[DustyC]

After reading up on the AVA bridging unit in Audio Basics,I have a general question about the type of amp that can be used.

Some background: I recently purchased 2 stereo amps that have an internal bridging circuit. To bridge the amp you flip 3 switches, connect the negative terminals together using a small metal bar and use just the positive terminals to connect the speakers. I tried this and the results were less then optimal. A low level buzz (audible thru the midrange and tweeter elements) is present and the amp's transformers hum a little more than in stereo mode. This buzz is similar to what I have heard prior to the start of large concerts with racks of speakers and amps. In stereo mode the amps work fine.

Since the hookup diagram in the Audio Basics article (and on the AVA website) show just the positive terminals being used can an amp that needs to have the negative terminals connected together be used? 

Has anybody tried using this AVA bridging unit with amps other than AVA's? Ones that require the negative terminals be connected together? 

Thanks!!

[avahifi]

First, all AVA amplifiers have common ground connections for the ground side of the speaker terminals.  They have, as is normal convention, the speaker ground terminals tied together and to chassis ground internally.

One way some amplifiers provide for bridge mode operation without an external phase inverter is to simpy change the operation of one channel from normal to inverted by switching a few components and wires in and out of circuit from an external switch or two.  Unfortunately the feedback arrangement between the two channels is different between the inverted and non-inverted channel. Thus each half the the bridged wave form will have different audio characteristics, not useful for the best possible result.

We choose to provde a very fast and wide band external phase inverter with inverted and non inverted outputs that will sum and nul completely within a wide range beyond audio hearing.  The top and bottom half of the wave forms are identical.  We think this is a better way to do this.

Of course be careful when going for higher power by bridging your amplifiers.  When bridged, the amplifier sees the speaker load at half of its normal impedence.  An 8 ohm speaker looks like 4 ohms, a 4 ohm speaker like 2 ohms, and so on.  Thus bridging is not a good idea with a very inefficient and low impedence speaker unless the power amps used ae very rugged.

Frank Van Alstine

[DustyC]

The amps in question are Classe DR-3's. They claim the amps are stable into a 1 ohm load. My speakers are 4 ohms so they would be a 2 ohm load as you pointed out. Looks like this might be more trouble than the increased power would be worth.

Thanks Frank!
 

[Hydro]

If you have two identical amps, I have had very good luck using just one channel of a stereo amp without bridging. You get the complete isolation of dual mono and the power supply is oversized for one channel. No problems with lower impeadences. It also leaves two unused channels for surround sound in home theater mode.

[srb]

If you have two identical amps, I have had very good luck using just one channel of a stereo amp without bridging. You get the complete isolation of dual mono and the power supply is oversized for one channel. No problems with lower impeadences. It also leaves two unused channels for surround sound in home theater mode.

In many amps, single transformers often have dual sets of secondary windings, one for each channel, and often the power supply capacitors are also divided between the channels.  For those amps you would have the isolation but not necessarily the advantage of a larger power supply.
 
Steve

[aln]

Rather than bridging, why not bi-amp?  One could use a vertical or horizontial configuration.

[Wayner]

Because bridging a amp will triple it's power output. Hence, a 200 watt per channel amp would then produce 600 watts in mono (8 ohms).

A tube amp would double it's power, 35 watts per channel would make 70 watt mono amp.

Running 2 amp from one source also cuts the output impedance in half (resistance in parallel), and I have not heard any real benefits.

Wayner 

[festuss]

Rather than bridging, why not bi-amp?  One could use a vertical or horizontial configuration.

  I have been running bridged/bi-amp Hafler P500 chassis AVA OmegaStar EX and Insight units 4 of em for around 4800-5200W or so into Legacy Whispers.  It's ultimate CONTROL and effortless realism.  Not louder just BETTER.  With almost unlimited current and control.  Though 2 AVA Ultra Hybrid phase inverters. Whic are fed from AVA Ultra preamp.  Four Haffer P500s running at 100dB or so into the Whispers 4 Ohms need plenty of room cooling, they put out a lot of heat, and some incredible SOUND.  Never too many watts, never too many amplifiers Bridge it, Bi-Amp it.  REAL is what it's all about.  It started at one amp then two, then 4, 4 is better, with each additional amp, not louder, just BETTER.  Control, clarity and SLAM!

[martyo]

  I have been running bridged/bi-amp Hafler P500 chassis AVA OmegaStar EX and Insight units 4 of em for around 4800-5200W or so into Legacy Whispers.  It's ultimate CONTROL and effortless realism.  Not louder just BETTER.  With almost unlimited current and control.  Though 2 AVA Ultra Hybrid phase inverters. Whic are fed from AVA Ultra preamp.  Four Haffer P500s running at 100dB or so into the Whispers 4 Ohms need plenty of room cooling, they put out a lot of heat, and some incredible SOUND.  Never too many watts, never too many amplifiers Bridge it, Bi-Amp it.  REAL is what it's all about.  It started at one amp then two, then 4, 4 is better, with each additional amp, not louder, just BETTER.  Control, clarity and SLAM!

That should make for one BIG dynamic full range presentation.

[festuss]

It DOES!  ITS ALIVE.  Its control, no stress, no strain.  Lots of drivers to use all the current, the bass is TIGHT, and full of detail, no such thing as too many watts, not louder CONTROL.  Bigger is BETTER.  AVA pristine watts.

[aln]

Festus:
Not to hijack this thread-but this question does relate.  How have you upgraded your electric supply to power all those amps?

Regards
ALN

[festuss]

Yes indeed.  My original service panel was full 150A panel, I put in a GE 200A panel so I could put in the 4 needed ckts to power the amps and all the peripherals.  The difference between a 150 and a 200 is BIG, the internal bus bars are extremely bigger.  I use several Furman rack units that monitor volts and current draw on the audio stuff, if I crank it, LOUD 105dB measured and some deeep bass comes along the total current draw on the four ckts is around 28A.  The gigantic Hafler P500 transformers which are much larger than a DH500 model need power.  These AVA rebuilds are musical bliss, with limitless ability.  A stock Hafler P500 is lifeless and dull, the AVA rebuild turns them into modern miracles.  big transformers in em, ensure extreme performance.  I love it!  It always impresses anyone who takes the ride!  Even the guy who made the original music I play my DSD recording of him from my KORG SR2000 DSD unit, they  are impressed.  All my dozen or so AVA units have been FLAWLESS for years. 

[DustyC]

If you have two identical amps, I have had very good luck using just one channel of a stereo amp without bridging. You get the complete isolation of dual mono and the power supply is oversized for one channel. No problems with lower impeadences. It also leaves two unused channels for surround sound in home theater mode.

Amps are dual mono, sharing just the power cord and switch. 2 xfmrs, 2 power supplies and 2 sets of circuits.

[DustyC]

Rather than bridging, why not bi-amp?  One could use a vertical or horizontial configuration.

Already doing this. I just wanted a little more juice on the top end.

[DustyC]

Yes indeed.  My original service panel was full 150A panel, I put in a GE 200A panel so I could put in the 4 needed ckts to power the amps and all the peripherals.  The difference between a 150 and a 200 is BIG, the internal bus bars are extremely bigger.  I use several Furman rack units that monitor volts and current draw on the audio stuff, if I crank it, LOUD 105dB measured and some deeep bass comes along the total current draw on the four ckts is around 28A.  The gigantic Hafler P500 transformers which are much larger than a DH500 model need power.  These AVA rebuilds are musical bliss, with limitless ability.  A stock Hafler P500 is lifeless and dull, the AVA rebuild turns them into modern miracles.  big transformers in em, ensure extreme performance.  I love it!  It always impresses anyone who takes the ride!  Even the guy who made the original music I play my DSD recording of him from my KORG SR2000 DSD unit, they  are impressed.  All my dozen or so AVA units have been FLAWLESS for years.

Interesting. I measured my current draw at just over 7 amps on what I consider loud volumes (90db) with 5.5 amps at idle (no signal). No way could I get 105db.  Yikes

[festuss]

I like to replicate LIVE my friend has a great band I have measured them at some live events at 105dB.  At home I can get it, with lotsa watts and lotsa drivers to move air and absorb the watts, pristine clarity. The Hafler P500 chassis have enormous aC line transformers they can supply lotsa power to the ckts.  The AVA ckts and design are totally SILENT, no hiss, no buzz nothing them the sound comes out of a dead sillent background, it's GREAT! The Ultra Hybrid pre amps are superb, the Ultra hybrid phase inverters work flawlessly, entire system is sillent but deadly!  kW makes it LIVE.  My neighbors think so