[tortugaranger]

Interesting development Morten, I can't wait to see the V4 come to life, but I am curious about two implications of this new design change. Pico's onboard ADC is 12 bit, does this mean you are giving up on the idea of having 16bit ADC in V4? Also, is there a threat of potential RF interference from the Pico's onboard wireless and bluetooth chips?

Thanks!

The V4 will not be using the PICO's 12 bit ADC. The V4 has a separate dedicated 4 channel 16 bit ADC chip used only for calibration plus a 4 channel 12 bit DAC chip used for both LDR calibration and LDR control during normal operation. The V3 had the opposite - a 12 bit ADC and a 16 bit DAC. In hindsight, I believe accurate measurement is more important than more granular control provided the 12 bit DAC control is monotonic and repeatable which is it. I'm tweaking the LDR calibration algorithm somewhat as well to further optimize around the 12 bit DAC while taking full advantage of 16 bit ADC.

In the event using the PICO's WiFi or Bluetooth creates any problems, I simply won't use them. Initially they'll both be dormant until such time as I've come up with remote control solution that warrants their use.

[tortugaranger]

Hi All,

I just published the first working draft of the V4 Hardware Manual which is now available online in our online documents section via this link: https://tortugaaudio.com/docs/epotv4-max-hardware-manual/

As the V4 remains under active development, there will likely be numerous changes to the manual over the next several weeks until the V4 is finally released. But those curious about the details of the V4, it's a fairly comprehensive description of the V4 Max hardware so far.

Cheers,
Morten


P.S.  We are currently having snowmageddon here in Bend, Oregon with probably a foot or more white stuff by tomorrow.

[wgraft5]

Hi All, P.S.  We are currently having snowmageddon here in Bend, Oregon with probably a foot or more white stuff by tomorrow.

Central Oregon will do that, then the sun will come out melt it and then Slushageddon! It freezes at night so then its Iceageddon and so on. lol Lived in the Bend area for 10 years or so. Back in the valley now. LOL

Wayne in Oregon

[stvnharr]

Looking forward to when the V4 comes out, when it comes out. I can do balanced without issues then.

[tortugaranger]

Hi All,

I've now published a draft manual for the new optional plug-in V4 Solid State Buffer Module (SSBM.V4) that mounts directly to the new V4 Max board. Treat it as a working draft since changes are inevitable.

https://tortugaaudio.com/docs/epotv4-max-hardware-manual-copy/

The buffer module converts the V4 Max from a passive preamp/attenuator into an active version with optional gain (up to +12 dB) by simply pugging the buffer module into the same socket on the Max as the LDR Module. Then the LDR Module plugs into the buffer module such that you end up with a 3-layer board arrangement that looks roughly like the diagram below.

The buffer module design is an evolution of my earlier stand alone buffer board which has been in circulation for the past 3 years or so and has performed well.

[tortugaranger]

A fair summary of the past 8 months...

July-Oct: Sort, cull & pack up everything while getting rid of 2 cars and a boat while recovering from a Cat 5 hurricane
Nov: Drive from Florida to Oregon and then stuff everything into a garage plus a storage shipping container next to the house
Dec: Holiday time with family
Jan: Unpack and set up Tortuga Audio operations
Feb: Get back to working on the ePotPi.V4 LDR Stepped Attenuator & Preamp Controller

And that's how you blow through 8 months moving from Florida to Oregon.

With all that behind me, I'm now focused again on completing development of the V4. The good news is over 90% of the firmware is directly portable from the V3 to the V4 hardware. The bad news is the I'm using a whole new development toolchain (collection of software applications) together with the new RP2040 based Raspberry Pi PICO microcontroller board which means an obligatory learning curve.

I can happily report that the initial firmware port is now basically done and is now ready for functional testing and refinement. I'm moving on to the 2nd gen V4 board prototype and with a little luck may only require 1 more iteration beyond that before it's ready for production. This means there's a chance of ordering production hardware as early as April with release/availability by May. And this could easily slip by 2-3 months because it can.

Meanwhile, back to work.

Cheers,
Morten

[wgraft5]

Thanks for the update. Glad to here you are settled in.
(Im)patiently waiting and saving my pennies for the V4 lol

Wayne in Oregon

[tortugaranger]

Hi All,

I'm opening up the V4 stepped attenuator & preamp controller for pre-ordering. Here's how the pre-ordering is going to work.

1) You can pre-order a V4 starting today, March 25.
2) You don't have to pay in full when you place the pre-order BUT you do have to pay a $50 refundable deposit.
3) There is no firm/estimated release date yet - May/June is achievable and I'm working towards that but no promises
4) Orders will be shipped in the order they came in - so FIFO (first in, first out).
5) When it's time to ship your order, you'll receive an invoice for the remaining amount due.
6) If you change your mind, your order will be canceled and the $50 deposit will be refunded in full.

The V4 product page is set up so that the default scope is: 1) a V4 board, 2) an LDR module, 3) an OLED display assembly, and; 4) an Apple compatible remote.  You can opt out of items 2, 3 and 4 if you already have these items but you will need them. The OLED display assembly includes infrared receiver and encoder plus cabling. A 5V power supply is NOT provided but minimally you can power the V4 from any Micro-USB cable.

Any existing quad LDR Module from your V3 board will work with the V4.
Most older OLED displays (Rev C or later) will also work with the V4.
An existing silver/metal Apple remote will work with the V4.

Here's the link to the V4 product page:  https://tortugaaudio.com/products/diy-preamp-components/epotpi-v4-max-electronic-stepped-attenuator/


Please PM or email (morten@tortugaaudio.com) me with any questions.

[tortugaranger]

The V4 pre-order web page had a glitch which I believe has now been corrected. If you run into any problems, please let me know.

//Cheers |  Morten

Hi All,

I'm opening up the V4 stepped attenuator & preamp controller for pre-ordering. Here's how the pre-ordering is going to work.

1) You can pre-order a V4 starting today, March 25.
2) You don't have to pay in full when you place the pre-order BUT you do have to pay a $50 refundable deposit.
3) There is no firm/estimated release date yet - May/June is achievable and I'm working towards that but no promises
4) Orders will be shipped in the order they came in - so FIFO (first in, first out).
5) When it's time to ship your order, you'll receive an invoice for the remaining amount due.
6) If you change your mind, your order will be canceled and the $50 deposit will be refunded in full.

The V4 product page is set up so that the default scope is: 1) a V4 board, 2) an LDR module, 3) an OLED display assembly, and; 4) an Apple compatible remote.  You can opt out of items 2, 3 and 4 if you already have these items but you will need them. The OLED display assembly includes infrared receiver and encoder plus cabling. A 5V power supply is NOT provided but minimally you can power the V4 from any Micro-USB cable.

Any existing quad LDR Module from your V3 board will work with the V4.
Most older OLED displays (Rev C or later) will also work with the V4.
An existing silver/metal Apple remote will work with the V4.

Here's the link to the V4 product page:  https://tortugaaudio.com/products/diy-preamp-components/epotpi-v4-max-electronic-stepped-attenuator/


Please PM or email (morten@tortugaaudio.com) me with any questions.

[familytree2000]

Hi Morton.  When will the stackable active v4 buffer and power supply be available? 

[tortugaranger]

Hi Morton.  When will the stackable active v4 buffer and power supply be available?

I expect both to be available soon after the V4 production boards are ready to ship. The plug-in buffer module and the PS are mostly done. Need to do final testing on both once the final V4 prototype has been proven out.

[familytree2000]

 

[tortugaranger]

Pic of latest V4 prototype board without any parts installed. With some luck, this may be the next to last iteration. Have already made some minor mods to this layout. Will be building and testing out this board next week.

[tortugaranger]

One thing I've learned the hard way (over and over again) is that the road to hardware/firmware development takes many turns and you never really know how long it will take until you actually arrive.

One of my objectives with the V4 has been to get away from having to use a very expensive and sometimes hard to find 4-channel 16 bit DAC chip. The 16 bit requirement is driven by the inherent behavior of LDRs when trying to regulate their resistance level in the high 10k's of ohms upwards of 100k. At these higher resistance levels, a very small change in control current translates into a big change in resistance (i.e. their gain becomes very large). This requires finer higher resolution control - hence the 16 bits.

Knowing this all too well, I still tried to get away with a low cost 12 bit DAC but was reminded all over again that the 16 bits used with the V3 build was indeed needed for a reason.

As a result I've opted to go with 16 bit pulse width modulation (PWM) instead of a 16 bit DAC. High resolution PWM doesn't require any special hardware and only requires 8 additional low cost passive resistors/capacitors for filtering. The PWM machinery runs as an independent peripheral within the microcontroller in parallel with with the firmware code.

Unfortunately, this requires yet another design/prototype iteration which means I have to wait until the first week of June to receive the updated boards that then have to be tested. So it goes.