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Old 30th April 2009, 02:18 PM   #621
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Send a message via MSN to mischa72
Hi Stefan,

I just sent you an email.

Regards,
Mischa
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Old 14th May 2009, 04:16 PM   #622
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Thanks to help received from members of this forum, I'm glad to report that my CD104 has been revived.

While the machine was taken apart, I took the chance to change some capacitors, output op-amps, added more ground links on the servo board, added RCA sockets and fixed the ground loop issue at the heat sink pointed out in this forum.

The sound coming forth now is very musical and "analogue". There are plenty of details but the sound is never sharp. Mid and low frequencies have good tone and presence. Listening to vocals, wind or string instruments is a joy with the player.

Attached are some pictures of the modifications to the CD104.

Click the image to open in full size.
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Old 14th May 2009, 07:12 PM   #623
jives11 is offline jives11  Europe
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Very nice work mcheong66
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Old 1st July 2009, 07:36 PM   #624
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Hi all.

At my Cd 304 i removed the SAA7030 for NOS. Everything is ok when i take the signal at the original output. When i took the Signal direkt from pins 22 at the 1540P into a Tubestage i hear teribble noise with.

Q: What is the minimum to let beetween the dac pin22 and the tube.


The spec. of the Tubestage:

Different to the spec. i bridged the 1MicroF C1 at input
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File Type: jpg tubestage.jpg (51.1 KB, 249 views)
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Old 2nd July 2009, 09:22 AM   #625
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Hi nanocamp,

I found during my internet research for my own CD204 project the two following websides that might be of interest for you:

http://www.lampizator.eu/LAMPIZATOR/...ips%20TDA.html

and

http://www.lampizator.eu/lampizator/...s%20cd304.html

I have no idea how a tubed output stage works, but maybe the value of the resistor for the I/V-conversion is to high and makes the pair of TDA1540s go into distortion. Or there is some DC left in the signal which is too much for your preamp.

By the way, have you added the 1k resistor between pin 16 and 18 on the SAA7000 to make it put out a 14bit signal?

Best regards,

Stefan
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Old 2nd July 2009, 12:20 PM   #626
simonov is offline simonov  Bulgaria
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Quote:
Originally posted by nanocamp
Hi all.

At my Cd 304 i removed the SAA7030 for NOS. Everything is ok when i take the signal at the original output. When i took the Signal direkt from pins 22 at the 1540P into a Tubestage i hear teribble noise with.

Q: What is the minimum to let beetween the dac pin22 and the tube.


The spec. of the Tubestage:

Different to the spec. i bridged the 1MicroF C1 at input
TDA1540 is a current output DAC. As such it likes to see as low load impedance as possible ideally a zero. In order to amplify the signal coming out of the DAC you need to convert it to voltage(i/v converter). The most common i/v conversion is usually done by opamp, because the i/v opamp converter represents a virtual ground to the Iout of the DAC. Rising the load impedance of the DAC increases the distortion.

Now from the schematic attached we can see that the input impedance set by R* is 1Mohm which is A LOT more that the preferred 0ohm load for this DAC chip. This R* input resistor acts as a passive i/v conversion, turning the output current into voltage, which can be calculated using Ohm's law. Not only are you causing the DAC to output a tremendous amount of distortion, but the input tube is overloaded.

Speaking of the tube stage. How on earth did you chose this stage? You cant just stuck some tubes into the player and expect it to work.

If you really want a tube output stage you should try this out:

http://www.fortunecity.com/rivendell...da/vasfda.html

As you can see the recommended I/V resistor for TDA1541 is 100ohm. This resistor is subject to experiments in order to find the correct value for your needs. In general the higher the resistor's value the higher the output level, but you get higher distortion as well.


Good luck
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Old 3rd July 2009, 06:12 PM   #627
tubee is offline tubee  Netherlands
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Forget the tube output. A THS4032 will do the job.
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Old 5th July 2009, 11:57 AM   #628
simonov is offline simonov  Bulgaria
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Quite impressive IC IMHO. And one can use those NULL pins to drive the DC output down to 0V. I've got some other favourites though, like SSM2017 An excellent IC.
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Old 6th July 2009, 04:00 AM   #629
Richard is offline Richard  Australia
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Hi Nanocamp,

I used the Lampizator tube stage in that link StefanAC provided. I would advise you to carefully read the word document Lukasz provides.

The SRPP tube stage is easy to construct and good to start with. As Simonov diagnoses you need to convert current out to voltage out. I simply used a 20 ohm resistor from pin 22 of the dac to ground. This is sufficient as the gain of the 6N2P in SRPP is about 50.

Used a small metal piece with the valves to ground the RCA (- ve) input, output, circuit (cathode R of bottom valve) and (- ve/ground) of the power supply. See pic attached (sorry about the quality)

I also used a different power supply with a valve rectifier and some chokes.

Rich
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File Type: jpg 6n2p srpp wiring.jpg (54.2 KB, 335 views)
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Old 6th July 2009, 04:04 AM   #630
Richard is offline Richard  Australia
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Here it is in action
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File Type: jpg lampizator 6n2p srpp output.jpg (39.0 KB, 278 views)
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