Home |
Search |
Today's Posts |
#1
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
A newbie at seperates and recenty aquired an adcom preamp tuner with a
couple of adcom gfa-545 stereo amps. My speakers a Magnepan SMGa's. My question is can each of the stereo amps be bridged to mono? If so, I need direction on wiring. Thx in advance. |
#2
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
On 7 Sep 2007 22:36:30 GMT, FredClark wrote:
A newbie at seperates and recenty aquired an adcom preamp tuner with a couple of adcom gfa-545 stereo amps. My speakers a Magnepan SMGa's. My question is can each of the stereo amps be bridged to mono? If so, I need direction on wiring. Thx in advance. Hi Fred: It doesn't mention bridging in the manual, check: http://www.adcom.com/prod/shopdispla...&prodid=1 182 For the manual for the GFA-545 -=Bill Eckle=- Vanity Web Page at: http://www.wmeckle.com |
#3
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
On Sep 7, 6:36 pm, FredClark wrote:
A newbie at seperates and recenty aquired an adcom preamp tuner with a couple of adcom gfa-545 stereo amps. My speakers a Magnepan SMGa's. My question is can each of the stereo amps be bridged to mono? If so, I need direction on wiring. Thx in advance. Why do you want to do this? |
#4
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
On Sep 7, 6:36 pm, FredClark wrote:
A newbie at seperates and recenty aquired an adcom preamp tuner with a couple of adcom gfa-545 stereo amps. My speakers a Magnepan SMGa's. My question is can each of the stereo amps be bridged to mono? If so, I need direction on wiring. Thx in advance. Some amps are designed to be bridged and others are not. I'd check with Adcom tech support on your amps. I have a pair of older NAD with switches for bridged mode. There is also a specific way to connect your speakers and pre-amp! Be sure and check with Adcom on how to do this. Just remember with bridged amps the power is doubled and also the speakers impedance is effectively halved as see by the amplifier. a 4 ohm load looks like a 2 ohm load, etc. With speakers like the Maggies that may be a problem. Rick |
#5
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
On Sep 8, 8:47 pm, rcs3 wrote:
snip Just remember with bridged amps the power is doubled and also the speakers impedance is effectively halved as see by the amplifier. a 4 ohm load looks like a 2 ohm load, etc. With speakers like the Maggies that may be a problem. Actually, the power is nearly quadrupled if the power supply can provide sufficient current. The impedance does not change but because the load voltage is doubled, the current will also be doubled. The current doubling is cause for concern since it could damage the the output transistors or result in higher power dissipation that could cause longterm problems. |
#6
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
"rcs3" wrote in message
... On Sep 7, 6:36 pm, FredClark wrote: A newbie at seperates and recenty aquired an adcom preamp tuner with a couple of adcom gfa-545 stereo amps. My speakers a Magnepan SMGa's. My question is can each of the stereo amps be bridged to mono? If so, I need direction on wiring. Thx in advance. Some amps are designed to be bridged and others are not. I'd check with Adcom tech support on your amps. I have a pair of older NAD with switches for bridged mode. There is also a specific way to connect your speakers and pre-amp! Be sure and check with Adcom on how to do this. Just remember with bridged amps the power is doubled and also the speakers impedance is effectively halved as see by the amplifier. a 4 ohm load looks like a 2 ohm load, etc. With speakers like the Maggies that may be a problem. Rick I have never heard that bridging and amp halves the speaker impedance. You don't wire the speakers differently when the amp gets bridged..the speakers remain the same and the amp sees the same load. If I'm wrong on this explain how the change occurs. Bob |
#7
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
Bob wrote:
"rcs3" wrote in message ... On Sep 7, 6:36 pm, FredClark wrote: A newbie at seperates and recenty aquired an adcom preamp tuner with a couple of adcom gfa-545 stereo amps. My speakers a Magnepan SMGa's. My question is can each of the stereo amps be bridged to mono? If so, I need direction on wiring. Thx in advance. Some amps are designed to be bridged and others are not. I'd check with Adcom tech support on your amps. I have a pair of older NAD with switches for bridged mode. There is also a specific way to connect your speakers and pre-amp! Be sure and check with Adcom on how to do this. Just remember with bridged amps the power is doubled and also the speakers impedance is effectively halved as see by the amplifier. a 4 ohm load looks like a 2 ohm load, etc. With speakers like the Maggies that may be a problem. Rick I have never heard that bridging and amp halves the speaker impedance. You don't wire the speakers differently when the amp gets bridged..the speakers remain the same and the amp sees the same load. If I'm wrong on this explain how the change occurs. Bob But the amp does not see the same load in bridging as in single-ended. To see this assume the speaker is R ohms. Let's say one amplifier is outputting V volts. In the single-ended case, current is V/R. In the bridged case, because the speaker's other end is connected to an amplifier, that other end actually sees a voltage of -V (instead of ground). Therefore the current drawn from the amp is 2V/R. Hence effective resistance is R/2 (current is V divided by R/2). Put some numbers in. Say R=8 ohms. Your amp is delivering 8V into the speaker. In the single-ended case, current = 8V/8ohm =1A. In the bridged case, the voltage across the speaker is 16V (since the other amplifier is delivering -8V), and therefore current into speaker = 16/8 =2A. So as far as the amp is concerned, the speaker looks like 4 ohms since 8V will draw 2A. |
#8
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
"Bob" wrote in message
... "rcs3" wrote in message ... On Sep 7, 6:36 pm, FredClark wrote: A newbie at seperates and recenty aquired an adcom preamp tuner with a couple of adcom gfa-545 stereo amps. My speakers a Magnepan SMGa's. My question is can each of the stereo amps be bridged to mono? If so, I need direction on wiring. Thx in advance. Some amps are designed to be bridged and others are not. I'd check with Adcom tech support on your amps. I have a pair of older NAD with switches for bridged mode. There is also a specific way to connect your speakers and pre-amp! Be sure and check with Adcom on how to do this. Just remember with bridged amps the power is doubled and also the speakers impedance is effectively halved as see by the amplifier. a 4 ohm load looks like a 2 ohm load, etc. With speakers like the Maggies that may be a problem. Rick I have never heard that bridging and amp halves the speaker impedance. You don't wire the speakers differently when the amp gets bridged..the speakers remain the same and the amp sees the same load. If I'm wrong on this explain how the change occurs. Bob Some many years ago I redeployed a pair of bridgeable stereo Adcom GFA-555s using each to drive the R and L panels of a Magneplanar Tympani IVa. (Later on I acquired a pair of Bryston 7B-STs to do the same job.) The Adcoms (which I still own) did the job admirably; great sound at any volume setting. They never ever clipped, shut down or burning any fuses, (speaker's or amp's). |
#9
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
jwvm writes:
On Sep 8, 8:47 pm, rcs3 wrote: snip Just remember with bridged amps the power is doubled and also the speakers impedance is effectively halved as see by the amplifier. a 4 ohm load looks like a 2 ohm load, etc. With speakers like the Maggies that may be a problem. Actually, the power is nearly quadrupled if the power supply can provide sufficient current. The impedance does not change but because the load voltage is doubled, the current will also be doubled. The current doubling is cause for concern since it could damage the the output transistors or result in higher power dissipation that could cause longterm problems. I agree that the power is quadrupled: P = V^2 / R and so P1 = V^2 / R P2 = (V + V)^2 / R = 4 * V^2 / R = 4 * P1. However, the impedance seen by the amplifier output stage, at least in the ideal case, is reduced by two, precisely because of the increase in output current you described. Algebraically, Rl = V / I, where Rl is the load impedance seen at the output of the power amp, V is the output voltage of the power amp, and I is the current running through the power amp. We can compute I as I = (V + V) / R, where R is the [ideal] load impedance of the speaker. Then Rl = V / ((V + V) / R) = R / 2. -- % Randy Yates % "With time with what you've learned, %% Fuquay-Varina, NC % they'll kiss the ground you walk %%% 919-577-9882 % upon." %%%% % '21st Century Man', *Time*, ELO http://home.earthlink.net/~yatescr |
#10
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
"Bob" wrote in message
... "rcs3" wrote in message ... On Sep 7, 6:36 pm, FredClark wrote: A newbie at seperates and recenty aquired an adcom preamp tuner with a couple of adcom gfa-545 stereo amps. My speakers a Magnepan SMGa's. My question is can each of the stereo amps be bridged to mono? If so, I need direction on wiring. Thx in advance. Some amps are designed to be bridged and others are not. I'd check with Adcom tech support on your amps. I have a pair of older NAD with switches for bridged mode. There is also a specific way to connect your speakers and pre-amp! Be sure and check with Adcom on how to do this. Just remember with bridged amps the power is doubled and also the speakers impedance is effectively halved as see by the amplifier. a 4 ohm load looks like a 2 ohm load, etc. With speakers like the Maggies that may be a problem. Rick I have never heard that bridging and amp halves the speaker impedance. You don't wire the speakers differently when the amp gets bridged..the speakers remain the same and the amp sees the same load. If I'm wrong on this explain how the change occurs. Bob When you bridge-connect a stereo amp, you connect the 'speaker to the two + terminals only, leaving the negative terminals unconnected. You then arrange for the two amplifier halves to be driven in anti-phase, either with a couple of op-amps, or more easily with a centre-tapped transformer. This assumes that each stereo half is a conventional amplifier, i.e. one that that loudspeaker -ve connection is at ground. Some high-power amplifiers (like some Musical Fidelity) are already bridge connected internally, so you can't then bridge connect again. As you double the voltage across the load, you quadruple the power, so a 100 watt 8 ohm stereo amplifier becomes a 400 watt into 8 ohm bridged mono amplifier. Each stereo half then is driving 200 watts into 4 ohms. All this assumes that the amplifier is "perfect" and you get a doubling of power going from 8 ohms to 4 ohms. Most amps will be a little off perfection, so typically, a 100 watt/8 ohm stereo amp will give 350-370 watt/8 ohm bridge connected. Clearly, if the load is lower than 8 ohms, each half of the stereo pair will see less than 4ohms when bridged, so you need to be sure that the amp is happy into 4 ohms or less before bridging. S. -- http://audiopages.googlepages.com |
#11
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
On Sep 9, 11:25 am, "Bob" wrote:
"rcs3" wrote in message ... On Sep 7, 6:36 pm, FredClark wrote: A newbie at seperates and recenty aquired an adcom preamp tuner with a couple of adcom gfa-545 stereo amps. My speakers a Magnepan SMGa's. My question is can each of the stereo amps be bridged to mono? If so, I need direction on wiring. Thx in advance. Some amps are designed to be bridged and others are not. I'd check with Adcom tech support on your amps. I have a pair of older NAD with switches for bridged mode. There is also a specific way to connect your speakers and pre-amp! Be sure and check with Adcom on how to do this. Just remember with bridged amps the power is doubled and also the speakers impedance is effectively halved as see by the amplifier. a 4 ohm load looks like a 2 ohm load, etc. With speakers like the Maggies that may be a problem. Rick I have never heard that bridging and amp halves the speaker impedance. You don't wire the speakers differently when the amp gets bridged..the speakers remain the same and the amp sees the same load. If I'm wrong on this explain how the change occurs. Bob Bob, I was referring specifically to the way my NAD amps are bridged. The right pre-amp out goes to one amp's right main in. The left pre- amp out goes the other amp's right main in. The speaker connections only use the L+ and R+ connections, they do not share a common ground. this is simalar to running two speakers in parallel. In this type of setup the amp "sees" a 8 ohm load as 4 ohms, or 4 ohms as 2 ohms. That is why I advised Fred to check with Adcom on this type of setup. Rick |
#12
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
On Sep 9, 8:29 pm, Randy Yates wrote:
However, the impedance seen by the amplifier output stage, at least in the ideal case, is reduced by two, precisely because of the increase in output current you described. We have an English problem here because "amplifier" is a fuzzy term in this context. When two amplifiers are bridged, the result is a single more powerful amplifier. The load impedance for this new amplifier is the same as for the unbalanced configuration. I agree that each individual amplifier channel will now see an effective load that is only half as large as previously. If Rick's wording was altered from "the speakers impedance is effectively halved as see by the amplifier." to "the speakers impedance is effectively halved as see by each amplifier." the ambiguity would have been removed. |
#13
Posted to rec.audio.high-end
|
|||
|
|||
Bridge stereo amp
jwvm writes:
On Sep 9, 8:29 pm, Randy Yates wrote: However, the impedance seen by the amplifier output stage, at least in the ideal case, is reduced by two, precisely because of the increase in output current you described. We have an English problem here because "amplifier" is a fuzzy term in this context. When two amplifiers are bridged, the result is a single more powerful amplifier. The load impedance for this new amplifier is the same as for the unbalanced configuration. I agree that each individual amplifier channel will now see an effective load that is only half as large as previously. If Rick's wording was altered from "the speakers impedance is effectively halved as see by the amplifier." to "the speakers impedance is effectively halved as see by each amplifier." the ambiguity would have been removed. I agree. The "total amplifier" will see the same impedance while each "channel amplifier" will see half the impedance. -- % Randy Yates % "Rollin' and riding and slippin' and %% Fuquay-Varina, NC % sliding, it's magic." %%% 919-577-9882 % %%%% % 'Living' Thing', *A New World Record*, ELO http://home.earthlink.net/~yatescr |
Reply |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Bridge Amplifier | High End Audio | |||
FS: Impedance Bridge | Pro Audio | |||
Bridge sound | Car Audio | |||
How To Bridge Xtant A4004 Stereo No Mono?? | Car Audio | |||
What's an LCR bridge do? | Vacuum Tubes |