Bi amping - More complicated than I thought?

[lordmortlock]

Whilst I understand the basic premise of bi amping I'm unsure on a couple of points. I understand that you run hi/mid from one amp and the lows from another but how do actually take the sound from the pre to two amps? Do you need a crossover between pre and the amps? It not a bit of equipment that gets discussed here much.

Wouldn't you also have to disable the crossover in the speaker for bi amping to work properly? All sounds a bit scary to me - have I misunderstood?

 

[jaxwired]

I'm no expert and I've never tried bi-amping, but here's my understanding for what it's worth. Many pre-amps have 2 sets of pre-out phone connections. On my pre-amp, there are 2 sets of phono outs for connecting to amps. Also, on my pre-amp, 1 of the outputs has a variable control that would allow a person to dial in the right power level for a second amp if it wasn't identical to the first amp.

The speakers are a simple matter. You just remove the factory metal bar connecting the two sets of binding posts. Then you connect Amp 1 to the bottom speaker binding posts, and amp 2 to the top set of speaker binding posts.

I'm not positive, but I suspect that if you only have 1 set of pre-amp outputs, you could use a 1 to 2 splitter cable to connect to 2 amps from a single pre-amp out. But obviously have 2 sets of pre-amp outs is a much better solution.

If you do have 2 sets of pre-amp outputs, but they are both fixed (no way to dial one up or down to match the other), then you have 2 options:

1. Use identical amplifiers. This is best anyway.

2. Buy an amp that has a dial to regulate the phono input signal. Some amps have this feature.

Now, all this makes bi-amping sound very complicated. It's not really. The simple solution is buy two identical amps and use the 2 fixed pre-amp outs to hook to each amp. Then hook each amp up to one single set of binding posts on the speakers. That's the simple approach.

Are you thinking about buying a second 909?

 

[Gwyndy]

Think jaxwired has covered almost everything there is, two things I can add are

1 Some amps allow you to daisy chain if you haven't got two pre-outs

2 If you can't use identical amps, amps from the same series or same manufacturer should be okay, the important thing is that the gain is matched, for example I have an LK140 on he bass and an LK85 to the treble.

 

[Gwyndy]

Directions for bi-amping the quad are on page 7 here
http://www.quad-hifi.co.uk/downloads/Quad%20909%20Manual_3.pdf

 

[SteveR750]

This is my simple understanding: Bi-amping, like bi-wiring relies on the crossover in the speaker in exactly the same way as conventional single-amping does. The benefit is that because the different drivers will probably present a different load to the power amp, which might compromise the signal to one or both drivers if driven from the same circuit. Using a separate amp for each driver (though the tweeter will be fed through the x-over, whilst sometimes the bass driver might not be; simply relying on its natural roll off) might reduce this differential load signal interference or similar...

 

[lordmortlock]

Thanks all - I'd found a couple of articles online that made the process sound a bit more involved than I'd wanted.

http://www.oregondv.com/Audio_FAQ_Bi-Wire_Bi-amp%20.htm

I'm using a Quad CDP2 which has both a fixed and variable output so I'll have a good read up and see whats what. It may be of course that I need a dedicated pre.

jaxwired:

Are you thinking about buying a second 909?

Hey Jax - yeah maybe. I saw one on a famous auction site that didn't hit reserve and it got me thinking that it might not be too expensive an upgrade. I'm wondering if a second amp or a dedicated pre would the most sensible upgrade path. Not that it doesn't sound lovely at the moment!

 

[jaxwired]

Well, my thoughts are that more power is always better than less power. I think that in your case though, bi-amping would probably be a pretty subtle improvement, just because your speakers are not especially hard to drive. 8 ohms at 88 db sensitivity isn't bad at all.

My dyns would benefit more, but they only have one set of posts...

 

[Bodfish]

Many (many) moons ago I ran a complete Meridian system initially with a 551 Intergrated. I bought a 557 power amp (200w per channel

) and ended up bi-amping my B&W CDM1SE's (so a total of 265 watts per channel

).

Now this was a massive improvement over the 551 on it's own (like alot of samller standmounts, the CDM1SE's really came alive with the extra oomph the 557 provided) but it was nothing compared to replacing the 551 with a dedicated 502 pre-amp.

My view is the dedicated box, PSU, signal path layout etc for the low level signals in the pre really benefitted from being away from the noisy power amp stage in the intergrated amp.

 

[lordmortlock]

Thanks Bodfish thats really useful. The CDP2 I use is a bit weird as its both a cdp and a pre amp so although its not in with the power stage its sharing the PSU and some circuitry. I've read up a bit today and I'm getting the impression that a dedicated pre might be the first purchase.

 

[Bodfish]

No problem!

One thing you could try pretty easily is purchasing a 1>2 RCA splitter from Maplin (a few quid at most) for your CDP pre out and then find a good Quad dealer who will loan you another 909 for a weekend. My experience is most dealers are happy to let kit go out on dem for a deposit (or in some cases a full value credit card swipe) or even on good will if you're a regular customer.

Like everything else hi fi - try before you buy!