Which dac do you have that can drive a 32ohms load with no detrimental distortions or attenuations? it must have an output impedance down into the single figure or less ohms.
Cheers George
Hi George, I've posted it already (also posted a link to a thread that reviews the NuForce uDac - which uses this ESS DAC) - I know, I couldn't believe it either
Nowhere could I find the output impedance of this unit, the best I found was this in Stereophile which goes with what I belive to be the case, ok into the high impedance Sennhiser's. Me thinks Nuforce maybe fudging figures a little.
Quote> The headphone jack offered a maximum gain of 15.1dB and an output impedance of 48 ohms across the audioband, which will make the Icon more suitable for use with high-impedance headphones like the Sennheisers rather than the low-impedance Grados and the Phiaton MS400<Quote
Cheers George
Quote> The headphone jack offered a maximum gain of 15.1dB and an output impedance of 48 ohms across the audioband, which will make the Icon more suitable for use with high-impedance headphones like the Sennheisers rather than the low-impedance Grados and the Phiaton MS400<Quote
Cheers George
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Don't worry about what NuForce say, I have tried this DAC driving Senn HD650 (300ohm), AKG701(32ohm), Sony MDR-XD200(70), Grado HF2(?ohm) & in all cases it drove them wonderfully. A friend & I compared it to his Aikido headphone amp & apart from higher volume in the case of the AKGs, he reckoned it was the match of the Aikido. I compared it against his Millet Hybrid h/p amp & the DAC probably sounded slightly cleaner driing the h/ps!
Do you have a link to the Stereophile article? Edit: I found it but you have it wrong - that's the Nuforce Icon amp they're talking about, not the NuFirce uDAC
Anyway, am I asking too much in expecting the matching of LDRs to track equally the full volume range? What about at the attenuation extremes - is this a problem?
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No not if they are matched properly, mine (series/shunt) in the production Lightspeed Attenuator are usually better than the tracking of a 20k log Blue Alps (Blue Velvet). I still say you'll need a buffer after it to get the best.
Attenuation extremes, max will be the dacs output you already say it's fine , and minimum will also be fine if sereis/shunt (MkII) is used, as series resitor and shunt ldr (mkI) will be not so attenuated and could be too loud.
Cheers George
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George, look at my edit above - Edit: I found it but you have it wrong - that's the Nuforce Icon amp they're talking about, not the NuForce uDAC
Ok, I won't try & convince you that I'm telling the truth! Have a read of that long thread I linked for others opinions
Ah, no I knew the lightspeed would not do it - I was just looking into a series LDR as the vol. solution & wondered was there any implications!
So you wish to use the resistance of the headphone as the shunt component and the LDR as the series component for the volume control, good luck never tried it, for starters the headphones (Sennhiser) will not be at 300ohms continually, they will be all over the place according what frequency is being feed in, much like a speakers impedance, which means the volume will also be all over the place.
Cheers George
Cheers George
Last weekend had my hi-fi group that I'm a member of a meeting where we tested different phono pre-amps what we did first was to try different pre-amps to get a good and fair representation of the sound one of them was my clone on georgehifi's lightspeed Attenuator. There were more expensive preamps such as Burmester now I understand how good this LDR volume control really is. The whole story ends with at least 5 of the members will build their own clones and replace their pre-amps.
I can only thank George for allowed us to take benefit from his Lightspeed Attenuator and build our own versions.
Anders
I can only thank George for allowed us to take benefit from his Lightspeed Attenuator and build our own versions.
Anders
Lightspeed remote control
Hello MarkusG,
I'm still out here, still monitoring this thread and I still have boards for VCCS and the remote control modules. These are available from stock but if you want built and tested modules these take 2-4 weeks from placing the order depending on my workload. Feel free to ask questions about anything you do not understand.
Regards
Paul
Hello MarkusG,
I'm still out here, still monitoring this thread and I still have boards for VCCS and the remote control modules. These are available from stock but if you want built and tested modules these take 2-4 weeks from placing the order depending on my workload. Feel free to ask questions about anything you do not understand.
Regards
Paul
Cool.
Now for some Q&A...
I haven't read the entire thread yet, it being 306 pages and all.
The VCCS is supposedly controlled with pushbuttons, right?
Would it be an easy swich to swap the pushbuttons for a rotary puls switch?
And, I think I read somewhere that one needed 15VDC to drive it? Are there regulators included in the VCCS design so one can cheap out and just go for a plain old wall wart? It'll get cleaned up anyway? Or will I have to build a high quality PSU to drive it?
Now for some Q&A...
I haven't read the entire thread yet, it being 306 pages and all.
The VCCS is supposedly controlled with pushbuttons, right?
Would it be an easy swich to swap the pushbuttons for a rotary puls switch?
And, I think I read somewhere that one needed 15VDC to drive it? Are there regulators included in the VCCS design so one can cheap out and just go for a plain old wall wart? It'll get cleaned up anyway? Or will I have to build a high quality PSU to drive it?
Lightspeed remote control
MarkusG,
The VCCS interface uses the DS1802 which is designed to interface with push buttons. Any alternative method of actuation should mimic the push button operation as described in the DS1802 datasheet.
You can use a 15 volt LINEAR wall wart as there is a 12 volt regulator on board which adds another layer of line noise reduction.
Regards
Paul
MarkusG,
The VCCS interface uses the DS1802 which is designed to interface with push buttons. Any alternative method of actuation should mimic the push button operation as described in the DS1802 datasheet.
You can use a 15 volt LINEAR wall wart as there is a 12 volt regulator on board which adds another layer of line noise reduction.
Regards
Paul
I think its the AD5227 or AD5220 datasheet that shows how to use it with a mechanical rotary encoder and a debouncer which probably isnt needed as signal isnt going through the DS1802. So no zipper noise. Anyway, I think you could use the same idea to activate the U/D pins of the DS1802.
Uriah
Uriah
Looking at the ds1802 sheet it should be the easiest thing in the world.
https://www1.elfa.se/data1/wwwroot/webroot/Z_DATA/03549268.pdf
Shows an example of a rotary puls switch.
"on" during changeover only (it connects either pin 1&2 or 3&4 depending on which way you're turning it).
https://www1.elfa.se/data1/wwwroot/webroot/Z_DATA/03549268.pdf
Shows an example of a rotary puls switch.
"on" during changeover only (it connects either pin 1&2 or 3&4 depending on which way you're turning it).
LDR pre- series resister in shunt LDR
Geaorge,
I built your Mk II vesrion and sounded terrific. thank you veru much.
After some time one channel volume wetnt dow. When I checked, one shunt LDR's red light was visible and the resistance when volume all the way down was jumping like anything.
The other channel showed 48- 50 Oms. I put some epoxy glue and did not work. So I repalced shunt LDRs ( matched set i had before) of both the channels instead of changing shunt and series. Measured again at zero volume. I got only 25 Oms on both channels instead of recomended 50 Oms.
So I changed series resister 100R in the shunt LDR to 440 Ohms ( 220+100+100) on both channels keeping the 100R in the series LDRs and got 45-49.
Finally when started listening to music volume was little down compared to the earlier one and Bass was week and finally not impressed.
technically any reason for this change. I am not that good in electronics.
thanks
Geaorge,
I built your Mk II vesrion and sounded terrific. thank you veru much.
After some time one channel volume wetnt dow. When I checked, one shunt LDR's red light was visible and the resistance when volume all the way down was jumping like anything.
The other channel showed 48- 50 Oms. I put some epoxy glue and did not work. So I repalced shunt LDRs ( matched set i had before) of both the channels instead of changing shunt and series. Measured again at zero volume. I got only 25 Oms on both channels instead of recomended 50 Oms.
So I changed series resister 100R in the shunt LDR to 440 Ohms ( 220+100+100) on both channels keeping the 100R in the series LDRs and got 45-49.
Finally when started listening to music volume was little down compared to the earlier one and Bass was week and finally not impressed.
technically any reason for this change. I am not that good in electronics.
thanks
Sounds to me like the ldr's may have got over heated during the soldering/building process, this is one of the reasons why I don't do diy kits.
Also look your volume pot if you use a single 100k log .5watt pot arrangement they can go bad as pots don't really like dc on them that's why it's best to use a 24mm dual 100k log as it shares the load better 1 watt total.
Cheers George
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