One thing I did not see mentioned in any of the responses is that whenever an amp is bridged, the load impedance it sees is halved and it is called upon to deliver twice the current. This means a nominal 8Ω load is seen as 4Ω by the amp, and a nominal 4Ω load is seen as 2Ω.
Not all amps, actually few, can operate in bridged mode into such low impedances without being adversely affected. Just something to be taken into consideration when thinking of operating amps in bridged mode. |
Hello Jimjoyce25,
"It must be nice having as intuitive a sense of electronics "....
I don't - I learn. See, for example, thougtful post on the subject:
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1215786174&openflup&23&4#23
I am out of this thread
All the Best
Rafael |
As I mentioned in my earlier post, I have been using two stereo amps as mono amps with excellent results. Perhaps a better way is to look at this would be to imagine 2 cars each with an available 300HP. One weighs 3000lbs, the other 1500lbs. Everything else being the same, which car will go faster? One of my reasons for doing this "experiment" was based on that sort of logic. The stereo amps existing power supply now sees only 1/2 of it's original specified load.
Note, I've only run single ended as balanced is not an option with the Forte units, wish it was.
So why do I run two stereo amps like this in the first place??? Well because I bought the first Forte amp and really enjoyed it! Since having hard to drive electrostatic speakers, I thought I would get another unit and have them bridged. Looked for and found a "deal" on E-Bay, but got jacked by the seller, one channel was toasted, guess he forgot to put that in the description?
Ok, what to do? Well, I was looking at two amps and three working channels or two amps and two channels and a spare amp module... or virtual monoblocks! |
I did this experiment many years ago for a relatively short time with two Parasound 750 stereo amps powering Paradigm Studio 100s V1, using only one channel of each amp for each speaker. It was OK but then I upgaded to a Bryston 4BST stereo amp and things got noticeably better. So it will work but it depends on the power and budget. My sense is that the price for one high quality stereo amp will provide better results than two amps added together cost the same. |
Spoken like a true audiophile. It must be nice having as intuitive a sense of electronics as you have of your own body! Why experiment indeed! |
Hello Jimjoyce,
Double no - I am not attorney and I did not do this experiment. I can't comprehend that someone having two channels which he/she/it can use "free of charge" in fully balanced mode will choose volunterely to use only one channel.
Its almost like experiment: to run on one leg or to run using both legs...well,almost. - we all did this experiment.
All The Best
Rafael |
Dob-----Are you by any chance an attorney? I noticed you didn't answer the question I posed: Have you actually done a comparison listening to the amps running in both modes? It would be interesting to hear from someone who has done this.
With the Sunfires, to run in mono-strapped mode, you need a single-ended cable input. My cables are balanced, so I can't do this, and I just run one channel through each amp. Hence, my interest in hearing from anyone who has actually done a comparison like this. |
You might want to try the configuration I'm using in a second system. It has two Forte 3's run as monoblocks. I've been very happy with the results. The biggest improvements were in the channel separation and soundstage/depth. Note that I've not bridged the amps. My set up was done by removing the +/- fuses from one of the channels in each of the stereo amps. This way you will have a virtual monoblock consisting of a dedicated chassis, transformer and power supply for the remaining amp to use without sharing these resources as in a typical stereo amp configuration. If the topology of your amp does not share anything other than the PS you would be good to go. |
Jimjoyce25,
The immense advantage of monoblock running as Spectron does - you can run them FULLY balanced and thus:
"...balanced mode of operation doubles the slew rate and bandwidth by virtue of the out of phase transmission. This also suppresses the noise and buzz originated upstream from the amplifier. The other major advantage of mono balanced mode in Spectron amplifiers is that transmission of both positive and negative signals (in each amplifier) is maintained separately from the amplifier's input to the speakers binding posts. Assuming that the signal path electronics are matched, all of the intrinsic amplifier distortions arrive at the speakers with practically identical amplitude but with opposed polarity and essentially cancel each other. The result is a largely noise and distortion free sound transmission, leading to a spectacular improvement in three-dimensionality and resolution of detail in the music"
i.e. utilizing two channels, as Spectron does, you can run them with two sets of signals but opposed polarity and practically eliminate any distortion.
When you run only one channel you double your headroom which is immensely important but you keep the same distortions in signal path.
All The Best
Rafael |
another option is to run them in a vertical biamp arangement, if your speakers accommodate it. This would give you all of the benefits you're after - separation, and power. |
Dob----Have you compared how your amps sounded bridged/mono vs. one channel per amp? Or have you only run them in the mono configuration? Undoubtedly, there would be a significant improvement either way as compared to running one amp in stereo. It would be interesting to know how the two methods of running two stereo amps actually compare to each other. (This may also vary from manufacturer to manufacturer.)
With Sunfire amps, the full power supply is utilized either way, and you get the same level of current either way. My understanding is that mono-strapping these amps only increases the voltage, which may or may not be desirable given the speakers they are driving. |
Yes, you can and in FULL balanced mode - see Spectron web site, monoblocks.
To use one channel when two available is simply stupid, stupid, stupid
All The Best
Rafael |
Thanks to all, I was going to call Edge before going down this road. I just cannot bare to sell these outstanding two channel amps for monoblocks. |
2 channel stereo into mono........gain little more power and headroom!! |
Jeff,
If you're only planning on using the LC on one and the RC on the other, then the main benefit, as Onemug notes, would be better separation.
In one of my systems, two Pathos Classic Ones are running in bridged mode and there is a noticeable difference in separation, sound staging, headroom and bass articulation.
Do a search on the Pathos in bridged mode and you'll likely hit Doug Schroeder's write up about this. Though his focus is on the Pathos, I'd imagine that similar benefits would accrue for amps that can be bridged. If the Edges can't be bridged and your speakers can be bi-amped (i.e., separate tweeter and woofer taps), perhaps you may try vertical bi-amping using one channel of each for the high and low of one speaker.
Cheers,
Garry |
This works great with Sunfire amps. I've tried it with both the 300s and the Signature 600s. Both are great improvements over using one amp in stereo, and the 600s are far superior to the 300s. |
In theory you should gain aeparation with 2 chassis and a little more power/headroom with one power supply for each channel. Will you hear a difference? Try it and let us know.
Only negative might be the unused amp channel not being hooked up to a load. With most SS, the amp doesn't mind but you might check with the manufacturer to be sure. |
I was planning on using the left channel on one and the right channel on the other, so I'm basically using one half of each two channel amp. So I guess your refering to a "stereo mono mode". My hope, since I have two identical two channel amps was in channel separation by using two independant power supplies. I have never tried this, but it seems feasable unless someone knows of any negatives in this approach. |
I'm not familiar with your amps, but are you bridging them to Mono, or using one channel of each in a "stereo-mono" operating mode?
I'm far from an authority on this topic, but I think it depends on the amp. Except for raw power output, many amps don't perform as well bridged (ie, sonically)as as the do un-bridge. Parasound published in some of their user manuals that using them in "stereo-mono" will produce better sonics than when bridged. In addition, because the power supply is only driving one channel, the power output is about 40% higher than rated for 2 channels driven. |
