AMB Laboratories DIY Audio

[linux-works]

how long is that wire from the stack of 4 lcd1/2 boards, over that 6pin molex, to the lcduino? then, now much wire is there from the lcduino to the 5v psu? is that how you feed power? (more close-ups on the photos would help).

it looks like its still too long but I can't tell.

and for testing, I'd remove the d2 boards, entirely and just run a double stack of d1 and lcduino. get the vol control working first just on its own.

to save some power you can remove the jumper on the d1 controller boards (that turns off all the led bargraphs).

[linux-works]

also, if you need extra 'help' in the cable, the 6pin i2c cable uses 2 wires next to each other for 5v, 2 middle ones next to each other for gnd, and then 1 data and 1 clock. the 2 gnds are tied at both ends (lcduino and d1 controller) but the 5v line is not at both ends; on the lcduino its shorted together (I think) but I know its not, on the d2/d2 controller side. there's a 3pin jumper to select which of the 2 wires to use for 5v. if both are the same, you can rig up something to short all 3 pins and that way you use both end wires for vcc instead of just 1. that halves your R in the cable and could help. I like doing that, anyway. we allowed for 2 diff voltages; one to run the board and one to run the relays; but in fact, its always the same 5v and so you might as well short the 3 pads together and use both wires in the 6pin i2c cable for vcc.

it can only help. note, do this on all 4 controller boards.

[Boinger]

the cable from the lcdduino to d1/2 is 12" and the cable from psu to the lcd duino is around 34"

I will try to isolate the attenuators first and get them working.

[amb]

Those wires are probably too long. What gauge are they?

[Boinger]

22g

[amb]

Try to make those wires no longer than absolutely necessary. High currents over a long wire == voltage drop and current-limiting.

[linux-works]

I did a test on my a10, a year or so ago, and I wanted to see how much droop there was locally. my probe is right on the d1 5v line and you can see that as I twist the knob or use IR to get the relays to dance, they dance downward on the scope a little (lol). about 40mv of 'hit' when they get up and dance.



that was a clean, local, proper connection and that amount is not significant. BUT if you add wire and drive 4 boards from it (I was using only 1 d1 and 1 d2) you could definitely have voltage drop problems. you also hinted at this by saying that 5.3v was helping you get more relay action.

can you show an overhead shot of just the d1 board stack and its power wire and where that wire ends up? then a 2nd shot of what sends 5v into the lcduino.

[Boinger]

ok will shoot some pics and get them to you asap um if i were to go pick up an oscilloscope how much should i spend ?

http://www.frys.com/product/6501473?sit ... IN_RSLT_PG

or

http://www.frys.com/product/3069619?sit ... IN_RSLT_PG

[linux-works]

now you're talking!!

that rigol I got is a very very good deal. its decent performance but not ever going to pass for a real tek.

if you can afford the tektronix, go for that. I believe in owning good tools and tek is no slouch! you'll get years of pride and service from top brand tools.

that said, the rigol is not at all a bad choice, either. you can save some money and get maybe 80% of what the tek is.

for audio, analog scopes are very useful, too.

don't forget the signal source. it can be a dac on your pc and use sound card test suits for generating waves; but waveform generators are not expensive, even used. a lot of labs are converting to DDS style digital function gens and the older analog ones are being sold cheap (I just bought one, myself). its handy to be able to sweep the audio range and see how flat things are on the scope output. or see if you have oscillations or psu wiggle.

dual trace is really a must-have, if you are buying today. most everything is dual trace anyway, but older ebay stuff isn't always.

be careful with gear from frys. not sure if everything 'factory sealed' really is...

[Boinger]

OK yea I can afford the tek... the frys in my area has been pretty good at marking open items but I can generally tell if it has been opened in which case I returnit