re: Passive Volume Control
Since volume controls can range from $0.50 to > $1,000, I'm not sure what you definition of inexpensive is, but here's my advice:
After much research on these and other audiophile forums combined with personal experience, I believe that LDR attentuators are the most transparent. The original is the Lightspeed Attenuator, which is extensively disscussed in this DIYaudio forum: http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp.html. Other versions of the Lightspeed, are Uriah Dailey's Lighter Note (Build An Amp), the Warpspeed (mentioned in another post above), and the DIYparadise EVA (Eva 2). These are all improved versions of the Lightspeed circuit, although George, the inventor of the original, would dispute that.
The DIYparadise EVA is an LDR attenuator with remote control of volume, mute and switching of three inputs. It is well built and good value at around $400. It is excellent with digital sources, but not a good match with my phono (and perhaps others). Since I have an extensive analog collection, I sold it on eBay and the Buyer, who is 100% digital, is delighted. I believe that my problems with the EVA were the common issues with passive attenuators. If the EVA works in your system (likely with digital), then it is an great bargain.
I next decided to build a buffered preamp. I purhased Uriah's Lighter Note for attenuation. It is available in kit form for $130, which is a phenominal bargain, and also assembled for $270. I am now assembling parts for the Salas shunt regulated DCB1, hot rod edition, which is a modified version of Nelson Pass' B1 buffer. This can be built for $200-300 depending on parts selection, and resolves the problems with purely passive solutions. See the DIYaudio threads at http://www.diyaudio.com/forums/analog-line-level/171715-salas-hotrodded-blue-dcb1-build.html and http://www.diyaudio.com/forums/pass-labs/145201-building-symmetrical-psu-b1-buffer.html. Be forewarned: these projects are so popular that the threads go on forever. You might want to read Nelson's white paper on the B1, which is available on the Pass Labs website. I will include a switch for passive/buffered mode. The B1 uses a single JFET per channel match impedences without adding any gain.
A level down from LDRs are transformer or autoformer attenuators. They are expensive and difficult to find as parts. Stevens and Billington used to offer the TX-102 as a DIY part, but it is now only availalbe in their expensive passive unit. Bent Audio (BentAudio.com :: TAP) now offer the Slagelformer (or something like that). John Chapman is a pleasure to deal with. I once owned the TX-102s, but sold them to pursue the LDRs. The transformer solutions are reported to have fewer system matching problems that other passive solutions.
A step below the transfomers are the ladder arrays, resistor networks, or stepped attenuators. These are widely available and frequently inexpensive. They can be a simple rotary switch or a PCB with relays and remote control. Quality varies depending on resitors, circuit design, PCB quality, switch quality, or relay quality. There are lots of them on eBay. I think DACT makes an economical rotary switch attenuator and Bent offers one too. Dantikit (Dantimax - Remote control audio kits), Bent, and AMB Laboratories DIY Audio Site (very elegant DIY) have remote controlled passives.
Of course you could always use a simple pot from ALPS, DACT or Bournes.
A final word on passives: In theory, a passive volume control has the potential to be the ultimate in transparency, but real world results can be dissapointing. Imepedence matching, cable capacitance, and voltage are critical. Cable must be short (<1M) and capacitance low. Amp imedance must be high -- 47K-100Kohms. Voltage is usually sufficient on digital sources but can vary on analog sources. In many systems highs are rolled off, volume is low, noise is high, bass is flat, and dynamics are constrained. If it works in your system great, but if not you need at least a buffer and many say active is the only way to go.
Since volume controls can range from $0.50 to > $1,000, I'm not sure what you definition of inexpensive is, but here's my advice:
After much research on these and other audiophile forums combined with personal experience, I believe that LDR attentuators are the most transparent. The original is the Lightspeed Attenuator, which is extensively disscussed in this DIYaudio forum: http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp.html. Other versions of the Lightspeed, are Uriah Dailey's Lighter Note (Build An Amp), the Warpspeed (mentioned in another post above), and the DIYparadise EVA (Eva 2). These are all improved versions of the Lightspeed circuit, although George, the inventor of the original, would dispute that.
The DIYparadise EVA is an LDR attenuator with remote control of volume, mute and switching of three inputs. It is well built and good value at around $400. It is excellent with digital sources, but not a good match with my phono (and perhaps others). Since I have an extensive analog collection, I sold it on eBay and the Buyer, who is 100% digital, is delighted. I believe that my problems with the EVA were the common issues with passive attenuators. If the EVA works in your system (likely with digital), then it is an great bargain.
I next decided to build a buffered preamp. I purhased Uriah's Lighter Note for attenuation. It is available in kit form for $130, which is a phenominal bargain, and also assembled for $270. I am now assembling parts for the Salas shunt regulated DCB1, hot rod edition, which is a modified version of Nelson Pass' B1 buffer. This can be built for $200-300 depending on parts selection, and resolves the problems with purely passive solutions. See the DIYaudio threads at http://www.diyaudio.com/forums/analog-line-level/171715-salas-hotrodded-blue-dcb1-build.html and http://www.diyaudio.com/forums/pass-labs/145201-building-symmetrical-psu-b1-buffer.html. Be forewarned: these projects are so popular that the threads go on forever. You might want to read Nelson's white paper on the B1, which is available on the Pass Labs website. I will include a switch for passive/buffered mode. The B1 uses a single JFET per channel match impedences without adding any gain.
A level down from LDRs are transformer or autoformer attenuators. They are expensive and difficult to find as parts. Stevens and Billington used to offer the TX-102 as a DIY part, but it is now only availalbe in their expensive passive unit. Bent Audio (BentAudio.com :: TAP) now offer the Slagelformer (or something like that). John Chapman is a pleasure to deal with. I once owned the TX-102s, but sold them to pursue the LDRs. The transformer solutions are reported to have fewer system matching problems that other passive solutions.
A step below the transfomers are the ladder arrays, resistor networks, or stepped attenuators. These are widely available and frequently inexpensive. They can be a simple rotary switch or a PCB with relays and remote control. Quality varies depending on resitors, circuit design, PCB quality, switch quality, or relay quality. There are lots of them on eBay. I think DACT makes an economical rotary switch attenuator and Bent offers one too. Dantikit (Dantimax - Remote control audio kits), Bent, and AMB Laboratories DIY Audio Site (very elegant DIY) have remote controlled passives.
Of course you could always use a simple pot from ALPS, DACT or Bournes.
A final word on passives: In theory, a passive volume control has the potential to be the ultimate in transparency, but real world results can be dissapointing. Imepedence matching, cable capacitance, and voltage are critical. Cable must be short (<1M) and capacitance low. Amp imedance must be high -- 47K-100Kohms. Voltage is usually sufficient on digital sources but can vary on analog sources. In many systems highs are rolled off, volume is low, noise is high, bass is flat, and dynamics are constrained. If it works in your system great, but if not you need at least a buffer and many say active is the only way to go.
Heh, I worried lots about preamp attenuators before but now I just use digital attenuation in my OS. Not only is it cheaper, it's better too =)
You'd have to use massive attenuation for the resolution loss to result in hearable noise. Even -48 db, -8 bits isn't enough to do that. And if you feel you have to attenuate too much and want more headroom just reduce the gain on the NCore and if that isn't enough maybe add an L-pad before the amp too and you're done
You'd have to use massive attenuation for the resolution loss to result in hearable noise. Even -48 db, -8 bits isn't enough to do that. And if you feel you have to attenuate too much and want more headroom just reduce the gain on the NCore and if that isn't enough maybe add an L-pad before the amp too and you're done
Nothing is wrong with my preamp's volume control you are right. My DAC's (V-DAC) output impedance is 47Ω, my preamp's is 600Ω.
That's quite the essay on passive volume control. You just saved me at least a week's worth of researching the internet.
Thank you guys both, for helping me decide, I will give my preamp a go until I read all this material on passive volume control and decide what to build (it turns out that passive volume control is more complicated than I thought it would be).
mike_mcf I'm sure your compilation of sources will help a lot of noobs like me as a starting point. Good job!!!
Cheers!
You are welcome. It seems kind of obvious that anything in the signal path can only degrade the sound, so less is better. Some of the reviews on passives were very positive, but not all listeners were satisfied. So as a minimalist, I did A LOT of research on passives.
George, the inventor of the Lightspeed, refuses to add input switching to his pruduct as it degrades the sound: change the interconnects to change sources. That's a little too minimalist for me. At a bare minimum, I want remote volume and mute, and I want switching, even if it is manual.
I was introduced to the Lightspeed in the DIYaudio newsletter, because the thread was really hot. I have come to believe that us mere mortals can have very close to the best available if we build it ourselves and the best place for DIY is right here.
I am very thankful to all those on this site who have helped me, so if I see an opportunity to pay back I am grateful for the opportunity. I hope that my research helps others get there quicker.
Passive Attenuator for Hypex nCore
Appologies for highjacking this thread, but I just had to add this link, which is the best discussion I have seen regarding attentuators:
http://wajonaudio.webs.com/GET%20THE%20PERFORMANCE%20of%20a%20$20k%20PRE-AMP%20for%20$200.html
I have no commercial interest in any of these products.
Appologies for highjacking this thread, but I just had to add this link, which is the best discussion I have seen regarding attentuators:
http://wajonaudio.webs.com/GET%20THE%20PERFORMANCE%20of%20a%20$20k%20PRE-AMP%20for%20$200.html
I have no commercial interest in any of these products.
PS2: forgot to mention, 20m of Gotham GAC-3 mic wire should be on its way, I read the Neil Muncy Paper
Are you using that as an interconnect?
I may grab some of that wire, it is only $0.75/foot which is really cheap compared to some other stuff I have in my "basket" at pcx which rings up at almost $10/foot.
yes, I'm going to use it as an IC.
I'm all for cheap upgrades. the wire is cheap and is proven to be superior to others. why should I spend instead hundreds on another product only because some stranger on a forum swears by it but can't back his claims with objective data?
"drawer" answer #173
I do know that the Warpspeed is different from other ldr applications, and I've seen more than a dozen or so owners remarks on the product, some claiming outright superiority to very expensive preamps.
In my system, it provides the cleanest, most pure sound possible, was far superior to the digital controls in dac and the pot in my integrated.
You would make a mistake in overlooking ldr's.
I'll let you know how mine works with the Ncore I imagine it will be truly stunning.
In my system, it provides the cleanest, most pure sound possible, was far superior to the digital controls in dac and the pot in my integrated.
You would make a mistake in overlooking ldr's.
I'll let you know how mine works with the Ncore
I imagine it will be truly stunning.
Nope, but then I haven't listened to NCore either and here I am, on the waiting list.
I do know there have been very positive subjective reports regarding LDRs, but if I purchased/built stuff based solely on subjective data, I wouldn't be looking at low distortion amps like NCore in the first place.
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I listen to LDR's all the time, in a compressor that I value for the color it puts on the audio. It is NOT neutral. Colorful, interesting, pleasant... yes. Clean ...NOT.
what goes in is not what comes out.
I can't believe people are trying to use them for level control under the adage they are clean. Go ahead and use them, enjoy them, but they are not clean.
Alan
that's not particularly relevent
Ldrs may not be clean, and all the information so far is that they aren't, but a compressor, by definition, is designed to distort and would be failing if it didn't. The Ldr is deliberately used for the ease with which it can be used as a non linear control device, not because it is innately non linear at a fixed setting, which is the equivalent when an Ldr is used to set the volume in an audio system.
By the same argument I could design a compressor based around a high quality digital volume control chip or a relay-switched resistor ladder and then claim that they must be innately coloured.
A pot as the feedback network around in inverting op amp circuit is the cleanest analogue volume control you can make. One I made with a 9mm car audio pot sounds completely transparent and with a decent op amp distortion is unmeasurable at all useful gain settings. For high input impedance, add an input buffer. For balanced input, make that an instrumentation amp. Actually the input circuit is more difficult to get right (as in "inaudible and unmeasurable") than the volume control section.
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