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Old 8th February 2010, 08:12 PM   #3031
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Quote:
Originally Posted by markusG View Post
georgehifi> I'm not trying to be difficult but could you please comment on the distortion figures? Looking at the diagrams at the silonex website the series/shunt cirquit show upward 4% distortion. The shunt cirquit has a THD+N(%) too low to measure with their measuring set-up.
To my eyes this would indicate that the series/shuncircuit has way more noise/distortion than the shunt circuit?
Am I reading it wrong or what? Are their measurements faulty?
They used to have many graphs, dig hard, or maybe they have removed them. As I said look series/shunt for the graph that gives the disortion at the null point, also the other distortion graphs remember the average that comes out of a cdp is 1v the max is 2v (Cannon Shot 1812 Telarc).
Cheers George
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Old 8th February 2010, 08:30 PM   #3032
markusA is offline markusA  Sweden
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It's the voltage scale on the x-axis that's messing it all up for me. :P
I guess the graphs doesn't say very much then.
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Old 12th February 2010, 08:33 PM   #3033
jkeny is offline jkeny  Ireland
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I have found a Vout DAC with 2Vrms output that works wonderfully well directly driving headphones. No output caps, no headphone amp needed. I've tried it on Senn HD650, AKG701 (slightly lower volume but loud enough for my listening), Grado HF2 cheap Sonys - from 32ohm upto 300ohm impedance. I wanted to use a LDR volume control on the output - I reckon only a series LDr will work. Any special considerations I need to consider? Is it possible to get a reasonable channel match across the full volume range needed or am I better off going with a stepped attenuator to avoid this issue?
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Old 12th February 2010, 09:23 PM   #3034
bkdog is offline bkdog  Australia
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You would probably want a volume control on the _input_ of the headphone amp, whatever it is. And you'd want a series-shunt LDR arrangement, stepped attenuators are a separate thread...
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Old 12th February 2010, 09:33 PM   #3035
jkeny is offline jkeny  Ireland
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Originally Posted by bkdog View Post
You would probably want a volume control on the _input_ of the headphone amp, whatever it is. And you'd want a series-shunt LDR arrangement, stepped attenuators are a separate thread...
No, as I said it doesn't need a headphone amp - the DAC drives headphones directly so the impedances in & out of the LDR are different to what is the norm here!
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Old 12th February 2010, 09:42 PM   #3036
bkdog is offline bkdog  Australia
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oops, missed that you are coming straight out of a DAC, sorry... I reckon you will need a buffer after the LDR attenuator.
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Old 12th February 2010, 09:52 PM   #3037
NicMac is offline NicMac  Italy
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Quote:
Originally Posted by jkeny View Post
I have found a Vout DAC with 2Vrms output that works wonderfully well directly driving headphones. No output caps, no headphone amp needed. I've tried it on Senn HD650, AKG701 (slightly lower volume but loud enough for my listening), Grado HF2 cheap Sonys - from 32ohm upto 300ohm impedance. I wanted to use a LDR volume control on the output - I reckon only a series LDr will work.
A bit OT but do you mind telling us which Vout DAC?
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Old 12th February 2010, 09:58 PM   #3038
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HD650's are a 300ohm load, most low impedance dacs say 50ohms or less will drive these if the 2v or more ouput voltage is loud enough for you, 50ohms into 300ohms is a 1 to 6 ratio which is OK, the moment you stick a passive volume controling device beteen them this 1 to 6 ratio will go the other way like ?kohms to 300. You will need a buffer after the passive to bring it back down to the 1 to 6 ratio or better like 1 to 10.
Cheers George
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Old 12th February 2010, 10:11 PM   #3039
jkeny is offline jkeny  Ireland
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One of the ESS DACs ES9022 - also used in Nuforce uDac which drives headphones directly & uses a vol control (no op-amps used) see here: FIRST IMPRESSIONS: Nuforce uDAC USB DAC AMP with line out and S/PDIF out - Head-Fi: Covering Headphones, Earphones and Portable Audio

This ESS DAC can do 24/192 but in the NuForce, it's limited by the use of PCM2707 USB receiver both in speed & in high jitter. I have a 24/192 USB low jitter transport that I wanted to use with the DAC

Last edited by jkeny; 12th February 2010 at 10:31 PM.
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Old 12th February 2010, 10:20 PM   #3040
jkeny is offline jkeny  Ireland
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Originally Posted by georgehifi View Post
HD650's are a 300ohm load, most low impedance dacs say 50ohms or less will drive these if the 2v or more ouput voltage is loud enough for you, 50ohms into 300ohms is a 1 to 6 ratio which is OK, the moment you stick a passive volume controling device beteen them this 1 to 6 ratio will go the other way like ?kohms to 300. You will need a buffer after the passive to bring it back down to the 1 to 6 ratio or better like 1 to 10.
Cheers George
AKG701s are 32 ohm & the DAC drives these to a loudness which is enough for my tastes i.e. below ear bleeding. I have seen it quoted that the DAC is happy driving headphones down to 16ohm.

I have driven my Sony MDR-XD200 (70ohm) with a pot volume control on the DAC's output, so the concept is proven - I just wanted a higher quality vol control with the LDR but is it out of the question to expect close LDR matching all along the vol range for a good channel to channel balance?

Last edited by jkeny; 12th February 2010 at 10:27 PM.
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