Bi amp versus Bridged amplifier

Paul explains the difference using a bridged amp versus stereo and bi-amping.

[@paulstubbs7678]

Many amps tend to work better, as in less distortion, better damping etc., when working into a higher impedance/less load. in bridging each side of the bridge kind of sees half the speaker, as in an 8 ohm speaker will be split 4 ohms into each side (that why you get more power/volume). On the other side bi-amping each amp only sees one driver, so even less load - so hopefully better sound.

[@thomasgunn4146]

To those that are wondering what that board is for, if you’ll indulge me, it would appear to be the main board for the “Analogue Box” of the TSS Obsidian DAC we saw at Axpona 2019 ladies and gentlemen. You know, the one that disappeared into obscurity that I myself had personally thought had just morphed into the DS Mkii. That board looks identical to the back of that chassis. The hype train is back on the rails!

[@hugobloemers4425]

Is that Paul showing off a discrete R2R DAC prototype? That would be awesome, and expensive!!

[@DJ_BROBOT]

I said the exact same thing...we know a R2R dac when we see it

[@BlankBrain]

The production boards probably wouldn't be hand-soldered.

[@birgerolovsson5203]

I have two Primare A34.2 that I can bridge and use one for each speaker but I can't stand that when you bridge a power-amp you get a very weak power-amp in lower impedance so instead of bridge my power-amps I bi-amp them so I have one power-amp for the bass to both speakers and the other for the treble/midrange.

[@sevestan]

Picked up a pair of those Rotels and a couple of B&Ws at an Estate sale that were originally bought in '99.....methinks that was a popular recommendation back then for higher end systems.

[@NoEgg4u]

@1:14 -- Hide the board from Jonathan. ;-)

[@janinapalmer8368]

Well said 👍... I totally agree 😀

[@randomtube8226]

Does that mean that it's best to have a dedicated mono block amplifier for each driver? With that said what is better for sound quality, passive or active crossovers?

[@bradstone2603]

Bi amping is best with an active crossover beforehand. But you should remove your passive crossover as well.

[@Skye_the_toller]

So, you need 2 sources (same Chanel with 2 outputs)? Or use a splitter? Or do you have a mono input on your amps?

[@EirkenElite]

That board denafrips style solid state dac

[@Roosville1]

Just to correct LassKinn747 and clarify. Bridge = 4X power in watts, votage into load is doubled, watts is *4. Running as Bi-Amp will mean that the treble amp will be working a fraction of watts of the low frequency amp, as the spectral power requirement in the low frequency end is _generally_ (audio meterial dependant) higher. Side note, if you are soldering SMT, get some solder paste with a suitable size nozzle and a compressed air foot operated solder deposition station. I can only see solder reels here, I hope that isn't what you used. The station will deposit identical solder amounts to pads, and the solder paste with a much higer flux content, solders a lot easier. Benign flux will save the wash.

[@glenncurry3041]

I think the writer confused bi-amping for bi-wiring. They start out saying they have bridged Rotel amps. A pair operating as mono-blocks? One combined output per channel to two sets of speaker terminals, thus bi-wired? And asking if they should not use the bridged mode and power each driver separately. A set of wires from each individual amp out to each speaker connector. Thus bi-amped. Yes you have greater power out in bridged, especially since the amp(s) individually see half the load and thus theoretically will power double. But now you are driving a single system which has passive devices for crossover and that total power is shared across multiple drivers. So going bi-amped might give less power out to the speaker terminals. The direct connection to the driver bypasses any cross over loss and the power is not divided across multiple drivers. So you would not expect a dramatic SPL reduction if much at all. And especially if the stereo amp chassis is dual mono PS, the extra headroom for the mids with the bass removed often allows more dynamics in that range.

[@bjornjagerlund3793]

I tested this once and it sounded cleaner when I biamped. It seemed like the distortion raised when I bridged the amps.

[@gotham61]

I don't understand the question. He says the speakers are being "biamped, using bridged Rotel amps" That implies that he's using four amplifiers in bridged mode. Maybe he meant to say that he's not biamping but using two bridged amps in mono, but is considering running the amps in stereo and then biamping.

[@tlinrin887]

Took me a few to figure it out also, he is running the two amps bridged, one for each speaker. He is wanting to know if it would be better to run them in stereo. One for the highs one for the lows.

[@hoobsgroove]

it's not going to be less volume you just have to drive the power amplifiers harder from the preamp what could be better. probably will be, listening volume will be the same as bridged you won't notice it being quiet just that you have to turn the volume up more on the preamp, what is a better thing. do horizontal bi-amping not vertical, get yourself an rcas low pass filter for the woofer depending on speaker but that it rolls off at 500 Hertz should be fine at 18-24 DB and Y splitters. for the mid range or and tweeter just have it direct from the amp. better still find out what the crossover point is and be slightly higher than that in the filter, say if it crosses over at 350 hertz then 500 Hertz filter.

[@mcspencer1723]

Mr. Paul McGowan, you do look like @doctorhoeflinger

[@ThinkingBetter]

Yes, as audiophile, stay away from running bridged operation. It's sort of doubling the components involved and for audio signal paths, less is often more. Double the output voltage quadruples the power or equivalent to 6dB gain. To subjectively sound twice as loud you need approx. 10dB. I rather run each speaker driver with a separate amp and do my cross-over on the line level or even better, cross-over the audio digitally. I hope at some point PS Audio will start looking into next-gen architectures for DSP based audiophile cross-over filtering and optimization.

[@jaakkolehto1487]

Yeah but also the output stage in bridged mode sees half the impedance as compared to single-ended. This can and will cause distortion, especially odd order harmonics as even order harmonics are mostly cancelled out. Active crossover bi-amping all the way. Also I always prefer a good DSP with FIR filter capabilities.

[@ThinkingBetter]

@@jaakkolehto1487 Yes, agree, bridge mode is a thing for a party setup and not for audiophile listening.

[@boydsargeant7496]

Thanks, I bi-amp mine. Ta.

[@RectifiedMetals]

The voltage is the exact same. Bridged or not, each side runs on the same +- rails. Bridged mode switches drops the output impedance by half, usually, and Rotel does that. The current does not “quadruple.” 😒

[@Paulmcgowanpsaudio]

No, sorry, but you're incorrect on the voltage. Let's say you have two amplifiers, each outputting 10v rms. If you bridge the two so that now you are measuring between the two Plus terminals, you will have 20V rms. A balanced circuit that starts with single ended and then gets doubled always has twice the voltage. You are correct that the impedance is halved, and when you have twice the voltage and half the impedance....you can figure that out. :)

[@sevestan]

Are you saying those Rotels are designed to possibly be used bridged?

[@RectifiedMetals]

@@Paulmcgowanpsaudio double the voltage but half the impedance is not different than doubling the impedance and halving the voltage. I don’t see where I’m incorrect here.

[@jonathanvanier]

@@RectifiedMetals Your initial comment was incorrect, and Paul correctly explained why. The voltage in this case is not only determined by the rail, because voltage is relative to a ground (that's why Paul underlined in his reply that you will be tying the two positive outputs and not one positive and one negative). The voltage will in fact be doubled in bridge mode. And combined with the halving of the impedence, you will indeed get quadrupled the current. Paul can make mistakes like anyone else, but this is not one. As for your second comment, it is incorrect because you neglected the implications of Olm's law (I=V/Z). If you double the voltage and halve the impedence, you get four times the current: I = 2V/(Z/2) = 4V/Z. But if you double the impedence and halve the voltage, you get one fourth: I = (V/2)/2Z = V/4Z. In other words, there is a sixteen fold difference between the current in the two scenarios. I'm afraid it's not entirely intuitive, but that's how it is.

[@Paulmcgowanpsaudio]

@@RectifiedMetals Let me see if I can help you. Let's take an example (this is all just using Ohm's Law). 20 volts fed into a 4Ω load uses 5 amps of current and produces 100 Watts. 10 volts fed into a 4Ω load uses 2.5 amps of current and produces 25 Watts (4X Watts as I had said in the video). If we take your example, 10 volts (1/2 20) into 8 Ohms (2X 4Ω) we get 12.5 Watts and we use 1.25 amps of current. Very, very different. Ohm's law isn't that hard. There's an online calculator you can use if you want ohmslawcalculator.com/ohms-law-calculator Hope this helps.

[@lasskinn474]

bridged is twice as much maximum peak to peak voltage. double the watts. in theory anyway. if you never run your amp at full blast when undbridged then it's completely useless to bridge and likely to add distortion.

[@spacemissing]

This is why you Need to Pre-Read Questions and Prepare Correct Answers before recording videos.

[@donny303]

Of course they do....even print them out for Paul to read!

[@gotham61]

I'm convinced that the "letters" are all written by someone at PS Audio, but also that Paul doesn't read them until he's on camera. If they actually were real letters from random people, he would be stumbling over a lot more confusing questions that are difficult to understand due to poor syntax, spelling, and grammar. The questions he reads all tend to have a very similar tone and voice.

[@Skye_the_toller]

@@gotham61I wrote to him… and the syntax was near mine… I do not think people at PS audio has time to write questions… there is enough people out there to do it😜

[@Mark-lq3sb]

@@gotham61 No