Bi-amp feature doesn't work

pie_man_25 · #1 10-20-2011, 02:33 PM

Hey,

I'm wondering if you guys can help me figure out this problem I'm having with my Acoustic B-3 head. It has a bi-amp feature - I've tried using it with my warwick 410 for the bass and a 6" tweeter for the high end. I can plug both cabinets into the amp, but they don't make any sound - any sound at all not even any white noise or hum. It works with thw mono-amp feature into my warwick 410, but not with bi-amping. What could possibly be wrong with it?

BassmanPaul · #2 10-20-2011, 02:44 PM

You are doing something wrong or the amp is faulty. That seems to be all that comes to me. A 6" is a midrange not a tweeter BTW.

RickenBoogie · #3 10-20-2011, 02:48 PM

I suspect the wiring or connections first, faulty equipment 2nd.

solodb · #4 10-20-2011, 04:26 PM

Are you sure the Acoustic B3 has 2 discrete power amplifiers inside- one for highs and one for lows? If it doesn't, those bi-amp outputs are internally crossed-over levels to go to a stereo amp and two speaker cabinets.

1n3 · #5 10-20-2011, 05:33 PM

I think solodb hit the nail on the head. Looks like there's only one internal power amp, so the biamp outputs are line-level. I'd guess you'll need to patch one side back into the internal power amp, and send the other side to a separate amp.

Since there's no switch to toggle between biamp and full-range mode, the details of operation aren't obvious. One of the biamp sends might be a switching jack.

pie_man_25 · #6 10-20-2011, 06:10 PM

Quote:

Originally Posted by RickenBoogie

I suspect the wiring or connections first, faulty equipment 2nd.

I know for a fact it isn't connections - the connections were the first thing I've checked when I got this amp.

Quote:

Originally Posted by solodb

Are you sure the Acoustic B3 has 2 discrete power amplifiers inside- one for highs and one for lows? If it doesn't, those bi-amp outputs are internally crossed-over levels to go to a stereo amp and two speaker cabinets.

actually, I'm not entirely sure, I'll have to check it out tomorrow before class.

Quote:

Originally Posted by 1n3

I think solodb hit the nail on the head. Looks like there's only one internal power amp, so the biamp outputs are line-level. I'd guess you'll need to patch one side back into the internal power amp, and send the other side to a separate amp.

Since there's no switch to toggle between biamp and full-range mode, the details of operation aren't obvious. One of the biamp sends might be a switching jack.

yeah, it doesn't really say much - maybe I should get the schematics here:
Acoustic*Schematics

I doubt that the amp is "faulty" in any sense, but it could be that a solder joint might have come loose. I do think now that it might just be a preamp/dual line out with a crossover.

1n3 · #7 10-20-2011, 06:42 PM

Quote:

Originally Posted by pie_man_25

yeah, it doesn't really say much - maybe I should get the schematics here:
Acoustic Schematics

Schematics shouldn't be needed. The rear panel photo (link above) shows only one set of power output jacks, This isn't an uncommon arrangement for amps with built-in crossovers.

You can confirm my hypotheses with a quick experiment: Run a patch cord from the low freq biamp out to the power amp in. Sweep the crossover point. Notice more treble content as you rotate CW?

If I'm correct, you'll need another amp for the HF side.

pie_man_25 · #8 10-20-2011, 06:55 PM

makes sense, I think it's a pretty interesting feature - although I don't know how practical it would be to carry around two heads - one being the B-3 and the other being a power amp for the treble of the bi-amp.

unfortunately, I can't test it out right now - I'm in class at the moment, but I'll test it out when I get home.

fourstringburn · #9 10-20-2011, 07:33 PM

I'm not familiar with that amp. However, any bi-amping is just that, 2 amplifiers. Any amp that I have seen that has complete bi-amping ability is a stereo amp which could be used for bi-amping if it has a built in crossover for using each of the stereo sides for the highs and lows.

Mono amps that have crossover outputs for the highs and lows so you can separate between both amps still need another amplifier and that's what it sounds like you have here. So yes you need another amp to bi-amp.

It is always a good idea to experiment with as many setups as you can to what works best for you and I encourage you to do so.

IMHO, While bi-amping seems like a great idea for bass, I have personally found running amps at full range sounds best for me while Bi-amping and/or tri-amping seems to be best for the total band mix thru the P.A. system because of the broader frequency spectrum between different band instruments and vocals.

fourstringburn · #10 10-20-2011, 07:42 PM

Update...I found a link which gave pics and spec's on your amp. It is not a stereo amp, it is only a mono amp. So yes you need another amp head to biamp but you only need a power amp since this amp you have would be the master tone control for the highs. A small P.A. amp about 150 watts would do fine.

You could use this amp for the lows and buy a small amp for the highs since high frequencies don't require a lot of wattage or do the reverse and get a more powerful amp for the lows and this would be great for the highs. Good luck!

pie_man_25 · #11 10-21-2011, 04:58 PM

I tried plugging the output for the "low end" into the power amp, it works. Go figure. This actually gives me some interesting options, like fourstringburn says - I could get a 1,000 watt power amp and plug the bass into that and then plug the treble side into the 320 watt built in power amp. Of course, now I just need an excuse to use that much power.

1n3 · #12 10-21-2011, 06:22 PM

Quote:

Originally Posted by pie_man_25

I tried plugging the output for the "low end" into the power amp, it works. Go figure. This actually gives me some interesting options, like fourstringburn says - I could get a 1,000 watt power amp and plug the bass into that and then plug the treble side into the 320 watt built in power amp. Of course, now I just need an excuse to use that much power.

A simpler, lower-power option would be to run the HF output to a small guitar combo amp. Would give you some interesting distortion and/or effects options.

pie_man_25 · #13 10-21-2011, 07:03 PM

Quote:

Originally Posted by 1n3

A simpler, lower-power option would be to run the HF output to a small guitar combo amp. Would give you some interesting distortion and/or effects options.

hmm.... I do have a small guitar combo amp - a tube 5 watt "regal", would that be enough?

1n3 · #14 10-21-2011, 09:46 PM

Quote:

Originally Posted by pie_man_25

hmm.... I do have a small guitar combo amp - a tube 5 watt "regal", would that be enough?

Power ratio will depend on crossover point, volume, tonal preference, etc. Your 5w amp will work at low volume, but would otherwise be swamped by the 410.

Can't hurt to see how far you can go with it.