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LDR Volume/Preamp Controller with 256x64 OLED Display & Remote

Hi All,

I'm please to announce that the ePot.V3 "Max" Electronic Stepped Attenuator & Preamp Controller is now available for pre-order for $249 which is $50 off the regular price.

We anticipate an August 10th release date same as the ePot.V3 Mini announced earlier.

The key differences between the Max and Mini is the Max is a bigger board intended for chassis mounting, does not have an embedded encoder, has built-in input switching for up to 6 single-ended stereo inputs, has built-in LDR calibration, and has a few additional control interface options not available with the Mini. We are still in the process of putting together detailed product documentation on all of that.

More info here: Electronic Stepped Attenuator | ePot.V3 Max | Tortuga Audio

..and here: ePot.V3 Stepped Attenuators set for August Release | Tortuga Audio

Features of the ePot.V3 Max include:

  • Input switching between 6 inputs via very low noise analog switches
  • LDR (light dependent resistor) attenuation module
  • .....100 step attenuator
  • .....-60 to 0 dB
  • .....adjustable impedance 1k to 100k | 20k default
  • .....built-in LDR calibration system
  • .....plug-in replaceable module
  • Optional alternative discrete resistor attenuation module
  • .....127 step attenuator
  • .....-63.5 to 0 dB
  • .....60k fixed impedance
  • .....plug-in replaceable module
  • Smooth stepping with no sonic artifacts
  • No mechanical parts in the signal path
  • Remote controlled (Apple infrared remote)
  • Manual control via rotary encoder
  • Chassis mounted
  • Smooth muting/unmuting
  • Left/right channel balance w/ reset (+/- 10 db)
  • Optional status LED
  • Optional high contrast menu driven OLED display with encoder & IR receiver
  • 2.7" wide by 4.4" long x 1.5″ deep
  • Solder pad or pin header for connecting audio input/output

Cheers,
Morten

The ePot.V3 Max is shown below with an LDR attenuation module installed on the left and a discrete LDR module shown on the right. The Max board shown in this pic is an earlier prototype - some minor changes were made in the production board.

We expect to have much better set of production hardware pics in about a week or so.

The second pic shows the relative size differences between the Mini and Max together with the 2 different types of plug-in attenuation modules.

ePot_V3_plugin_boards_compared.jpg


ePot_blackwhite_withlabels.jpg
 
Hi Morten,

Does ePot.V3 "Max" come with both R2R and LDR modules or we choose when preordering? If we choose upon ordering, can we order the other module after and swap or we need to update the firmware?

thanks
Do

Hi Do,

Your question actually prompted some adjusting to how we're going to price/sell the new ePot.V3. To maximize flexibility the Max can now be purchased bare without any attenuation module at a reduced price. An LDR module is added in by default but you can opt for no module, an LDR module only, a discrete module only or both. The modules are priced the same at $49 each.

Either module type can be purchased separately but we haven't stood those up as individual products yet.

The 2 attenuation module types are interchangeable but you have to turn the unit off, change out the module, and then turn it back on. You don't even have to power it down, just turn it off to do the change over.

The firmware is already set up to operate with either module type. You don't have to tell the Max or Min what module type it has - no jumpers etc. It detects what type module is plugged in automatically.

Cheers,
Morten :D
 
Hi All,

We've started production on the new ePot.V3 Mini and Max stepped attenuator/controller boards this past week. Woo hoo! Work continues on polishing the firmware but it's the nature of software that it's never done....just shipped. The V3 Mini will likely get released first by mid-August followed shortly thereafter by the V3 Max. We'll be sending out a detailed newsletter on all that later in the week.

I plan to have a new set of pics by the end of the week showing the production hardware in more detail.

We are currently taking discounted pre-orders for both the Mini and the Max per the links below.

Pre-order your Mini: Electronic Stepped Attenuator | ePot.V3 Mini | Tortuga Audio

Pre-order your Max: Electronic Stepped Attenuator | ePot.V3 Max | Tortuga Audio
 
The "ePot.V3 operation and controls" document has now been posted in our "Docs" section on the website. The document explains how the controls work for both the new V3 Max and Mini electronic stepped attenuator / preamp controllers.

The operation/controls documentation complements the ePot.V3 Mini hardware documentation which is also listed below. We are still working on editing a similar document for the Max.

Mini/Max Operations/Control Manual - ePot.V3 Mini & Max operation & controls | Tortuga Audio

Mini Only Hardware Manual - ePot.V3 Mini hardware manual | Tortuga Audio
 
Is it possible modified the modules to use 10k linear pot instead of the optic encoder ?
I want to install it to my old integrated amp
Thanks

The short answer is no. The encoder we use is a mechanical type that includes a push button switch function in addition to its directional left/right sequencing. It's 3 signals are interfaced to a microcontroller which decodes these signals for volume control plus certain other adjustments.

Similar functionality could be derived from an analog pot connected to one of the microcontroller's ADC inputs were it designed that way but that would require a redesign of the board. But there wouldn't be any inherent advantage in that approach that I can see. Also I'm not sure if pots are available with pushbutton features.

An encoder is a far more flexible device once you're in the digital control domain. You can interpret or shape its input anyway you want within the software essentially emulating the behavior of any analog pot be it linear or logarithmic.

What are you trying to achieve with the use of a linear pot as an input device?
 
I am thinking to replace my Macintosh amp malfunctioned 50k log
motorized volume pot.
I ask whether a linear 10k pot can use to feed the adc of yr volume modules. If it can work , it is a upgrade , and i can still use the amp's remote controller.

To clarify further our current design does not have the ability to accept an analog input to drive the volume level and we have no plans to redesign the product to include that feature.

It may be possible to modify our firmware to accept control inputs from your existing remote but we would need the actual remote to determine if that's doable. Our system uses the NEC infrared protocol that operates with a 38 kHz IR receiver. We could probably accommodate any remote that uses the NEC protocol. I don't know what protocol the McIntosh uses.
 
Low noise is good. Have you measured distortion of the complete discrete attenuator?

We have yet to get around to measuring that. And I should explain why that is.

The topic of audio distortion gets a lot of attention around some audio technology enthusiasts and is often treated as a de facto metric for audio quality, especially on technically oriented audio forums. So much so that it gets taken for granted that anything with lower distortion is "better" than some other thing with higher distortion. And as an engineer I get the logical seduction of that notion.

And yet when I've listened to music on various systems over the years I've noticed practically no correlation between distortion specs/measurements and whether I liked what I was hearing or not.

When I investigated the topic of distortion relative to human hearing I discovered a fairly consistent body of research that indicates human beings are unable to perceive distortion below a certain threshold. One can argue the finer points of what that threshold is but it appears to be somewhere around 1% THD although some claim it's much higher.

This raises an interesting question. If you can't perceive distortion below a certain threshold, then what is the relevancy of measured distortion below this threshold? No doubt measured distortion is useful in guiding the design process and it does satisfy the engineer looking to judge how well one system performs under the hood relative to some other system.

But I never confuse measured distortion with whether something sounds good to me.

LDRs exhibit rather high distortion characteristics. They are often criticized by audio engineers as being inferior devices because of that and other reasons. Yet, when deployed thoughtfully in a volume control application I consistently prefer listening to music through an LDR attenuator compared to all other alternatives.

When we first listened to our new discrete resistor attenuator I was very curious what we'd hear. It did sound OK. But when we switched back and forth between the LDR and discrete attenuator is soon became obvious which one we preferred to use.

I have zero doubt that the discrete thin film attenuator has far lower distortion measurements than the LDR attenuator.

What would really be a distortion is to claim that the low distortion discrete attenuator is a better attenuator than the higher distortion LDR attenuator.

And that is why we haven't gotten around to measuring the distortion on the thin film discrete attenuator....yet.
 
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I don't have any doubts about film resistors.

I have doubts about switches, both mechanical and electronic.

If you feel that THD measurements are lame, how about Gedlee metric by Earl Geddes and Lidya Lee? I suppose it would be good for comparing different attenuators.

The analog switch we use is a Texas Instruments part with a stated THD spec of 0.004% which even if off by an order magnitude is so low as to be irrelevant. It requires a bipolar +/- 5-6 V supply which is a pain but I'm very happy with the results.

I don't view THD measurement as being lame. It's a useful tool design. But I do believe it's all too often waved around without context or perspective because it's simply not directly synonymous with sound quality.

As I understand it the Gedlee metric grew out the recognition of THD's shortcomings as a meaningful metric of perceived sound quality. And while it's considered a better approach it's not exactly a simple matter to do it properly as in you can't just plug in an analyzer and set it to Gedlee mode and get an answer.

In a perfect world we would measure everything clinically, sort the results best to worst and then buy the best you can afford. For audio, for wine, for cars, whatever. Instead we get to listen, taste and drive. Imperfect yet mostly enjoyable human experiences. :)