Discrete Preamp to be used with DAC and Frontpanel. - diyAudio
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Old 27th September 2015, 10:02 AM   #1
sonnya is offline sonnya  Denmark
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Default Discrete Preamp to be used with DAC and Frontpanel.

Just to give you all an teaser. I will of course make an seperate thread for the Discrete preamp but here is an picture of the PCB.

The board has servo but also in this case we have decided to use an discrete approach. The servo can pull the output with +/-20mV. It is mainly the JFET vgs mismatch that sets the limit here.

Feature list:
  • Discrete Servo
  • JFET input discrete opamps
  • Volume control based R2R DAC 16 bit from TI (DAC8812)
  • +12dB Gain
  • 5 channel DIFF/SE input
  • Balanced output.
  • No relays, only MOSFET switches.
  • All stages runs in class A.
  • Small size : 140x100mm

The price for this board is 389. To get it functioning it needs the frontpanel and +5.5V,+15V and -15V supply.

No information will follow the next days.
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File Type: png discrete preamp V1.0.png (158.2 KB, 477 views)
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Old 27th September 2015, 04:39 PM   #2
sonnya is offline sonnya  Denmark
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Ahemmm!!! I have made an calculation error here. The price of 389€ is with frontpanel! But you have to add 26€ to the encoder EM14A0D-C25-L032N.

But it is a better price for all.

BR

Sonny
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Old 27th September 2015, 05:44 PM   #3
sebbyp is offline sebbyp  United Kingdom
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Does the front panel include an IR receiver?
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Old 27th September 2015, 05:50 PM   #4
sonnya is offline sonnya  Denmark
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Yes for apple remote.


Sent from my iPhone using Tapatalk
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Old 28th September 2015, 11:22 AM   #5
sebbyp is offline sebbyp  United Kingdom
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Excellent - do you have a time-scale on the LPS and cost?

Ill take a pre-amp, screen and LPS.
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Old 28th September 2015, 03:41 PM   #6
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Hi Sonny,

Please put me down for the preamp (without the front panel...already ordered separately) and LPS.

Thank you,
Todd
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Old 28th September 2015, 05:28 PM   #7
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Much better than my expectation. Please count me in for preamp & frontpanel (the pre-order of frontpanel would be canceled automatically? )
May I dismiss my SE output shied and connect to this preamp board directly?
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Old 28th September 2015, 05:32 PM   #8
sonnya is offline sonnya  Denmark
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Quote:
Originally Posted by rogerchou View Post
Much better than my expectation. Please count me in for preamp & frontpanel (the pre-order of frontpanel would be canceled automatically? )
May I dismiss my SE output shied and connect to this preamp board directly?
I will cancel the frontpanel order. (The other that have paid frontpanel should only pay difference of course)

You will need the output shield to connect to the preamp or any other selector.

BR

Sonny
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Old 28th September 2015, 05:39 PM   #9
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May I know what is "any other selector'? That means I cannot wire to preamp board from J10(pin3-5-7-9)? Why?
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Old 28th September 2015, 06:49 PM   #10
sonnya is offline sonnya  Denmark
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Quote:
Originally Posted by rogerchou View Post
May I know what is "any other selector'? That means I cannot wire to preamp board from J10(pin3-5-7-9)? Why?
You need to filter the signal (The DAC puts out HF noise on those pins. Also they have an offset voltage of approx. 3.1Vdc).

That why you need an output filter in some form here. All you need to handle the +3.1V offset.
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