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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Salas DCG3 preamp (line & headphone)
Salas DCG3 preamp (line & headphone)
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Old 15th January 2017, 03:22 PM   #1001
Salas is offline Salas  Greece
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Salas DCG3 preamp (line & headphone)
Quote:
Originally Posted by xrk971 View Post
Thanks for the song - very nice. I also like this one for testing head phone amps.

https://www.youtube.com/watch?v=s6_B1AB9nu8&sns=em
Just listened to it on the 770s. Yes good on the Beyer's sonic style indeed.
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Old 15th January 2017, 03:28 PM   #1002
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P.S. Maybe try some Beth Hart tracks too
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Old 15th January 2017, 06:11 PM   #1003
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Default I have a problem

I just measured the spectrum of my DCG3 and it looks like there are some oscillation issues. I can't really hear it all that well but it shows up like a xmas tree on the FFT. My simple 2 transistor amp measures clean so I know the rig and software are not at fault. Using UCA202 and RightMark software.

What do you all think could be causing this?

Click the image to open in full size.

As a comparison of a clean amp, the same rig measures this:

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Old 15th January 2017, 06:24 PM   #1004
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Signal or rails cabling issues? PSU interaction? Bad grounding? Non grounded vol pot body? It can do 1MHZ even with 20K pot in between source and input so it takes some caution. Did you have a pot when running the RightMark?
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Old 15th January 2017, 06:31 PM   #1005
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No pot. Let me take a look at PSU - try different one. I am using 100nF caps instead of 150nF caps in amp. Would that matter?

Must be no earth grounding.

Last edited by xrk971; 15th January 2017 at 06:50 PM.
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Old 15th January 2017, 06:35 PM   #1006
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In op-amp's rails decoupling? Not likely to matter.
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Old 15th January 2017, 06:50 PM   #1007
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Are your C4s 1uF indeed? Looking kinda small size.
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Old 15th January 2017, 06:57 PM   #1008
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Must be no earth grounding.
Meaning?
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Old 15th January 2017, 07:05 PM   #1009
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Amp ground is not connected to earth ground. Only AC mains connected to trafo primary for now.

1uF is 50v MLCC.
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Old 15th January 2017, 07:31 PM   #1010
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Could even be radio interference or rails oscillation. It shows lower noise floor even to the clean one in areas its not excited and that's weird. If you will ground the Jfet cans with crock clips to the signal ground, does it change something?
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