remote control: RF or IR? also external or internal controller?
Nov 1, 2008 at 4:56 PM Thread Starter Post #1 of 11

linuxworks

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I'm building yet another amp, it seems. this one is finished up to the point where it needs the motors to be controlled. here's an internal view of what I have so far:

2989323767_b90ac4ceea_o.jpg


details on internal space:

2988030541_ed803ec995.jpg


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you can see I don't have a lot of extra space to spare. but at least I did allocate room for the pots and their motors
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if you were at this point and had a nice PPA amp all boxed up but wanted remote control over those 2 pots, would you prefer RF or IR? I have receiver modules for both.

here's a shot of an RF module that I have handy and have used a few times before (shown inside a plastic box I used to build with):

88483107_3f719df9de.jpg


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IR has the advantage that its learnable and so I won't need my custom remote once its learned by my main one. but IR needs a window cut in the front and also line of sight to have it work.

RF can work with a hidden antenna easily. RF isn't learnable (normally) and so I'd need to keep this remote around when I use the amp. the RF receiver circuit is very very small and pretty plug-and-play.

I think the RF receiver will take up less space and also not dirty up my nice front panel (once its done). I have a few spare rf receiver modules and so that is a good choice for me. as for not being learnable, I'm not sure how annoying it will be to have to handle 2 remotes if I want to use my headphones.

other issue: noise inside the chassis. right now I have only 'analog' power in my chassis and nothing for +5v for control circuits. I don't think I want to regulate OFF of the existing TREAD supply I have in there, do I? I assume for higher end design, I want a separate trafo, bridge, filter and 7805, right? I'm a bit tight on space and the power supply 'area' is mostly full, too. then there's the whole issue of having the opto receiver or RF receiver inside the chassis and how to keep it from affecting the high end sound of the amplifier, itself.

so, I wonder - how acceptable would it be to just feed the control wires from the motors OUTSIDE the chassis (via some molex's on the rear panel) and then 'defer' the problem to some other shielded metal box that sits outside this one, has its own +5v for control logic and motor voltage (or a 2nd 12v line for motors if needed) and then this box would 'add' control to this 1U rackmount thing I built and the 2 features would be in 2 separate boxes. no sharing of ground or power supply or even proximity.

but it sounds clumsy to have the control stuff in another box and also some wall wart supplying power to it.

should I try to knock myself out trying to shoehorn control INSIDE my nice 1U rackmount box or is it 'ok' to just doing it outside the box?

what would you do?

I'm trying to balance elegance in design, low hassle factor (to install and use), and of course purity of sound.

opinions?
 
Nov 2, 2008 at 3:05 AM Post #2 of 11

randytsuch

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I would think IR would be better, since it's a headphone amp, I wouldn't think line of sight would be a problem. Has it ever been a problem with your pimeta?

I would look for a circular lens cover, then you can drill a hole in the front of you chassis to put the cover, and the ir receiver behind it.

I would go with the seperate supply, if it was me. But, I built a modded squeezebox with 5 seperate transformers in it
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I would see if I could fit in a little transformer into it, a hammond or signal or something like that.

BTW, nice looking amp.

Randu
 
Nov 2, 2008 at 3:55 PM Post #3 of 11

linuxworks

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thanks randu.

if I go with a separate supply, then I can put the control guts in that box, too and hide that box behind the stereo rack (it doesn't need to be seen at all). if I prepare my faceplate on my main unit to have an IR receiver module and then wire it to the back panel of the amp, as an 'expansion port' sort of, then I can pick those wires up by this 'hidden remote box' and it can decode the IR and send 5v to the right motor and at the right polarity. its a hybrid style solution with a 'pure' analog system that shows, up front; and a remote plugin-box that 'adds remote ability' via and expansion port (maybe a 5pin din on the back, real simple stuff).

or does that sound too hacky?
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part of me wants to box this all up in one unit and be done with it. but the purist in me wants to keep this stuff OUT of the analog box as much as possible. so I just don't know, yet...

here's the new front panel, just trimmed and labeled yesterday:

2994829495_fde64af5d5_o.jpg
 
Nov 2, 2008 at 5:10 PM Post #4 of 11

guzzler

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Go with a single unit; unless you do something very wrong you won't hear a difference. Just use a second rectifier and power supply on a small board. Your receiver can be a microcontroller that only wakes up on detecting a signal so the only change in current is when you're changing volume or bass.
 
Nov 2, 2008 at 5:21 PM Post #5 of 11

linuxworks

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I won't have control over wake-up of the control board. lets assume its always running. in the ebay cheapie ($10 or so) RF modules, they aren't power saving at all, i don't think ;( and on the 2 opto rx boards I have (2 diff kits that I bought in advance, to try) they also don't have any sleep or wake at all.

I am willing to be realistic about how nuts I should go about 'isolation' of the 2 PS's.
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I have a TREAD as my main 24v dc clean audio supply. if I hang a 7805 off of THAT, isn't that going to be too much volt diff between input and output? and that would cause a lot of heat?

so I was assuming I would have to go 'before' the reg and that means putting in a 2nd trafo or finding one with dual non-symmetrical windings. its HARD to find those! ;( why is that? I'd love to find a high-current 20ish secondary #1 along with a 5ish secondary #2 that is an amp or less, for control and motor use. having that would simplify my life a lot!
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make it toroid and I'm a happy guy. is there such a thing?

the control board and the rest isn't what annoys me, its power. I think if I can get a dual voltage true isolated setup out of the same space I'm using now for my single, then I can skip the 'expansion module' idea and just put all things into this box and be done with it
wink.gif
 
Nov 2, 2008 at 5:33 PM Post #6 of 11

linuxworks

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hey, how about a dc-dc converter module?

I happen to have one around that takes in 9-18v dc and puts out a 'new' 5v from its 2 output pins. a semi-small enclosed potted module that I bought a long time ago for some other project.

I would run my ppa at 18v (I would not notice it going from 24v down to 18v, I doubt) and then I could simply clip this dc-dc module at the output of the TREAD board and have my separated 5v for motor and control.

what do you think? do dc-dc converters push back a lot o crud to their source? would that 'ruin' the TREAD output for analog use?
 
Nov 2, 2008 at 7:20 PM Post #7 of 11

randytsuch

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Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif
hey, how about a dc-dc converter module?

I happen to have one around that takes in 9-18v dc and puts out a 'new' 5v from its 2 output pins. a semi-small enclosed potted module that I bought a long time ago for some other project.

I would run my ppa at 18v (I would not notice it going from 24v down to 18v, I doubt) and then I could simply clip this dc-dc module at the output of the TREAD board and have my separated 5v for motor and control.

what do you think? do dc-dc converters push back a lot o crud to their source? would that 'ruin' the TREAD output for analog use?



Personally, I would stay away from a dc-dc, if you are going to stick it on the PPA 18V. I would expect the the dc-dc to be a switcher internally, and that it would add noise back on it's input.

You could try an experiment, but I don't know if its worth the trouble. You could try powering the circuit off of a wall wart, and then power it off of the ppa transformer, and see if you can hear a difference.

BTW, in case it was not clear in my previous response, I personally would try to keep it all in one box. Probably would have been better if you had planned for the remote from the start though. Hindsight is always easy.

If you are worried about noise from the RF or IR receiver, aluminum foil is a good EMI shield, just make sure it is well grounded. You could also try as a temperary thing, to see if it makes a difference.

Randy
 
Nov 2, 2008 at 7:26 PM Post #8 of 11

linuxworks

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sorry I called you randu
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I could not tell if it was a typo or not.

I had sort of planned to do the motor control stuff - you can tell since I did allocate all that room for the motor versions of the pots. and I knew I'd be able to fit stuff in the box somehow as the extra circuits won't be nearly as bad as the ppa itself was.

I'll take a stab it at. first step is to assemble some H-bridges that I just learned about. then once that is done I can worry about how much space is left over for a crossfeed module, its control relay, the ir rx module and maybe even a tiny wallwart located inside just to power the control stuff.
 
Nov 2, 2008 at 7:36 PM Post #9 of 11

linuxworks

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transformer question: is it ok to stack 2 toroids on top of each other?

I could have a larger one on the bottom (24vac) and a smaller one (7vac) on top, separated by a rubber washer. 2 could mount very compactly like that.

any electrical or interference/emi issues I should care about? is this a good or bad idea?

I could fit a small and a ultra-small toroid in the place of that large monster one I have now. that one was just a spare I had lying around and was admittedly overly large for this job.
 
Nov 2, 2008 at 8:18 PM Post #10 of 11

randytsuch

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Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif
transformer question: is it ok to stack 2 toroids on top of each other?

I could have a larger one on the bottom (24vac) and a smaller one (7vac) on top, separated by a rubber washer. 2 could mount very compactly like that.

any electrical or interference/emi issues I should care about? is this a good or bad idea?

I could fit a small and a ultra-small toroid in the place of that large monster one I have now. that one was just a spare I had lying around and was admittedly overly large for this job.



Ideally, you try to mount transformers at 90 degree angles to each other, to reduce the magnetic field interference between them.

But, most designs involve some compromises. To me, it is a reasonable compromise.

Randy
 
Nov 2, 2008 at 8:45 PM Post #11 of 11

error401

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I'd go with IR. It's less likely to cause issue with the rest of the amp, easier to implement and as you say, more convenient. Also it looks like you've got a metal case. If it's grounded, your antenna will need to be outside the case to receive any signal.

As for power, I'd just regulate off the main supply myself.
 

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