Univeral Power Amplifier Control Center UPACC

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JPS64

JPS64

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Joined 2011
#1
Some power amplifier needs temperature monitoring.
Some amplifier needs fan control like ALPHA BB.
They´re builders who want VU-Meter or FFT real time visualization.
All power amplifier needs AC main power filtering; perhaps controlled powering.
Some power amplifier owner needs DC blocking.
All power amplifiers needs inrush current limiter.
Power amplifiers works with 115/230VAC 50/60Hz.
Some owners wants volume control.
And at last (but not least), some owners prefers symetrical inputs.

I´ve started the development of an electronic consisting in one panel with different boards with following features.

Note: the PWM and temperature is part of the ALPHA BB board but I´m thinking about additional panel board with only temperature sensing expending universality.

First board, schematics ready:
- 115/230VAC 50/60Hz filtered inlet with switch and fuse or wire to board for main power inout
- additional X2 filter capacitor and varistor protection
- two AC/DC +/-24VDC converter powered by switch main power to supply analog power supplies
- one AC/DC +12VDC converter powered by switch main power to supply digital power supplies
- microcontroller (SW) controlled main power relay before powering amplifier
- 4mm châssis grounding hole

Second board, schematics ready:
- wire to board input connector from first board
- DC-blocking electronic
- NTC inrush current limiter
- bridged central ground to châssis (4mm châssis ground hole) over 6.3mm faston or cable soldering

Third and fourth boards, schematics needs some modifications:
- wide ranging VU-Meter based on THAT Corporation design Note 119: http://www.thatcorp.com/datashts/dn119.pdf
- two channel I2C(SPI?) ADC (separating VU-Meter and FFT data streams)
- ADUM1250 as I2C isolator
- +/-15VDC analog supplies powered
- +5VDC digital supply powered
- faston 6.3mm or NEUTRIK NL2MD-V or holes for 4mm bananas for loudspeaker outputs

As pointed by user @obh, we can´t use E-Ink display because of bad refreshing rate.

Fitfth board, still in development, three possibilities:
First one:
* ATMEL microcontroller based board using SPI display (schematics ready)
* low resolution small LCD display: cheap, a lot of programming but in fine bad quality
* using N OLED displays, one per function (VU-Meter, FFT, temperature, RPM, settings): YouTube
* using expensive EA Assembly TFT with touchscreen (up to 7.0"): eDIPTFTSerielle TFT - ELECTRONIC ASSEMBLY
Second one:
* new development based on Raspberry Pi compute module; needs OS LINUX but allows using cheap TFT RGB displays (up to 10"): Compute Module - Raspberry Pi Documentation
Third one:
* new development based on 4D SYSTEMS gen4 HMI Display Modules (up to 7.0" and touchscreen) using Workshop4 IDE SW development environment: 4D Systems | gen4-uLCD-70D
Fourth one:
* new development using Particle Photon WiFi connected microcontroller solution and smartphone application: https://docs.particle.io/datasheets/photon-(wifi)/photon-datasheet/
* starting today to think about feasability

I don´t know if there is a demand for this kind of electronic!?

Would be nice to become constructive remarks.

P.S.: I´m working with senior SW programmer to bring this project ahead.

JP
 
#3
I would add control of B+ voltage and bias control to your list...
To be able to control power usage depending on if need the extra power.
Maybe run a completely passive heatsinking as default or late quiet nights
but with fan full spinning at loud parties 🙂

Somebody wrote that a rule of thumb was that use arduino when you
are going to do one or two things only, and rasberry pi for those moments
when doing more things.
 
#6
Progress today: TPS LDO´s will be proposed fully tested (QFN with thermal pad are difficult to solder).

Wide range dB-Meter must wait then I´m on travel tomorrow.

Comments already welcome.

And a nice weekend.

JP
 

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#8
That sounds good. I wondered, I count three big relays. One for power, the other two for loudspeakers muting ? Have you considered going for SSR rather than physical relays ? It's hard to find relays with really great DC current ratings (except maybe the amplimo ones).
 
#11
I´ve an answer about Arduino Micro single solution tomorrow (left and right FFT performance?).

Nonetheless, I´ve started another version using Raspberry CM3 Compute Module (VU-Meter, TFT, RPM, temperature and RS232 display) with Arduino Micro (encoder, IR receiver, elapsed time recorder, RTC and GPIO):
- USB2.0 HOST and OTG interfaces
- HDMI interface
- and I2S interface!

Icing on the cake: NXP i.MX 6ULL - ARM Computer/System on Module iMX6ULL

JP
 
#16
Arduino Micro standalone solution with limitation possible (R/L TFT performance checked by my programmer).

I´ve posted questions about Raspberry PI Compute Module CM3 GPIO usage.

If the answer is positive then the new configuration will be:
- Raspberry PI Compute Module CM3
- ESP (8266) Wi-Fi Module
- optional NEXTION display

I´ll propose to use Blynk App (IOS, Android): Blynk

JP
 
#18
Starting layouting for the prototype:
- Arduino Micro
- ESP-05 Wi-Fi Module or ITEAD NEXTION display

JP
 

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#20
I just read the last project of Rod Elliot. Maybe it can be a useful reading.

Fully Differential Amplifier

http://sound.whsites.net/project176.htm

Input/ Output Filters

If you have to ensure that RF or other high frequency noise does not cause problems, you may need to add an input and/ or output filter. This becomes critical, because the capacitors have to be carefully matched to ensure that CMRR isn't affected at high frequencies. Ideally, any caps used should be matched to the same tolerance as the resistors, which is likely to be an arduous task. The caps must be high stability types, so don't use 'high-k' ceramic caps, which have very poor stability with both voltage and temperature. Polyester is good, polypropylene is better, or if you can get them, use polystyrene. You can also use G0G (aka NP0) ceramics, but you'll have to match them yourself. I'll leave this to the constructor, but an example is shown in the article referenced [ 1 ].

Some basic input filtering that doesn't affect the CMRR can be provided by adding a small cap (C101) between the non-inverting inputs of each opamp. A value of 100pF to 220pF will help get rid of most high frequency noise above 70kHz or so. Adding ferrite beads to the inputs and/ or outputs (right at the point of entry into the chassis) can also be helpful, but most of the time the circuit will be used as-is. For truly intractable noise issues, use a good quality transformer with an electrostatic shield in front of the balanced input.

An output transformer can also be used, but you'll have to ensure that there's no DC offset, and the values of R9 and R10 will need to be reduced to provide a low impedance source to the transformer. Around 22 ohms is the minimum I'd normally suggest, but it might be possible to use less. This has to be tested with the transformer you intend to use. Driving a transformer with a balanced driver may seem like overkill, but if you need particularly high performance it's a simple (if expensive) solution.
Click to expand...


By the way, polystyrene inside hot case is a bad idea.
 
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