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noDAC DHT output stage
noDAC DHT output stage
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Old 1st March 2019, 03:08 PM   #1
merlin el mago is offline merlin el mago  Europe
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Default noDAC DHT output stage

Hi guys,

I want to add a valve DHT output for my noDAC to reach the 2VRMS, attached schematic used.

TIA
Felipe

N.B. using the low pass filter gives 1.1V RMS at full output.
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File Type: gif RC filtro paso bajo 1K y 3.3nF.gif (53.1 KB, 475 views)

Last edited by merlin el mago; 1st March 2019 at 03:24 PM.
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Old 2nd March 2019, 01:14 PM   #2
merlin el mago is offline merlin el mago  Europe
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Any suggestions like only one stage or two stages, best DHT tube to reach the 2VRMS, etc.
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Old 2nd March 2019, 01:24 PM   #3
50AE is offline 50AE  Bulgaria
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noDAC DHT output stage
For the start, it must definitely be as little microphonic as possible. That excludes the cheap 4P1L.
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Old 2nd March 2019, 01:25 PM   #4
merlin el mago is offline merlin el mago  Europe
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26 can be enough or it will need a driver?
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Old 2nd March 2019, 06:05 PM   #5
euro21 is offline euro21  Hungary
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noDAC DHT output stage
Quote:
Originally Posted by merlin el mago View Post
26 can be enough or it will need a driver?
#26 has -about- 8x amplification factor.

2A3 has about 4x.

Last edited by euro21; 2nd March 2019 at 06:08 PM.
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Old 2nd March 2019, 06:49 PM   #6
Koifarm is offline Koifarm  Netherlands
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Felipe, i have 2.25Vrms output signal after isolator board and filter.
So i use a cathode follower schematic( 0,95x amp). I use not dht but 6N6P.
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File Type: jpg IMG_0449.jpg (443.4 KB, 362 views)

Last edited by Koifarm; 2nd March 2019 at 06:54 PM.
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Old 2nd March 2019, 07:45 PM   #7
merlin el mago is offline merlin el mago  Europe
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Quote:
Originally Posted by euro21 View Post
#26 has -about- 8x amplification factor.

2A3 has about 4x.
Enough 2A3 but expensive.

Quote:
Originally Posted by Koifarm View Post
Felipe, i have 2.25Vrms output signal after isolator board and filter.
So i use a cathode follower schematic( 0,95x amp). I use not dht but 6N6P.
What LPF do you use?

Quote:
Originally Posted by Koifarm View Post
Felipe, i have 2.25Vrms output signal after isolator board and filter.
So i use a cathode follower schematic( 0,95x amp). I use not dht but 6N6P.
What LPF do you use?

Quote:
Originally Posted by Koifarm View Post
Felipe, i have 2.25Vrms output signal after isolator board and filter.
So i use a cathode follower schematic( 0,95x amp). I use not dht but 6N6P.
Used I2S isolator but introduces noise.

Quote:
Originally Posted by euro21 View Post
#26 has -about- 8x amplification factor.

2A3 has about 4x.
Bela is not too much amplification 4X, do you know another DHT 2X to reach the 2VRMS output?

2A3 is the same like the Russian 6S4S or 6C4C?
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Old 2nd March 2019, 11:23 PM   #8
gmant123 is offline gmant123  Argentina
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71A gain is 3x....
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Analog as the sound of the nature....
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Old 3rd March 2019, 09:05 AM   #9
Koifarm is offline Koifarm  Netherlands
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Quote:
Originally Posted by merlin el mago View Post
What LPF do you use?
See schematic below.
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File Type: jpg IMG_1782.JPG (57.2 KB, 318 views)
File Type: jpg IMG_1781.JPG (330.7 KB, 295 views)
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Old 3rd March 2019, 10:04 AM   #10
merlin el mago is offline merlin el mago  Europe
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Quote:
Originally Posted by gmant123 View Post
71A gain is 3x....
Thank you

Quote:
Originally Posted by Koifarm View Post
See schematic below.
Neat, what's the corner frequency Fc? What's the pourpose of resistor 1.5K?

Last edited by merlin el mago; 3rd March 2019 at 10:26 AM.
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