LPT Chip DAC - Covox Speech Thing with Headphone Amplifier

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LPT Chip DAC - Covox Speech Thing with Headphone Amplifier

Postby matze79 » 2018-1-14 @ 16:20

Hi ppl,

I'm working on the Covox Speech Thing with a Chip DAC.
This is using a AD7524 Digital to Analog Converter, a LM358 OPAmp and the TDA7050 Amplifier.

There is also still Room for improvments of the Device.
It already sounds pretty clear and will hopefully beat R2R DAC's soon :)

DSC_0017.JPG

DSC_0012.JPG

DSC_0013.JPG


The CVX-1-4 inspired me again to dig out my old DAC800 and other Stuff i collected to make a Covox like Device.

As you can see it looks pretty good for now :D

Homebrew PCB with tonertransfer method.

I need another Amp, because the TDA7050 is no longer in Production,
i thinking about using a Class D one.
But most of them that are suitable are BGA packages.. or MLF
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Re: LPT Chip DAC - Covox Speech Thing with Headphone Amplifier

Postby dreamblaster » 2018-1-14 @ 18:01

wow, looks good.
let us hear it, too ! :-)
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Re: LPT Chip DAC - Covox Speech Thing with Headphone Amplifier

Postby matze79 » 2018-1-14 @ 18:39

Yeah but TDA7050 is working in bridged mode, i don't think my line in will like it :)
Need to grab Signal before the Headphone Amp then :D

how do you record from your devices ?

just using line-in of my main pc isnt that good, i get additional noise that way
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Re: LPT Chip DAC - Covox Speech Thing with Headphone Amplifier

Postby dreamblaster » 2018-1-14 @ 19:09

I use my Zoom Q4 : this has line in, and of course records video at the same time.
--> I upload this to youtube (no processing).
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Re: LPT Chip DAC - Covox Speech Thing with Headphone Amplifier

Postby matze79 » 2018-1-15 @ 13:39

I will try to record, as soon as i find a suitable configuration :)

Designed a DropIn Replacment for TDA7050 in Bridge Configuration (Using LM386):

drop_in.jpg


And i solder in a new Poti later.
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Re: LPT Chip DAC - Covox Speech Thing with Headphone Amplifier

Postby matze79 » 2018-1-15 @ 18:08

Bought some Cables for recording :)

But i need to improve a few things.
The LM386 sounds pretty shitty.
The TDA7050 is far superior.

The LM386 sounds a little bit skewed.

Maybe i should try to generate some Signals and measure with the osciloscope.
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Re: LPT Chip DAC - Covox Speech Thing with Headphone Amplifier

Postby Super_Relay » 2018-1-18 @ 01:58

If you have the LM386's handy still theres a good article here on getting the best out of them

https://hackaday.com/2016/12/07/you-can ... ead-hands/

I am working on a raspberry pi audio project of similar scale and was recently checking out what i could use for an op-amp as my output is not fantastic into headphones.

its sad the tda7050 and 7052 are all end of life parts now
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Re: LPT Chip DAC - Covox Speech Thing with Headphone Amplifier

Postby matze79 » 2018-1-18 @ 09:50

Hi,

i recorded Crystal Dream, Amplifier installed is LM386.
Record is not perfect, as LM386 is making some noise..

I want to try some Class D Amps and try to get some Samples :)

Hear me:

https://soundcloud.com/matthias-werner- ... dream-demo

44Khz / Mono played by AMD K6-2 450Mhz

EDIT:

OPAmp Stage can be fine tuned.
A additional variable resistor can improve it a little bit.
But i need some program to generate some test signals to fine tune it.
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