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Old 15th December 2003, 11:47 PM   #1
Ryssen is offline Ryssen  Sweden
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Default Tube outputstage

I am planing to use this outputstage http://www.fortunecity.com/rivendell...da/vasfda.html
on my PCM1704 DAC is it okay to use this filter?
It says itīs okay to use 6SN7 whitout changing the cathode resistor, What about 6SL7, I think itīs better than 6SN7.

Anyone tried this.Or have an other schema?
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Old 16th December 2003, 02:50 AM   #2
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Default Resistor values.

You could use 1K for the 6SN7 tube. I used 3k3 for the 6SL7 tube.
I am refering to the first circuit (SRPP).
The 6SL7 sounds very good.
Note that both cathode resistors must be changed and both are the same value.
Cheers.
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Old 16th December 2003, 02:56 PM   #3
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Quote:
I am refering to the first circuit (SRPP).
Could You please tell us what Dac are you using this output stage with,and how does it compare soniclly to op-amp stages and other discrete designs?

Bartek
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Old 16th December 2003, 10:09 PM   #4
Ryssen is offline Ryssen  Sweden
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Thanks for the answer.
If I donīt want to use "deem" should I short the 470K resistor
or not?
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Old 16th December 2003, 10:19 PM   #5
dhaen is offline dhaen  Europe
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Default De-emphasis not required...

Leave the switch open. The 470k resistor, C2 & R2 are then not required.
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Old 17th December 2003, 08:59 AM   #6
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Default The DAC.

Hi Bartek,

My DAC chip is a TDA1541. The output goes directly to a 'pi' filter and is then amplified by the tube.
In the same machine I can use an opamp also. I used the OPA2134 and later the AD826 . The 826 is much better. The opamps are very good but there is a difference in midrange sounds with the tube. The tube is smoother and easier on the ear.
The circuit is somewhere around. Search the forum and you should find it. I posted it several months ago. I guess you can do a TDA1541 search.
I left out the 'deem' circuit .
This set up sounds better than a stock CD-17 Mk II !
Cheers,
Ashok.
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Old 17th December 2003, 10:33 AM   #7
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Thanks,
I'm modifying old Marantz player now (CDM4/SAA7220/SAA7210/TDA1541A).I'm building Thoresten's OPA660 I-V output stage now,but would like to try tube output ,too.

How do you leave the "deem"?
I've heard about this mod. but couldn't find any posts how to do it.

Bartek
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Old 17th December 2003, 04:17 PM   #8
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Default The DEEM.

Hi Bartek,
You can leave out R2,C2 and the 470K resistor. Keeping the switch open cuts out the deem . But if you want it out ( like me ) just skip those parts.
Cheers.
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Old 17th December 2003, 04:58 PM   #9
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Thanks a lot,
I think I get it.

Bartek
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