I'm a firm believer that bwiring has done nothing for me. Maybe I did it wrong. However Tom mentions biamping. I could easily add that since my outboard 3way xovers are already separated into three filters. I'd just have to add a second set of binding posts to each outboard enclosure. And in my next Mod86 build use 4 Mod86s in a larger enclosure.
Is there a consensus that an amp for the woofer and an amp for mid and tweeter really make a significant difference. I've found speaker position and room treatment have given the most bang for the...wait nothing.
Is there a consensus that an amp for the woofer and an amp for mid and tweeter really make a significant difference. I've found speaker position and room treatment have given the most bang for the...wait nothing.
Ideal? I guess that depends on the ideal. With that said, if he's content with the crappy amp he has now then a newer, better performing amp would be welcome. I've used my Mod86 with a Super MMG with 2 DWMs setup for awhile and because my music peaks never go above 90dB, I've never had a problem. Unless your dad is rocking out at an 85dB average listening level in a large room, I would find it implausible he would run in to any power related problems.
Magnepans are about as close as a loudspeaker gets to performing like a resistor as far as the amp is concerned. In that aspect, they are a very benign load. The Mini-Maggie/Parasound anecdote relayed earlier in this thread is bizarre. FWIW here are some electrical damping measurements I did awhile back comparing the MMGs vs. a couple cone speakers. It's one aspect that demonstrates how "unreactive" magneplanars are:
MMGs
Cone speakers
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Beginner’s soldering question. The Cardas binding posts I bought have two posts in a plastic frame. Each post solder cup has a 1/8” Dia. through hole. I’m guessing that is to run the wire through the hole against the outer diameter of the post. That would allow heating the wire and post body at the same point on the outer diameter. That should make both the body and wire hot enough to solder the wire to the inner diameter of the post. Is that correct? I plan on tinning the wire and inner diameter of the post. I thought it would not be appropriate to put the solder tip against the wire and inner diameter of the post, where solder will flow.
Tinning the wire is optional. Tinning the solder cup is not necessary. I'd strip the wire, twist it, and stab it through the hole. Then solder. I generally find that resting the tip against the solder cup and up against the wire heats up the joint nicely. Be prepared to feed a fair amount of solder into the joint. Watch the insulation on the wire. You don't want it to start shrinking from the heat.
Tom
Tom
Thanks Tom. Do you mean you position the soldering iron tip against the wire and the outer diameter of the solder cup were the wire sticks out of the hole? Or do you just put the tip in the cup and against the wire?
Sorry for such a basic question.
Sorry for such a basic question.
Just made my first attempt at winding an inductor. It was rubbish. Far too much space between the windings. Hopefully my second attempt will be better.
I don't know as I would call it "bizarre". I was quite surprised, admittedly. Nevertheless, it occurred multiple times with that amplifier. Now there is nothing to say that there isn't something funny going on with that amp. It is getting on in years and hasn't had a thorough check-up since leaving the factory...
I like using the inner diameter of the solder cup to rest the solder tip in. That maximizes the contact area between the tip and the solder cup. Make sure you touch the wire as well.
It doesn't matter if you do it one way or the other. The objective is to get both the solder cup and the wire heated to the point where they'll melt the solder. Then add solder and remove the heat. Keep everything still until the solder is completely solidified. The end result should be a smooth and shiny cone draping up the wire. The end result is the important part. How you get there is up to you. Many roads lead to Rome.
Tom
Thanks I like the idea of putting the tip in the cup and against the wire...more focused, quicker, heating. From all the "learn how to solder" sites I got the usual contradictory answers.
To get a "good process recommendation" I sent Kester an email and one of their engineers sent me a reply asking me to call him to discuss what I was doing. Very nice guy and he recommended the tinning, then heating from the outside and once the tinning melted, adding a bit more solder. He said tinning the cup would dissolve the very thin layer of gold plating thus avoiding any embrittlement.
Also most of the youtube videos, some made by solder manufacturers, showed the tinning and heating from the outside.
Bottom line is I'm doing it your way. One can't argue with success.
To get a "good process recommendation" I sent Kester an email and one of their engineers sent me a reply asking me to call him to discuss what I was doing. Very nice guy and he recommended the tinning, then heating from the outside and once the tinning melted, adding a bit more solder. He said tinning the cup would dissolve the very thin layer of gold plating thus avoiding any embrittlement.
Also most of the youtube videos, some made by solder manufacturers, showed the tinning and heating from the outside.
Bottom line is I'm doing it your way. One can't argue with success.
I know I over engineer things but can't help it. I've got the time, the machine shop and my compulsive disorder to make things as perfect as I can. The heatsink surfaces, where the chips will mount, have been lapped flat w/in .00002. I'm tempted to do the same to chip mounting surfaces. I really like doin things like this. Is there some coating, on the chip faces, that I shouldn't mess with? It would be very easy to make the chip mounting surfaces flat w/in <.00005. Probably 10 minuets.
I believe the DAP is tinned copper. There's no other coating to worry about. I guess there are worse things to geek out about, but I wouldn't worry about the surface roughness of the DAP. If it was an issue that affected chip reliability National or TI would have done something about it. That said, I also see no harm of smoothing out the surface as long as you're confident you can make it flat.
Tom
Tom
I routinely surface grind package mounting tabs....old habit.
I have a 2cm thick slab of glass, and to this I place a wetted sheet of fine wet and dry.
A few rubs and any high spots are gone.
Dan.
If you are running at the bleeding edge then you can gain an extra watt or two of dissipation, but at that juncture you would be better off changing the way you do the heatsinking and having a 'live' spreader under the chip. And yes I have considered that approach 🙂
How are these thermal pads? Help in heat conduction for slightly uneven surfaces?
4180G Aavid Thermalloy | Mouser
4180G Aavid Thermalloy | Mouser
These are a hard insulator (and brittle).
You need thermal goop on both sides like Kapton and mica.
The thickness is stated as 80thou (0.080" 2.03mm) this is ~ 80 times thicker than 1thou mica.
Mouser's datasheet doesn't give any thermal data to be able to compare thermal performance.
You need thermal goop on both sides like Kapton and mica.
The thickness is stated as 80thou (0.080" 2.03mm) this is ~ 80 times thicker than 1thou mica.
Mouser's datasheet doesn't give any thermal data to be able to compare thermal performance.
Ever finding things to argue about/contradict, eh Bill....it does get wearisome.
IME it is worth the 15 seconds to ensure that heatsink and devices are free of bumps, burrs and other defects.
I have repaired equipment where a minor burr/defect caused punch through failure of silpads and/or lousy thermal coupling causing failure of devices.
Not chasing 'bleeding edge', just long term reliability.
One thermal advantage of 'upside down' discrete OPS topology is direct mounting of devices to chassis isolated heatsink.
Dan.
Not arguing with you. Was not even responding to your post. Why are you so sensitive this morning?
Knocking the bumps off is one thing. Lapping to a mirror finish is another, which was where my comment was focussed. It makes sense if you are keeping the tab live to a spreader, but not if you are then putting a washer in between as that blows any gain.
Knocking the bumps off is one thing. Lapping to a mirror finish is another, which was where my comment was focussed. It makes sense if you are keeping the tab live to a spreader, but not if you are then putting a washer in between as that blows any gain.
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So I had another go and managed to produce 2 inductors that I deem to be as good as I'm ever going to make them. ( Can't compete with UncleJoe's). Anyway FWIW to any other non- dexterous types like me and who might similarly struggle, this is the method I employed. For the former I cast about the garage and house and came upon a wooden ladle amongst my kitchen utensils that had a round handle. The diameter was a little too thin so I wrapped some gaffer tape around it. I then clamped it firmly to a work bench with the handle protruding off the edge. I then cut a notch across the end of the handle that I could slide the end section of the magnet wire into and that would hold it in place. I then pulled hard on the wire to tension it and proceeded to wrap it around the handle. Initially I used pliers to hold the wire but I actually found it easier to just hold it with my hand whilst wearing a grippy work glove. It's probably an obvious thing to say but using wire that is kinked is a non- starter; the straighter the better.
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If the LM3886 has burrs, bumps, flash, etc. beyond what's specified in the data sheet, you should send it back to TI.
I agree that you should check that the surfaces are smooth. If there are any burrs, nicks, or bumps on the heat sink, remove them. There is no reason to polish everything to a mirror finish, however. I mean... If that's your hobby, you enjoy it, and can actually obtain a mirror finish more power to you. Have at it. Just note that it won't make a bit of difference. At least not in my circuits. I would never ever design a circuit that required you to sand the bits to a mirror finish before assembly. I don't operate that close to the edge. Ever.
Tom
I recall someone posting pics of a LM3886 (or LM3875?) all chopped up with a hacksaw or Dremel cutoff wheel, mainly to find out exactly where the plastic, metal and chip all are in relation to one another. I forget exactly why, the idea might have been to see how much one could sand down the plate before getting to the silicon, in an effort to reduce the thermal resistance that extra little bit.
I looked and didn't find the thread. This is a different one I haven't seen before, someone cutting the tab off to mount the chips in a smaller space:
http://www.diyaudio.com/forums/chip-amps/114806-cutting-off-piece-lm3886-yes-saw.html
Needless to say (or maybe not!), this sort of thing totally and completely voids any warranty on these chips. If you really want to do this, you might test the chips BEFORE
doing any of this so if they're bad afterward you know it was your doing.
I looked and didn't find the thread. This is a different one I haven't seen before, someone cutting the tab off to mount the chips in a smaller space:
http://www.diyaudio.com/forums/chip-amps/114806-cutting-off-piece-lm3886-yes-saw.html
Needless to say (or maybe not!), this sort of thing totally and completely voids any warranty on these chips. If you really want to do this, you might test the chips BEFORE
doing any of this so if they're bad afterward you know it was your doing.