Stephens Phase Linear 400--In for the works.

laatsch55

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Bridging a WOPL 400 would get you 1600, yes. But it wouldn't live. You could only drive an 8 ohm load. The Macs get by with driving a 4 olm load due to it's output transformer. Distortion in a quasi would also double or quadruple. It's a very dirty way to to get more power. Bob Carver tried it in the beginning, in fact there were 4 bridge amps manufactured (not sure on the number) when the outputs only totaled 4 per row like the 400's. They went to 6 per row after serial #5 IIRC. Very unreliable.
 

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Bridging a WOPL 400 would get you 1600, yes. But it wouldn't live. You could only drive an 8 ohm load. The Macs get by with driving a 4 olm load due to it's output transformer. Distortion in a quasi would also double or quadruple. It's a very dirty way to to get more power. Bob Carver tried it in the beginning, in fact there were 4 bridge amps manufactured (not sure on the number) when the outputs only totaled 4 per row like the 400's. They went to 6 per row after serial #5 IIRC. Very unreliable.
Ok, gotcha. So your also saying 400s can't be used as mono blocs right or can you? I thought when you bridge an amp, your just combining the two channels into one mono signal. So how far am I off with that theory? I was hoping I could run both WOPL's as monoblocs but that seems to not be possible then. I can still use one amp for each speaker though by going off the left channel + and the right channel - right? I am lost again because that make it a monobloc though right? Time for some schooling for me Lee

I found this online

Basically, one channel's signal is inverted, and then the two channels are combined to form one channel with twice the voltage of either of the original channels.

Ohm's Law for Alternating Current states that I = V/Z where I is current, V is voltage, and Z is impedance. We also know that P = IV, where P is power. If we use Ohm's Law and substitute into the power equation, we get P = V(V/Z), which can be rewritten as P = (V^2)/Z. Therefore, power is the square of voltage divided by impedance.

Now, why do we care about all that? Because it explains precisely what happens when an amp is bridged. I'll give a practical example and explain the theoretical basis of that example.

Imagine you have a two-channel amp that puts out 50 watts into each channel when driven into a load of 4 ohms per channel. Since we know P and Z, we can plug these numbers back into our power equation and find V. 50 = V^2/4 -> V = sqrt(200). So, we're seeing a voltage of 14.1 volts across each channel.

Now, imagine we bridge this amp, and use it to push just one of those 4 ohms loads. When the amp is bridged, the voltage is doubled. Since we know the voltage (2*14.1 volts), and the impedance (4 ohms), we can calculate power. Remember that P = V*V/Z. That means P = (28.2)^2/4, which is 198.1 watts. It should be clear by now that the new power is approximately 200 watts - quadruple the power of a single, unbridged channel!

You can probably see that should be the case, especially if you look back at the power equation. Since P = V*V/Z, if you double V, you quadruple power, since V is squared in the power equation.

Now, all this assumes the amp is stable into 4 ohms mono. The mono channel is putting out four times as much power as a single unbridged channel, so it must be putting out twice as much as the two single channels combined. Since the voltage on the supply side of the amp is dependent on the car's electrical system, it doesn't change (OK, the increased current might cause a voltage *drop*, but let's not worry about that now). Looking at the first power equation, at the supply side of the amp, we see P = IV. Now, when we bridged the amp, we doubled the power, but the input voltage stayed the same. So, if we hold V constant, the only way to double the power is to double the current

I also understand that impedence is only a speaker thing now. I just wonder why there is 4ohm specific amps then
 
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Northwinds

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Would a different tranny allow bridging of the PL amps then Lee. I have a couple huge Drakes from Marshall amps buried in the garage. I think I also have a Mercury Magnetics out there somewhere. They allow loads of 4-16ohms
 
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laatsch55

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And the power supplies have to be able to support the additional current needed. Power is proportional to the square of the voltage. Thus if the voltage is doubled into a given load, power is quadrupled. Power=watts, Watts =volts X amps, thus if the volts are doubled so is the current . There is where the problem lies. Think about sticking a 16 amp fuse where you stick the 8's now. Power supply has to be twice as big TO DELIVER THE SAME LOAD TO 4 oHMS, but an amps design in consumer applications isn't even designed to handle full rated music ouput because music is never a steady state, it's constantly going up and down so transformers are undersized relative to full continuous load.

In bridged mode I have no doubt the Macs can get around 400. Mac derated bridged operation to be able to advertise bridged mode into 2 ohms......
 

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Yes they would Ron, but you still cannot escape the physics of bridged operation. Sure you could blow up any speaker made but it's gonna sound terrible to what we're used too. All the bad habits of the amp are gonna quadruple too. Noise, distortion, SNR would suck, Freq response is going to suffer due to power supply constraints.
 

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I wonder why my Yorkville amp only gives me figures for a 4ohm load when in 2 ohm mode. It shows N/A for a 4ohm load in 4ohm mode and show N/A across the board for a 2 ohm load in 4 and 2ohm mode.
 

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Yes they would Ron, but you still cannot escape the physics of bridged operation. Sure you could blow up any speaker made but it's gonna sound terrible to what we're used too. All the bad habits of the amp are gonna quadruple too. Noise, distortion, SNR would suck, Freq response is going to suffer due to power supply constraints.
Thanks for explaining Lee. These WOPL's are already insanely powerful and beautiful sounding. I guess I can use each amp to run a set of speakers since my preamps have multitple outs. I will be more then content but I pity my neighbors LMAO
 

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Of O had time to experiment I woud bridge a stock PL 400 and then video the amp blowing up. Cause if you push it it will. It can't help it.
 

BubbaH

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I guess I can use each amp to run a set of speakers since my preamps have multitple outs.
Thats what I do. One day I hope to double that and go full quad with 4 speaks up front and 4 out back. Also utilizing 4 amps.
 

laatsch55

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You don't need multiple pre outputs to drive multiple amps. Get a Y connector, drive 4 amps if ya want. Most pre amps are perfectly capable of driveng multiple amps. We're talking line level here. 100-200mv at less than 1/2 amp...


Ben , where your spec sheet says N/A, the amp cannot be driven in that scenario. And I see RMS nowhere, do not know wht BCD rating means.
 

BubbaH

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You don't need multiple pre outputs to drive multiple amps. Get a Y connector, drive 4 amps if ya want. Most pre amps are perfectly capable of driveng multiple amps. We're talking line level here. 100-200mv at less than 1/2 amp...


Ben , where your spec sheet says N/A, the amp cannot be driven in that scenario. And I see RMS nowhere, do not know wht BCD rating means.
Sure does help though having 4 sets of outputs on the pre as well as a double balance to separate front and rear as well as right/left for front and rear and tone controls for front an rear.

Ok I figured it was something like that. Not that it matters to me I never run the thing in mono or bridged mode. Was just looking over the specs after reading this discussion.
 

laatsch55

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I'm sure BD could shed some light on this also, he was a sound reinforcement guy most of his life and has probably forgot more tricks than we know...
 

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Helps for running multiple amps and possible multiple 901's mixed with amps not running 901's if you know what I mean.
 
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