Hello, I have two Marantz HD DAC1 headphone amps.
so I thought to mod the one.
the headphone part has distortion and is a shame I was thinking to go to waste since it has a super nice alps motorized pot and nice components.
Is anyone skilled enough to mod the headphone part for me and make the headphone amplifier sound clear without distortion?
the schematics are readily available online
https://www.manualslib.com/manual/2859921/Marantz-Hd-Dac1.html
thanks in advance
so I thought to mod the one.
the headphone part has distortion and is a shame I was thinking to go to waste since it has a super nice alps motorized pot and nice components.
Is anyone skilled enough to mod the headphone part for me and make the headphone amplifier sound clear without distortion?
the schematics are readily available online
https://www.manualslib.com/manual/2859921/Marantz-Hd-Dac1.html
thanks in advance
Your distortion, if very evident, comes from somewhere else I would think... what is your headphones?
I think many people are scared to enter such sites as manualslib and will not follow that link.
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I think many people are scared to enter such sites as manualslib and will not follow that link.
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that’s not for the headphone amplifier. It’s for the analog outputs of the DAC.
I already contacted Marantz and they won’t tell me the Headphone amp specs. Go figure.
Sure! Pop it open, take some pics, and we can get started!
Here is the service manual until I get some pics up
@Andersonix
https://www.manualslib.com/manual/2859921/Marantz-Hd-Dac1.html?page=54#manual
@Andersonix
https://www.manualslib.com/manual/2859921/Marantz-Hd-Dac1.html?page=54#manual
It sounds simple enough and all it might take is perhaps increasing the bias or removing some the muting and gain setting transistors but it is an all discrete design with no op-amps to roll and it might take more. Have you considered building a dedicated headphone amp of a different type.? That would give many more options including one that may be possible to retrofit to the Marantz.
yeah I was thinking about the bias.
I might take a look at that later on today
the service manual says it should be biased at 25mA .
but I thought the distortion would increase if I increase bias?
just a shame as a peek inside reveals really top notch components were used throughout.
@Andersonix
the idle current was around 90mV on each transistor.
I put my multimeter on 2000m and it read 090 so I biased to 053
is that correct? Just doing a sanity check
the idle current was around 90mV on each transistor.
I put my multimeter on 2000m and it read 090 so I biased to 053
is that correct? Just doing a sanity check
Here’s some pics of the headphone board.
I need to take some better ones today
odd thing, well odd to me, is that they use electrolytics on the output .
I need to take some better ones today
odd thing, well odd to me, is that they use electrolytics on the output .
@Andersonix , yeah it would get pretty hot sometimes .
i have no idea why it was set like that. But it sounds better now. I have to recheck the bias to make sure it didn’t drift.
I wish I had a scope to check it out though
i have no idea why it was set like that. But it sounds better now. I have to recheck the bias to make sure it didn’t drift.
I wish I had a scope to check it out though
someone mentioned he changed two voltage regulators to Dexa ones and the whole unit sounded better.
this is what he said.
I had swapped the IC98/IC99 Vregs for Dexa ones and bypassed the C609/C610 and C709/C710 caps.
These?
https://www.audiophonics.fr/en/volt...7805-50v-uwb-voltage-regulator-5v-p-6403.html
Seem promising! Does anyone know what IC they're based on?
Attachments
The only caps I see for the headphone power section are two 2200uf 25v ones C626 and C625
can you see them on the manual ?
if you trace the blue and red power lines you can find them easily.
im thinking maybe 4200uf or something similar will fit.
https://www.manualslib.com/manual/2859921/Marantz-Hd-Dac1.html?page=60#manual
can you see them on the manual ?
if you trace the blue and red power lines you can find them easily.
im thinking maybe 4200uf or something similar will fit.
https://www.manualslib.com/manual/2859921/Marantz-Hd-Dac1.html?page=60#manual
Can you see them in my screenshot in post #9?
Yes, make them as large as possible, and also consider adding more in parallel in any nearby empty space...