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Class D Switching Power Amplifiers and Power D/A conversion

My new TPA325x DSP/Bluetooth/X Amplifier made for mobile Application
My new TPA325x DSP/Bluetooth/X Amplifier made for mobile Application
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Old 8th March 2017, 11:37 PM   #71
mantabernd is offline mantabernd  Germany
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Join Date: Aug 2012
Location: Germany near Munich
Quote:
Originally Posted by doctormord View Post
Define "low noise".

A gain of 26dB is a bit high for a normal smartphone source, is it not? (At 1Vrms output)
Sorry it's a gain of 15.7dB, not 20dB like I wrote before.

You also need to add around 9dB gain because of post filter feedback configuration. Regular Smartphones have a output level between 0.7V - 1V(rms).

I needed to fit my gain chain to the DSP which has a output of 0.9V(rms) but in fact I prefer to not go obove 0.7V(rms).

Low noise for me is a noisefloor of -100dB and better.

I will make some measurments and post them tomorrow evening.
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Old 9th March 2017, 11:08 PM   #72
mantabernd is offline mantabernd  Germany
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Attached the measurment of preamp.

My setup

Sig Generator ----------------------------------------> DSP ----------------------------------------> Preamp Out
0.46V/0.65V(rms/pkpk) ----------------------------- Gain: 0dB ------------------------------------ 3.28V/4.634V(rms/pkpk)

This ends up in a gain of 17dB just for the preamp stage.

I was a bit confused first because the gain must be 15.7dB but then I realized that I took a bit different resistor values as in schematics

CH1 is measured at the output of DSP, CH2 at the output of Preamp.

FFT Plot is for CH2.

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Last edited by mantabernd; 9th March 2017 at 11:10 PM.
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Old 10th March 2017, 12:31 AM   #73
3eaudio is offline 3eaudio
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Join Date: Oct 2014
Quote:
Originally Posted by RobFreak View Post
I know the frustration! Perhaps you should consider a bigger batch if you are confident doing that? I work with semi-massproduction of electronics, so i know the feeling of prices not being what they should be..
is the BT module chipset from CSR? APTX?

another question is that there are also many cost effective material from china,but you need some time to source.
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Old 10th March 2017, 09:24 AM   #74
mantabernd is offline mantabernd  Germany
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Join Date: Aug 2012
Location: Germany near Munich
Quote:
Originally Posted by 3eaudio View Post
is the BT module chipset from CSR? APTX?
BT module is from bluegiga:

WT32I-A-AI6-APTX


Quote:
another question is that there are also many cost effective material from china,but you need some time to source.
Is this a question or a fact? What exactly do you mean this this?
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Old 10th March 2017, 11:44 PM   #75
mantabernd is offline mantabernd  Germany
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Location: Germany near Munich
Some more pics and measurments:

FFT Ampout 1W@4Ohms

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THD+N 0,009% | 10W@4Ohms from a 162mV(rms) source

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THD+N 0,86% | 224W@4Ohms from a 763mV(rms) source

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Amp from the back

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Amp from the side

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Amp from the front

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Old 11th March 2017, 10:53 AM   #76
mikey_audiogeek is offline mikey_audiogeek  New Zealand
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Nice work!
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Old 12th March 2017, 01:34 PM   #77
RobFreak is offline RobFreak  Denmark
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Looks pretty neat!
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Old 24th January 2018, 11:08 AM   #78
r0b is offline r0b  Germany
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Hi Bernd,

is this still in development? Always looking for good all-in-one packages for my next boombox build!

Cheers,

Robin
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Old 24th January 2018, 03:12 PM   #79
cacao ambiance is offline cacao ambiance  United Kingdom
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Join Date: Oct 2015
I like a lot what you have done. price is understandable idk for myself, would like it a lot... finishing boxing new TPA325* boards iíve already got, hmm.... ooww....


Ive been following a chap that has been progressing making products in china and how he designed the products using cheap, ready available components. been quite interesting to read the details... anyway with potential interest in a batch, maybe he can put you in contact with good Chinese people that could help do a production run and get better component pricing, production optimisations, etc

i made a pledge to the crowdfund he ran/running
Earth-friendly EOMA68 Computing Devices | Crowd Supply
Rhombus-Tech
Mailing list best place to ask: The arm-netbook Archives
hes lkcl on the net/maillist/irc.
His info: Visionary - Technology - Poems - Stuff
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