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Old 4th April 2004, 10:44 AM   #1
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Default DIY tube output in DAC - needs advice...

HI!

I have built the "Elektor DAC 2000" some time ago. Efter modding it with AD797 instead of OPA627 the sound has improved a great deal.

I would like to have switchable tube output though. Like the Shanling CD-players.

I need advice on:

1. What kind og tube design to add (SSRP, etc.
2. What kind of tubes. I have a few 12B4A, 6N1P, E80CC to try out.
3. Where and how to break in to mu exsisting circuit to add the new tube output.

Any ideas?

Best regards,

Peter Lund
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Old 4th April 2004, 09:38 PM   #2
Ryssen is offline Ryssen  Sweden
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I am building the same Dac, and I plan to use a relay from Iout (pin 14)from the Dac so I can switch beetwen the two outputs.
I am going to use a SSRP with 6SL7,and the simple solid state I/V converter from this forum.
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Old 5th April 2004, 05:37 PM   #3
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Do you have any schematic for your tube output stage that you want to share?
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Old 5th April 2004, 06:48 PM   #4
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Default Audio note tube output stage

Ryssen,

Take a look at this schematic: http://mparvi.republika.pl/DAC2sig_small.gif

It's a tube preamp output stage from an Audio note DAC with ECC88/6DJ8 in SRPP config and low voltage. Sound is said to be excellent.

What about adding it after the V-I stage?

- Peter
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Old 5th April 2004, 09:24 PM   #5
Ryssen is offline Ryssen  Sweden
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The Ecc88 should work as well,I use 6SL7 because I like it better,
Here are some posts that Ive done on the outputstage Tube outputstage
I am going to use this stage with 6SL7.

Easy-to-build I/V stage

I am going to try this I/V stage might work with the IC one on the board but you better ask sommeone who knows better than me,might be interesting for me to know to......
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Old 6th April 2004, 10:54 AM   #6
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The Thorsten Loesch tube dac project looks nice.

I just don't get if the V/I-stage is needed or if you can connect it straight to pin 14 of the PCM1704?


- Peter
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Old 6th April 2004, 11:38 PM   #7
Ryssen is offline Ryssen  Sweden
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I had a Ecc83 SRPP on my Pioneer PDS904,connected direct from the DAC,The sound was quite well,I dont think it will do any harm to
try it without I/V stage,someone correct me if Im wrong.
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Old 7th April 2004, 02:35 PM   #8
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Default Re: DIY tube output in DAC - needs advice...

Konnichiwa,

Quote:
Originally posted by jazzpeter65
I would like to have switchable tube output though. Like the Shanling CD-players.
You are aware that what Shanling does is to add a Cathode follower after the solid state audio circuitry? Is that what you want?

Quote:
Originally posted by jazzpeter65
1. What kind og tube design to add (SSRP, etc.
2. What kind of tubes. I have a few 12B4A, 6N1P, E80CC to try out.
Whatever sounds good to you.

I personally use something rather different in a commercial mod set for Shanlings Tubed CD & SACD Player, but that circuit will not be available in the public domain. It provides great sound and excellent technical performance (Zout around 100Ohm, Frequency Response well into the MHz range, THD with WE396A is around 0.05 to 0.1% at digital full scale, less at lower levels), but the good old SRPP is not a bad choice, especially if the load is low.

Quote:
Originally posted by jazzpeter65
3. Where and how to break in to mu exsisting circuit to add the new tube output.
Directly at the DAC output Pin.

Quote:
Originally posted by jazzpeter65
The Thorsten Loesch tube dac project looks nice.
ThanX for the Flowers....

Quote:
Originally posted by jazzpeter65
I just don't get if the V/I-stage is needed or if you can connect it straight to pin 14 of the PCM1704?
Straight to pin14, all solid state parts disconnected.

Alternatively, if you wish to have both stages operational you could add a resistor (same value as intended I/V Resistor for Tube section) in series with inverting input of the I/V Op-Amp after the DAC.

However, this does not remove the Solid State circuitry from the signal path and hence the Valve Stage will retain a trace of "solid state" sound. I tried this forst for my Shanling Mod's as I intended to leave the solid state stage in place. I found it compromised the sound much more than I was happy to accept, so my mod's to the Shanlings dispose of the SOlid State section completely (the headphone Output is gone too).

Sayonara
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Old 7th April 2004, 09:09 PM   #9
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Old 8th April 2004, 09:46 PM   #10
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Just to be sure that why are talking about the same circuit, I am attaching the Thorsten Loesch tube dac.


/ Peter
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