biamplification wiring how-to

Hi George,

I have 10t's as well so I'm very interested in your bi-amping experiments. I have been trying to find tube and SS amps that have gains and input impedances that match well enough to not use an external x-over. BAT amps usually come to mind but the Rogues are looking like another option here. I have not been able to find any gain specs on the M-150's so I'm hoping you'll know. The Levinson 27.5 looks to have a 26 dB gain which is a better match with some tube amps like the BATs. The Classe's I'm using have 29 dB gain so they may not match up well without the use of a x-over or I may have to swap them out with something else. As you know the 10t's like alot of power so I agree that the bi-amping is a great way to go. And the tube amp on top and SS on the bottom is great way to get that tube sound short of using 4 high powered tube amps.

I found the same thing about running stereo amps in bridged mode. Classe said it was fine to do. But I found that they weren't as smooth and ran hotter. I believe that there is also an issue with the load that the amp sees. In bridge mode an 4 ohm load looks like 2, and so forth. I agree, true mono-blocks are preferable.

I'll have to check out the Bryston x-overs. I couldn't find a Marchand that had balance connections.

Dan-ed Hi
No actually I haven't try active yet,but for sure I will one day.Bryston's Active crossovers are very well regarded.My Aerial 10T have very nice build in crossovers though.Perhaps my current set-up is a compromise, can't say for sure.I am experimenting and upgrading as my budget allows,also life gets in the way sometimes with our audiophile hobby,I think.Years ago I bought a new pair of JBL L7 speakers,they came with a nice manual by JBL.It was in that manual that I first read about bi-amping with four tubed monoblocks or two tubed monoblocks for mids/highs and solid state monoblocks for lows.My Mark Levinson is in fact a dual mono power-amp .In it's manual Madrigal cautions that a performance of the 27.5 degrades slightly when user turns the amp into monoblock configuration.I believe this holds for other high-end amps as well.Unless they are made true monoblocks from factory.I got a CJ MV55 as well and years back I wrote to Conrad Johnson regarding turning the amp into monoblock they told me that it wasn't a great idea but they could do if I insisted.
I didn't do it.
Both amps sound great as they are.That is why I bought my Rogue M150's since they are true monoblocks ,I use then as they were intented.
Best
George

Tripper,

I also have NAD power amps in a second system that are bridged mono. I found that by far the best sound IMHO was achieved by isolating right and left channels. No splitter used in this configuration. The L and R fixed level preamp outputs are each connected to the left channel input of a power amp. This is required when operating in bridged mono mode. One power amp is then connected with a pair of matched speaker cables to the left speaker (one run to the +/- bass connections and the other to the +/- treble connections). Same thing for right speaker with the other amp. This gives complete channel separation and provides plenty of clean power.

Cmpromo,

If your pre has 2 sets of outputs you can either use 2 pairs of IC's out to the amps or splitters and just 1 pair of IC's. From George's, Yioryos, posts I gather that he and I are bi-amping in very similar fashion. My IC's out to the amps are perhaps 1 meter shorter than his. As you can imagine, a quality IC of this length will not be cheap so I elected to use only one set of outputs and a single pair of IC's out to the amps. I then use a Cobalt Cable XLR-XLR y-connector to feed each channel of the amps. There could be a slight degredation with this setup vs. using a pair of IC's, but with truely balanced components I doubt it would be much.

I'm using the vertical bi-amp configuration that Tripper described. I found that in my system this had the best sound vs. the horizontal method. I have also found that the amps I have owned have sounded best when not used in bridged mode. I have not owned true monoblocks to date. Maybe someday.

George, if you're still following this thread, did you need to use an active x-over with the ML and Rogue amps?

Would you need the y splitters if you already have two sets of preamp outs. Also, do the forte amps have a mono switch. Will you have 100wpc class a with two 50 watt stereo amps?

Dq10tom
It i always better to keep all speaker cables the same length for each channel.8 feet is the normal.6 is nicer.No problem though if someone needs extra long runs.Interconnects follow the same rules.Others try for longer interconnects and shorter speaker cables,that way the amp is closer to the speakers.Physical and electrical.My speaker runs are 6 fet and my interconnects 25.I didn't need a 25 feet interconnect run but found a good deal in the used cables market.
Best
George

Nomadicslacker
Both methods are passive kind of bi-amping.The second is known as vertical.In first method we allow the internal crossover to do the signal spliting and send it to the various drivers for reproduction.So we use one pair of speaker cables per channel and keep the straps on.The interconnects are connected on the back of the pre-amp out L,R and before they connect on the back of the power amps they get a Y spliter.Therefore Left pre out to the left power amp inputs with a Y RCA spliter in place.Right channel the same way.Then the speaker cables for each channel go from RED of power-amps to RED of speakers for each channel and BLACKS to BLACKS.Straps ON.
The other method is a little different .We choose to by-pass the crossover's spliting task.We use TWO pairs of speaker cables per channel.Shotgun cables.The ends near the power amp get twisted together.All positives together and all negatives together.The positives connect with the RED terminal and the negatives with the BLACK terminal.From there they run to both speakers inputs.STRAPS OFF.The one pair of positive/negative goes to the left speaker LOW inputs .Keep the polarity the same.Positive to positive and negative to negative connections.The other amp will do the HIGHS of both speakers with same connection method.Straps off.
There is also the active bi-amplification but it is more costly and needs an active crossover with it's own power supply and all.Usually the crossover that comes in every speaker is optimized by the manufacturer for top performance.Therefore passive is more popular way of bi-amplification.
A lot of people in the hobby go for tube monoblocks for mids-highs and solid state dual mono power amp or monoblocks for the lows.That is my preffered method.
Best
George

When biamping, does the interconnects need to be the same length to both amps, such as the rule for speaker cable?

hello yioryos and tripper, thanks for the responces to my question but i don't understand leaving on the strap that connects the high input and the low input to the speaker. would that not cause some kind of shorting out effect? keep in mind i am not electrically savvy YET. hopefully i will gain some knowledge from my experimentations with audio gear and this forum, which i have found to be the best.

George's response is well-considered. I would opt for the former, where each amp handles just the left or right channel [i.e. left ch on the tweeters and right ch on the woofers]. The advantage is that the power supply of each amp is only driving one bass channel, not two. I used this method very successfully a long time ago with a pair of NAD amps and some NEAR 50 spkrs if anybody remembers those.

Let us know what spkrs you get. Good luck.

Hi
You got two options here I think.
You can use the one Forte power amp for the left channel,and the second Forte for the right channel.You also will need two pairs of speaker cables,one pair for each channel,and one pair of interconnects plus two (Y )RCA adapters.Make sure you keep the jumbers on at the back of your speakers.
The other option would be to take out the speaker jumbers and use one Forte for the highs of BOTH speakers and the other Forte for the lows of BOTH speakers.
You are at an advantage point either way simply because you got two identical power-amps.My set-up uses different brands and models of power-amps.Rogue M150 monoblocks for mids-highs and ML 27.5 for lows.
Best of luck
George