Lightspeed Attenuator

Tech Guy · Nov 22, 2015

Anyone tried the Lightspeed Attenuator? I have. I picked one up last week and have been listening to it. Brilliant! So neutral and accurate. If you need something simple, inexpensive and dead easy to use, this puppy is for you.

More seriously, I doubt there is a preamp available at any price, which can equal this sucker. It's THAT good.

Now, the downsides:

* It doesn't look like it cost $10,000.00.
* It has no gain. (No biggie)
* RCA cables need to be low capacitance and load impedance should be 33,000 Ohms or higher.

Honestly, the damned thing is so cheap, just buy one and try to prove me wrong.

[DISCLAIMER] I have no financial interest in Lightspeed, but I do know the designer. (he is a grumpy bugger and ex-surfer)

www.lightspeedattenuator.com

TG

Ric Schultz · Nov 30, 2015

The Tortuga Audio stuff is the same except you get remote control. You can also make your own attenuator using their boards and it is costs about the same as the Lightspeed but you have remote control and the ability to do balance, mute, and change the impedance of the attenuator system. I just put one of the DIY boards in a Grounded Grid Preamp for someone....He Loves it! Steven Stone did a review in the latest Absolute Sound and found it had no sound (straight wire bypass test). Link to review: http://www.tortugaaudio.com/documents/docs/TAS_Review_LDR3.V2_December2015.pdf
Link to Tortuga Audio forum: http://www.audiocircle.com/index.php?PHPSESSID=icm8ojuu9fpe4n6k814jpbektdcpnkv5&board=85.0

amirm · Nov 30, 2015

Well how much is it?

Tech Guy · Nov 30, 2015

Ric Schultz said:
The Tortuga Audio stuff is the same except you get remote control. You can also make your own attenuator using their boards and it is costs about the same as the Lightspeed but you have remote control and the ability to do balance, mute, and change the impedance of the attenuator system. I just put one of the DIY boards in a Grounded Grid Preamp for someone....He Loves it! Steven Stone did a review in the latest Absolute Sound and found it had no sound (straight wire bypass test). Link to review: http://www.tortugaaudio.com/documents/docs/TAS_Review_LDR3.V2_December2015.pdf
Link to Tortuga Audio forum: http://www.audiocircle.com/index.php?PHPSESSID=icm8ojuu9fpe4n6k814jpbektdcpnkv5&board=85.0

Sounds very interesting. I may try one. Does the Tortuga Audio one use critically matched LDRs like the Lightspeed? The whole idea behind the Lightspeed is the KISS (Keep It Simple Stupid) principle. Hence, no muting, balance, or remote. Stereophile seem to think it is a very impressive product (for what it's worth).

BTW: The full schematic of the Lightspeed is easy enough to locate:

http://diyaudioprojects.com/Solid/DIY-Lightspeed-Passive-Attenuator/

Trouble is, matching the LDRs is quite difficult. For the low price of the Lightspeed, I just bought one ready to go. Since I am not disabled, I can easily get out of my chair and adjust the volume, should I wish to do so. Building a remote option would be a doddle, but I really can't be bothered.

Andre Marc · Nov 30, 2015

Ric Schultz said:
The Tortuga Audio stuff is the same except you get remote control. You can also make your own attenuator using their boards and it is costs about the same as the Lightspeed but you have remote control and the ability to do balance, mute, and change the impedance of the attenuator system. I just put one of the DIY boards in a Grounded Grid Preamp for someone....He Loves it! Steven Stone did a review in the latest Absolute Sound and found it had no sound (straight wire bypass test). Link to review: http://www.tortugaaudio.com/documents/docs/TAS_Review_LDR3.V2_December2015.pdf
Link to Tortuga Audio forum: http://www.audiocircle.com/index.php?PHPSESSID=icm8ojuu9fpe4n6k814jpbektdcpnkv5&board=85.0

That is not all. Morten completely redesigned the product with better chassis, and even more importantly, with self correcting software that keeps the values LDR values from drifting.

The Tortuga stuff is groundbreaking. Best passive I have heard outside of uber expensive, bespoke TVC solutions.

Andre Marc · Nov 30, 2015

Tech Guy said:
Sounds very interesting. I may try one. Does the Tortuga Audio one use critically matched LDRs like the Lightspeed? The whole idea behind the Lightspeed is the KISS (Keep It Simple Stupid) principle. Hence, no muting, balance, or remote. Stereophile seem to think it is a very impressive product (for what it's worth).

BTW: The full schematic of the Lightspeed is easy enough to locate:

http://diyaudioprojects.com/Solid/DIY-Lightspeed-Passive-Attenuator/

Trouble is, matching the LDRs is quite difficult. For the low price of the Lightspeed, I just bought one ready to go. Since I am not disabled, I can easily get out of my chair and adjust the volume, should I wish to do so. Building a remote option would be a doddle, but I really can't be bothered.

Tortuga is a completely different level. I have heard both and the Tortuga is a much better product...sound and feature wise. It is not even that close. But don't get me wrong. The Lightspeed as you said is quite good, and simpler, which may be a good thing. Sam Tellig at Stereophile, who does not suffer fools, owns one and has recommended it for a long time.

"Auto Calibration: Similar to tubes, LDRs are analog devices subject to aging and drifting over time. Unlike tubes, the LDRx employ self-contained auto-calibration to keep the unit in precise calibration. This provides added assurance that the LDRx will hold its value over the long haul."

Tech Guy · Nov 30, 2015

Andre Marc said:
Tortuga is a completely different level. I have heard both and the Tortuga is a much better product...sound and feature wise. It is not even that close. But don't get me wrong. The Lightspeed as you said is quite good, and simpler, which may be a good thing. Sam Tellig at Stereophile, who does not suffer fools, owns one and has recommended it for a long time.

"Auto Calibration: Similar to tubes, LDRs are analog devices subject to aging and drifting over time. Unlike tubes, the LDRx employ self-contained auto-calibration to keep the unit in precise calibration. This provides added assurance that the LDRx will hold its value over the long haul."

Thanks for the explanation. I got some more reading to do and, maybe, another drain on the bank account.

EDIT: EIGHTEEN HUNDRED BUCKS! Yikes! I hope it is a whole lot better than the Lightspeed. It is a whole bunch more expensive.

Nonetheless, it is a very impressive beast.

TG

Andre Marc · Nov 30, 2015

Tech Guy said:
Thanks for the explanation. I got some more reading to do and, maybe, another drain on the bank account.

EDIT: EIGHTEEN HUNDRED BUCKS! Yikes! I hope it is a whole lot better than the Lightspeed. It is a whole bunch more expensive.

Nonetheless, it is a very impressive beast.

TG

FYI, you can get more stripped down version in the smaller, less fancy chassis for just under $1200.

Ric Schultz · Nov 30, 2015

For those that can solder:

Main Tortuga board: $200
12V Power supply: $100 or build your own or battery
Display modules: $60 for one or $100 for 2
Encoder module: $23
Apple Remote: $25

That is $450 plus shipping. You supply the case, jacks and wire. This is for a one input unit. You need their switcher or a switch for multiple inputs. If you have only one source then you can cut your cable in half and literally solder the hots to the inputs and outputs of the series LDR avoiding all other traces and connectors. This is what I did in my install in the Grounded Grid Preamp. I will have pic soon and show you. You actually do not need the Encoder module or the display modules to make it work.....just makes it a lot easier to maneuver and see what is going on if you have those goodies. I did not put any display modules in the Grounded Grid preamp. Brilliant design and works great!

Blizzard · Nov 30, 2015

Ric Schultz said:
For those that can solder:

Main Tortuga board: $200
12V Power supply: $100 or build your own or battery
Display modules: $60 for one or $100 for 2
Encoder module: $23
Apple Remote: $25

That is $450 plus shipping. You supply the case, jacks and wire. This is for a one input unit. You need their switcher or a switch for multiple inputs. If you have only one source then you can cut your cable in half and literally solder the hots to the inputs and outputs of the series LDR avoiding all other traces and connectors. This is what I did in my install in the Grounded Grid Preamp. I will have pic soon and show you. You actually do not need the Encoder module or the display modules to make it work.....just makes it a lot easier to maneuver and see what is going on if you have those goodies. I did not put any display modules in the Grounded Grid preamp. Brilliant design and works great!

Better watch it. Solder is a swear word around here

Blizzard · Nov 30, 2015

Ric Schultz said:
For those that can solder:

Main Tortuga board: $200
12V Power supply: $100 or build your own or battery
Display modules: $60 for one or $100 for 2
Encoder module: $23
Apple Remote: $25

That is $450 plus shipping. You supply the case, jacks and wire. This is for a one input unit. You need their switcher or a switch for multiple inputs. If you have only one source then you can cut your cable in half and literally solder the hots to the inputs and outputs of the series LDR avoiding all other traces and connectors. This is what I did in my install in the Grounded Grid Preamp. I will have pic soon and show you. You actually do not need the Encoder module or the display modules to make it work.....just makes it a lot easier to maneuver and see what is going on if you have those goodies. I did not put any display modules in the Grounded Grid preamp. Brilliant design and works great!

Have you ever compared it with a resistor R2R ladder volume control? I was on the fence a couple years ago between the lightspeed and the Bent Audio resistor attenuator module. I ended up going with the balanced Bent system with remote sensor and remote.

http://www.bentaudio.com/index2.html

In my latest system I'm using the TI8812 R2R. The same system Sim Audio uses. they call it M-eVOL-2. It's pretty good as well.

http://www.scanteknik.fi/moon-hifi.fi/userfiles//MOON_700i_Lit.pdf

Occam · Nov 30, 2015

Blizard-

What are you using to control the multiplying dac?

TIA,
Paul

Blizzard · Nov 30, 2015

Occam said:
Blizard-

What are you using to control the multiplying dac?

TIA,
Paul

SPI via a custom OLED panel/controller. The OLED panel has an IR sensor programmed for apple remote.

Ric Schultz · Nov 30, 2015

I have never listened to an LDR attenuator (I do have a board here I will hook up sometime). I have read on a couple of forums where people have A/Bed LDRs with nude Vishay Shunt attenuators and preferred the LDR. Ladders are not a good as shunts as you still have a switch in the series signal path. However, ladders are way better than series types.

Blizzard · Nov 30, 2015

Ric Schultz said:
I have never listened to an LDR attenuator (I do have a board here I will hook up sometime). I have read on a couple of forums where people have A/Bed LDRs with nude Vishay Shunt attenuators and preferred the LDR. Ladders are not a good as shunts as you still have a switch in the series signal path. However, ladders are way better than series types.

You can avoid putting anything in the signal path by placing it in the opamp feedback loop instead. Then it just controls the opamp gain.

See figure 6 for an example:

http://www.ti.com/lit/an/slyt612/slyt612.pdf

Ric Schultz · Dec 1, 2015

The feedback loop is not in series with the signal path but it is still "in" the signal path. Same with ground. Everything everywhere affects (changes) the sound. No free lunch. Wherever you put anything....it needs to be transparent.

Blizzard · Dec 1, 2015

Ric Schultz said:
The feedback loop is not in series with the signal path but it is still "in" the signal path. Same with ground. Everything everywhere affects (changes) the sound. No free lunch. Wherever you put anything....it needs to be transparent.

It's not in the audio path. It just sets the gain level of the opamp. If you don't put a digital pot, or R2R there, you have a fixed resistor anyways. I was told this is a good way to do things, but it's not how I'm doing it right now

Ric Schultz · Dec 1, 2015

The feedback path is also the audio path. Every brand of resistor, solder joint is audible. You just have not listened, you do not know. Stop quoting others.....speak from direct experience only.

Blizzard · Dec 1, 2015

Ric Schultz said:
The feedback path is also the audio path. Every brand of resistor, solder joint is audible. You just have not listened, you do not know. Stop quoting others.....speak from direct experience only.

This isn't my area of expertise. But this is what my output stage designer had to say about adding a pot into the feedback loop when I asked if there would be any sound degregation:

"the pot is not in the audio path. its in the feedback loop of the opamp. If the pot was to cause some issue with the signal, the opamp is going to correct for it because it is IN the feedback loop. The myth of pots being bad for audio is because it is a single point contact on cermet or carbon film. if one passes to much CURRENT thru this single point contact on the wiper, both the contact and the resistive element heats at the contact point and the resistance changes locally. this can be heard and measured easily with the right gear. In our case, the feedback current is very small due the the resistors in the loop so there is no chance of this happening."

Over my head, but this guy knows what he's doing.

Ric Schultz · Dec 1, 2015

Again, you are quoting someone and not speaking from direct experience. My direct experience is that all the resistors (whether fixed or variable) in the feedback loop affect the sound. Every brand of resistor will sound like itself there. Same with the brand of solder you use there.....you will have a different sound. The man you quoted may have much knowledge on how to make a circuit, but it does not mean he listens to everything. Very few designers are seriously tweaky. Anotherwords, he has no knowledge of how resistors sound in the feedback path unless he has done extensive listening tests on a very tweaky system using super recorded music. The stuff here is not measureable. All resistors measure the same (except for inductance). All resistors sound different....you have to listen to know. The only real knowledge is direct experiential knowledge. I wish you would keep to that. Stop quoting other "experts"!!!!!! Just tell us what you have directly experienced....this is the ONLY TRUTH.

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