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LPT Chip DAC - Covox Speech Thing with Headphone Amplifier

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First post, by matze79

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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 😀

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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 😁

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

https://www.retrokits.de - blog, retro projects, hdd clicker, diy soundcards etc
https://www.retroianer.de - german retro computer board

Reply 1 of 7, by dreamblaster

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wow, looks good.
let us hear it, too ! 😀

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Reply 2 of 7, by matze79

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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 😁

how do you record from your devices ?

just using line-in of my main pc isnt that good, i get additional noise that way

https://www.retrokits.de - blog, retro projects, hdd clicker, diy soundcards etc
https://www.retroianer.de - german retro computer board

Reply 3 of 7, by dreamblaster

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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).

Visit http://www.serdashop.com for retro sound cards, video converters, ...
DreamBlaster X2, S2, S2P, HDD Clicker, ... many projects !
New X2GS SE & X16GS sound card : https://www.serdashop.com/X2GS-SE ,
Thanks for your support !

Reply 4 of 7, by matze79

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

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

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And i solder in a new Poti later.

https://www.retrokits.de - blog, retro projects, hdd clicker, diy soundcards etc
https://www.retroianer.de - german retro computer board

Reply 5 of 7, by matze79

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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.

https://www.retrokits.de - blog, retro projects, hdd clicker, diy soundcards etc
https://www.retroianer.de - german retro computer board

Reply 6 of 7, by Super_Relay

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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-have- … old-dead-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

Reply 7 of 7, by matze79

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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-matze/ … stal-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.

https://www.retrokits.de - blog, retro projects, hdd clicker, diy soundcards etc
https://www.retroianer.de - german retro computer board

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