Well the critical stuff fits.

http://gilmore.chem.northwestern.edu/kgitsojc.jpg

I can't figure out why I want one of these so bad. Must not look anymore.

Well you want 2 for balanced.

Are there any suitable right-angled connectors we can use on these boards, so that we can stack one on top of the other?

Edited March 9, 201214 yr by ujamerstand

Not sure what you mean, for the terminal strips, they make 45 degree versions.

For balanced its definitely stacked boards on top of each other.

I already see a silkscreen error, so there will be for sure a couple of very

minor changes for the production version.

Edited March 9, 201214 yr by kevin gilmore

Ok, so we're at 4 x preamp boards + 2 x input boards + 2 x KG attenuator boards for balanced!

How're things on the software side? Any progress?

I'm going to be helping out on the software side, but I haven't really started yet. Need to get some of the hardware in place first.

I'm going to be helping out on the software side, but I haven't really started yet. Need to get some of the hardware in place first.

Excellent! If there is any way to get some sort of remote control capability (similar to the LCDuino), that would be perfect. I like how the HifiDuino guy set his up to work with the cheap and simple apple remote.

I was hoping for a screwless type connector so that I don't have to mount the wires before stacking the boards.

Not sure what you mean, for the terminal strips, they make 45 degree versions.

So is this thing set on using the 4d system touch interface?

You'll need to find something in 5.08mm (0.200") pitch. I've used the Molex SPOX connectors like this one

but they aren't available in right angle versions. Also, these fit in place of the Phoenix terminal blocks that these guys like to use, but the pin diameter might be a bit large for connectors other than power.

http://www.mouser.co...Qixpihfsw%3d%3d

Something like this might work for you:

http://www.mouser.com/ProductDetail/Amphenol-PCD/ELFH03210/?qs=sGAEpiMZZMsDddcp1dBDJK2doOjtsIcj%2fmF1ZM3ZuFk%3d

Edited March 10, 201214 yr by Pars

The connectors are on .2 inch centers. But i can certainly change it for production.

There are right angle plugable connectors that work great, its the kind of connectors

that crestron uses on just about all their products. Will look tomorrow.

Excellent! If there is any way to get some sort of remote control capability (similar to the LCDuino), that would be perfect. I like how the HifiDuino guy set his up to work with the cheap and simple apple remote.

Should be trivial just as long as we have enough I/O pins for the IR receiver.

How's the prototyping going?

I'm almost done. Going to order different opamps for the servo's today.

And i've redone the output using the audio quality opamp for that purpose

and now a different opamp for the servo.

Currently the input stage dc offset is 200 microvolts which is perfectly

fine, but i'll get it down more. Without the servo its actually 4mv which

is known to most people that use ths part, but evidently not others.

The output stage with the audio opamp as the servo comes in at

about 5mv, and while fine for headphones, driving monster power

amps is not a great idea.

I got to listen to it over the weekend, and compared it to a number

of the most expensive preamps out there, and it holds its own

just fine.

Kerry is testing the multiamp outboard amplifier.

Sure seems that for control the way to go is an arduino with the

ethernet board, a ethernet to wireless converter, and then your

favorite ipad like device talking to the preamp via a webpage.

And then an oled display on the preamp to show levels.

The biggest mess up with this was the fact that the discontinued

omron relays had a different pinout than the panasonic relays

i'm now using.

Edited March 22, 201214 yr by kevin gilmore

Sporting a glitzy new Samsung G2 Android for control, I just have to get on this bandwagon. Then I can retire the Audio Research LS3.

Tablet for a remote? OLED to show levels?

I like the sound of that.

I think the best way to control this thing would be a raspberry pi actually. for 5 dollars more than the cheapest arduino, you get 256mb of ram, 700MHz ARM processor, 2 usb ports and 1 ethernet port. Runs linux, so you can program in any programming language you are comfortable with it and run a webserver right off it. Plugin a wireless usb dongle and you are set. Available now at farnell and rs-components.

Anything is ok by me.

Just has to write to the pcf8574 chips and write to a color display.

We already have some of the code for arudino for this,it's minimal.

I don't know if the linux for the raspberry pi does real time or not,

an interrupt in the middle of programming the volume control could

lead to interesting noises. The video output or the hdmi is probably

not suitable for our uses unless someone knows of a really small

display that takes composite or hdmi. Touch screen also a real

sweet idea for local control.

Edited March 23, 201214 yr by kevin gilmore

Even with a tablet style remote, it would be preferable to also have some sort of local control. A touch screen would definitely be sweet for this. Sounds like someone is going to be busy doing some programming for this preamp.

Edited March 23, 201214 yr by Horio

I'll take a look at the rasberry pi. I've got experence with the Arduino stuff (very simple to make a board) and I could easily do something with Windows embedded as well. Not as much a of a Linux programmer, though I'm not against learning if needed.

The thing is to define what's required in-amp vs. on the controller. I like the idea of separating the functions and having a rich interface on a smart device, but I'd also like to have a simple rotarty encoder with push button in the amp and menus to drive an OLED. This way you can control the amp stand alone. Just simple and basic functionality using the OLED.

In terms of the smart device, I wouldn't mind playing with some HTML 5. Would need to think through where to host the html. It would make sense to put it in the amp, but not required and it would definitely complicate the amp side.

I'm open to thoughts and suggestions here, but ultimately need to keep this relatively simple to make it easy on everyone putting this together.

although i think that this is a bit expensive compared to everything else, it would be a complete

plug and play stack.

http://www.liquidware.com/shop/show/TSL/TouchShield+Slide

plus and arduino uno and the ethernet board.

as long as there are enough pins left over to drive the i2s bus and a rotary encoder

with buttons, should be ok.

Looks cool, though do you think its a touch on the small side?

I've looked at the liquidware site. The unit doesn't have the ethernet/wifi option bundled so would be additional. I'd love to get some more options to evaluate for an all-in-one. I've seen a few things that include wifi and the display, but haven't found the perfect package yet.

My thought above was that if we have a good remote (iPad, etc) option, then maybe only use an encoder/OLED on the amp with no touch. Wanted to see if this was worth exploring.

A touch screen would be cool, but I could easily make due with an encoder/OLED (no touch) on the amp for local control.

My thought above was that if we have a good remote (iPad, etc) option, then maybe only use an encoder/OLED on the amp with no touch.

I like this idea.