Inside an ATC SCM100ASL

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ThomasOK
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Inside an ATC SCM100ASL

Post by ThomasOK »

Rather than tie up the interesting JBL 3677 thread I thought I would start a new thread about this. Since it is about what is literally inside an ATC 100 it actually fits very well in this category. As mentioned elsewhere I have procured passive ATC 100 crossovers in order to evaluate the difference between active with the built in ATC amp/crossover module and passive using Tundra Mono 2s. If the Mono 2s are indeed the most musical amps currently available, which has so far been my experience, then the hierarchy states that the ATCs should be more musical passive. Unless, of course, the ATC amps are much better than many people, myself included, suspect. It should be an interesting comparison.

The passive crossovers are quite massive and came with their own set of aluminum back plates with 6 rather solid five-way binding posts. There are three pairs of wires going both into and out of the crossovers so you can triple-wire or passively multi-amp them if you choose. There are also bridges for double or single wiring. When I first got the crossovers I had this grandiose idea of putting the crossovers and the ATC amp packs (which are also quite massive) each in their own wooden boxes, wiring the drivers direct to the new plates and triwiring form either the external crossovers or the amps. However, after considering the fact that I would have to modify the speaker cabling and the wiring from both the crossover and the amp packs, get four really big wooden boxes, fasten the units in them and solder a whole bunch of banana jacks to them all I decided against it for the time being. This decision was made easier by the fact that ATC uses a pretty solid 6 pin plug and socket to connect the drivers to either the amp pack or the passive crossover. So to swap them you remove 8 bolts and pop out the amp pack, then pop in the passive crossover and attach the other panel and vice versa to swap them back. It also means I can keep everything stock in case I end up wanting to sell the ATCs (I admit a not completely unlikely result considering all the hoopla about the 3677s).

Once they are passive it also makes it easier to compare them to the JBLs or the Isobariks if I desire. So there is no end to the loudspeaker fun I will be able to have. (That is if you consider hauling around three different pairs of speakers all weighing between 84 and 143 pounds each fun!) Should I end up preferring the ATCs passive over the JBLs I can always do the external crossover mount and internal speaker rewiring later on.

Since I have mentioned that these ATC parts are massive I thought you might enjoy a couple of photos to illustrate it.

First the passive crossover:
Image

And then the active amp pack:
Image

To give you an idea of the size the passive crossover is 14" long and 8.5" wide. That big coil you see in the upper right with the "4" on it is 3" tall and 3" in diameter. I would guess that by itself that coil might weigh as much as the entire 3677 crossover. As you can see ATC doesn't exactly scrimp on parts. (Not that there is any guarantee of musical quality because of this.)

The amp pack has the 3-way active crossover and three power amps all on that board and powered by that rather massive transformer. The amps are rated at 200 watts, 100 watts and 50 watts continuous (woofer, mid and tweeter respectively).

All of this shows ATCs typical heavy duty build quality which, I'm sure, endears them to studios as the stuff plays quite loud and basically doesn't break. How will it do in battle with the 3677s we will find out in about a month. In the meantime I will let everybody know the active vs. passive findings when I get a chance to do them.
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Re: Inside an ATC SCM100ASL

Post by anthony »

Considering I prefer 350P by a significant amount to the 350A,
I would be surprised if your findings were not for the passive ATC.

Look forwards to see if you confirm the same!
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Re: Inside an ATC SCM100ASL

Post by Charlie1 »

Yes, looking forward to reading about your findings. How long do you think the passive crossovers will take to run-in? Mind you, if you prefer passive to active from day one then it doesn't really matter.
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Re: Inside an ATC SCM100ASL

Post by lejonklou »

Interesting experiment. Most likely the differences will be very big, as so many things change at once. Active to passive and two completely different power amps.

The massive passive filter had me thinking of the later passive filter for Linn Kaber. Similar to this one it had air wound inductors and giant plastic film capacitors. The late Kaber filter also had a very detailed and "audiophile" sound. I always felt that although impressive, it wasn't 100% right and seemed to loose some of the ease of the original filter with much less expensive components.

One detail on this ATC passive filter is that the inductors are all facing the same way. This makes their magnetic fields interact and normally one positions them at right angles to one another to minimise this effect.
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Re: Inside an ATC SCM100ASL

Post by ThomasOK »

lejonklou wrote: One detail on this ATC passive filter is that the inductors are all facing the same way. This makes their magnetic fields interact and normally one positions them at right angles to one another to minimise this effect.
Interesting, I wasn't aware of that. I suppose that is why they spaced them as far apart as possible. I do doubt the differences will be subtle.

Charlie1, these crossovers are used so they should already be well burned in.
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Re: Inside an ATC SCM100ASL

Post by More wants more »

Follow this topic with interrest. I have "Christian's" old ATCs and they served me well, but It would be great if it possible to upgrade them.
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Re: Inside an ATC SCM100ASL

Post by Azazello »

Ashley, you need to read the forum rules as well as learn some general manners. This is not a place for you. Posts deleted because we want this forum to be a database of knowledge, not "debate".

Questions about moderation in PM please, not in this thread.

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Re: Inside an ATC SCM100ASL

Post by vintageaxeman »

Hi folks.

I have been working on some ATC gear recently....namely SCM150ASL parts....the 15" SuperLinear bass unit, the Superdome 150S Midrange, ATC's own tweeter and the active AmpPack's.

I thought anyone interested in this thread might like to know of my experience...

I was planning to replace the (rather ordinary) cables between the amp-pack and the drive-units in my ATC speakers.

I was therefore trying to find out what connectors ATC actually use in their speakers and on their amp pack circuit boards. I discovered (with a magnifying glass and a look for confirmation on the RS website) that they are made by ITT Cannon.

After a bit of searching, I found them....(ITT-Cannon type 192923, RS Reference 466-731) So, you can get spares from RS to experiment with. You DO have to buy them in multipacks though...and the pins are separate items. The main trouble is, the ITT Cannon connectors won't take cable much thicker than the stock cable, which I think is 1.5mm.

BUT...the big news....
I had spotted something on the Amp Pack circuit board. (mine are Amp Pack12s...)

There are 6 ¼" male spade connectors soldered onto the circuit board....marked bass+, bass-, mid+, mid-, treb+, and treb-. Because the circuit board is bolted down to the heatsink with a multitude of bolts through the power transistors, you cannot trace the circuit board tracks on the rear of the PCB without undoing these, to confirm that these are connected in parallel with the ITT multiconnector. Nor can you trust a multimeter, as the readings are all so low as to be indistinguishable.

So, with a bit of help from an ATC retailer, we contacted ATC who confirmed that these fixed tags are connected in parallel to those on the ITT Cannon connector. And ATC's R&D guy told us that you CAN therefore use these tags as an alternative for connecting speakers, thereby allowing experimentation with thicker or different cables.

So it's really easy to experiment now.

Also...If anyone is interested, I bought several packs of the ITT connectors and the pins....and still have a few spare....just send me a PM if you want to buy a set off me....
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