THATDIP Preamp - THAT1570/5171 Digitally Controlled Mic Pre [PICS]

promixe · Jul 16, 2011

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Hi All,

I just finished doing preliminary testing on my ~~THATDIP~~ Lucidity Preamp PCB and it seems to work great. Next step is to plug a mic in and LISTEN. =)

UPDATE: Just plugged a mic in and tested the preamp on vocals - wow... I'm actually very impressed, after having worked with Prism, Grace, Lavry stuff, this sounds damn clean, yet not "sterile" i.e. unmusical - paired to a cheap dynamic mic (Audix OM-3xb is what I immediately had access to, serious condenser testing is ahead =)

The board features my THATDIP adapter that utilizes THAT1570 & THAT5171 digitally controlled preamp chipset. The board also features flexible output stage making it possible to do either balanced or single-ended out. The PCBs are very tiny - 147x36mm (1.4"x5.8") so it's easy to fit 8 of them in 1RU.

I will be preparing documentation to get people started with this project. Up to 8 channels can be controlled via a single front panel controller. I have a few pilot-run PCBs for both the preamp and the controller if someone is interested.

I'm also working on a MIDI controller board for the project to emulate Digidesign PRE if hooked up into Pro Tools. Also I may be making a digitally controlled minimal compressor to be inserted past the preamps - ideal for mobile recording workflow.

Is there any interest in the project? =)

Ptownkid · Jul 16, 2011

Radness!!!

spreemusik · Jul 16, 2011

How far can the controller and the preamps be apart?

promixe · Jul 16, 2011

spreemusik said:
How far can the controller and the preamps be apart?

I haven't tested max length yet, but the SPI bus works at 8Mhz = 125ns clock cycle. Generically speaking it's 1 ft per 1ns...
Having said that, this particular controller was designed for FRONT PANEL control and assumed it will be in the same chassis with preamp boards. If you need a REMOTE controller it is better to use something like RS-485 over twisted pair or similar. Then we're talking 100+ ft easily done. I'm going to investigate if I can do a simple SPI to RS-485 board for this project specifically for remote use.

Meathands · Jul 16, 2011

Whoah! Awesome. I am just finishing up an 8-channel rack of MCS' 1512-based boards and I was likewise impressed by their musicality. Might embark on a rack of these next...

spreemusik · Jul 17, 2011

promixe said:
If you need a REMOTE controller it is better to use something like RS-485 over twisted pair or similar. Then we're talking 100+ ft easily done. I'm going to investigate if I can do a simple SPI to RS-485 board for this project specifically for remote use.

Yes, I really need a remote controller, and a rack of 8 pres in the piano room. That's about 20m (65ft?) of cable, so MIDI won't cut it. RS-485 sounds good. I suppose, given a bit of time, I could devise my own controller.

nielsk · Jul 17, 2011

If it could use the same protocol as the Aphex 1788RC then one could use the Aphex remote (a great unit and not very expensive) and go 1,000 feet over CAT5 or +1kM over fiber w/ converters.
One could also use the free software to control using a PC...http://www.aphex.com/1788A_downloads.htm
As the system started using MIDI, I suspect the data protocol is based on the same format, & the basic configuration is 8x8 (8 banks of 8 channel units)

promixe · Jul 17, 2011

nielsk said:
If it could use the same protocol as the Aphex 1788RC

I initially thought of using Digidesign PRE OR Aphex 1788 MIDI format, switchable. It would basically emulate either unit MIDI message wise, receive their commands, translate to SPI, my front panel controller would grab it and talk to the actual preamps. If front panel settings are modified, send SPI to MIDI board, the MIDI board translates to either Aphex or PRE MIDI message and sends it out... Kind of like that.

But the initial idea was to control these preamps via Ethernet with anything that has a HTML5 compatible browser (i.e. iPad, laptop, etc.)

You would basically connect the preamp to your LAN, it would use Bonjour to set up itself and find other units and have unified interface (kind of like above) for, say, 64 channels of clean goodness. =)

promixe · Jul 17, 2011

nielsk said:
Aphex remote (a great unit and not very expensive)

It is a good unit, BUT $1299 seems a bit steep for me personally, compared to the DIY nature of the project it would control... Then its protocol would need to be reverse-engineered, which assumes I'd have to obtain a unit somehow. =) Therefore I am interested in making my own version of DIY RCU for these preamps, then it would be a sub-$300-400 remote, much more affordable, with similar features, and a lot of time would be saved by just implementing my own protocol to suit what I have already coded for the front panel controller (picture below).

I don't know availability of which additional PCB (MIDI, Remote, PSU, Metering, Compressor) would make this project more desirable for people to undertake. Also, there is a lot to think about in terms of how to interconnect everything (the logical part of it, i.e. what is master/slave at what level, etc.).

=)

radardoug · Jul 17, 2011

Very cool project! One thing to bear in mind, you can convert MIDI to RS485 very easily, you just have to put the signal through an RS485 interface chip at each end. Tie the chips so they only transmit or receive as appropriate at each end. It all runs off 5 volts which you could steal at each end.

Joelv · Jul 17, 2011

Awesome! I'm interested in 8 units for sure, possibly more. Any idea on when these will be available?

12volts · Jul 19, 2011

I'm thrilled with this design/implementation. I'll have 8 boards (PGA2500) and a controller when they are available, just for starters.
Have an ethernet controller and I'll cream my pants! Please keep us up to date with developments.

Frank B.

Matador · Jul 19, 2011

What about using a Microchip ENC28J60? There's a lot of very simple PIC based web servers (a few in the sub $25 range) that include SPI: each of your boards could run a simple web server where you could make adjustments just using the standard HTTP protocol.

12volts · Jul 19, 2011

Hmmm, The PIC range is .... unreliable, the claims made in documentation don't necessarily
apply to the device . Anything in the ATMEL range???

Frank B,

desun · Jul 20, 2011

Yes, interested in this, 8ch in a 1U case would be great project to do! Would be nice to have a play around with the control for these too and come up with a neat front panel design.

fazer · Aug 3, 2011

Very nice fit for me as well. I have Protools and a command 8 with control for PRE 8ch. I'm following this with great interest. Makes a nice remote setup.

Great Job Promixe!

delphi · Aug 8, 2011

Count me in as an early participant to put together a 1U 8 channel version. Excellent work!

GnS · Aug 23, 2011

I would be in as well. Gaining and Pad On/off and P48 and Phase over MIDI would be awesome!

Amit · Aug 25, 2011

Nice work!
I'm in for two units, possibly four.
All the best!
/Ami

Moby · Dec 9, 2011

Any news? I would like to build dual unit

THATDIP Preamp - THAT1570/5171 Digitally Controlled Mic Pre [PICS]

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