Which TOA Amps Are These?
- Thread starterLes
- Start date
Amiers
Renting to Corporate One Fixture at a Time.
Peel the name plates and pull it out of the rack and check the underside.
Also, there is the top left that says MK2 are the amps connected if so TOA makes an MK2. I would guess a 900 series.
After 15 mins of searching.
https://www.ebay.com/p/TOA-Electronics-M-900mk2-8-Channel-Pre-amp-processor-Amplifier/1400107704
Also, there is the top left that says MK2 are the amps connected if so TOA makes an MK2. I would guess a 900 series.
After 15 mins of searching.
https://www.ebay.com/p/TOA-Electronics-M-900mk2-8-Channel-Pre-amp-processor-Amplifier/1400107704
Les
Well-Known Member
Thanks @Amiers . Wow, there are some deals to be had on eBay. Which is awesome since I have one dead unit and another with its Protect light on. I intend to inspect those amps more closely and make sure that at least the issue isn't further down the line (especially with the one in Protect Mode), but it's good to see that I can get cheap replacements.
There isn't anything in a mixer to protect, and the load it is driving can't hurt it. The protect light is probably just an indication that the power-up mute timer isn't working. It's a 5-second timer circuit to keep transients from the output when the unit is turned on and off. A dead electrolytic capacitor is the likely culprit.
Chances are you can bring both units back to life by replacing all the electrolytics, or at least those in the power supply and audio output sections. Is that rack rather warm? I don't like to see any equipment in a rack without a blank rack space above and below for air flow. Cooling is overlooked in too many installations. What is a necessity in a touring rack isn't proper in a permanent install.
Chances are you can bring both units back to life by replacing all the electrolytics, or at least those in the power supply and audio output sections. Is that rack rather warm? I don't like to see any equipment in a rack without a blank rack space above and below for air flow. Cooling is overlooked in too many installations. What is a necessity in a touring rack isn't proper in a permanent install.
Les
Well-Known Member
@FMEng - Thanks for the advice. You're probably right about the electrolytic capacitors. This is a 1995 install, so the timing would be about right.
Actually, these amps seem fine, though I did notice a lot of dust I will need to clean from the top unit. I'll likely need to pull the top cover and clean the inside too. The problem amps are up in the booth.
It's the bottom two in this picture:
Although ventilation looks good, I'll bet they need to be cleaned. I highly doubt anyone has done that in the history of this theatre.
Actually, these amps seem fine, though I did notice a lot of dust I will need to clean from the top unit. I'll likely need to pull the top cover and clean the inside too. The problem amps are up in the booth.
It's the bottom two in this picture:
Although ventilation looks good, I'll bet they need to be cleaned. I highly doubt anyone has done that in the history of this theatre.
@Les Just a thought on your 150 Ohm output tap. Long ago, before manufacturers began providing constant voltage output taps, some manufacturers provided a multitude of impedance taps. It's said: "You NEVER forget your first." My first was a dark brown and cream Stromberg Carlson from their pre grey finished days. The outputs were a pair of parallel wired 8 contact octal sockets with each providing one common contact and seven different output impedances. From memory, the output impedances were: 4, 8, 30, 60, 125, 250 and 500 Ohms. I tested them all but only ever seriously used the 4 Ohm tap. Up here, Hammond Manufacturing, in Guelph Ontario and nothing to do with the Hammond Organ Company, used to offer all manner of power and audio transformers including transformers to source and bridge your constant voltage output lines as well as a range of impedance matching transformers for folks running high impedance speaker lines.
Toodleoo!
Ron Hebbard.
Les
Well-Known Member
@RonHebbard - Thank you for that pearl of wisdom. I guess that begs the question, where is the 70v output? I checked one of the ceiling speakers that this is connected to and it has a 70v transformer (Atlas Soundolier tapped at 8w with remote volume control, for those playing along at home).
@Les Check your amp's manuals, they MAY list their taps both ways, constant voltage and impedance, in their manual but possibly only one way on their chassis graphics. Bogen used to have the low end of their output secondaries tied to ground but they also provided a link you could unbolt if you wished to run your output floating [Which MAY have only been legal at 10 and / or 25 volts.] In my mind, your NEC ALWAYS required one end of 70 volt lines to be bonded to ground. I believe I'm also recalling Bogen providing an option for grounding the center-tap of their 25 volt outputs. I never installed any balanced output installations. I THINK this may have been something your NEC liked to see in school installations.
Toodleoo!
Ron Hebbard.
@Les Page six of an on-line TOA manual shows detailed information for wiring their outputs. It lists info for constant voltage as well as impedances of the various output taps of a variety of modules. One model I remember reading was listed as having an 83 ohm output. I've attempted a 'cut and paste' of an on-line page for you but who knows what's going to materialize here when I key in Control V.
"Total impedance 83 Ω (A-706) 42 Ω (A-712) 21 Ω (A-724) 4 – 16 Ω COM 4Ω 25 V 70 V 70 V Line COM 4Ω 25 V 70 V 25 V LINE Total impedance 10 Ω (A-706) 5.2 Ω (A-712) 2.6 Ω (A-724) 25 V Line COM 4Ω 25 V 70 V 6.3. Remote Volume Control Connection Volume control 10 kΩ (linear-taper) MUTE CONTROL REMOTE VOLUME POWER REMOTE The external volume control can remotely adjust the signal level at post-master volume control. When performing the remote volume control, adjust the master volume control in advance noting that its setting limits the maximum signal level adjustable with the volume control. Be sure to avoid turning fully down the master volume control. Notes • Do not use both the 4 Ω, 25 V and 70 V terminals at the same time. • Impedances indicated in the figures represent the total speaker system (load) impedances. 6"
There you go, make of it what you can.
Toodleoo!
Ron Hebbard.
Robert F Jarvis
Well-Known Member
Amiers
Renting to Corporate One Fixture at a Time.
@Les A couple of comments.
1; I'm surprised that your transformer is dumping 8 Watts into one speaker.
2; When adding speakers to your 150 Ohm / 70.7 volt line, keep track of your total connected load. My personal 'rule of thumb' that lets me sleep nights is not to exceed 50% of the amp's output rating.
On one decent sized paging installation, the electro-acoustic PEng specified 70.7 volt output loads thus: Neither more than 50% nor more than 10 speakers per amp output channel. We pushed it to eleven on a couple of corridors rather than running another home run all the way down to the amp rack room in the second level basement.
It ended up being an excellent system, I'll elaborate a little:
All the front end was BSS Blue series.
There were 12 QSC four channel amps, 11 70 volt for 44 channels with 43 in use and one spare plus one low impedance amp for four channels with three of the four used leaving one spare channel. The architect was forever adding and removing speakers, often against the electro-acoustic PEng's wishes, thus we lost an exact count of installed speakers but there were well in excess of 400, mostly 8" cones but with one high ceilinged corporate room specified with eight 15" co-axials tapped at 25 watts per cone. There were also a number of extremely narrow width Bose columns specified in the multi-story lobby. There was a small amphitheatre within one of the lobby levels and it had a tall column of four or five of the narrow Bose columns in their 70 volt configuration. Elsewhere in the lobby there were 3 more of the narrow Bose columns installed as singles and they were our three low impedance channels. In the end, the whole paging system sounded very 'FM', clear, understandable, silent and click-free. It was a joy to pump CD's through when working overnight.
If you want to get into LARGE paging systems, with tons of zones and priority levels, talk to folks who install paging systems in large, international, airports.
Toodleoo!
Ron Hebbard.
Les
Well-Known Member
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:
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...
According to TOA:
- Three Models: A-903MK2 (30 W), A-906MK2 (60 W), A-912MK2 (120 W)
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...
Last edited:
teqniqal
Well-Known Member
The pictures presented by Les (the OP) were for the top two devices, which are only mixers (no power amp section, TOA M900MKII), so this was for the Line Level output (either 600 Ohm - Line Level, or 150 Ohm Mic Level), as this signal feeds a separate set of devices. This is also probably why they were not installed with a vent space between them - very little heat generated by a mixer.
As to Les' question about setting a delay for each of these zones, there are numerous DSP (Digital Signal Processor) products available in the marketplace that can provide signal delay. Many offer multiple In's and Out's, so if you need 4-12 delays for different signals you can insert a single DSP signal chain in the Mixer Out / Amplifier In insertion point of the Mixer/Amps. This also facilitates setting the EQ, Compression, and Limiting for that signal path. OR, if the whole system is getting long in the tooth, replace all the mixers with a multiple input / multiple output DSP and re-matrix all the signals with EQ, Delay, Compression / Limiting and even auto-mixing, then add a multi-channel 70V output power amplifier to replace all the amplifier sections. Two boxes, all done. The one convenience with the current set-up is that the volume controls are all analog and easy to understand -- if you convert to a DSP you may only be able to adjust it with a computer connected (which can be a blessing, or a curse). Some DSP products allow you to have analog potentiometers (usually 10K linear taper, but not always) to control internal gain / mixing points, but this requires you to fabricate a control panel with labeling for the knobs, so it can get a little pricey / labor intensive. The analog simplicty of the multiple TOA Mixers & Mixer / Amplifiers may be 'old school' to some, but it works and is easy to wire and service.
Side note: The broken / missing lenses for the push-buttons on the custom panel in the picture with the ClearCom KB-111 are all easy arts to source, and were either EAO or IDEC switches. The lamps inside the switches can be replaced with LED's, too (they were probably incandescent at the time of the install).
Les
Well-Known Member
Sounds like I've been misunderstanding this system the entire time. So these two components on the SM console are mixers and probably drive these amps in the booth. Guess I've been barking up the wrong tree.
Novice question: What is the difference between "Stage Page" and "Stage Program", and why is Stage Program duplicated on each amp?
@Les ; Purely as a guess: Stage Page is probably just what it sounds like, an input from a microphone, or paging output of the SM's ClearCom to "Page" the stage as in: "Attention ladies and gentlemen, places please for act one, act one beginners." Stage Program is probably an input from a monitoring mic, or monitoring mic mixer, feeding performance audio into the system for denizens of the various back stage areas who want to hear the production and follow along. Why is "Stage Program duplicated on each amp?"
Here'd be my guess: One ,mixer and / or amp MAY feed the lobby and / or public areas such as coat checks and washrooms. This system probably wants to hear the production in progress BUT NOT all of the mundane pages going on behind the scenes. The system including the pages likely doesn't cover public areas. Somewhere along the way a "God MIc" and / or a prompt mic may enter into it.
Toodleoo!
Ron Hebbard.
