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Old 24th June 2011, 11:33 AM   #551
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Originally Posted by opc View Post
If you use the Nichicon low profile 8mm polymer caps, the total PCB height including components would be less than 10mm. If you get crafty and solder some SMD caps on the PTH pads, you could probably get that even lower. You'd have to use 3.5mm jacks for input and output to keep things small, but that's probably what you'd want for a portable setup anyway.

Batteries are a whole other can of worms, but there are cell phone batteries out there that are less than 5mm thick, so you could potentially make something that is very low profile.

Cheers,
Owen
wow, good observation..since i haven't get any first hand experience on this amp, i'm judging merely from the pictures in the first post

what is the dimension of the amp's pcb, anyway?
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Old 24th June 2011, 12:02 PM   #552
qusp is offline qusp  Australia
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Originally Posted by ilardi View Post
The LT3032 looks like a great chip but I could never figure out how to properly solder, by hand, a DFN chip so that I get good contact with the thermal pads on the underside of the chip. How did you do that?

Terry
by designing the pcb yourself to cater for this problem. this reg was so very appealing that i thought long and hard about the problem. it is solved by creating a custom pattern for the part. the pads for power pads underneath have pth vias that link to the correct plane/copper pour (its a 4 layer board) and after tacking/gluing in place, very lightly tinning the pad on the device and adding a bit of flux, solder from the bottom of the board. the side 'leads' also extend up the side face a touch, so the pattern has extended the leads out a further 2mm, flux, solder. soldering a 14 pin part that is only 3 x 4mm is another issue but doable.

of course you can (and i will) build toaster over reflow controllers for not much money, i do enough smd to make this an interesting idea.

yeah owen, thats what i did with the buffalo 2 as well, the oscons have been replaced with panasonic SP caps and tantalum/polymer 7343 package. thats the package all the high performance lowz caps are in these days it seems. cheaper than sanyo oscon, but not high enough voltage for this board, maybe the input stage, there are ones that are 20v+ but not the really high grade ones
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Old 25th June 2011, 07:26 AM   #553
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Hi opc,

I'd like to sign up for 1x SE-SE + PSU kits.

What is the recommended pot resistance to use as an input attenuator?
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Old 25th June 2011, 11:00 AM   #554
agdr is offline agdr  United States
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Aarrgghh... the 1200 mAh lithium cells out there are primary (non rechargeable) cells. That isn't feasible.

opc - please change mine to just one single SE->SE board from the 3. I've recently bought another SE headphone and I don't see balanced gear happening in the near future. Thanks!
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Old 25th June 2011, 11:40 AM   #555
qusp is offline qusp  Australia
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how about this 11.5v 1500mah battery?

has protection pcb built in
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Old 25th June 2011, 02:21 PM   #556
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@ thegreatbrian
whatever suits you and your gear, its not actually designed with an input pot in mind (at least v1 wasnt), but you will apply one in the voltage gain (input) opamp feedback loop. i presume this time opc has put some pads for this?

regardless a good place to start is 25k, this is not too high for noise, but also not too low so should be well driven by just about anything.
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Old 25th June 2011, 04:13 PM   #557
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Originally Posted by qusp View Post
@ thegreatbrian
whatever suits you and your gear, its not actually designed with an input pot in mind (at least v1 wasnt), but you will apply one in the voltage gain (input) opamp feedback loop. i presume this time opc has put some pads for this?

regardless a good place to start is 25k, this is not too high for noise, but also not too low so should be well driven by just about anything.
Wouldn't I be able to just put the attenuator between the inputs and connect it to the input pads of the pcb like in post #440?
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Old 25th June 2011, 04:52 PM   #558
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you could, but personally i would install in the loop. either will work. actually you would probably want to go lower than 25k if you put it in the loop and you would want to adjust the other gain resistors to suit. i feel its the better way to do it, but i suppose its a matter of taste

Last edited by qusp; 25th June 2011 at 04:54 PM.
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Old 25th June 2011, 05:24 PM   #559
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you could, but personally i would install in the loop. either will work. actually you would probably want to go lower than 25k if you put it in the loop and you would want to adjust the other gain resistors to suit. i feel its the better way to do it, but i suppose its a matter of taste
Can you provide some insight as to why you prefer this method?
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Old 25th June 2011, 08:10 PM   #560
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noise created by the resistors and contacts is to a degree averaged out with feedback, no extra resistors are added, as they simply replace those that are already there.

one problem is that you must find a way to achieve having the pot mechanism as close to the opamp as possible, extending the feedback loop to the front panel and back is not such a great idea.

best way imo would be a relay based attenuator in the loop, this allows very short paths.

again, all a matter of taste
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