More crap on lakewest facebook. JohnW through his proxy Renata:
--------------------------------------------------------------------------------------------------
Renata Cizmarova
Hi all, here is an update from John:
I’m sorry for the long delay in posting any updates,
but I have been working on both VFET and the DAC platform.
VFET:-
During testing of the various DAC modules I’ve been using both tube and Class A power Amps which has been interesting – both have their virtues and failings. I’ve designed the Class A section of the VFET around a tube front end with VFET’s for the Class A stage and a Non-Switching class B stage for the current dumping “High Current” output stage.
The VFET’s implementing a variation of Quads current dumping feature a feedforward topology – so no global feedback –
it’s been interesting to listen to the effects of feedback (the tube amps I’m using during the DAC development can be operated without feedback). Feedforward correction should avoid the sonic negatives of feedback.
I’ve drawn up the schematic for the VFETS and
a third-party will design the PCB’s under my supervision – they will then use a modification of the design (without the VFETS – replaced by transistors) for a production design.
Realistically, they should be available in 6 months or so – and not impacted by the semiconductor shortage. So, the VFET
design is now active once again and being moved forward.
DAC:-
Has been slower these past two months – I had to part ways with the
mechanical designer working on the DAC as he
was pretty useless – he did not seem to understand the project and gave no constructive input to the design –
working with him remotely
was just not working out –
we made good progress while he worked beside me in the lab, but we were unable to complete the design in the time available while he visited me.
I’ve now a new designer ready to move forward with, she works with Solidworks – the original designer with Fusion, there is no direct import between the 2 softwares, so
we will have to import the parts in Step format and
recreate the parts in Solidworks…
I’ve seen Renata for 2 days since January 1st – I’m working offsite on these projects –
I’m just struggling with time,
I REALLY want to complete the mechanical design of the DAC “Mainframe” + modules,
this is the first big step to completing the project – I can then start to move the prototype PCB section into the modules.
The USB Module schematic (+ Detox) is ready to be designed into the DAC module format (tested and in use), so is the CM4 based streamer – the secondary Sub-woofer / ambiance rear channel “secondary DAC channels” have been tested, I’m listening to them in the development system – these can be repackaged in the DAC module format once the mechanicals are completed.
I’ve also been testing the CD transport “Clock Lock” module – I’ve currently been testing with a customer’s CDM0 based Revox B225 – I’ve added a digital output and Clock lock interface to the ReVox – this is now serving as my CD transport test system for the DAC.
I’m still waiting for the system MCU’s I ordered in December (
I sold my turntable setup to finance the purchase of the IC’s for production). The original delivery date was January 15th – it’s now been pushed back to August.
In part, the DAC module concept has been developed as a method to work around the IC shortages – the system MCU is contain within its own module, so I can design and manufacture the other section (modules) and the compete the DAC once the MCUs are available – I have a handful of MCU’s for testing /development.
It’s looking more likely that the discrete Low bit DAC array with octal modulators will be the first DAC option as this is the design,
I’ve recently spent most time developing /
listening to.
The
DAC’s Clock Deck is progressing (the DAC’s most complex section) –
I’m about to issue the production version PCB files for the main Audio clock modules / system clock (x3 modules per DAC).
Attached a pic of development listening step-up, I’m using my CLSII as the main front channels, with x2 subwoofers + my Aeons located behind the listener as the ambiance field DAC channels. The Revox is clock locked to the development DAC board.
If time goes well,
I should have the Mechanicals’ completed this week.
------------------------------------------------------------------------------------------------------------------------
I have highlighted some of the usual bullshit for the casual and newer readers.
Key:
red = the usual bullshit
pink = epic bullshit
pale blue = poor JohnW accidentally the whole bottle! Is it dangerous?
and if not I will survive since I stopped holding back on upgrades a couple of years ago and probably saved more than I invested by only doing modest upgrades before the latest upgrades.
