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Old 8th April 2004, 10:26 PM   #11
Ryssen is offline Ryssen  Sweden
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Its the one Im talking about,but I am going to leave out the R1
C1 and deem.
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Old 8th April 2004, 11:31 PM   #12
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Hi,

Quote:
Its the one Im talking about,but I am going to leave out the R1
Those two alone aren't responsible for the de-emphasis IMO.

Where's the I/V done? Isn't that what's R1 for?

What's the B+ for the SRPP? Is it tightly regulated?

Cheers,
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Frank
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Old 9th April 2004, 12:51 AM   #13
Ryssen is offline Ryssen  Sweden
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For Deem I am going to leave out R2 C2 relay and the 470K resitor.
Yes its in R1 the I/V is done,but if I use the Easy-to-build I/V stage i was going to leave out R1.
I thougt of using the same B+ as I did with my SRPP for my PDS904 witch is regulated at ca 250v.
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Old 9th April 2004, 07:33 AM   #14
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Thumbs up Why leave out R1?

Ryssen,

Why do you want to use an active I/V converter circuit when the same function can be made by a simple resistor?

I think the whole idea of a simple analog output gets lost if you use an opamp for I/V. Most DACs exspect to send current into a virtual ground. In most cases in form of an opamp.

A load resistor is a more simple way to do this, but its not working with all DACs. Multibit DACs are not a problem, though. PCM1704 is multibit DAC. A load resistor will give less distortion than using an opamp. IMHO you should keep R1 since its a clever way of keeping the signalway short.

/ Peter
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Old 9th April 2004, 07:36 AM   #15
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The PSU for this DAC tube stage is not regulated. Wouldnt is be better to use tube regulation? In the end, the PSU is what we listen to.......

/Peter

PS>I have attached the original PSU.
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File Type: png psu.png (4.9 KB, 1229 views)
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Old 9th April 2004, 07:38 AM   #16
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Something like this maybe?
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File Type: gif frank-pre-regps.gif (12.3 KB, 1734 views)
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Old 9th April 2004, 07:40 AM   #17
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Or this?
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File Type: jpg regulated-ps.jpg (43.2 KB, 1661 views)
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Old 9th April 2004, 11:06 AM   #18
Ryssen is offline Ryssen  Sweden
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I agree that a resitor is simpler (shorter way) of doing I/V convert.
I got this advise "Try it, you won't be sorry" in this thread:Easy-to-build I/V stage
Question number 2:I have read somewhere It sometimes sound
better with the right (Different value on the resistor)would it be possible to use variable resistor to find the right value?

Quote:
won`t solidstate regulators be better since they do not display any symtoms of noise?
I am thinking about it 2

To regulate or not?
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Old 9th April 2004, 12:43 PM   #19
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Konnichiwa,

May I suggest to all involved to re-read (or read) my short essay on Tubes and Digital from which these schematics are taken?

Thermionic Valve Analogue Stages for Digital Audio

I hope this will answer most questions sufficiently. You might also find some other essays and projects presented on my pages informative in the context, so please have a look:

the Thunderstone Audio Website!

Any remaining question, please ask in this thread.

Sayonara
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Old 9th April 2004, 09:55 PM   #20
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Sayonara,

I have read your arcticles and so far, I get most of it. I have a few questions though, before I start building>

1. Would a regulated solid state PSU give a better signal-to-noise ratio? See attached circuit.
2. PSU: Can I substitute the special resistors for normal ones?
3. What do I have to change to use E80CC or 12Bb4H?

- Peter
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