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Old 14th March 2012, 10:09 PM   #131
JimM is offline JimM  United States
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Ok let's see if we can agree on some things or if I'm all wet. In simulation with a +/- 32 volt supply in simulation one side of the front end will swing 24 volts peak or for a total swing of 48 volts peak to peak. As I understand the balanced circuit it acts the same as a bridged amp so V1(side 1 ) - V2(side 2) equal to 2 times the voltage swing of one side.
Therefore the output at the speaker would be 48 volts peak or 2 times that for 96 volts peak to peak at the speaker. I understand this does not include any loses in the output stage. If this is not correct please let me know where I am going wrong.
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Old 14th March 2012, 11:11 PM   #132
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You were going along just fine until the "Therefore the output at the speaker would be 48 volts peak or 2 times that for 96 volts peak to peak at the speaker. I understand this does not include any loses in the output stage."
In the previous sentence you said "one side of the front end will swing 24 volts peak or for a total swing of 48 volts peak to peak" Good enough. While this is happening, the other side is doing the opposite. -24V peak
At a point during the positive peak, you have +24V on one side and -24V on the other. Some 180 degrees later, you might have that same side doing a - peak, while the other side is doing a + peak. Measureing across those 2 outputs will measure 48Vp-p. Thats all your gonna get
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Old 14th March 2012, 11:28 PM   #133
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what's Upp of Aleph X , considering PSU voltage ..... for , say , light or no load conditions ?
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Old 14th March 2012, 11:47 PM   #134
rsdio is offline rsdio  United States
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Originally Posted by JimM View Post
Ok let's see if we can agree on some things or if I'm all wet. In simulation with a +/- 32 volt supply in simulation one side of the front end will swing 24 volts peak or for a total swing of 48 volts peak to peak. As I understand the balanced circuit it acts the same as a bridged amp so V1(side 1 ) - V2(side 2) equal to 2 times the voltage swing of one side.
Therefore the output at the speaker would be 48 volts peak or 2 times that for 96 volts peak to peak at the speaker. I understand this does not include any loses in the output stage. If this is not correct please let me know where I am going wrong.
I think you're right. An unbalanced amplifier would ground one terminal of the speaker, and vary the other between +24 V and -24 V, for a total of 48 Vpp. A balanced amplifier does not ground either terminal of the speaker, so when one terminal is at +24 V the other is below ground at -24 V, thus, the speaker sees a potential that ranges between +48 V and -48 V, for a total of 96 Vpp.

Apart from the fact that you originally said 45 Vpp and now you're saying 48 Vpp, that would nevertheless be upwards of 30 Vrms measured across the speaker terminals, not across a single output pin versus ground.

EDIT: In other words, the maximum voltage that a speaker sees from an unbalanced amplifier (half the BA-3b) is +24 V, the minimum is -24 V, and the peak-to-peak is 48 V. But, you have to take into account that the balanced BA-3b exposes the speaker to a maximum voltage of +48 V, and minimum of -48 V, and a peak-to-peak of 96 V. It doesn't quite make sense, at first, that a 64 V power supply (+/- 32V) can create 96 Vpp, but it really can because the reference voltage for the speaker is constantly moving rather than being fixed at 0 V. I've missed this detail on paper when dealing with DAC circuits, so I totally understand how others in this thread got confused by thinking of everything in terms of ground-referenced voltages without remembering that the speaker is not referenced to ground.

P.S. You do have to make sure that the +/-32 V power supply can provide enough current.

Last edited by rsdio; 15th March 2012 at 12:00 AM.
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Old 15th March 2012, 12:00 AM   #135
Zen Mod is offline Zen Mod  Serbia
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it's easy

one (plain , common , usual ) channel of amp have 1x power

same amp , with two channels bridged , have - in ideal conditions (or unloaded) 4x power

so - Upp must be 2x

sort of backward thinking , but useful as mental trick ........ before analysis
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Old 15th March 2012, 01:18 AM   #136
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Now is when we need pictures
Or maybe, now is when you go build it and try and measure it. You probably would have to use rms to measure it, and I don't think I'm willing to go there just yet...
The BA-3 your trying to engineer, not the balanced thingy, produces +and- 24Volts out with an input of 1V (Hypothetically). 24Volts maximum, in any language 24V. No 2X B.S. 24Volts peak!
Stop making me bang on my kybd!
You could call that output from 1 BA-3 48 Volts Peak to Peak. But it is still 24 Volts peak. The difference between the 2 terms is one does not take into account the polarity. It is an absolute value of 24 Volts peak! 48 Volts peak to peak is between the 2, as in, the difference.
You could put 2 BA-3s together...
When feeding them out of phase inputs. Did you read that? Go reread it again. When feeding them out of phase inputs, you will still get 24V peak out of each. But then, in differential, or Ballanced mode, if one has a peak 24 Volts positive, and 180 degrees later, 24V negative, it also has the other side producing 24V Peak. The same as 2 seperate amplifiers. Since it has a + and a - input, at the same time, we can, as you did, treat them like a balanced or bridged amplifier. And, call the output 48V peak to Peak. Don't be adding your car stereo buddies 'ol addage of it makes 2X the power or whatever. I'm tellin you, 1 BA-3 produces 24V out, two of'em in balanced/bridged mode would produce 24 Volts out of each, but, out of phase that can be called 48 Volts out. If you feed 2 BA-3s both an in phase signal you get 0, Nothing, Nota balanced or diferential out. Measureing between them will give you paratically nothing! Measureing 1 output to ground would be 24 Volts Peak. Measureing the other output would be the same 24 Volts Peak. In phase they are only in parallel and only current adds.
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Old 15th March 2012, 01:42 AM   #137
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In simulation with a +/- 32 volt supply in simulation one side of the front end will swing 24 volts peak or for a total swing of 48 volts peak to peak.
Yes - that is correct; and you can never have a peak higher than the rail voltage. Being on 'one side' has nothing to do with it.

Quote:
As I understand the balanced circuit it acts the same as a bridged amp so V1(side 1 ) - V2(side 2) equal to 2 times the voltage swing of one side
No. Perhaps that equation is true concerning current, but you can't have a voltage peak higher than the rail.

Quote:
Therefore the output at the speaker would be 48 volts peak or 2 times that for 96 volts peak to peak at the speaker.
No. It's impossible to have a voltage higher than the rail.

Quote:
I understand this does not include any loses in the output stage. If this is not correct please let me know where I am going wrong.
The losses are real, of course, but that's not actually important in this case. The thing to remember is that you can't have an output voltage higher than the rail voltage. There voltage can't be created out of nowhere -- the voltage has to come from the rail.

Remember that an amplifier is nothing more than an AC oscillator for your DC power supply.
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Old 15th March 2012, 01:49 AM   #138
JimM is offline JimM  United States
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Please explain how Papa pass got 100 watts as shown in his graph at the beginning of this post.
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Old 15th March 2012, 02:00 AM   #139
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Please explain how Papa pass got 100 watts as shown in his graph at the beginning of this post.

Click the image to open in full size.

This is not the whole amplifier. This is the driver portion of the amplifier. To get the 100 watts you need a BA- output stage, (it would be easiest to use the Push-Pull), a bunch of power mosfets, a big power supply, and an enormous amount of heatsinking.
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Old 15th March 2012, 02:29 AM   #140
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And, for this discussion, we are talking about 2 BA-2 output stages, per channel. Yep, 2 more for the other channel. Hmmm, did Nelson say these output stages draw in excess of 300W for 2ch? O.K. this amp is sucking 600W of power even without a signal...
Back to the 24V out of this BA-3X. N.P. ussually talks in 8 ohm outputs. 24V on a bridge loaded 8 ohms is (48V across 8 ohms) 6A (first approximation easy math)??? 6*6*8=288 Watts peak! Is that what you have in mind?
Oh yea, the question was How did N.P. get 100W at the begining of the thread? Were those rms watts or peak watts?
100W/8ohms=(12.5)sqrt=3.535A He got 3.535A through an 8 ohm speaker probably. Might have needed almost 28.3 Volts on that 8 ohm speaker.
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