Halo A23

[Pookie007]

Maybe this is a question that Peter can answer, but I have been playing around with my amps trying to figure out what to buy next. I have a couple A23 and was thinking about getting a third. I decided to use the pair bridged to mono to see how they performed on 2 channel audio on my B&W mains. Two things shocked me.
1) They sounded incredible.
2) They seem to run cooler than they did in stereo.

Is there any problems with running these in mono for the long term? If I get the third amp, I could run a amp to each of my front speakers in my work apartment system. At the price I could also get a 4th to use in stereo for the surrounds. This would give me matching amps all the way around. I was thinking of going with Monitor Audio speakers or possible Martin Logans (I live in Lawrence, KS and want to support the home town team).

[dancremeans]

Hey, I've also been using a pair of the A23's in bridged mode, and like you, find the sound to be pretty amazing. I've recently compared them against my Nuforce ref 9 (V2 upgrade) monoblock amps, and I think they hold up pretty well. The A23's really shine at staying open and un-congested at high volumes, and dynamic musical passages, which I really like. I also like the sound of the A51's, which I also own.

Dan

[Peter Nielsen]

1) They sounded incredible.

That's an indication that your speakers need more power than the A21 can deliver non-bridged.

Non bridged, the A21 delivers 200W to your 8 ohm speaker.

Bridged, the A21 delivers 800W to your 8 ohm speaker (which presents itself as a 4 ohm load to each channel of the A21).

If you connect a 4 ohm speaker to a bridged A21, it should theoretically deliver 1600W, but as you might expect, the amp will choke on this low impedance load.

Bridging increases distorsion and the halved impedance makes it harder for the amp to cope with impedance dips.

Is there any problems with running these in mono for the long term?

No, but beware that your speakers need to be 8 ohms. Also, beware about speakers that are "difficult loads". If the speaker is 8 ohms, but can dip down to the 4 ohm range, this means that when you run the amp bridged, that speaker will dip down to 2 ohms per channel. This can put a lot of strain on the amp...

Instead of bridging, consider passive bi-amping (if your speakers have two pairs of terminals that allow this to be done). This will work with 4ohm speakers too. All you need is a pair of Y-cable for the XLR or RCA input, and another pair of speaker cables.

IMHO bridging should be avoided. Passive bi-amping is better, and of course, the best thing is active bi-amping with an electronic crossover (but the latter requires that you can physically remove the passive crossovers in the speakers).

Martin Logan electrostats are 4 ohms, so they are not an option if you want to bridge. The models with powered woofer (e.g. Summit), are not good candidates for bi-amping either... Consider Maggies instead :W

Peter

[Chris D]

Just to make sure, we are talking about the A23, not the A21, right?