AMP9 Volume Control and Interface Board

[V-bro]

10Kohm little less noise, but higher load to the source, 50Kohm will perhaps raise the noise floor a little, but will be very mild on the source output circuit....

[CathyinBlue]

The source output circuitry will universally be the sound card of a PC. I think it can take the load you say a 10 kOhm pot will place on it at full muting.

And it was late last night when I made my previous post, so I forgot to add, after the first line about having taken delivery of three AMP9 kits, "Look upon my works, ye mighty, and despair!"

[CathyinBlue]

And things go *SPROING*.

I started trying to wind the toroidal inductors, per http://www.41hz.com/forums/content.p...idal-Inductors , but something's not working out. The tightest winding I can manage can only get 30 turns of the supplied wire in before half of one of the 4 strands of wire is used up.

Even using a bench vice to insure tight windings with two hands on the core, I can't see how these four strands of 1.25 m long 0.7 mm wire are gonna wrap 8 toroidal cores to 42 turns each.

[V-bro]

Can you shoot a pic of what the end result is now?

[krilli]

Four strands for eight toroids - hmm! AT LEAST it sounds like you're missing four pieces of wire.

[CathyinBlue]

@ krilli:
At first, I thought not. I bought three AMP9 kits and they all came with the same amount of wire, but then I consulted the BOM. It does indeed stipulate 0.6 mm (NOT 0.7 mm as I said in my previous post) x 1.25 m x 4 spools of copper wire, but then I noticed the 2 in the quantity column. I only got one such spool in each of my AMP9 kits.

I assumed, through a brain fart if nothing else, that each of the 4 wires were for a separate channel and I was to get two inductors out of each, so I folded the wire in half and snipped two equal lengths. That's how I know that when I topped out at 30 turns, I'd used exactly half of a 1.25 m length.

@ V-Bro:
Here's what I have:

http://www.flickr.com/photos/3233766...ream/lightbox/

The one on the left is the first inductor I hand wrapped. It's sloppy and would have to be redone anyway. I got 29 turns out of it, but would have gotten 30 if I'd kept it tight.

The one in the middle is the one I wound while pulling the wire tight by gripping the opposite end of the wire with a pair of channel locks. Don't worry. I know my own strength. I would not have applied enough power to actually crack the core. That one's a lot tighter, but still only managed 30 turns. Spacing needs work, though.

I pulled the virgin spools of wire from my other two AMP9 kits waiting in the wings, and the two spools from the two kits are at the right. Each has just 4 selarate wires.

I think I got shorted. At least, I have plenty of wire to procede with the first kit while waiting for the wire for the second and third... of course, I'm also waiting for the new soldering station and finer gauge solder before I can try soldering my first kit as well. I grossly over-estimated the fine work needed for these kits. My existing soldering irons don't have any tips or solder small enough. I'm getting a 1/16" and 1/32" tips to be sure I can deliver heat only where I need it.

I think I'll also need one additional wire, seeing as I snipped one wire in half in ignorance.

Picking up a cheap inductance meter from Radio Shack might not go awry either.

[V-bro]

I have forgotten what gauge wire it is, but I have sent Jan a message about this problem. Not so nice if there are several kits arriving over the globe with too short wire...

A little too short would be acceptable, but you can not even place these...

[CathyinBlue]

Argle-Bargle Glop-Glyph!

Tried winding my third inductor with a full 1.25 m length of wire, the second from my one spool used so far. I thought that I might be pulling too hard, and I guess I really don't know my own strength. I had a suspicion that the wire was getting ductile and necking down, but it took the wire snapping for me to realize, yep, pulling too hard, idiot!

According to this chart I got from some anonymous website: http://www.powerstream.com/Wire_Size.htm
21 AWG = 0.7239 mm ~ 42 Ohms/km ~ 9 A
22 AWG = 0.64516 mm ~ 53 Ohms/km ~ 7 A

If those figures jive with yours, I should be able to snag a small spool of 22 AWG enamelled copper magnet wire if I keep snapping them.
I've also managed to accidentally crush one of the 10 nF capacitors. That third AMP9 kit I build better be a masterpiece with all of the experience I'll have by then. Definition. Experience. Knowledge you gain immediately after you needed it.

Incidentally, and I'm sure it's meaningless, but is there a preferred direction of winding? I'm just wondering about any EMI effects of having two inductors next to one another that are both wound in the same direction vs wound in opposite directions.

I just went to my go-to place. http://www.jameco.com/webapp/wcs/sto...001_2098401_-1
39 m of 22 AWG for 19 US¢/m. So, it's only about US$3 worth of wire I'm missing. Incidentally, for that link to really work, you need to click here http://www.jameco.com/ first. They don't like deep-linking.

Also, for some reason, people don't like odd American Wire Gauges. (I know. European. ALL American Wire Gauges are odd.)

Hmmm. Pay US$7.50 for the spool of magnet wire and finish handwiring my own inductors. Or pay US$7.50 for 30 of these: http://www.jameco.com/webapp/wcs/sto...0001_386901_-1 . Decisions, decisions.

BAH! Nevermind. Those ready-made inductors are 10 mm too big. The AMP9 close up bulk capacitors would get in the way.

Okay. Just found where my confusion over 0.6 mm vs. 0.7 mm came from. The Assembly instructions say 0.7 mm, changed from 0.6 mm, but the BOM still says just 0.6 mm.

[Jan]

Hi,

If you need more wire, let me know and I will send some...

Jan