quote:Originally posted by XtremeProbeGT: Hey whats up, this topic is very interesting, I was just wondering if you ever tryed to do this with D2's or if its possable.
I haven't yet, I have only attempted it with Crossfire VR202's, and it was a success. In theory though, it would work with ANY amp (in any number too . If you wanted to get really crazy, you could even strap different types of amps together.... altough i'm not sure why you would want to do that, or how well it would turn out
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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This is a picture of what we are attempting to do. Essentially creating the largest possible AC voltage across the coil of the speaker.
Note, in this diagram I did not include any wiring with regards to the battery connections, or the Input signals.
Hopefully I can make myself more clear as to why the signals need to be isolated. As the diagram shows, the amplifiers will have large potential voltages between them during burps. Thus, an RCA cable connecting the grounds of the amplifiers would not work, due to the fact that it would be essentially short-circuitng the amplifier. This is the difficult part. We need each amplifier to be fed an identical signal that is perfectly in phase with all of the other amplifiers, and yet not have continuity between them.
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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Netlohcs: Wiring amps like you show is not possible. Let me try to explain.
When batteries are wired in series there is a difference of 12 volts across each battery. If only one battery is used the negative is connected to ground, so its potential is zero. The positive terminal will have a potential of 12 volts because that is the voltage difference across the battery. If two batteries are used the second battery will have its negative connected to the positive of the other, therefore that terminal has a potential of 12 volts. Since the positive terminal of the battery is 12 volts above its negative, the voltage difference across both batteries will be 24 volts. This works with batteries because they are a source of power, unlike an amplifier which only raises its input voltage.
With an amplifier the output power is an AC voltage that is referenced to the negative terminal of the amp. The negative terminal has a reference voltage that is half the total output of the power supply. For example if the power supply can make 60 volts, the negative terminal will be 30 volts, so the amp can make a sine wave with a +/-30 volt peak. If two amps are strapped their signals are also wired 180 degrees out of phase. Since the sine waves are 180 out of phase the max potential between the two terminals is 60 volts, one amp outputs +30 volts, the other -30 volts. Now since the speaker is getting a peak potential difference of 60 volts, that is the max possible because the amp power supply can only make 60 volts. No matter how many amps you have, the voltage output of all the amp's power supplies can only be 60 volts above ground. Without changing to a more powerful amp you cannot make any more than a peak AC voltage of 60 volts, which you can get with two amps.
If the amps are each powered by their own power source, it could be possible to get a higher AC voltage than 60 volts peak to peak. Of course the amps would have to be designed to work with this different system. But in a car all amps are powered by one power source. Therefore you cannot strap more than 2 amps, just like you can't bridge more than two channels of an amp.
Posts: 327 | From: Pleasanton & Sacramento Ca | Registered: Dec 2001
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quote:Originally posted by ddstang: But in a car all amps are powered by one power source. Therefore you cannot strap more than 2 amps, just like you can't bridge more than two channels of an amp.
This is where what you are seeing and what I am seeing is different. I never said anything about all of the amps having the same power source. Just because you have 24 batteries in a competition vehicle doesnt necessarily mean they are all wired directly together. I Will modify my drawing a little bit, and show you what I mean. I guess I thought I was a little more clear on that before, sorry.
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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Making any sense now? DDstang - You seem to be concerned only with giving me reasons why it CANT be done, but like i said.... I already did it You just need to think about how you CAN do it... instead of how you CANT
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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posted
OK you said you have done this before, these amps, do they reference the Neg slope to the amps ground?
Posts: 26 | From: FL | Registered: Jan 2004
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quote:Originally posted by CognLac: do they reference the Neg slope to the amps ground?
I'm not sure what you mean by negative slope?
What I did was essentially just like the diagram above, with a few other details missing (Signal input).
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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quote:Originally posted by CognLac: is the amplifiers "-" output connected to the power ground
I think what he is trying to ask is the "-" speaker output on the amplifier have a reference to the battery ground? If this is the case then your amp would be back feeding AC signal into the battery since there is no negative speaker output reference ground.
Posts: 141 | From: here | Registered: Mar 2003
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posted
It can be done It can be done It can be done
Thats all I have to say weather or not its technically within the rules of db drag racing, that I couldn't tell you. I guess we will just have to wait and see.
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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Now that you've done this have you metered the output voltage to see if it really is 120v as your diagram shows?
I could see how it would work but I don't see how you would gain any voltage.
Posts: 340 | From: Trenton, Ontario | Registered: Dec 2003
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quote:Originally posted by McFrosty: Now that you've done this have you metered the output voltage to see if it really is 120v as your diagram shows?
I could see how it would work but I don't see how you would gain any voltage.
My test was this: First I took an mtx 9512 dual 4 ohm subwoofer and wired a crossfire VR202 to each coil. I then clamped a mic in the port, and conducted a series of tests to measure the in port SPL.
Once that was done, I wired the two coils in series, essentially giving me an 8 ohm, single voice coil speaker. I then strapped the two VR202s to the 8 ohm coil, and repeated the test. The result confirmed waht I stated before, I was able to reproduce the same in-port SPLs to within 0.3 dB.
In short, to answer your question, Yes, the AC voltage was doubled when the amplifers were strapped.
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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quote:Originally posted by netlohcs: My test was this: First I took an mtx 9512 dual 4 ohm subwoofer and wired a crossfire VR202 to each coil. I then clamped a mic in the port, and conducted a series of tests to measure the in port SPL.
Once that was done, I wired the two coils in series, essentially giving me an 8 ohm, single voice coil speaker. I then strapped the two VR202s to the 8 ohm coil, and repeated the test. The result confirmed waht I stated before, I was able to reproduce the same in-port SPLs to within 0.3 dB.
In short, to answer your question, Yes, the AC voltage was doubled when the amplifers were strapped.
Have you tried this with more than two amps?
What you say here is strapping just two amps which can be easily done. But with more than two amps it is not anywhere near as easy if even possible with regular amps. With two amps strapped together you have the input signal of one amp 180 degrees out of phase with the other. If more than two amps are strapped how do you connect the input signals?
Posts: 327 | From: Pleasanton & Sacramento Ca | Registered: Dec 2001
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posted
do it again and video tape it, it looks "good" on paper but i also dont see how you gained voltage. IM not doing this to be a dic* but i would love to see proof in the pudding. otherwise i can tell some awesome stories about that one fish Posts: 26 | From: FL | Registered: Jan 2004
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quote:Originally posted by netlohcs: My test was this: First I took an mtx 9512 dual 4 ohm subwoofer and wired a crossfire VR202 to each coil. I then clamped a mic in the port, and conducted a series of tests to measure the in port SPL.
Once that was done, I wired the two coils in series, essentially giving me an 8 ohm, single voice coil speaker. I then strapped the two VR202s to the 8 ohm coil, and repeated the test. The result confirmed waht I stated before, I was able to reproduce the same in-port SPLs to within 0.3 dB.
In short, to answer your question, Yes, the AC voltage was doubled when the amplifers were strapped.
Have you tried this with more than two amps?
What you say here is strapping just two amps which can be easily done. But with more than two amps it is not anywhere near as easy if even possible with regular amps. With two amps strapped together you have the input signal of one amp 180 degrees out of phase with the other. If more than two amps are strapped how do you connect the input signals?
Crossfire VR202s are not "strappable" amps. They are two channel amplifiers. So essentially, I bridged each amp, and then strapped them. If i had 4 in inventory, I would have used 4. I would have needed a 16 ohm coil though, I'm not sure where I could have found one of those. Trust me, It would have worked though.
Oh and as far as the input signals.... now we are really getting to the fun stuff
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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quote:Originally posted by CognLac: do it again and video tape it, it looks "good" on paper but i also dont see how you gained voltage. IM not doing this to be a dic* but i would love to see proof in the pudding. otherwise i can tell some awesome stories about that one fish
It gained voltage in the exact same way that two batteries gain voltage when you wire them in series. Like I said... the only difference is that batteries are DC, amps are AC. The same fundamental laws of electricity still apply.
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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You say there would be large potential differences between the batteries, which makes sense to me. Seems to me that if each amp can produce a +/- 30 voltage output (60V difference between the rails) and the lowest voltage possible is referenced to ground (is that right?), then you'd essentially have the lower voltage rail of the second amp at the same level as the higher voltage rail of the first amp, meaning that the battery for the second amp would be at 60V higher potential than the first battery, measured between the negative terminal of one batt to the neg. of the other or from + of one to + of the other, right? I'm just trying to piece together what I've read here and figure out how this could work. I don't know as much as you guys about how amplifiers work, so if that's way off, let me know. I'm just trying to figure out where this statement: "As the diagram shows, the amplifiers will have large potential voltages between them during burps" comes from.
Also, you mentioned that it can be done using commercially available 12 equipment, which implies (to me, anyway) that you are interested in being able to compete legally. I don't know if that would be legal or not since it would be possible to measure a voltage greater than 18V across the terminals of the batteries, even though they are not exactly connected in series.
I'm just trying to understand this better because this seems interesting to me. Keep us posted when you try more than 2 amps.
posted
Nomad, You acutally seem to understand the concept pretty well. You are correct, there will be voltages of +/- 30 volts (or whatever your amps can produce) between the negative posts of each sequential battery system.
As far as the rules for DB drag. You are correct, there is a rule stating that that the maximum potential voltage is 18 volts DC. Notice that it specifically says DC, and mentions nothing of AC. If you put your voltmeter on DC and measure between the - terminals of the batteries during a burp, your going to get a big fat 0
And just so everyone knows, I'm not trying to find a way to circumvent the rules or exploit any "gray areas". This is just a "what if" thread, at least for now
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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So lets go over a few things now. We know that during a burp, there is going to be a potential AC voltage of (insert whatever your amplifier is capable of producing here) present between the - posts of each sequential battery. Knowing this, and also knowing that the RCA grounds are connected to the battery ground, If we were to take an RCA and run it from one amp to another, we would be essentially short-circuiting the entire amplifier. Not good.
This is why we need signal isolation. Like I stated previoulsy, we need to have perfectly identical signals (both in amplitude and phase) fed to each amplifier, but at the same time keep them COMPLETELY isolated (essentially coming from two different sources). Anyone have any good ideas on how this could be accomplished?
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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quote:Originally posted by netlohcs: This is why we need signal isolation. Like I stated previoulsy, we need to have perfectly identical signals (both in amplitude and phase) fed to each amplifier, but at the same time keep them COMPLETELY isolated (essentially coming from two different sources). Anyone have any good ideas on how this could be accomplished?
This can easily be done with op amps (operational amplifiers, not audio amplifier). They are capeable of isolating two circuits, but keep the same voltage (signal) between them.
For example, if you had a 2V source (which includes an internal deck resistance), normally connecting a load (an audio amplifier) you would get some voltage drop. With an op amp in the circuit, it would provide that 2V signal to the audio amp without any voltage drop to the deck.
What they basicly do is "sample" a source/signal, and copy it exactly with it's own power source. So you get two (or more) isolated identical signals.
quote:Originally posted by netlohcs: This is why we need signal isolation. Like I stated previoulsy, we need to have perfectly identical signals (both in amplitude and phase) fed to each amplifier, but at the same time keep them COMPLETELY isolated (essentially coming from two different sources). Anyone have any good ideas on how this could be accomplished?
This can easily be done with op amps (operational amplifiers, not audio amplifier). They are capeable of isolating two circuits, but keep the same voltage (signal) between them.
For example, if you had a 2V source (which includes an internal deck resistance), normally connecting a load (an audio amplifier) you would get some voltage drop. With an op amp in the circuit, it would provide that 2V signal to the audio amp without any voltage drop to the deck.
What they basicly do is "sample" a source/signal, and copy it exactly with it's own power source. So you get two (or more) isolated identical signals.
Interesting. Tell me more about the "op amp" I assume (perhaps incorrectly) that it has just one ground. If this is the case, how does the op amp achieve ground isolation for each RCA signal?
Net - Couldn't you just run the + pole on the rca and split it up, then disconnect each shield from each other and battery ground each?
Steve
-------------------- 2005 Florida Street C Champion 2004 SBN Street C Champion 2004 SBN IDBL No Wall Champion 2003 NOPI Nats Street B Champion
quote:Originally posted by Bumpin' Yota: Interesting. Tell me more about the "op amp" I assume (perhaps incorrectly) that it has just one ground. If this is the case, how does the op amp achieve ground isolation for each RCA signal?
Net - Couldn't you just run the + pole on the rca and split it up, then disconnect each shield from each other and battery ground each?
Steve
As for the op amp, you are correct, they still do use common grounds, making Op amps unsuitable for what we need them to do in this particular situation.
As far as splitting up the rca signals go, that unfortunately wont work either An RCA signal delivers a potential voltage to the amplifier. Unfortunately without a ground present, there can be no "potential".
You guys are having some good ideas... we are getting much MUCH closer Any other thoughts?
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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Why wouldn't you be able to use a ground loop isolator. It is a transformer, so the signal going to the amp would be completly isolated. But I would still like to see some hard fact on that you have proved this. Lets see some numbers. Otherwise I will have to agree with Cognlac about the fish stories. B/c believe me that I can give some good ones. Posts: 141 | From: here | Registered: Mar 2003
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quote:Originally posted by MTX_TECH: Why wouldn't you be able to use a ground loop isolator. It is a transformer, so the signal going to the amp would be completly isolated. But I would still like to see some hard fact on that you have proved this. Lets see some numbers. Otherwise I will have to agree with Cognlac about the fish stories. B/c believe me that I can give some good ones.
Belieive whatever you want man, i'm not forcing you to think anything. You don't even have to read this post if you don't want to.
As far as "numbers" go, I already gave them to you... apparently you chose not to believe me, which is fine.
Ground loop isolator.... that could possibly work, if it was truly a fully independent signal, I'm not totally sure.
P.S. If you really do work at mtx, why don't you go down the hall and talk to some of the people that have engineered your amplifiers and ask them if what I'm saying holds water. Get back to us with what they say......
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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Well, I just got done reading this post for the 1st time, and I might have an idea about the RCA isolation problem. I am pretty sure that a company makes a piece that has multiple isolated outputs with one input. I will let you know.
Later,
Jason Meyer
-------------------- 2004 SS 1-2NW World Champion 2005 World Finals SS 1-2NW 2nd Place 2006 World Finals SS 1-2NW 3rd Place Team Maxxsonics Member of Broken Silence Competition Team Posts: 194 | From: Sedalia, MO, USA | Registered: Aug 2000
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