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Review and Measurements of New JDS Labs Atom Headphone Amp

magicscreen

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This should be very easy to record using a sound card.
Can you make a recording with the 2 different cables ?
I can through the pre-output of the Atom. But I have only a simple motherboard sound card in my PC, has it got good enough sound quality for the recording? It will be an interesting experiment.
 

thomasjast

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I can through the pre-output of the Atom. But I have only a simple motherboard sound card in my PC, has it got good enough sound quality for the recording? It will be an interesting experiment.

Generally it is. I've used this loopback method of testing to compare changes I've made. Really takes the guesswork out of it.
 

solderdude

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Atom can provide about 8.2V in 50 Ohm = 1.3W = about 120dB peak SPL so can make it play quite loud.
 

solderdude

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In this case it is.
When you want a 'modified sound' you need to look elsewhere.
 

jak

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Just got my new 2xRCA → 2x1/4" cable (Cordial CFU 1.5 PC, with those nice REAN connectors) and connected my JBL LSR305 to the pre-outs. Sweet.
 

jak

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What I don't understand about the JDS devices and their pre-outs is why the gain affects the pre-out? Shouldn't a pre-out usually be before that? (not that it matters a lot in practice :D)
 

solderdude

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The pre-out = headphone out, just from an RCA socket on the back.
 
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jak

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The pre-out = headphone out, just from an RCA socket on the back.

I was wondering what the "pre" refers to. My understanding was that pre was referring to pre amp, that is, before the amp, so it was odd to read that the Atom runs the pre-outs through the amp stage.
 

solderdude

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Normally in integrated amplifiers pre-out is before the volume control and directly behind the input selector and , if present, the RIAA pre-amp.
Sometimes buffered, often not.

In this case it means it is meant as the output where it is functioning as a pre-amp (pre-out) so you can use that output to drive active speakers directly and use the volume control as well as amplification for it.

So pre-out in this case has a different meaning as pre-out in integrated amps.
It is the same signal as the headphone out but different socket (RCA instead of TRS).
The RCA output might switch off when a headphone is inserted, or it might not ... depends on whether the RCA output is wired through the 6.3mm TRS socket (it has a switch function in it).
 

hyperknot

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The RCA output might switch off when a headphone is inserted, or it might not ... depends on whether the RCA output is wired through the 6.3mm TRS socket (it has a switch function in it).

It is actually a mechanical switch, so it physically switches between either RCA or headphone out.
 

JohnYang1997

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What opamp's you tested ?
opa1612
lme49720
opa1656
opa2156
opa1642
opa2140
njm4585
njm8068
and more I can't remember.
Limitation is the ground layout and the lme49600 itself. High frequency distortion just doesn't go as low as I like. 1khz and below stays at 1ppm mark.
Please refer to lme49600tsbd datasheet for basically the ceiling performance of single lme49600 and refer to neurochrome hp-1 for ceiling performance of dual lme49600 per channel.
 
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