What is the advantage of bridging two amp vs one big amp?

Another point to consider is that people who go to bridged amps often own one of the amps already, and probably have for some time. So the cost for the second amp is more incremental than a decision to outright buy two amps or one bigger.

As far as advantage, again, power. If bridging provides headroom to avoid clipping then it's likely to sound better than the same amp not bridged. Yes, as mentioned, some negative characteristics may be additive in bridging, but the scope of those things is still small in the big picture; i.e. 1 penny to 2 pennies is a 100% increase...but it's still just two pennies.

I think the simpler and better way is to sell the original amp and buy a used one to save money. One can find an Acurus 200W/ch I have for like $450 on ebay. It has ok size heatsink and 4 pairs of output transistors. I have used it for 18 years driving 4ohm speakers until I replaced with a used Nakamichi PA-7 designed by Nelson Pass for $600( not working). I fixed it and recap it. I spent total of $800 and I have an amp almost identical to Threshold S300. You find a two channel 200W/ch Acurus for less than $400, put in $100 to recap it and is as good as new. For close to $1000, you have a lot of higher end amps available. Recap and you have a very good amp for life.
 
To clarify--the specs on Kappa 9's do indeed state 4-6 ohm "nominal impedance". This is borderline on an outright lie--ask anyone who owns them and has looked at the impedance curve. I have a pair here--used to have 3 pair of the monsters--there is an impedance dip down to approx. 0.7-0.8 ohm in the upper 30 Hz range, and another dip to 0.9 ohm at approx. 7 KHz--this is where they get their "amp killer" reputation. I don't care what your amp says it can do at 8 or 4 ohms (bridged or stereo), but what matters is if it is stable into a 1 or 2 ohm load. I have vertically bi-amped mine with a pair of Aragon 4004's in stereo mode, but now use 4 Krell KMA 160 monoblocks--pure class A 160w/8ohm, 320w/4ohm, 640w/2ohm, 1280w/1ohm, and protection adjustable to lower than 1 ohm operation.
I've a few amps on hand that'll drive those 9s ...
 
Tell me what else did I miss.

Alan
Personal experience with the sound so you can end the speculation? Measurements do not tell the whole story as the set guys can attest. Perhaps get a quality pair of amps and spend some time critically listening without the test equipment and theories.
 
Personal experience with the sound so you can end the speculation? Measurements do not tell the whole story as the set guys can attest. Perhaps get a quality pair of amps and spend some time critically listening without the test equipment and theories.
Of cause I know bridge get more power, more head room. Question is how does it compare to another amp that is twice the price as you need two amps to do a bridge, so it's only fair to compare to a single amp twice the price.
 
So, do we have a conclusion yet? - it seems to me from the discussion that Bridging is just a quick and dirty method of getting more power output? From the discussion - it seems likely to increase THD, complicate the system setup, and is not guaranteed to reduce cost, so why would you want to do it?
 
So, do we have a conclusion yet? - it seems to me from the discussion that Bridging is just a quick and dirty method of getting more power output? From the discussion - it seems likely to increase THD, complicate the system setup, and is not guaranteed to reduce cost, so why would you want to do it?

I don't see it necessary increase THD, definitely does not reduce THD for sure.

I can see people already have two amps, then it's worth trying as you only have to build the inverter preamp to make it work. You don't even have to have identical amps, I think it will work even the two amp are different. You might get lucky that the two amps has totally different distortion characteristics and the THD does not add, you might end up with more harmonics, but each harmonic is lower amplitude.

Unless someone telling me a compelling reason I did not list in post #61, I would not go out and buy two amp to do it. I would buy one twice the price to get better sound. The question is not whether it improve the sound, of cause you have 4 times the power, you have that much more headroom, you better see some improvement. The question is can the sound beat a single amp that cost the two amps you are using to do the bridge. Also, can your bridge amp able to drive the speaker load. Some good speakers are 4ohm, this means your amp has to be able to drive 2ohm before the bridge.

As I said before, until someone gives me a compelling reason, I'd take my chance on a single amp that cost twice the amp used for bridging. Want to save money, buy used and fix it up. I've seen great amp like Threshold S300 for $1100 used on ebay. I even saw an Aleph for $1200. You're on this forum, I expect you have no problem doing the recap and clean it up when you buy one used.
 
^^^^^^^So from what I gather it's still speculation on your part? I speculated pretty much the same thing a while back that one good capable amp will be just fine. My ears have told me a different story now that I've had experience and currently use a couple pair of bridged amps.
 
^^^^^^^So from what I gather it's still speculation on your part? I speculated pretty much the same thing a while back that one good capable amp will be just fine. My ears have told me a different story now that I've had experience and currently use a couple pair of bridged amps.

The stage has been set with somewhat presumed outcome all along. In hindsight, to some of 62caddy's earlier points in post #18, has this really even been about bridging, or simply a different twist on "average" amp vs. "good" amps?
 
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So, do we have a conclusion yet? - it seems to me from the discussion that Bridging is just a quick and dirty method of getting more power output?

From the discussion - it seems likely to increase THD, complicate the system setup, and is not guaranteed to reduce cost, so why would you want to do it?

THD: Maybe but even if it doubled, 2x next to nothing still pretty much nothing.

Complicated: Generally no moreso that hooking up monoblocks...as long as one can (typically) move a switch from the "normal" to "bridged" position. In some cases, like a Yamaha C-80 preamp, both normal and inverting outputs are provided. You can use those to bridge pretty much any amp that has common ground.

Cost: Cost will almost certainly increase unless you already own the two amps. But, what is that cost vs. performance relative to effectively starting over again with one different "better" amp?

I'll again mention my two Crown CE4000s that I run in bridged mode. When I got these amps I'm not even sure you could get a single/2-ch amp with 3600 wpc output - that's what each one of the CE4000 put out in bridged mode.

Today you can get 2-ch amps with 3600 wpc or more. But, even used, just one of those amps will cost around 2x-3x more than I paid for both CE4000s combined.
 
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I really did not set out bridge vs higher end amp. I really want to have a technical discussion on the merit of bridging. Before this thread, I just know Nelson Pass use bridge on his highest end models. I did not realize it actually increase the power by 4 times, but much harder when driving 8 ohm speaker. But as the thread progress and I really was thinking about this for the last few days that lead me to draw the conclusion from last night.

Below is my thinking only, I can only speculate. Feel free to add your idea:


At some point THD is not nothing. If THD is below 0.005% you can argue it's nothing. But if THD is like 0.1%, it is really not nothing. Just by a single frequency itself like we test with FFT, it sounds like it's very low, it's like the signal is 1V, the harmonic is 1mV. That really sounds like nothing. BUT music is a complicated spectrum with many frequency peaks. If you take many many nothing mix together, it becomes a constant hum or hiss like background varying with the input signal. That will become an issue. It's not just the harmonics of the signal, it is the IM( inter modulation) of the harmonics that actually create new frequencies when the harmonics mixing with each other. It will muddy up the music. In particular if the new harmonics is close to the main signal frequencies. It can changes the sound.

I am not an expert, I am still learning about audio. But I suspect this is what's happening. Like old tv vs HDTV. HDTV has a lot more bandwidth, you would expect the edge is a lot sharper. But in real life watching, it's a lot more than sparper, it actually looks more 3D, everything just looks deeper. Being more pixels not just make the image sharper, it greatly reduce the smear in the image like the low BW of the old tv standard. Back to audio, the harmonic mixed together form a background that vary with the original signal and form a smear that reduce transparency and sound stage.

One thing I notice is the better system feels like it's 3D, that if you close your eyes, you feel like you are in the concert and can hear different instrument in different spots. It just sounds a lot deeper.

Another thing that the books of Doug Self and Bob Cordell talked a lot is crossover distortion. It is the most offensive distortion for hearing because it creates higher harmonics like 7th, 9th and beyond. Bridging does not help in crossover distortion, so far, running class A or optimal biasing class AB ( Self called class B) minimize crossover distortion. Optimal biasing dissipates quite a bit of power...bigger heat sink, more output pairs.

Again, this is my speculation only.
 
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I want to emphasize, I mean no disrespect to anyone here. I am new and I am very interested in hifi. I am more like thinking out loud( saying out loud) here. I am making a lot of assumptions and try to bounce off to you guys and think at the same time. For all I know, I could be completely wrong. I am sorry if I offend anyone.

Alan
 
I understand that and I hope everyone else does too, this is a good tempered discussion, carry on. :thumbsup:
 
I use two Crown XLS amps in my band. I use a 600 watt per channel (wpc) amp for the PA and a 400 wpc for my bass. These are electronic class D amps and have various electronic settings. I can, via the push of a button:
1. Bridge an amp
2. apply a 12db per octave high pass filter to both channels
3. apply a 12db per octave low pass filter to both channels.
4. Apply low pass to one channel and high pass to the other, effectively making it a mono amp for one side of a bi-amplified system.

I bridge my bass amp because it powers one large speaker.
I apply the 50 hz high pass filter to both amps because it saves the speakers and power without really affecting the sound.

Modern equipment is very versatile.
 
. But if THD is like 0.1%, it is really not nothing.

0.1% may as well be nothing as far as human hearing is concerned. Many would also argue, with studies confirming this, that even 1% THD is still inaudible for the vast majority of the population.

It should also be pointed out that except for perhaps a handful of the very finest loudspeakers, distortion is in the multiple percents - so the question (and sonic advantage) of anything under 1% THD in electronics becomes all the more dubious.
 
I can speak from my experience. I have 2 Dynaco ST-400 amps that are rebuilt to new condition. I bridged each one for approx. 600w @ 8ohms available running each speaker. Sounded very nice but not as good as I was expecting. To make a long story short, I unbridged them and did a "vertical" bi-amp. In stereo mode, one amp runs the woofers on both speakers, the other amp runs the tweets. It's audio gold and the difference in clarity is amazing.
I don't really understand the technicals about it, but it has something to do with the woofers not upsetting the crossover that's trying to regulate the high pass. All I know is that it works great. Just my $.02
Jim

Edit: It's also nice having separate gain controls for the tweeters to dial them in perfectly. No messing with an L pad
I built a dynaco 400 back in 1975. I loved it until I took it to a macintosh clinic. One channel produced 203 watts and the other produced 86. I must have done something wrong. :(
 
I want to emphasize, I mean no disrespect to anyone here. I am new and I am very interested in hifi. I am more like thinking out loud( saying out loud) here. I am making a lot of assumptions and try to bounce off to you guys and think at the same time. For all I know, I could be completely wrong. I am sorry if I offend anyone.

Alan
We're not precious snowflakes. It's ok to say what you mean as long as it's not just plain offensive. ;)
 
0.1% may as well be nothing as far as human hearing is concerned. Many would also argue, with studies confirming this, that even 1% THD is still inaudible for the vast majority of the population.

It should also be pointed out that except for perhaps a handful of the very finest loudspeakers, distortion is in the multiple percents - so the question (and sonic advantage) of anything under 1% THD in electronics becomes all the more dubious.
When I sold hi-fi back in the 70's I would tell customers that the weak links in any system were the pieces with moving parts - speakers and needle/cartridge. It helped people buy fairly balanced systems.

That being said, I got a friend turned on to this stuff about 8 years ago. I bought a beautiful late 70's 50 watt or so per channel Pioneer receiver and it sounded great. He loved it.

Fast forward only two years. He finds a Marantz 2230 for fairly cheap in really good condition. It was also fantastic and beautiful in its way. So, one day we A/B them and I was dumbfounded. The Marantz really did sound better. We both noticed it. And it was obvious. Both still sounded really good, but there was no mistaking the difference.

And before anyone asks, I honestly can't remember the specifics. I just remember that it sounded "better".
 
Speculation or experience? The amps you've mentioned you have experience with are on the clinical side. What 'better' system do you have an opinion on? For me the goal has always been transparency. I'm not interested in a 'certain sound'. The most transparent amps I've heard vary widely in terms of THD. From .1% to .02%. But they may as well all be rated at .02 or .1 depending on how they were measured. They're all great sounding amps with their own character that strikes you each in a different way. The Bedini 100/100 is eerily holographic but the Meridian 105s have incredibly fast transient response, but the Son of Ampzilla is amazingly transparent. A well rounded example of all these attributes is the LSR&D model 101 or 102. The Acoustat TNT200/120 are also well rounded, bridged or not. The HK Citation 16 I find distant sounding. The HK Citation XX is exceptional in every regard. But the King of the heap in a league on it's own is the Acoustat direct drive OTL monos. If you want to truly bring speaker distortion down to the order of the amplifier, just throw a few ESL panels in front of these amps. The membrane has an equivalent mass of the air between it and the stater. Now you have an accurate sonic example of the amp's performance. No crossover or interface between them. Don't know what the actual specs are for them but I can confidently wager they are way higher than probably most here, However, the best expletive I can come up with is to say the sound is live. They really demonstrate how little influence the amp's THD actually has on the sound once it reaches the minimal figures we're used to seeing.
 
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I don't know if anyone still does this, but back in the day, when it was common for esoteric systems to have only one input, and that being a turntable, People would wire the cartridge out of phase and then undo it by wiring the speakers out of phase. The idea was that the two sides of the pre-amp and amplifier were working out of phase with each other, and that was to somehow reduce cross-channel distortion in some way.

I never did it, but maybe there are some here who could speak to that. Or am I too outside the thread subject?
 
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