, with 2 independent symmetrical +/-15V outputs. This is because separated power possible for left and right channels.
  • 2 inputs on the PCB with volume control and jack or RCA inputs.
  • Master volume and output jack.
  • Mini audio mixer after inputs.
  • After the mixer, unbalanced/balanced converter.
With this board I can use the features of TPA6120.

The new schematic:


The transformer and the voltage regulators placed to the PCB, with two independent outputs with 4 regulator devices. With inputs, you can choose what you like, 2 pcs 6 .3mm jack, or stereo RCA. Maybe 1 jack and 1 RCA. The balanced converter make better quality and more volume.

This is the PCB:


The longer side of PCB is about 15cm. Around the inputs have something "chaos". You can choose between RCA and Jack inputs this is the reason why 2 footprints on one place, but the inputs have to be placed to the bottom side (must be soldered on the top) and the volume potentiometers placed to the top layer (must be soldered on the bottom). But I think this is no problem on assembly. Because the transformer is on the board, 230V must be connected to the header called "Conn2". The regulators on the edge of the board can be screw to the wall of case or to heatsink. 3 "power filter" circuits required as module for this board, one for mixer, 1-1 for left/right unbalanced/balanced converter.

See also:

PCB sales of this project
Module name Size
(mm)
Area
(cm2)
PDF SCH PCB image Tested Price (US$)
Des. Sim.1 Full2 Sim.1 Full2 Man3
2 input headphone amplifier
90x160 144 Yes
Yes Yes - - No 21
31 Ask
How to order? Please read the rules carefully!

New power supply with 48V phantom power and 24V for relays

I have simple power supply for my preamplifiers (and all other) projects, but the 48V phantom power is missing from this device. This required for micrphone premplifier only, if the source is condenser microphone instead of dynamic microphone. Condenser mic source is useful on studios, for live singing, home amplification the simplest and cheaper dynamic microphones more useful. I searched some good solution, but the circuit which convert 48V from 30V AC is not simple enough. IT is true, one transformer not required with this circuit, but I think small PCB transformer with 48V (or 2x24V) is good and cheap solution. This is the reason why 2 transformers inserted to my design. The another thing with this new power supply, that I like relays to switch something if required, therefore I made one more output for 24V for relays (for example switching audio input, or switching speaker protection).

In current design the AC input is for 230V, because the PCB transformers soldered to the board. I like LM317/337 pair of adjustable regulator, the result is much better for me like 78xx/79xx circuits. The output voltage depend on the zener diode connected to the adjust of regulators. All regulators placed to the edge of board, if heatsink required.

The simple schematic:


The PCB:


If 24V for relays not required:


The original PCB for +/- 15V only without transformers:



PCB sales of this project
Module name Size
(mm)
Area
(cm2)
PDF SCH PCB image Tested Price (US$)
Des. Sim.1 Full2 Sim.1 Full2 Man3
Power supply for preamplifiers
168x89 150 No
Yes Yes - - No 22
32 Ask
How to order? Please read the rules carefully!

Wednesday, November 16, 2011

Modified microphone preamplifier with INA217

I really like the microphone preamplifier with INA217. No noise, very good sound and dynamic, no feedback, very high (max 10.000x) gain, very simple application. Lot of websites testing and comparing this design with another industrial devices. The article, when this is the best mic preamp and the cost is USD5 only, maybe not true. Not only the INA217 required, you need PCB, transformer, 2 potentiometers, input and output connectors, power supply.

I modified the original design recommended on the datasheet. The original application circuit on datasheet is really simple and very good microphone preamplifier. I added a better unbalanced/balanced converter after unbalanced jack input. I have this feature before, but now I have better circuit. The another modification is the output. Because this preamp is mono, the simple connection to stereo system is not the best. The result may increase the crosstalk between left and right channels. This is the reason why I included two line driver circuits to separate left and right channels. Finally because this new design contains 3 integrated circuit, I inserted 3 "power filter" for less noise.

The modified preamp design with input unbalanced/balanced converter and output line drivers:


The PCB with simple connectors:


The same design without connectors, because this PCB can be inserted to the mainboards of modular mixers. The connectors changed to P4 header:


Now here is the list of features:

  • Balanced input
  • 6.3 jack as Unbalanced input, but with unbalanced/balanced converter
  • Gain adjustment
  • Volume adjustment
  • Connector for 48V phantom power
  • Switch for 48V phantom power
  • Switch between unbalanced jack and balanced XLR input
  • Divided line driver inputs connect to stereo systems
  • Power filter circuits for all 3 integrated circuits for less noise
PCB sales of this project
Module name Size
(mm)
Area
(cm2)
PDF SCH PCB image Tested Price (US$)
Des. Sim.1 Full2 Sim.1 Full2 Man3
Mic preamp pro with connectors
79x104 82 Yes Yes Yes - - No 13
21 Ask
Mic preamp pro as mixer module
67x103 69 Yes Yes Yes - - No 11
19 Ask
How to order? Please read the rules carefully!

Tuesday, November 15, 2011

Expandable, modular audio mixer for any number of channels

This is my second audio mixer project. The difference between current and previous design is, that this design can be expandable to any number of channels, the previous is made for 4 or 8 input channels only. At the end of the PDF manual of this project I inserted examples how to build audio mixer for any number of input and output channels.

I made paper models of my design to check how possible to build the complex device:



This gallery is funny, but very cheap to find mechanical problems before manufacturing the PCBs. With this test, I detected the problem, that the PCBs of "power filter" circuits are too big, have to be smaller than 25mm. This is the reason why I have 5 several power filter PCBs, and here is the smallest, with 22mm height, and 25mm width for the modular mixers:



The schematic of power filter module to decrease the preamplifier's noise and the crosstalk between left and right channels:


This PCB is very small, much harder to build....

The required preamplifiers for input channels are exactly same as than my simplest mixer project. The new on this design, that the small mainboards can be expanded with female/male connectors to build bigger than 8 channel audio mixer.

The first module of expandable mainboard:


...and the PCB for the first mainboard module:


This design is simple 4 channel audio mixer. Possible to finalize with 4 several preamplifiers. The blue potentiometers on the bottom of PCB is the L/R balance adjustment, but these parts are ignorable if not important. These potentiometers have blue color, because must be soldered to the bottom layer. There are mono, metal case parts. The first mainboard contains connectors for powers, phantom powers, line outputs, and balanced microphone input for all channels if mic preamp inserted. The main difference is the P1 female connector. This is the part where possible to connect another mixer mainboard to make more input or output channels. This first 4 channel module working without another connected boards, but on this one no connectors for outputs, only one stereo line output on the PCB via H5 connector.

For more inputs, here is the required module can be connected to the right edge of the first board to the connector P1:


and the really small PCB with P21 male connector:


This is an input channel for 2 arbitrary preamplifiers. Upper left is the male connector can be connected to the first, to the same, or to the output boards too. Here is the reason why expandable this device to any input or output channels.

If output channels required, here is the new schematic:


And I have 2 PCB design for upper schematic:


The difference between two PCBs is the L/R balance potentiometer only. This mainboard-module made for output circuits. The board can be connected to anywhere and anytime within the whole system. I offer several output modules:

The line outputs with master volume adjustment:


...and the PCB:


The difference between this, and the previous version of line output board, that this board contains line driver circuits, not the mixer's mainboard. This board contains adjustable master output of mixer with volume potentiometer with following variations:
  • 2 6.3mm jack
  • 1 6.3mm and 1 3.2mm jack
  • 1 6.3mm jack and 1 stereo RCA
  • 1 3.2mm jack and 1 stereo RCA
This board contains only one stereo volume adjustment, but possible to soldering to the board with L/R balance potentiometer if this feature required.

Another output circuit:

This is headphone amplifier with TPA6120. I modified my previous design of this module.

The PCB:

This is the simplest application of this really good IC with 6.3mm jack output and volume adjustment feature.

I made another version of this output for my audio mixer. The difference, here is an unbalanced/balanced converter for less noise, higher dynamics, higher possible volume. The official 120dB dynamics range is really high quality.


The required PCB is bigger, with two power filter module on P3 and P4 connectors:



PCB sales of this project
Module name Size
(mm)
Area
(cm2)
PDF SCH PCB image Tested Price (US$)
Des. Sim.1 Full2 Sim.1 Full2 Man3
Power filter module
17x25 4 Yes Yes Yes - - No 3
11 Ask
1st mixer module
103x95 98 Yes Yes Yes - - No 15 24 Ask
2nd mixer module
51x93 47 Yes Yes
Yes - - No 8 16 Ask
3rd mixer module
26x93 24 Yes Yes
Yes
- -
No 5 13 Ask
Line outout board
65x76 49 Yes Yes Yes - -
No 9 16 Ask
Headphone output board
56x71 40 Yes Yes
Yes
-
- No
7 15 Ask
Balanced headphone output board
58x105
61 Yes Yes
Yes -
-
No 10 18 Ask
Microphone preamp module V2
67x103
69 Yes Yes
Yes
Yes
-
No 11 19 Ask
Microphone preamp module V3
67x103
69 Yes Yes
Yes -
-
No
11 19 Ask
1 dual opamp preamp module
61x103
63 Yes
Yes Yes
-
-
No 10 18 Ask
2 single opamp preamp module
64x103 66 Yes
Yes
Yes
Yes
-
No 11 19 Ask
HQ 2 single opamp module
67x103
69 Yes
Yes Yes
-
-
No
11 19 Ask
jFET guitar preamp module 65x102 66 Yes Yes
Yes -
-
No 11 19 Ask
Switch module
18x34 6 Yes Yes
Yes Yes
-
No 3 11 Ask
Simple Power supply
121x57
69
Yes
Yes
Yes Yes
-
No 11 20 Ask
Power supply with 48V phantom
168x89 150 Yes Yes
Yes -
-
No 22 32 Ask
How to order? Please read the rules carefully!

Modular audio mixer for 8 and 4 input channels

I uploaded two new PDF documents about my audio mixer projects (1 - 2). The circuit called "audio mixer" is really simple, the required preamplifiers are little harder, if you need poweramp and EQ the device will more harder. But already I have tested and passed preamplifier project with headphone amplifier. And I have two modular equalizers ready to build. So I need audio mixer to collect these circuits to the simplest solution.

As I wrote already I have two of audio mixer project, because first time I designed very simple, with 4 or 8 input channels only, with master volume and line two outputs only. This project contains 2 very simple mainboards for 4 and 8 channel inputs, two output panels, and preamplifiers as module. The preamplifiers for mixer is same as my first designs, but can be connected with 12 pin male connectors to selected mixer mainboard.

For example, here is the microphone preamplifier with INA217:


The "original" PCB for this device is here:


But for modular mixer I have to modify the board design, the input and power connectors are removed, and changed to P4 connector on the bottom of board:


These preamplifier modules are smaller than the original versions, and contains "power filter" circuits as module (P5 and P6 connector at upper board). The preamplifier modules can be connected to the mixer mainboards, any preamplifier can be connected to the any connector of the mixer. The distance between preamplifiers is 25mm. This is the reason, why I have to design new versions of PCB for circuit called "power filter". This module must be smaller than 25mm. I have 5 versions of this module, with several sizes. All my preamplifiers (mic preamp with INA217, stereo dual jFET preamp, Dual OpAmp, 2 versions of single OpAmp) re-designed for modular mixer system.

The picasa gallery:


For the simplest version of my mixer project I have two mainboards with connectors for preamps, outputs, power supply, and balanced inputs for microphones:


4 channel mainboard for 4 inputs and 2 outputs:

For this board required 2 "power filter" modules, 4 preamplifiers, 1 volume board, and 1 line output board.

For the board can be connected two output PCBs. The one is for the master volume:

This PCB must be soldered after the 4th preamplifier via P5 male connector. This board working as 2 separated volume potentiometer for left and right channel, and possible to use only one stereo potentiometer for both channels on the pins of P1.

The another output module made for 2 line level outputs:

This board must be soldered to the last connector of mixer board via P1 header. The line level circuit designed to the mainboard, so this PCB contains the connectors only. The board useful for:
  • 2 6.3mm jack
  • 1 6.3mm jack and 1 stereo RCA
  • 1 6.3mm jack and 1 3.2mm jack
  • 1 3.2mm jack and 1 stereo RCA
The main output of full mixer is connected to the mainboard. This is the output for equalizers, poweramps, headphone amps, etc....

I designed 8 channel mainboard:


This circuit is same as than the upper 4 channel design. But here is 8 connectors for input channels can be connected to preamplifiers. The two of output boards is same too. This board width is 25cm, I think this is something big, very hard to manufacture, this is the reason why i designed "expandable" version of my audio mixer with connectable small mainboards for more than 8 channel inputs.

PDF manuals for audio mixers:
PCB sales of this project
Module name Size
(mm)
Area
(cm2)
PDF SCH PCB image Tested Price (US$)
Des. Sim.1 Full2 Sim.1 Full2 Man3
Power filter module
17x25 4 Yes Yes Yes - - No 3
11 Ask
4 channel mixer mainboard
149x84 125 Yes Yes Yes - - No 19 28 Ask
8 channel mixer mainboard
240x80 192 Yes Yes
Yes - - No 27 36 Ask
I/O board
37x60 22 Yes Yes
Yes
- -
No 5 12 Ask
2 Potmeter board
31x62 19 Yes Yes
Yes
-
- No
5 12 Ask
Microphone preamp module V2
67x103
69 Yes Yes
Yes
Yes
-
No 11 19 Ask
Microphone preamp module V3
67x103
69 Yes Yes
Yes -
-
No
11 19 Ask
1 dual opamp preamp module
61x103
63 Yes
Yes Yes
-
-
No 10 18 Ask
2 single opamp preamp module
64x103 66 Yes
Yes
Yes
Yes
-
No 11 19 Ask
HQ 2 single opamp module
67x103
69 Yes
Yes Yes
-
-
No
11 19 Ask
jFET guitar preamp module 65x102 66 Yes Yes
Yes -
-
No 11 19 Ask
Switch module
18x34 6 Yes Yes
Yes Yes
-
No 3 11 Ask
Simple Power supply
121x57
69
Yes
Yes
Yes Yes
-
No 11 20 Ask
Power supply with 48V phantom
168x89 150 Yes Yes
Yes -
-
No 22 32 Ask
How to order? Please read the rules carefully!

Wednesday, November 9, 2011

Headphone amplifier with TPA6120

This is my first SMD circuit. The small size of SMD parts was my problem before. The opinions about TPA6120 is very good on all other related pages, the official datasheet is unbelievable. I have 5 pcs 6120 circuit, so I have to test it with my own PCBs.



The headphone circuit is very simple. With unbalanced balanced converter is much better, but in this first version this feature is missing from these PCB-s. I have design with unbalanced/balanced converter, but for modular mixer only. Now I posting about "independent" headphone amplifiers. Fortunately, this circuit is not the smallest SMD footprint. The distance between foots is 50 mill, the foot width is 20 mill. This size is no problem for homemade prototype.

The main IC is:


This chip have 20 "foots", but the half of these pins are not internally connected. On the bottom, small heatsink available, but this is not only heatsink, this is the GND as 21st pin. Footprint not available, have to be draw on the CAD software. The full circuit without dual power supply, and unbalanced/balanced converter is very simple:



These modifications possible:
  • For both channels (left and right) have + and - inputs for balanced sources. This is optional,
    but maybe the result is better. On this schematic has no input for balanced sources.
  • Separated dual power supplies possible for this one circuit. this is reduces the crosstalk between left and right channel. The dynamics of this circuit on the official datasheet is 120 dB, what is very good if true. Class D amplifier. I have "power filter" circuit to separate power sources of left and right channels, but I don`t want to use this for headphone amplifier because maybe the current source is not enough.

Therefore I have 3 versions of PCBs:

The first is the biggest one, to screw with another preamplifier circuits. The position of rear hole is the reason why this PCB so large:


If the same hole positions are not important between preamplifiers and the headphone amp, then here is the smaller PCB:


Finlay I have smaller. This PCB have separated inputs for balanced inputs of left and right channels, and inputs for left and right powers. this is the reason why volume potentiometer missing, and the power filter capacitors are too:


This is the smallest PCB, but possible to use after unbalanced/balanced converter and with separated dual power supply. But these solutions are required with another circuits.

6.3mm jack input soldered to all of these boards, the 1st and 2nd version of PCB have volume potentiometers too. This volume pot missing from the 3rd version, because the pot must be soldered before unbalanced/balanced converter. The TPA6120 circuit fitted to the bottom layer of all PCBs (this is the reason why this part mirrored), all another placed to to top.

See also:
PCB sales of this project
Module name Size
(mm)
Area
(cm2)
PDF SCH PCB image Tested Price (US$)
Des./3D Sim.1 Full2 Sim.1 Full2 Man3
TPA6120 headphone amp V:1
67x71
48
Yes
Yes
Yes
-
-
No
8
16 Ask
TPA6120 headphone amp V:2 55x71
39
Yes
Yes Yes
-
-
No 7 15 Ask
TPA6120 headphone amp V:3 55x49
27
Yes
Yes Yes
-
-
No 6 13 Ask
Power supply +/- 15V
212x57 69 - Yes Yes
Yes - No
11 20 Ask
How to order? Please read the rules carefully!

Friday, November 4, 2011

8 channel mainboard for modular audio mixer

I working on the PDF doc of the modular audio mixer project, but the PCB design is ready to try. This project is same as like the preamplifier project, but the preamplifiers connecting with 12 pins connectors to the mainboard of mixer circuit. First time, I made 4 channel mainboard only, but now I designed new PCB board for 8 channel audio mixer. This new mainboard is bigger, the width is 25cm. This is maximum size what I can finis with my homemade PCB creation method. In the future I will done new PCB design with 4 channel PCB with connectors to 8, 12 or 16 channel mixers.

The 8 channel mainboard:


The 8 connector on the board is for preamplifiers. The last 2 is one for master potentiometers, the another one is for 2 stereo line outputs.

PCB sales of this project
Module name Size
(mm)
Area
(cm2)
PDF SCH PCB image Tested Price (US$)
Des. Sim.1 Full2 Sim.1 Full2 Man3
Power filter module
17x25 4 Yes Yes Yes - - No 3
11 Ask
4 channel mixer mainboard
149x84 125 Yes Yes Yes - - No 19 28 Ask
8 channel mixer mainboard
240x80 192 Yes Yes
Yes - - No 27 36 Ask
I/O board
37x60 22 Yes Yes
Yes
- -
No 5 12 Ask
2 Potmeter board
31x62 19 Yes Yes
Yes
-
- No
5 12 Ask
Microphone preamp module V2
67x103
69 Yes Yes
Yes
Yes
-
No 11 19 Ask
Microphone preamp module V3
67x103
69 Yes Yes
Yes -
-
No
11 19 Ask
1 dual opamp preamp module
61x103
63 Yes
Yes Yes
-
-
No 10 18 Ask
2 single opamp preamp module
64x103 66 Yes
Yes
Yes
Yes
-
No 11 19 Ask
HQ 2 single opamp module
67x103
69 Yes
Yes Yes
-
-
No
11 19 Ask
jFET guitar preamp module 65x102 66 Yes Yes
Yes -
-
No 11 19 Ask
Switch module
18x34 6 Yes Yes
Yes Yes
-
No 3 11 Ask
Simple Power supply
121x57
69
Yes
Yes
Yes Yes
-
No 11 20 Ask
Power supply with 48V phantom
168x89 150 Yes Yes
Yes -
-
No 22 32 Ask
How to order? Please read the rules carefully!