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Bridging NAD C270 with 6 ohm speakers.
- Thread starter NISSE
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JeremyFife
Major Contributor
More power cannot possibly improve low volume sound (assume that's what you mean by 'lower levels') because the power you already have is not being used. You are just adding more unused power.I will. Bridging might not be the thing I need or want, but overall I want more power. My hope is that 2xC270 bridged will perform better, specially on lower levels, than one do in stereo. I will try with the 6 ohm Dalis and keep both eyes (and one hand) on heating. Again it`s all about what I hear, not what I read. The two C270 I have is in very good shape.
Thx. I
The caveat is if your amp(s) are already clipping at those low levels, but I think you would hear that and you wouldn't be able to turn up the volume.
Perhaps re-think what you are trying to achieve? Or can you explain it differently if I have misunderstood
- Thread Starter
- #23
Hi, and thanks for reply.
Yes, by lower levels I mean lower volume. So by adding another amp, there are nothing to gain, like better dynamic, better bass, a.s.o.? My idea, with more power, is that the speakers would preform better. I guess I`m wrong
.Thx
staticV3
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I fix the 6ohm problem by putting 2ohm 25W or 50W resistors in series with each speaker so the amp doesn't overheat. The sound is awesome for power and sound quality
Wouldn't that *significantly* alter the frequency response of the speakers?
Edited to add: Not to mention that now you're just burning (ie, wasting) power into the resistor.
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A resistor is a linear device unlike inductors or capacitors so it has no effect on frequency response. That is what makes it such a simple way to solve a heat problem when dealing with speaker impedance issues to get the perfect power envelope for the amp keeping it cool and getting maximum power transfer to the speaker.. Try it out you will discover your speakers sound even better when the amp is running cool. Heat in the output stages of the amplifier transistors does introduce distortion, so cool is always better.
Nope. Depending on one's point of view, it either changes the amplifier's output impedance or the speaker's crossovers. Either way, it's going to alter the system frequency response. That's because your speakers are not going to be a perfect resistor.
The amplifiers output impedance is a component of its circuitry not what is connected to it. I have a spectrum analyzer that I have connected to prove the resistor has NO affect on the frequency response only the load impedance.. If you go online and download a speaker crossover network program and load your speakers circuit then add a resistor to the front end you will see it acts on the entire crossover equally and has no effect on frequency only the loading of the amps output stage. I have been designing building and repairing audio systems for 50 years and there is no end of miss information people believe in but the test equipment doesn't lie . A resistor put in series with any speaker will alter the output impedance but has no affect on the frequency response. It is a linear component it has no phase shifting action. The current and voltage are in phase with each other no matter what frequency you put across it. The only thing the series resistor does is alter the transfer of energy as a function of time. This reduces the current load seen by the amplifier with no affect on the frequency response!
When you buy a signal generator and it says "OUTPUT IMPEDANCE 50 OHMS" it doesn't matter what you connect to it. Its internal output impedance does not change! Same with an amplifier or any electronic device. It's output impedance is never altered by the load. Connect a resistor still 50 ohms...connect a capacitor or inductor or any combination the output impedance is not altered. it is always 50 ohms. The amplifier is the same, the load makes NO change to the amps output impedance.. So if you put a series resistor of 2 ohms from the amps output the output impedance looking back into the amp is 8 ohms (a common amp output impedance) plus the 2 ohms you added in series. It will never change dependent on the output load. It will however alter the overall system impedance dependent on the load. The laws of physics don't change because you have been told incorrect information. The C270 output impedance is 8 ohms. to get maximum power transfer the load needs to be 8 ohms. Any other value causes a poor power transfer issue, heating distortion to name a few.. I taught Electronics Engineering, Physics, Mathematics and Computer Science for 10 years. If I got it wrong then the entire University all my peers and hundreds of students got it wrong. So thousands of people are wrong and you are right...who do you think has it right?
You're embarrassing yourself.
Aah, the loudness effect due to a high impedance source feeding a load with varying impedance. A cheap way to emulate tube amp sound with SS amps, but burns part of the available power in the resistors.
Of course, a loudness knob is the better way.
Up to here this is correct.
The output impedance of SS amps is not 8 Ohms, it's very low (say less than 0.1 Ohm). I think you misinterpret the recommended load impedance with the output impedance.
Correct.
No, see above.
No, see above. Audio amplifiers are voltage sources, and the maximum source current defines the minimum load impedance. They are not designed for maximum power transfer which in audio is a relict from 70+ years ago, if it was used at all.
No, see above.
Ouch.
From a practical standpoint (having worked on both the C370 and C372, which feature nearly identical power stages):The output stage uses four parallel pairs of 2SC5200/2SA1943 devices, enabling it to drive lower-impedance loads smoothly until the SOA protection engages. While the power supply reservoir capacity is adequate (40000muF), the main limitation lies in the mains transformer. Supply rail sag under load prevents the amplifier from achieving anywhere near a theoretical 2-times power output increase into lower loads.
A more pressing concern is NAD's original thermal layout and component rating choices. Almost all power resistors should be upgraded to the next higher power rating, and the surrounding solder joints should be overhauled to fix heat-induced stress.
A more pressing concern is NAD's original thermal layout and component rating choices. Almost all power resistors should be upgraded to the next higher power rating, and the surrounding solder joints should be overhauled to fix heat-induced stress.
Unclevanya
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I have heard the effects of bridging vs both horizontal and vertical biamping with a set of speakers that had the option to bypass the passive crossover and use an electronic crossover.
Speakers: infinity RS 4.5’s
AMPS: perraux 2150b pair
Crossover: dalquist (don’t recall model).
Bridged was louder than any other config but it seemed a little harsher. These were not blind tests per se, but the system wasn’t mine and my friend made changes between sessions without informing me. To be fair the bridge condition removed the electronic crossover and relied on the passive one which was a major difference and might account for the sonic differences.
Condition two (horizontal) was each amp driving either lows or highs of the pair.
Condition three was each dedicated to a speaker, one channel driving wife and the order other driving tweeters/mids.
None of these sounded s as good as his normal biamp setup with a 100w tube amp on top and the perraux on the bottom. This is likely due to some harshness on the top that the tube amp rolled off.
In any case horizontal and vertical biamping seemed roughly the same to me. The advantage of vertical from what I have read is only going to be realized if there’s a shared power supply between channels (I think the Perraux was true dual mono) or if there’s a thermal issue with the amp. This because bass will tend to require more current than mid/treble.
My current speakers offer separate terminals for high/low but have no way to bypass the crossover so even if I had multiple amps I wouldn’t expect benefits other than with vertical biamping and only if the amps were on the edge and needed thermal help or were prone to power supply exhaustion Running both speakers. But I never listen loud enough for that with my typical gear and it would be easier to simply buy a larger amp in my situation.
As for the earlier practice of running only one channel - in a non dual mono amp if you pushed it hard (not low volume) I can see how the power supply would be less stressed and able to maintain the amp output better. Another person mentioned that the input transformer on those amps is undersized and the thermal design is also undersized. Thinking a single side at a time will allow both of those problems to be minimized.
Buying a different amp or pair of amps is also an option.
I did hear the system with the tube amp on top and the pair of perraux amps on bass bridged. I honestly didn’t hear any difference. The tube amp ran out of steam and our ears ran out of steam before the single non-bridged perraux gave out so bridging was not going to do anything useful in theory and practice designed to confirm this subjectively at least.
Speakers: infinity RS 4.5’s
AMPS: perraux 2150b pair
Crossover: dalquist (don’t recall model).
Bridged was louder than any other config but it seemed a little harsher. These were not blind tests per se, but the system wasn’t mine and my friend made changes between sessions without informing me. To be fair the bridge condition removed the electronic crossover and relied on the passive one which was a major difference and might account for the sonic differences.
Condition two (horizontal) was each amp driving either lows or highs of the pair.
Condition three was each dedicated to a speaker, one channel driving wife and the order other driving tweeters/mids.
None of these sounded s as good as his normal biamp setup with a 100w tube amp on top and the perraux on the bottom. This is likely due to some harshness on the top that the tube amp rolled off.
In any case horizontal and vertical biamping seemed roughly the same to me. The advantage of vertical from what I have read is only going to be realized if there’s a shared power supply between channels (I think the Perraux was true dual mono) or if there’s a thermal issue with the amp. This because bass will tend to require more current than mid/treble.
My current speakers offer separate terminals for high/low but have no way to bypass the crossover so even if I had multiple amps I wouldn’t expect benefits other than with vertical biamping and only if the amps were on the edge and needed thermal help or were prone to power supply exhaustion Running both speakers. But I never listen loud enough for that with my typical gear and it would be easier to simply buy a larger amp in my situation.
As for the earlier practice of running only one channel - in a non dual mono amp if you pushed it hard (not low volume) I can see how the power supply would be less stressed and able to maintain the amp output better. Another person mentioned that the input transformer on those amps is undersized and the thermal design is also undersized. Thinking a single side at a time will allow both of those problems to be minimized.
Buying a different amp or pair of amps is also an option.
I did hear the system with the tube amp on top and the pair of perraux amps on bass bridged. I honestly didn’t hear any difference. The tube amp ran out of steam and our ears ran out of steam before the single non-bridged perraux gave out so bridging was not going to do anything useful in theory and practice designed to confirm this subjectively at least.
Unclevanya
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I wouldn’t bridge these NADs based on the input already received. Using the two amps with one channel unused seems a possible value if listening loud to reduce thermal stress and power supply concerns. Running then bridged seems to increase both of these concerns with no benefit.
