My Building Plans: Comment and suggest...

[asgorath]

Ok, I'm going to make a stereo IGC with the following features....

-stereo out
-3 inputs
-volume control
-front power button
-front source selector button

Implimentation...

-RCA Inputs
-Discreet Transistor Buffer as shown on Decibal Dungeon w/ BC547 transistors
-- Question: Should I buy a bunch of these transistors and run a test circuit to find the 3 best matches?
-Big input caps, I'm thinking 4.7uF solen poly's
-alps blue 50k log pot for volume
-Analog SSM2404S to control audio switch
-Wood Casing with copper foil for shielding of signals
-320VA 22+22 secondary torroid transformer from parts express
-Quantum Research QT110 capacitive buttons for front panel (to keep a nice clean front) through wood
--1 button per input
--Single Power Button to turn off and on
-Led's behind power knob glow when the amp is on, letting light leak out from behind the volume knob.
-Passive Heatsinks with slots in bottom of casing to vent heat
-Soft Power on (delay) to minimize power on thump and buzz
-Discreet Rectifier bridge
-Snubberized Power Supply
-Seperate power supply & small shielded transformer for logic chips
-Seperate power supply for buffer (fed off main torroid)
-Shielded Input Line Filter (inductors, caps, and resistors)

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These are just ideas I've been plinking around with. If you have any recommendations let me know. Also just so you know, the first pair of speakers this amp will see (other than my disposable crappy test set) are a pair of Paradigm Atom v.3's. So the load is pretty easy, but I want to make this amp power most speakers.

Question: Is there any merit to the T-Feedback setup? I read about it, but there isn't too much talk on it.

Question: Can I just setup my pot in front of my buffer as I normally would?

[Doovieman]

I like it. I'm doing something quite similar actually and will be interested to see how you do your final construction (with regards to the qtouch). My only word of advise is to make sure you do seperate digital and analog grounds.

[homer09]

since you are going inverted path, i suggest you look into the mauro penasa design. it is supposedly a leap in the inverted style gcs.

My "audiophile" LM3886 approach

there is a group buy for it to

edit: just noticed you want back lit volume knobs. i was building a case with that myself, how are you implementing this?

[asgorath]

I plan on making the whole face flat. Then a volume knob sticks out on top of that. Then drill 3 holes equally spaced near the volume knob center (lil ways out) in the casing. Install normal brightness LEDs pointed straight at the knob but recessed so they don't stick out at all. Finish the back of the knob in a high gloss finish. Then just let the LED light hit and bounce back and forth between the knob and caseing, making a nice smooth, not harsh light.

[Stocker]

Stand by for three points of light around the knob. Unless you do some further surface treatments, you will have a good deal of a point-source effect from each LED, I think.

[asgorath]

Originally posted by Stocker
Stand by for three points of light around the knob. Unless you do some further surface treatments, you will have a good deal of a point-source effect from each LED, I think.

I think with 3 LED's spaced 120 degrees off from each other around the shaft it would be pretty even, maybe a slight off glow. And don't forget the light will be diffused behind a pretty large knob. Plus the given light is purely from reflecting back and forth from the knob. I have a feeling it will work. Maybe I'll get some scrap and do a test run before I go all out on the casing.

I'll post pics of what I find.

[homer09]

i think the closer you place the leds to the shaft, the better it will look.

also, i would caution you against a high gloss finish. i personally will be use a very bright white paint finish on the back of my knobs. think about it, a mirror finish will reflect light precisely and laser like. it wont diffuse it, a white finish is still reflective, but will tend to diffuse more.
kind of like seeing a led through saran wrap versus through waxed paper.

[asgorath]

Originally posted by homer09
i think the closer you place the leds to the shaft, the better it will look.

also, i would caution you against a high gloss finish. i personally will be use a very bright white paint finish on the back of my knobs. think about it, a mirror finish will reflect light precisely and laser like. it wont diffuse it, a white finish is still reflective, but will tend to diffuse more.
kind of like seeing a led through saran wrap versus through waxed paper.

Point taken, high gloss white finish it is.

[homer09]

also, from what ive been thinking, look to buy large angle LEDs. there is something called a viewing angle usually specified in the datasheets. the wider, usually the less bright and led is, but you dont care, you want the light to be spread. i got 70 degree ones, that are also HI brightness.

just some stuff i came up. also thinking, test matte paint too, or semi-gloss, if you get spotted diffusion.

[mangrovejack]

If you sand or otherwise scuff the surface of the LED, you'll also get some diffusion out of it. Obviously this only works if the LED's are just on the point source side, if they are really strong, then sanding the surface won't do that much.