Which TOA Amps Are These?

[Les]

@RonHebbard - that sounds like a very good guess. I've been involved with this theatre for about 15 years, with a hiatus between 2008-2012. In that time, they installed a new mixer and neglected to pay attention to this part of the system - hence my being clueless about the way it works. Even when it was connected, I doubt it was used properly. "Lobby Page" probably controls our Audience Recall Chime, though I'll need to test that theory.

 

[RonHebbard]

I might have to watch out on the power handling, if I only have 30w to work with -- or find a larger version of the same amp on eBay.

According to TOA:

• Three Models: A-903MK2 (30 W), A-906MK2 (60 W), A-912MK2 (120 W)

If @Chris15 's hunch is correct, that would make my amp an A-903MK2.

This is the speaker layout that exists:
• SL Wing (single in-wall speaker)
• SR Wing (single in-wall speaker)
• SL Corridor (Atlas ceiling-mount speaker)
• Scene Shop (single in-wall speaker)

This is my plan for additions:
• Greenroom (Bogen S810-T725 4-watt ceiling speaker)
• Dressing Room 1 (Bogen S810-T725 4-watt ceiling speaker)
• Downstairs Restroom/Shower (Rauland ACC1204A 5-watt wall-mount)
• Dressing Room 2 (Bogen S810-T725 4-watt ceiling speaker)
• Men's Restroom (Rauland ACC1204A 5-watt wall-mount)
• Women's Restroom (Rauland ACC1204A 5-watt wall-mount)
• Dressing Room 3 (Bogen S810-T725 4-watt ceiling speaker)
• Dressing Room Corridor (Bogen S810-T725 4-watt ceiling speaker)
• Stairwell (Bogen S810-T725 4-watt ceiling speaker)

Most likely, the restroom speakers will be tapped at less than 1-watt each. Not sure about the ceiling speakers, but probably closer to 2w each. I was going to opt-out of wall attenuators for the time being, as it's not in the current budget or timeframe. Each dressing room is about the same size, so proportional volume control shouldn't be too much of an issue unless one group is yakkin' more than the others. The greenroom does have a water fountain, mini-fridge, and microwave generating white noise, plus a door to outside, so I may need to tap higher to compensate for that.

I'll go through and pull the grills off the existing speakers to see what kind of load we already have on the amp. I could have sworn that Atlas was tapped at 8w, but I could be mistaken. Each of the existing speakers have remote attenuators, so I would imagine they are tapped to their highest potential at the transformer. If those other three speakers are tapped at 8w as well, this amp was overloaded during install, which obviously doesn't leave any wiggle-room for expansion. Of course, the main volume knob stays at about 12:00 so there is that...

@Les I understand what you're saying when you write "the main volume knob stays at about 12:00 so there is that..." but keep in mind the more transformers and speakers you parallel off the amp's output, the more you're loading it in the sense of closer and closer to placing a low impedance short across its output regardless of how loud you're turning it up. A shorted amp is NOT a happy amp even if you're not asking it to push out any signal.
Toodleoo!
Ron Hebbard.

 

[Les]

Good news @RonHebbard . I found the actual amp and it has a 120w capacity. I did some math and I should be coming in at around 50% of that once I put the additional speakers online. I'll be adding about 30w (max) to the system, and it has probably 32 watts (at most) already connected to it. That Atlas speaker is in fact tapped at 8w. And it is L-O-U-D.

It also already has ClearCom paging capabilities. Hurrah! I was going to add CC speaker stations to the dressing rooms, but I don't think that's necessary anymore. Two-way communication would be nice, but I don't think anyone would use it. Heck, I can't remember when they ever used the paging system they have now. Most probably don't even realize it can do that (including myself).

 

[RonHebbard]

Good news @RonHebbard . I found the actual amp and it has a 120w capacity. I did some math and I should be coming in at around 50% of that once I put the additional speakers online. I'll be adding about 30w (max) to the system, and it has probably 32 watts (at most) already connected to it. That Atlas speaker is in fact tapped at 8w. And it is L-O-U-D.

It also already has ClearCom paging capabilities. Hurrah! I was going to add CC speaker stations to the dressing rooms, but I don't think that's necessary anymore. Two-way communication would be nice, but I don't think anyone would use it. Heck, I can't remember when they ever used the paging system they have now. Most probably don't even realize it can do that (including myself).

@Les A 120 Watt amp with a single 8 Watt transformer and speaker. I guess it's safe to say headroom's not an issue, at least not when it was initially installed.
Toodleoo!
Ron Hebbard.

 

[Les]

I recently had the opportunity to dig in to the dead TOA mixers. It was interesting. Each one of them had multiple issues with the main amplifier PCB. Notably, the large resistors had presumably reflowed their own solder joints and had fallen through their holes. Many of the other solder joints also looked suspect, with what appeared to be the start of ring cracks around most of them.

I reflowed both boards, and added additional solder to many of the components. That seemed to make one of the amps happy again and it has survived multiple shows. The other blew its fuse immediately after starting, so I will be planning on replacing it entirely.

One other thing I noticed just tonight was that when the sound system was powered down, one of the amp's green power LEDs stayed on but in a dimmer state. I initially thought this was because there are some capacitors inside that could power the LED for a while, but now I think it's possible that the relay controlling that part of the cabinet could be to blame. I will need to meter it tomorrow. If the amp is continuously getting some low trickle voltage, that certainly isn't good and could possibly even explain why the amps have problems in the first place.

The irony is that the amp showing a "protect" light is the one that refused to come back. The completely dead one sprung back after resoldering the components and even adding a solder bridge to bypass a lifted solder pad.

Luckily these 120w TOA amps can be picked up off eBay for less than $100. I'll try to have them buy at least one. The cool thing is that they sometimes come with input modules, which I suppose might be handy.

 

[Les]

Update: I metered the power and it was a steady 123v. I guess it was my own bias suggesting that the "power" LED was dimmer than normal. Everything is all on one installed power strip in the amp rack, but the top two plugs appear to be constant power - probably for a worklight or something like that. In any event, I got it sorted and a "new" amp is on its way. I'll bury the dead one later.

One more positive side to getting these amps working is that I've discovered the audience recall chimes ring through the greenroom and dressing rooms, which is handy. The last two SM's have also really enjoyed calling "places" via ClearCom.