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Two amplifiers w/ one audio source
v.wochnik
post Feb 15 2013, 12:12
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Hello Guys

This is my first post here, great forum btw!

Anyway, in our gym we have this setup: We have two different areas and for each area, we have a seperate amplifier. For the entrance area, we have a smaller amp and for our "room of pain" we have a big ass amp for some loud music.

The smaller amplifier is mostly sourced by an online radio and that's fine. The big amp is connected to a PC. However, sometimes we want the PC not only to provide the big amp, but also the small one to have the same music everywhere.
We tried to put them in parallel with a special cable, but that almost killed one of the amps. It got really hot and the amp almost started catching fire.

Is there a way to put the two amps in series so that we can switch the smaller amp from radio to PC? Like this?

http://dl.dropbox.com/u/1706321/amp.png

Can anyone please help me?

Thank you.
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julf
post Feb 15 2013, 12:58
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Does one of the amps have a tape out / aux out? That would allow you to chain them. If not, I suggest getting a small, cheap 2-channel mixer (or making one with a couple of resistors).
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rick.hughes
post Feb 15 2013, 14:53
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Don't really understand what went wrong since you don't provide many details about the equipment.

It's usually OK to split an output to feed multiple inputs. Splitting the line out from the computer and feeding each to a different amp should work. It's when you try to have multiple outputs feed a single input that you can get into trouble and that's when you need a mixer.

If one of the amps has a line out then you could probably hook them up in "series" as you call it though that is not exactly what I would call it. But you should be able to make it work the way you originally tried.

Maybe you hooked something up wrong. When you tried before did it work at all? If it was working maybe it just seemed like the amp was getting hot because you never noticed how hot it usually runs.

This post has been edited by rick.hughes: Feb 15 2013, 14:58
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Speedskater
post Feb 15 2013, 14:57
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Connection instructions from Rane Corp.

RaneNote:

"Why Not Wye?"

Splitting Signals
Subwoofing in Mono
Unbalanced Summing
Balanced Summing
Output Impedances

http://www.rane.com/note109.html


--------------------
Kevin
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rick.hughes
post Feb 15 2013, 15:04
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From that Rane article:
QUOTE
A wye-connector used to split a signal into two lines is being used properly; a wye-connector used to mix two signals into one is being abused and may even damage the equipment involved.

Unless I have misunderstood he was trying to split a signal so it should have worked. But who knows what his "special cable" was or how he used it.

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mixminus1
post Feb 15 2013, 15:25
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...and just to be absolutely clear to the OP: all discussion here assumes/is pertaining to splitting line-level signals going into the amps.

Under no circumstances should you ever attempt to combine/"split" the *output* of two amplifiers into the same load - that would most certainly lead to an amp getting "really hot", if not outright destroying itself.


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"Not sure what the question is, but the answer is probably no."
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Arnold B. Kruege...
post Feb 15 2013, 17:30
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QUOTE (v.wochnik @ Feb 15 2013, 06:12) *
Hello Guys

This is my first post here, great forum btw!

Anyway, in our gym we have this setup: We have two different areas and for each area, we have a seperate amplifier. For the entrance area, we have a smaller amp and for our "room of pain" we have a big ass amp for some loud music.

The smaller amplifier is mostly sourced by an online radio and that's fine. The big amp is connected to a PC. However, sometimes we want the PC not only to provide the big amp, but also the small one to have the same music everywhere.
We tried to put them in parallel with a special cable, but that almost killed one of the amps. It got really hot and the amp almost started catching fire.

Is there a way to put the two amps in series so that we can switch the smaller amp from radio to PC? Like this?

http://dl.dropbox.com/u/1706321/amp.png


Your goal of having the same music in both places would be satisfied by hooking the same source to the inputs of both ampliifers. Forget about messing with the outputs!
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v.wochnik
post Feb 15 2013, 19:20
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Thank you guys.

YES, the output of the PC is splitted and these go in the amps. Actually, we DO know, that it was kinda hot, also the amp started not working after a while. We had music on both amps though, w/ decent quality.
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julf
post Feb 15 2013, 19:46
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QUOTE (v.wochnik @ Feb 15 2013, 19:20) *
Actually, we DO know, that it was kinda hot, also the amp started not working after a while. We had music on both amps though, w/ decent quality.


So do you actually know it wasn't hot before you connected the inputs? The problems with the amp might be completely unrelated to the cable splitting...
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DVDdoug
post Feb 15 2013, 21:55
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I agree... Something strange is going on... Unless you overdrive the input (which you can't do from a computer), nothing at the input should cause any problems. For example, if you short-out the input, that won't damage the amp, but you are also shorting-out the computer's output, and that could potentially damage the soundcard. (Except of course, a loud-input with the volume turned-up will "push" more power out the output and create more heat.)

Are you running that 2nd amp louder with the computer than with the radio? I'm just thinking that if it was talk radio or news, and now you're playing music, you might be running the amp "harder". If running the amp hard causes it to overheat & shut down, you might need a just different amp, or maybe you have too many speakers connected.

It might just be the long wire causing some sort of RF oscillation. That would be very unusual... It's just the only thing I can think of... Is it the smaller "far" amp that's getting hot? Actually, the long cables are electrically connected to both amps, so a strange issue like that could affect either amp...

If the amp is still "alive", you can try the long cable-run with just the one amp connected, with or without the splitter plugged-in.

These are both stereo amplifiers (with left & right), right? A mono amp wouldn't cause that problem, but it creates another issue with the connections.

If it is the long cables, a cheap little mixer (or preamp) near the "problem amp" should take care of the problem. The mixer won't be used as a mixer to mix signals... just to "condition" the signal. But, a little mixer is usually cheaper than a preamp.

QUOTE
We tried to put them in parallel with a special cable...
Your average-everyday "splitter cable" like this should work fine.

This post has been edited by DVDdoug: Feb 15 2013, 21:59
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Simple creature
post May 8 2014, 12:09
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Can anyone help dispel my ignorance? I am unsure what is possible and my web searches are showing me my question may (sic) require more education than I posses.

I live on a boat and all of our power starts as 12 volt dc. And wafts into the batteries via solar panels. We are very conscious of power consumption. In the hope of a flexible stereo system I was looking at a Bose Acoustimass 5 and thought to use either an SMSL SA-S3 (25w T-class amp the larger ones need higher voltage) or a 200w 12v D-class depend ending on volume and power consumption.

I would also like to use two SA-S3's one input via a Y (Wye) connector and combine their output in parallel into the Bose.

I thought this would be running the amps in parallel, though I have heard that 'summing' output causes the world to end.

I am not bright enough to read schematics or understand the, necessarily, jargon filled explanations.

Can anyone help the bewildered?
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julf
post May 8 2014, 12:46
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QUOTE (Simple creature @ May 8 2014, 13:09) *
I would also like to use two SA-S3's one input via a Y (Wye) connector and combine their output in parallel into the Bose.


To achieve more than 25 W of power?
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Simple creature
post May 8 2014, 13:24
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Exactly so. The amps are lovely, cheap and 12v the higher output are 32v so require transformers.

Is this putting the amps in parallel and is it safe/advisable?
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Arnold B. Kruege...
post May 8 2014, 13:48
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QUOTE (Simple creature @ May 8 2014, 08:24) *
Exactly so. The amps are lovely, cheap and 12v the higher output are 32v so require transformers.

Is this putting the amps in parallel and is it safe/advisable?



Generally speaking paralleling power amps is a really bad idea that often results in something being permanently damaged.

If you want power amps that run well off of 12 volts, look at the carsound people. Tons of alternatives at any reasonable or unreasonable power level.
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rick.hughes
post May 8 2014, 13:50
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QUOTE (Simple creature @ May 8 2014, 08:24) *
Is this putting the amps in parallel and is it safe/advisable?

No and No

Have you considered something based on car audio? They also use 12v power and there are a lot of products available.

Arnold was faster.

This post has been edited by rick.hughes: May 8 2014, 13:51
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pdq
post May 8 2014, 13:53
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NEVER NEVER NEVER connect the outputs of two power amps in parallel. This will immediately destroy both of them!!!

If you really need their combined power then if possible connect each to a separate speaker.

The only safe way to combine the power of two amps is to invert the signal into one of them, tie the speaker commons together, and connect the speaker between their outputs. You must be careful, however. This will only work if the speaker impedance is at least twice the rated output impedance of the amps.

It would be much simpler to just get an amp with the wattage rating that you need.

Edit: I type too slowly (and I was interrupted).

Edit2: On second thought, just get a better amp. My other suggestion is a technique that is commonly used in amplifiers, but the amplifier needs to be designed specifically to work that way.

This post has been edited by pdq: May 8 2014, 13:58
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Arnold B. Kruege...
post May 8 2014, 13:55
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QUOTE (rick.hughes @ May 8 2014, 08:50) *
QUOTE (Simple creature @ May 8 2014, 08:24) *
Is this putting the amps in parallel and is it safe/advisable?

No and No

Have you considered something based on car audio? They also use 12v power and there are a lot of products available.

Arnold was faster.


Yes, but its a good idea either way! ;-)

The SQ of most car audio power amps is generally as good as anything. Thing to watch out for is inflated power ratings. Its easy to find "100 watt" amps that are really and truly 12 wpc.
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pdq
post May 8 2014, 15:36
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QUOTE (pdq @ May 8 2014, 08:53) *
NEVER NEVER NEVER connect the outputs of two power amps in parallel. This will immediately destroy both of them!!!

If you really need their combined power then if possible connect each to a separate speaker.

The only safe way to combine the power of two amps is to invert the signal into one of them, tie the speaker commons together, and connect the speaker between their outputs. You must be careful, however. This will only work if the speaker impedance is at least twice the rated output impedance of the amps.

It would be much simpler to just get an amp with the wattage rating that you need.

Edit: I type too slowly (and I was interrupted).

Edit2: On second thought, just get a better amp. My other suggestion is a technique that is commonly used in amplifiers, but the amplifier needs to be designed specifically to work that way.

I forgot to add that paralleling two amps, even if it did no harm, would not be any louder than a single amp because the voltage would still be the same.
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Simple creature
post May 8 2014, 17:43
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Thanks guys. The second SMSL shall be used for tunes on the back deck (or gin drinking station) and the lounge amp options will be small or large.

It was going to be car audio anyway. Can anyone recommend any car audiophiles I can pester for 200w RMS amp suggestions?

Also, running an amp in. All amps? How long and what sort of volume permissible if so?
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DVDdoug
post May 8 2014, 18:54
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QUOTE
It was going to be car audio anyway. Can anyone recommend any car audiophiles I can pester for 200w RMS amp suggestions?
Just try to buy one from a reputable manufacturer, so when they say "200W RMS" it's hopefully true.

Note that most car audio amps are power-rated rated at 4 Ohms. The Bose speaker appears to be 8 Ohms, like most home audio speakers. (The specs say "Compatible with recievers or amplifiers rated for 4-8 Ohms.")

If you no spec is given for 8 Ohms, assume you are getting half the power. (For a given voltage output, power is inversely related to load impedance.)*

QUOTE
Also, running an amp in. All amps? How long and what sort of volume permissible if so?
You don't need to burn-in electronics. The performance of a solid state circuit should not change for years or decades unless something fails. If the performance changes after a few hours use, it's a very-poor design. A good manufacturer will test the item before it leaves the factory to make sure it meets (or exceeds) the specs.

A speaker might "loosen-up" after several hours of use. But if that's the case, the manufacturer should burn it in and confirm the final specs before shipping... Otherwise, their published specs and in-house tests are worthless!

I work for a small (non-audio) electronics manufacturer. We test everything, put it our burn-in room and run it at elevated temperature for one week, and then re-test again before shipping. The purpose of our burn-in is to weed-out early failures. (More than 99% of the time, nothing changes and the boards/units pass after burn-in.)





* Solid state amps are "constant voltage devices". That doesn't mean the output voltage is truly constant, because the audio signal is constantly changing and it obviously depends on how loud the music is and the volume control. It means that the output voltage doesn't change when you change the load impedance. And with a stable power supply, the maximum available output-voltage depends on the power supply voltage.

In the real world there are other factors such as current, power, or thermal limits, so you don't always double the power every time you cut the impedance in half. Actual real-world results depend on the design of the amplifier.

A car amplifier that truly puts-out 200W has an internal power supply that boosts the voltage, because you simply can't get 200W into 4 or 8 Ohms with a 12V supply.

This post has been edited by DVDdoug: May 8 2014, 19:01
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Simple creature
post May 8 2014, 19:18
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Thanks Doug. That exceeds my current level of comprehension- though not by too much I hope. I certainly understand the difference between PMPO(wtf!) and RMS but some manufacturers 'forget' to reference the yardstick by which they're testing.

Yeah, I read the Bose manual, before pennies leave my wallet, I want to be sure that the kit will perform as stated at 4 ohm, as the kit I have and intend to buy will be... The SMSL particularly offers 25w RMS AT 4ohm and only 13.5w at 8. The claimed requirements are 20-200w so the small amp will fall short of ooomph if the Bose internal wizardry won't run sweet at 4 ohm.

If anyone has thoughts, or even figures, I would love to hear them and counter suggestions for a similar setup would be appreciated. Our particular requirements lie somewhere between home hiving and car audio and being barely/partly technical leaves me mostly discombobulated.
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Arnold B. Kruege...
post May 8 2014, 20:10
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QUOTE (Simple creature @ May 8 2014, 12:43) *
Thanks guys. The second SMSL shall be used for tunes on the back deck (or gin drinking station) and the lounge amp options will be small or large.

It was going to be car audio anyway. Can anyone recommend any car audiophiles I can pester for 200w RMS amp suggestions?

Also, running an amp in. All amps? How long and what sort of volume permissible if so?


Do men "Breaking in" an amplifier?

If so - that is an audiophile myth.
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DVDdoug
post May 8 2014, 23:33
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QUOTE
The claimed requirements are 20-200w so the small amp will fall short of ooomph if the Bose internal wizardry won't run sweet at 4 ohm.

If anyone has thoughts, or even figures, I would love to hear them and counter suggestions for a similar setup would be appreciated.
The truth is, it's almost impossible to predict how much power you need. It starts with the fact that most of us don't really know how much loudness (dB SPL) we want or need. Arnold discuss the other factors and offers a link in this recent post.

I've seen a case where a speaker manufacturer's recommended minimum amplifier power was higher for their bigger speaker, even though the bigger speaker was more efficient than the smaller one (louder at the same power). The speaker could handle more maximum power, and was more expensive, so they recommend a bigger amp.

A typical TV probably has about a 2W amplifier driving the built-in speaker, and usually we are not listening at the maximum volume. Good bass requires more power and bigger woofers.

Note that a doubling of power is only a 3dB increase (and halving the power is -3dB). It's a noticeable change, but you might not notice it if you came back the next day and somebody had reduced the volume by 3dB. Ten times the power is a 10dB increase.

This post has been edited by DVDdoug: May 8 2014, 23:39
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andy o
post May 9 2014, 07:19
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Has anyone taken a look at those Bose speakers, anyway? It seems those Bose people are as sketchy as ever. I thought they didn't sell those speakers without their own amp, but seems they do. The most you'll get out of their published specs is the speaker size!
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Arnold B. Kruege...
post May 9 2014, 09:41
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QUOTE (andy o @ May 9 2014, 02:19) *
Has anyone taken a look at those Bose speakers, anyway?


Yup, here: http://www.hydrogenaudio.org/forums/index....st&p=865333

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