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Old 21st July 2010, 05:59 PM   #1831
udailey is offline udailey  United States
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Wonder if the program or card you are using is inserting some noise at every 1k increment. Would be a weird coincidence for the DCB1 to do that itself.
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Old 21st July 2010, 06:13 PM   #1832
Salas is online now Salas  Greece
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Why you wonder? Its there in the Emu Tracker's solo loop. In Grufti's it ain't. But it can reveal 10dB less so it hides some loop gremlins. Its mainly the settings to get the floor so low and the artifacts created.
The simple thing to see is that the DCB1 just lifts the noise floor a bit and improves the distortion. -130dB to -140dB (ref 0dB=1V), give or take, given the card and software beyond 1kHz is seriously silent. Must be one of the cleanest things line.
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Old 22nd July 2010, 12:29 AM   #1833
Salas is online now Salas  Greece
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P.S. Here is an Arta capture of the Emu Tracker's loop. See how software changes artifacts. This one dithers also.
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Old 22nd July 2010, 05:48 AM   #1834
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Salas

how about different wiring at mute relay - output signal goes to output RCA connector and between there Is connection with mute relay NO contact to com to gnd
at first the relay Is not powered so output signal goes to gnd, when cap Is charged the relay click and the gnd goes to NC which Is not connected and the output signal goes to output RCA
that way signal Is not passed through relay contacts
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Old 22nd July 2010, 07:37 AM   #1835
Salas is online now Salas  Greece
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Oenboek has shown that and has been tried with success. See a few pages back.
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Old 25th July 2010, 04:37 PM   #1836
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Default In use ...

Now that I have had some time to listen to the DCB1 I can say that I am really pleased with what it is doing. It is a better preamplifier than a NAD C160 by no small margin.

Subjectively it does less to the signal that passes through it than the NAD does, which is what I was hoping for. It is easier to hear some of the subtle sounds that are on the recordings. More of the bodies of the instruments than just their voice if that makes sense. It does less to supress the dynamics than what I had and the stereo image is enhanced. But what I am the happiest about is how it performs in the bass region. Definitely more definition. I had mistakenly thought that with the planar speakers that I am using that I had not found the right placement for them yet. Now I know ... the NAD wasn't quite letting loose of the bass notes as well as the DCB1 does.

The only out of place quality that I was hearing was a little mis-proportion in the vocals which were just a little ... chesty. However that disappeared after I had played it long enough (about 18 hours) And it was interesting when it happened, too. It audibly faded away in a few seconds. I've never heard anything like that but it that was the last caveat to it. Great pre-amp.

The basic measurements ...

2 sets 2SK170 matched at 7.7 mA lds in the buffer circuit
20K Ohm Alps volume control
DC offset of 1.1 mV and -.6 mV
Regulator voltage +10.65 and - 10.00 Volts.
Regulator current is about 130 mA with 2.01 & 1.96 Volts across each 15.4 Ohm resistors.

The system I am using it in ...

Musical Fidelity A324 DAC > DCB1 > Marchand XM-9 > Sunfire Cinema Grand Signature II amplifier > Magnepan 2.6 speakers and Velodyne CT-150 subwoofer ... And it has never sounded better!

The next steps are to use film caps for the LED strings and for attaching the Lightspeed volume control. Perhaps increasing the regulator current to 150 or 180 mA as I am still a little consevative with where I have that set.

Thanks very much for this project. I have to admit this is a lot more fun than just going out and buying a new piece of gear.

Last edited by Macronaut; 25th July 2010 at 04:51 PM.
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Old 25th July 2010, 04:44 PM   #1837
Salas is online now Salas  Greece
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Happy end for you then, cool. Yeap, keep us posted for when you will perform new mods.
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Old 7th August 2010, 04:51 PM   #1838
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Quote:
Originally Posted by korben69 View Post
I've pointed the pins for measuring voltage on the pic.
What value should I find there ?
I found -9.48 and +10.14v at the pins.
-26 and +25.6 at the 2x68R.
Correct ?
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Old 7th August 2010, 05:01 PM   #1839
Salas is online now Salas  Greece
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Is your transformer more that 15+15 AC when measured feeding the project? Your Vout(s) are OK. If your filter capacitors are 35VDC and there is sinking to the Mosfets, then the 15VDC Vin-Vout isn't a problem. Its expected to be about 10-11V most difference so not to create surplus heat. If you can tackle that, it will be safe. Are you taking those measurements on a fully stuffed board?
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Old 7th August 2010, 05:06 PM   #1840
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The transformer is a RCore 30VA 2x15v.
Caps are 4700uF/35V Pana 105.
Board is fully stuffed, except inputs and pot.
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