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DAC line out too strong. how to fix it?
DAC line out too strong. how to fix it?
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Old 4th May 2015, 11:33 PM   #1
devgcl is offline devgcl  Australia
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Default DAC line out too strong. how to fix it?

Hi,
I have a Lenehan PDX DAC which runs a Hiface USB input. Dac is feeding analog signal to my HK990 amp. When i set my Foobar volume to max, at some stage, my amps volume get overriden and goes to max dangerously.
I tried feeding my Pioneer receiver and got the signal OVER alert indicating the analog signal is too high from the DAC.
I am told maybe i have to reduce something in the DAC resistors. Can i have some thoughts please?
Thanks
D
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Old 5th May 2015, 12:57 AM   #2
abraxalito is offline abraxalito  United Kingdom
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If you have the schematic I might be able to help. Isn't the PDX using PCM1704s? If its using some output buffers after the DAC chips then a step-down trafo might be a better solution rather than fiddling inside, voiding any warranty you may have and negatively impacting its resale value. Step down trafos improve dynamics too in general.
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Old 5th May 2015, 12:52 PM   #3
devgcl is offline devgcl  Australia
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Thanks abraxalito. I could not find the schema.
Unsure if the link below helps
MWTS: Lenehan Audio PDX Level 2 DAC.

The one i bought is below

SOLD: Lenehan Dac PDX L2 with Duelunds - Classifieds Archive - StereoNET

Can you pls elaborate your views.
Thx
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Old 5th May 2015, 12:57 PM   #4
Mooly is offline Mooly  United Kingdom
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DAC line out too strong. how to fix it?
Any reason why you can't just use a simple resistive attenuator on the analogue output from the DAC. Four resistors in total for the left and right channels.
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Old 5th May 2015, 01:48 PM   #5
abraxalito is offline abraxalito  United Kingdom
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Using a resistive attenuator stands a fair chance of reducing the dynamics because of heavier loading on the output buffers. Once you know how much attenuation you need I suggest getting a transformer with the appropriate step-down ratio. This is far preferable to tweaking resistor values inside with no schematic to guide you.
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Old 13th May 2015, 11:22 AM   #6
devgcl is offline devgcl  Australia
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RESOLVED !!!!!!! Halleluja
I spoke to the designer, Clay, who was so helpful. Turns out this particular DAC has a higher voltage output than what my amps accepts as source input. Had the resistor changed to a lower ohmn and VOILA it all worked out.
I can now play with max volume in Foobar and no issue with volume in my amp.
Synergy of components is so important - learnt the hard way.
Thanks for all help and advice... Much appreciated
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Old 13th May 2015, 01:16 PM   #7
abraxalito is offline abraxalito  United Kingdom
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Great! No-one better than the designer himself to tweak it.
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