old altec amps

[Rob 515]

A 70V system is not constantly 70V. The 70V system output looks just like any other power amplifier. 70V is the constant in calculating power taps.

70V speakers have transformers. Usually these transformers have four power "taps" or step-down windings.

1W transformer tap connected to 8 ohm speaker = 5000 ohms [(70.7V x 70.7V)/1W]
5W transformer tap connected to 8 ohm speaker = 1000 ohms [(70.7V x 70.7V)/5W]
30W transformer tap connected to 8 ohm speaker = 167 ohms [(70.7V x 70.7V)/30W]

70V loads (speakers with transformers) are paralleled to each other. Add the power taps and connect a 70V power amplifier 20% bigger (or more). It is perfectly OK to drive a single 5W load (loudspeaker with transformer tapped at 5W) with a power amp capable of 240W @ 70V. The amplifier does not care. It is not OK to connect ten loudspeakers tapped at 30W (300W total) to a power amp rated at 240W @ 70V.

one 2271 is rated at 75W into 66.6 ohms [(70.7V x 70.7V)/75W]
two 2271s are rated at 150W into 33.3 ohms [(70.7V x 70.7V)/150W]
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eight 2271s are rated at 600W into 8.3 ohms [(70.7V x 70.7V)/600W]

You could drive an 8 ohm loudspeaker, or a couple of loudspeakers wired for an 8 ohm load, with the full compliment of a 2280 (8 x 2271). However, there are lots of easier power amplifiers to use.

"A 70V system is not constantly 70V. The 70V system output looks just like any other power amplifier. 70V is the constant in calculating power taps."

This is the part that I seem to be having a hard time understanding.I didn't know that a 70V system output looks just like any other power amplifier. So if I connect just one 8 ohm load (one loudspeaker) to the one 600 watt 8 ohm output of the amp then I shouldn't need a step down / line matching transformer? Is this correct? Only if I want to connect more than one loudspeaker to one 8 ohm output of the amp , say two or more in parallel, then I will need the step down / line matching transformer?

"70V speakers have transformers. Usually these transformers have four power "taps" or step-down windings".

My speakers aren't 70 volt from the factory, but I do have some 80 watt 70 volt transformers I could use one for each speaker. But if I am using only one 8 ohm load (one 8 ohm speaker) on one 8 ohm output of the amp (eight 2271 combined) do I still need the transformer at the speaker?

1W transformer tap connected to 8 ohm speaker = 5000 ohms [(70.7V x 70.7V)/1W]
5W transformer tap connected to 8 ohm speaker = 1000 ohms [(70.7V x 70.7V)/5W]
30W transformer tap connected to 8 ohm speaker = 167 ohms [(70.7V x 70.7V)/30W]

"70V loads (speakers with transformers) are paralleled to each other. Add the power taps and connect a 70V power amplifier 20% bigger (or more). It is perfectly OK to drive a single 5W load (loudspeaker with transformer tapped at 5W) with a power amp capable of 240W @ 70V. The amplifier does not care. It is not OK to connect ten loudspeakers tapped at 30W (300W total) to a power amp rated at 240W @ 70V."

SO... if I'm not going to parallel several speakers onto one output of the amp then I shouldn't have to use the step down /line matching transformer? correct?

one 2271 is rated at 75W into 66.6 ohms [(70.7V x 70.7V)/75W]
two 2271s are rated at 150W into 33.3 ohms [(70.7V x 70.7V)/150W]
three
four
five
six
seven
eight 2271s are rated at 600W into 8.3 ohms [(70.7V x 70.7V)/600W]

You could drive an 8 ohm loudspeaker, or a couple of loudspeakers wired for an 8 ohm load, with the full compliment of a 2280 (8 x 2271). However, there are lots of easier power amplifiers to use.

The reason I have all amps (8 x 2271) paralleled is so the output is 8 ohm, because if I split the amp into 2 channel of 300 watts ( 4 x 2271) + (4 x 2271) then the outputs would be 16 ohms and my speakers are 8 ohms.

I have 2 of these amps 2280A and each is set for 600 watts (8 x 2271) so if I connect one 2280A to one speaker and the other 2280A to the other speaker and connect left channel of preamp into one 2280A and right channel of preamp into the other 2280A then I should be able to connect one speaker 8 ohm with no transformer to each 2280A. Is this correct?

I think I get what you are saying about overkill and I guess if a person is not going to connect a string of speakers in parallel then he probably don't need this type of amp or this many watts.

thanks for your help

[whitebroncoii]

"This is the part that I seem to be having a hard time understanding.I didn't know that a 70V system output looks just like any other power amplifier. So if I connect just one 8 ohm load (one loudspeaker) to the one 600 watt 8 ohm output of the amp then I shouldn't need a step down / line matching transformer?" Correct

"Only if I want to connect more than one loudspeaker to one 8 ohm output of the amp , say two or more in parallel, then I will need the step down /line matching transformer?" Correct again, if the speakers are 8 ohms. BTW; a line matching transformer is used to match line level impedance, not 70V distributed systems.

"SO... if I'm not going to parallel several speakers onto one output of the amp then I shouldn't have to use the step down transformer?" You need to load with 8 ohms. This could be two 16 ohm speakers in parallel. You could also series two 8 ohm speakers (for 16 ohms) and configure half the 2280 (300W) for this 16 ohm load.

"I have 2 of these amps 2280A and each is set for 600 watts (8 x 2271) so if I connect one 2280A to one speaker and the other 2280A to the other speaker and connect left channel of preamp into one 2280A and right channel of preamp into the other 2280A then I should be able to connect one speaker 8 ohm with no transformer to each 2280A." Correct

[Old Guy]

If I could expand, a 70 volt amp output looks just like a regular amp. but the voltage is shifted higher.

Adapting a regular amp circuit would require a transformer to "step up" the voltage.

Some solid state engineers got an idea to simply design an amp capable of operating at that voltage.

From a cost standpoint the transformer is then not needed.

Generally though such amps will only load to 8 ohms, the output stage is designed for higher voltage, not higher current as needed by lower impedance designs.

I wasn't clear on exactly what you were asking.

[Rob 515]

Thanks to you both for all the help. I really appreciate it. I plan to get this all set up soon and will post an update on how it sounds.
I may just use the jbl's with the Altec amps and theater project and use the altec A5's for a tube amp stereo. I said A7 earlier they are actually A5 with 500hz crossovers and Montaray horns.
thanks again
rob

[Rob 515]

"This is the part that I seem to be having a hard time understanding.I didn't know that a 70V system output looks just like any other power amplifier. So if I connect just one 8 ohm load (one loudspeaker) to the one 600 watt 8 ohm output of the amp then I shouldn't need a step down / line matching transformer?" Correct

"Only if I want to connect more than one loudspeaker to one 8 ohm output of the amp , say two or more in parallel, then I will need the step down /line matching transformer?" Correct again, if the speakers are 8 ohms. BTW; a line matching transformer is used to match line level impedance, not 70V distributed systems.

"SO... if I'm not going to parallel several speakers onto one output of the amp then I shouldn't have to use the step down transformer?" You need to load with 8 ohms. This could be two 16 ohm speakers in parallel. You could also series two 8 ohm speakers (for 16 ohms) and configure half the 2280 (300W) for this 16 ohm load.

"I have 2 of these amps 2280A and each is set for 600 watts (8 x 2271) so if I connect one 2280A to one speaker and the other 2280A to the other speaker and connect left channel of preamp into one 2280A and right channel of preamp into the other 2280A then I should be able to connect one speaker 8 ohm with no transformer to each 2280A." Correct

Thanks for the info.
I have another question about these amps if you have time. I am wondering if I can come out of the preamp outputs on a regular 5 channel Yamaha or Denon home theater processor and into these? Going from the pre-out RCA output on the home theater digital processor to the RCA input on the amp (I HAVE CABLES MADE UP FOR THE SPADE INPUTS ON THE AMP TO CONNECT TO RCA TYPE PREAMP OUTPUTS). One RCA out to each 2280A input. I'm wondering so if I decide to add more amps and rear and center speakers to this. I know I can physically connect it, but not sure about modern digital processor output impedance and vintage 2280A input impedance. Each 2280A has one 15335A transformer installed which is 15k:15k. Is this the correct transformer I have in them or do I need a different transformer to connect to modern gear like the yamaha processor? Or do I even need the plug in transformer at all? All of the other transformer sockets have 2 straps in them. I don't know about 600 ohm or 15k ohm input and output impedance or any of that.
thanks again for all the help
rob

[Rob 515]

Nobody knows? Could someone point me in the direction of output and input impedance on vintage verses modern gear. Not speaker and speaker tap impedance, but the line input and output impedance. Balanced and unbalanced. I want to connect some gear (newer preamp to vintage amp) but don't want to blow anything up.
tanks!

[bfish]

...Could someone point me in the direction of output and input impedance on vintage verses modern gear. Not speaker and speaker tap impedance, but the line input and output impedance. Balanced and unbalanced. I want to connect some gear (newer preamp to vintage amp) but don't want to blow anything up.
tanks!

There's far less difference between vintage and new gear in that regard (line level connections) than there is between consumer and pro gear. The generic basics;

consumer - unbalanced
pro - balanced

Line level @ 0dB
consumer (other than phono) - 0.7V
pro - 1.0V

Line impedance for interconnect
consumer (other than phono) - 15K ohm
pro - 600 ohm

You can generally get by directly connecting low(er) Z outs to equal or high(er) Z ins. Going the other way can be problematic. Remember this when you start to freak out over matching xfmrs...

Rane's tech library holds all the details;

Library

Speaker level connection is a different story, but the guys here pretty well covered that.

[Rob 515]

There's far less difference between vintage and new gear in that regard (line level connections) than there is between consumer and pro gear. The generic basics;

consumer - unbalanced
pro - balanced

Line level @ 0dB
consumer (other than phono) - 0.7V
pro - 1.0V

Line impedance for interconnect
consumer (other than phono) - 15K ohm
pro - 600 ohm

You can generally get by directly connecting low(er) Z outs to equal or high(er) Z ins. Going the other way can be problematic. Remember this when you start to freak out over matching xfmrs...

Rane's tech library holds all the details;

Library

Speaker level connection is a different story, but the guys here pretty well covered that.

Thanks! I want to connect a consumer preamp into a pro amp, but the amps (altec 2280A) have 15335A input transformer (15k:15k) so should be a perfect impedance match.... you think?
thanks
rob

[whitebroncoii]

Thanks! I want to connect a consumer preamp into a pro amp, but the amps (altec 2280A) have 15335A input transformer (15k:15k) so should be a perfect impedance match.... you think?
thanks
rob

I will gently disagree with bfish on a couple points;

Line level for professional Altec Lansing stuff was 0 dBu (0.775v).
This points out that you need to always check the gear's specs

Impedance matching was critical a couple of decades ago. "Matching Transformers" were needed once upon a time. Today we select an input or an output transformer. They will usually be 1:1 (15k:15k, 10k:10k, 600:600). This 1:1 ratio means that what you connect across the secondary windings is pretty much what you see on the primary windings. Because transformers have no impedance of their own, the input/output selection is needed simply to handle a little more current on the output.

Voltage transfer is the goal for most of the gear you are messing with. Good voltage transfer needs better than a 1:10 impedance ratio. Your 2280 inputs are 15k ohms with or without the input transformers. A good source impedance would be less than 1.5k ohms. The source impedance of most pro gear is listed as "600 ohm". This is not really the impedance, it is the maximum rated load. Actual source impedance of pro gear tends to be at or below 100 ohms.

[Panomaniac]

Yes, very much agree with the above. :2thumbsup: