[maxwalrath]

Most warpspeed options have 1 input. How are 1-input owners switching sources? Swapping cables each time, or some other method? Forgive me if I'm just missing something..

added: my impression is that most people are running a warpspeed directly into a power amp

[BFitz]

hey bob, don't sell me short - i also am fond of tuna that ain't sparrow feed!   

like the rotel rht-10 i am presently enjoying.  the rotel rht-10, in fact, is one of the better sounding tunas around.  let bob have his way with one, tho, and i dare say it doesn't get any better.    

Doug, yes, tried to keep my comments in context of *this* forum.
Guess I forgot to mention Doug has also owned, and  contributed reviews for, almost every high end FM tuner ever made. As he mentions, I've done complete RF alignment, IF filter mods, and modded the audio stages on a few high end tuners for him over the years.

I have an RF/Acoustics/Vibration/Audio lab with lots of $ investment in instrumentation that is part of my eclectic interest in audio and other stuff. It helps in developing boards and circuits, all for my own consumption, as a hobby. My career, and present job, is selling test and measurement instruments, with over 25 years doing that at B&K, HP,Agilent, and other companies. I don't have time to think about selling my audio hobby investigations, it doesn't pay for me. 

Back to LDR optocouplers. All of them use the Silonex NSL-32SR2 parts, google it for the data sheet. You can buy 50 of them for $100. USD from Allied Electronics. They need to be matched, but this gives you an idea of the actual costs. You can build control electronics for as little as $10.- 20., depending on the design you use.

I looked at the guts of the NSL-32SR2, each of which has a light source (LED), and a light sensitive resistor. The light sensitive resistor is used in the volume control. The LED is connected through various means, eventually, to a volume control.
The important thing to understand, is these two elements face each other in a light sealed tube, and there is no electrical interaction between them.

As the voltage/current applied to the LED increases, the LED gets brighter, and the resistance of the light sensitive resistor decreases. When the LED is fully off, the resistance is really high, say 1 Mohm. When current to the LED is at max. for the part, say 20ma, the resistance is very low, say 50 ohms.

In almost every implementation, you arrange 2 of the device's variable resistor side in series, and take the audio output from the middle of the 2 variable resistors. The audio signal comes in the at the top of the upper variable resistor, and goes out at the bottom of it. Below this, the bottom of the 2nd lower variable resistor is connected to ground.

At min./ zero volume, the top resistor = 1 Mohm, bottom = 50 ohm. At full max volume, the top resistor = 50 ohm, bottom = 1 Mohm.
 
This is how the whole shebang works.

So the control system needs to control the LEDs, 2 each for L, 2 for R, to create the volume control.
 
How you do it is where the creativity comes into play. It can be as simple as driving the LED from a dual gang volume pot fed by +5V, to implementing a voltage controlled current source.

But hopefully this explains, to some extent, previous statements to the effect that the actual parts the audio signal sees, the light sensitive resistors, are common to all designs, and likely responsible for positive listening impressions across different control implementations of designs, all using the same common passive attenuator parts.

Geez, sorry, this was a longish post.     
         
Bob   
 

[doug s.]

hi bob,

i, for one, appreciate your "longish post", and the time you took to explain in detail how these things work.  the transparency they offer is truly fantastic, imo.

i use my eva-2 between my tube preamp, and active x-over, which feeds my bi-amped or tri-amped system, depending on which speakers i am using.  my preamp's gain controls are max'd out, and the eva-2 does the wolume controls...  even tho my preamp - a melos ma333r - uses a form of "photentiometer" wolume control, it is not as transparent as it is now, w/the eva-2 in the chain...

doug s.

[corndog71]

Warpspeed CE,
I tried sending you a PM but your mailbox is full. 

[Warpspeed CE]

maxwalrath, 1-, 2- and 3-IN options are available. 1-IN (V4) owners will just have to unplug at the Source end of their interconnects and plug-in to their other Source -components should be powered down first.

corndog71, just PM'd you...

InfernoSTi, thanks once again!

[ejfud]

It's a real shame the Warpspeed DIY version went away. For a low on skills DIYer like myself it was a simple solution that even I could have handled.

The touring version was here for a week and I still miss it.

[Rclark]

I remember NOT wanting to put it back in the box... and being quite dissatisfied with system until I got one in there.

[BFitz]

I remember NOT wanting to put it back in the box... and being quite dissatisfied with system until I got one in there.

What did you compare it to? Was this your first passive volume control? Did you compare it to another LDR based volume control? Since *you* started the thread, I'm curious if you ever listened to another design based on the same parts, say a Lightspeed design for instance?

[Rclark]

My first ldr for sure. It was compared to the digital volume control from my then xda-1 dac, and indeed blew it the hell away, no comparison. The cleanest sound, like mountain spring water, and due to the pure nature of the device I have absolutely no interest in trying other pre's at this time. I consider it that I am now building my system around the Warpspeed. Surely the dozens of posts here must be reassurance to you.

Once you hit on something that is just so good, you know. It's obvious.

[jk@home]

...Surely the dozens of posts here must be reassurance to you...

RC you killin me I know you have great taste, cause of the speakers your using now, but lets not get too carried away here. Of coarse nobody is going to buy every LDR out there to compare, that's the job of StereoMojo or some outfit like that. And systems, rooms and listeners are so different anyway, one has to take all opinions with a grain of salt.

But since this is C&C, and Allan doesn't offer a kit anymore, I plan on looking at the Lighternote kit. It's not potted, (meaning it's serviceable) it has setup adjustments for different power amp impedance, and the kit is very well documented.

I'd love to see a shoot out with a bunch of the prebuilt units, and imagine if these things get popular enough, we will someday.

[ejfud]

I compared the Warpspeed to a Slagle based TVC, a B1 with shunt power supply and a Grounded Grid tube pre. All are very good to my ears, but the Warpspeed was a step up in my system using my mono F5's and a single ended el84 amplifier. The B1 is a close second.

I'll say it again that it's a shame the kit version went away. I'll have to look and see what else is out there.

[Letitroll98]

In addition to the Lighternote mentioned above and linked to previously, I did see this one.
http://www.ska-audio.com/diy/optivol.html  Albeit from Australia so it might be harder to source for some members here.

[jk@home]

And two more kits:

http://www.tnt-audio.com/accessories/ph_ldr_volume_control_e.html

http://www.tnt-audio.com/accessories/p&s_optopot_e.html

[Rclark]

Jk, other than the issue with the remote, I really just can't imagine anyone not liking it. Has to be the ultimate, if not as a fully functioning preamp in larger, more sophisticated systems, then at least as the volume control you'd want for that pre. I feel pretty confident in saying that.

[jackman]

My first ldr for sure. It was compared to the digital volume control from my then xda-1 dac, and indeed blew it the hell away, no comparison. The cleanest sound, like mountain spring water, and due to the pure nature of the device I have absolutely no interest in trying other pre's at this time. I consider it that I am now building my system around the Warpspeed. Surely the dozens of posts here must be reassurance to you.

Once you hit on something that is just so good, you know. It's obvious.

So you compared this thing to the digital volume control of a low-end DAC and have no interest in seeing how it compares to an actual preamp?  Don't get me wrong, it's cool that you like it, and the price is right, but do you think this closed minded approach is the best way to put together a great sounding system?   

[Rclark]

the XDA-1 isn't a low end dac at all, it's just not top shelf. $400 internet direct is a nice dac.

A pre is just going to have a lot of stuff in there that I personally won't need. I like that this is as simple as it gets for the path, and the fact that I've read hundreds of pages on this stuff, and that the total of that says these types of controls are the best, and that credible people who run them have even replaced megabuck pre's with them and are astounded by them, is enough for me, that and my own ears telling me it really can't get any more clear/seperated than that, pre wise.

 Far more interested in dacs than pre's now.

 Sure, we all make decisions and stick by them, and then someday we might come across a device that is even better, and we revise. My reviews are no different than anyone else's in that regard. Same as yours even.

 I feel like all I need is this ldr and some great amplification, a supreme dac, and I'm set. Purity.

[jackman]

the XDA-1 isn't a low end dac at all, it's just not top shelf. $400 internet direct is a nice dac.

A pre is just going to have a lot of stuff in there that I personally won't need. I like that this is as simple as it gets for the path, and the fact that I've read hundreds of pages on this stuff, and that the total of that says these types of controls are the best, and that credible people who run them have even replaced megabuck pre's with them and are astounded by them, is enough for me, that and my own ears telling me it really can't get any more clear/seperated than that, pre wise.

 Far more interested in dacs than pre's now.

 Sure, we all make decisions and stick by them, and then someday we might come across a device that is even better, and we revise. My reviews are no different than anyone else's in that regard. Same as yours even.

 I feel like all I need is this ldr and some great amplification, a supreme dac, and I'm set. Purity.

I'm not saying this device is not good.  It might be great for all I know but comparing it to the volume control of an entry level DAC and concluding it's the best thing ever invented might seem shortsighted.   I like to try things and see how they sound before concluding I've heard the best.  I've read so many positive reviews of audio gear and speakers from so many enthusiastic owners and reviewers only to be disappointed when I actually hear it.  Your reviews ARE slightly different than mine in this area.  I have never bought a piece of gear based on solely a review and have tried to evaluate as many new components in my system as possible before shelling out cash. 

Would you accept someone's opinion on a car if that person's only point of reference was a Yugo and just upgraded from a horse and wagon?  Just saying...

Cheers,

Jack

[Rclark]

That would be true if I hadn't done research too. I was scared to post my review but everyone else's experience matches mine, people with far more experience than me. So there's nothing wrong with my statements and I stand by them. LDR's are simply better than other means of volume control.

 I think I understand your rancor, you own one of the pre's that someone dropped for this ldr. Not a cheap device either.

I am as honest as I can be. I could lie and say, OH SURE, I've heard dozens of pieces of gear. I am merely relating my experience. The device isn't good, it's flipping awesome. I have seriously no interest in a pre after this. Give me a good reason I should? If you could hear what I hear, you'd understand.

 Far more interested in stepping up my amps, dac, and doing treatments. If I get a chance to try out another conventional pre, sure, I'll give it a go! This is my hobby and I love trying new stuff, but I won't actively search for one anymore.

 I have heard other pre's before, obviously, I don't live on an island, but I can only relate what is in my system. Trust me, if I were even slightly dissatisfied, I'd be on the hunt for a pre, you can believe that.

[jackman]

That would be true if I hadn't done research too. I was scared to post my review but everyone else's experience matches mine, people with far more experience than me. So there's nothing wrong with my statements and I stand by them. LDR's are simply better than other means of volume control.

 I think I understand your rancor, you own one of the pre's that someone dropped for this ldr. Not a cheap device either.

I am as honest as I can be. I could lie and say, OH SURE, I've heard dozens of pieces of gear. I am merely relating my experience. The device isn't good, it's flipping awesome. I have seriously no interest in a pre after this. Give me a good reason I should? If you could hear what I hear, you'd understand.

 Far more interested in stepping up my amps, dac, and doing treatments. If I get a chance to try out another conventional pre, sure, I'll give it a go! This is my hobby and I love trying new stuff, but I won't actively search for one anymore.

 I have heard other pre's before, obviously, I don't live on an island, but I can only relate what is in my system. Trust me, if I were even slightly dissatisfied, I'd be on the hunt for a pre, you can believe that.

I have no rancor.  It just makes me laugh when I read a guy say he is done auditioning preamps because he found one that beat out the digital volume control on his $400 DAC.  I'm happy with my system but always try to hear new gear and other people's systems to gain exposure to new ideas and possible future acquisitions. 

I never said the Opto wasn't a good preamp.  I hope to hear one someday in my system and I'll give my honest opinion.  If I like it, I'll buy it.  Don't know if I'll rant and rave like a little schoolgirl on this thread and mention the Opto in every post, but I'll give an honest and informed opinion as I always do.  At least I'll know my decision was an informed one, not one made based solely on the opinions of other people.  Then again, who knows, maybe ignorance is bliss...

Cheers,

Jack

[Rclark]

My only mistake was not having something better than the xda vol control, which, again, is a fine dac otherwise. But the cool thing is, you dont have to take my word for it  . Ask anyone else here.