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Old 21st September 2012, 10:12 PM   #1
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Default tube to replace opamps in cd player

hello all.
I am trying to use valves to amplifiy the o/p from a tda1541 dac so to bypass the opamps.
I am using this circuit basesd around a quad 22 phono stage .
When I use a 1m as R1 and feed a normal un modded cd o/p It works like a buffer with only a small gain increase.
So I tried a 100k R1 and it over loads so I know it has gain but I am unsure how to get the gain I need so I can use the o/p from the Dac chip
This is my first time playin with tubes and I have now made a discharge lead for the caps....ouch!!so I dont get zapped.
Can anyone help me make this work

Thanks
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Old 22nd September 2012, 04:48 AM   #2
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I just looked at the tda1541 datasheet.

I have limited experience with these devices but it looks like this DAC would really be happy with a 0V current sink. Fig 1, top right.

I don't think a tube cct can work this way.

Anyone with more experience should be able to add to this.
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Old 22nd September 2012, 05:52 AM   #3
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How much of the circuit is left ?

The I/V resistor still there ?
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Old 22nd September 2012, 07:45 AM   #4
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check out Lukasz Fikus Lampizator

for instance, http://lampizator.eu/LAMPIZATOR/REFE...H/IMG_5501.jpg

Lots of info about TDA1541 and replacing opamps with valves in CD players
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Old 22nd September 2012, 07:48 AM   #5
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Make R1 47ohm to get proper loading of the 1541. Unfortunately the EF86 has far to much gain so it won´t work anyway. If you triodestrap it it will work well, but gain will be a little on the low side.

This is good stuff that you probably missed: Thorsten's tube Stage for TDA1541A

But stay away from Lampizators tube designs! Lots of good info on his side except for them.

Last edited by revintage; 22nd September 2012 at 07:51 AM.
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Old 22nd September 2012, 10:08 AM   #6
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What you say about my circuit:

Click the image to open in full size.


It has 19 dB voltage gain, steep attenuation above 20 kHz and low distortion and output impedance.
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Old 22nd September 2012, 11:22 AM   #7
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This is the frequency response. The gain scale seems odd, but it is due to current feed input and corresponds 19 dB voltage gain.

Click the image to open in full size.
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