[NIGHTFALL1970]

I have an AVA 400R amp running my 1.7s with 400wpc@4 ohms.  If I get the phase inverter option on my preamp I will run 1200wpc into them.  Is this O.K. to do?  Anyone else have 1.7s that they drive with high wattage?

[Davey]

You may want to check with Frank VanAlstine on that.

If you bridge two channels together you'll apply an approximate two ohm load to each channel of the amp.  Whether it will continue to supply the advertised power without needing to be de-rated for the low resistance load is a big question.
Regardless, if you bridge the channels together you'll need another 400R amp for the other speaker.  You have another one?

Anyways, this is not really a Magnepan question but an amplifier question.  If you play the speakers at the same SPL then they're consuming the same amount of power.  It make no difference whether the amplifier is specified as 400wpc or 4,000wpc or 40,000wpc.

Cheers,

Dave.

[NIGHTFALL1970]

Dave,
I don't have a second 400R.  Franks site says that you can use the phase inverter on a single amp to improve imaging and triple power.  My worry is: will the i.7s take the increase in power?

[josh358]

I'm kind of confused about the phase inverter. As Davey said, you can double power by bridging two amps, but not, with most amps, into a 4 ohm load.

Anyway, to answer your original question, yes, the 1.7's will be fine with that much power. The fuses protect the tweeters from overheating under most circumstances. Whether you need it is another question, that depends on the levels at which you listen. If you sometimes find yourself blowing speaker fuses, chances are you do.

[kevin360]

Dave,
I don't have a second 400R.  Franks site says that you can use the phase inverter on a single amp to improve imaging and triple power.  My worry is: will the i.7s take the increase in power?

Here's text lifted from his ad: "The AVA Insight + Phase Inverter/Bridge provides for directly mono-bridging any pair of common-ground amplifiers for more than tripled single-channel power."

The result is a mono amplifier. The device is an external bridge which combines the two channels, but bridges also add the non-linearity of one amp to that of the other - just the nature of the beast. Does that matter? That's hard to say, but it probably isn't that big of a deal as long as they are quite linear on their own. Still, I've never been much of a fan of the concept. As has been pointed out, the other consequence of bridging is the fact that each amp sees half the load - 2 ohms is asking a lot, and will likely increase any linearity issues (that then get combined).

I was going to suggest a much better way to utilize a pair of stereo amps, but then it hit me - 1.7s aren't exactly 2-ways.  (I'm sure it could be done.)

[Davey]

$750.00 for a simple polarity inversion line-level circuit?  Goodness gracious. 

Anyways, yes, the concept seems pretty clear.  It's a simple bridging adapter that can tie two amplifier channels together...if they have a common ground.  (Two amplifiers needed.)

http://www.avahifi.com/index.php?option=com_content&view=article&id=174&Itemid=171

The alternate usage is for a single amplifier to polarity-invert one input and then connect one of the speakers in reverse to restore correct polarity.  (One amplifier needed, but of course, no power increase.)

http://www.avahifi.com/index.php?option=com_content&view=article&id=175&Itemid=218

Here's the theory.....and a nice example:

http://sound.westhost.com/project14.htm

Cheers,

Dave.

[simon wagstaff]

yes, you can do this if you listen in mono...

Be better to get yourself a pair of AVA U70's and use the inverter to bridge them. 60 tube watts will trump 400 SS watts any day, at least in my opinion....

[NIGHTFALL1970]

Thanks for all of your replies.  This is from Frank's website:

Using an inverter bridge to make a single stereo amplifier sound better is even easier. Run one amplifier channel from an inverted output and the other from a non-inverted output. (Here's a diagram of the connection.) This puts the two amplifier channels out of phase so that the common drain on the power supply is reduced and residual cross-talk between the channels is attenuated. Reverse one loudspeaker connection to get the channels back in phase and enjoy *MORE POWER*, better separation and improved imaging. (I added emphasis)

$750 is for a SEPARATE phase inverter.  It is only a $200.00 option on the new Fet Valve preamp (which I am considering purchasing).

Tebejo did this with two amps.  You can read about it here:
http://www.audiocircle.com/index.php?topic=105167.0

[jhm731]

Get a Sanders Magtech.

900 watts/ch into 4 ohms.

[Davey]

Maybe still some confusion here?  (I can't tell for sure.)

"*MORE POWER*" doesn't equate to the REAL increase in power you'd get from a bridging reconfiguration.  (Not even close.)
I would be very surprised if the increase in power is even measurable.  In fact, if it is measurable, that would indicate to me marginal power supply design in the amplifier to begin with.

$200.00 is much better than $750.00, but still overpriced for what is a very simple job.

Cheers,

Dave.

[josh358]

Thanks for all of your replies.  This is from Frank's website:

Using an inverter bridge to make a single stereo amplifier sound better is even easier. Run one amplifier channel from an inverted output and the other from a non-inverted output. (Here's a diagram of the connection.) This puts the two amplifier channels out of phase so that the common drain on the power supply is reduced and residual cross-talk between the channels is attenuated. Reverse one loudspeaker connection to get the channels back in phase and enjoy *MORE POWER*, better separation and improved imaging. (I added emphasis)

$750 is for a SEPARATE phase inverter.  It is only a $200.00 option on the new Fet Valve preamp (which I am considering purchasing).

Tebejo did this with two amps.  You can read about it here:
http://www.audiocircle.com/index.php?topic=105167.0

Yeah, he's bridging the amp. This is a very old trick, in fact, some power amps have a bridging switch. As Davey pointed out, though, with most amps this doesn't work into 4 ohm as opposed to 8 ohm speakers, because the amp can't supply sufficient current. Make sure, before you try it, that your amp can feed a 4 ohm load in bridged configuration. Most cannot, and manufacturers often warn against trying to do so.

[rw@cn]

I have an AVA 400R amp running my 1.7s with 400wpc@4 ohms.  If I get the phase inverter option on my preamp I will run 1200wpc into them.  Is this O.K. to do?  Anyone else have 1.7s that they drive with high wattage?

If you like the way the amp sounds, keep it and spend your money on something else.

[BaMorin]

I have an AVA 400R amp running my 1.7s with 400wpc@4 ohms.  If I get the phase inverter option on my preamp I will run 1200wpc into them.  Is this O.K. to do?  Anyone else have 1.7s that they drive with high wattage?

which raises the question of how loud do you want it?

http://www.crownaudio.com/apps_htm/designtools/elect-pwr-req.htm

your 400wpc should be plenty

[medium jim]

Agreed, 400wpc is more than enough.   No and then I put my BGW 500D amp into service on a pair of 2.5's and it will go louder than I would ever want, well over 100db.  The BGW is around 400wpc...

Jim

[TONEPUB]

yes, you can do this if you listen in mono...

Be better to get yourself a pair of AVA U70's and use the inverter to bridge them. 60 tube watts will trump 400 SS watts any day, at least in my opinion....

Where do you guys keep coming up with this "tube watts" vs. "transistor watts" stuff?  Watts are watts.  Non class A transistor amplifiers have different distortion characteristics than a tube amp, and what you're mistaking for "tube watts" is really headroom.

Bring your 60 watt tube amp over and try it next to my 300wpc Burmester amp or 200wpc Pass 200.5 monos, won't even come close.  I've owned 25wpc SS amps from Levinson and Luxman that were full class A with massive power supplies (i.e. more headroom) that sounded like they could play as loud as or louder than other 100wpc amps, tube and transistor.

So much boils down to power supply design and amp/speaker interface, especially with tube amplifiers.

Having tried a LOT of tube amps with Magnepans (of all kinds) over the last 30 years has usually been disappointing.

That doesn't mean don't try it, but don't be surprised if it doesn't rock.  And these are speakers that really don't rock to begin with.

[medium jim]

TONEPUB:

Great post, it puts it in proper perspective. Maybe this is why tube amps seem to be more powerful (as a general rule) than their counterpart SS amps of the same wattage.

Jim

[josh358]

I've owned 25wpc SS amps from Levinson and Luxman that were full class A with massive power supplies (i.e. more headroom) that sounded like they could play as loud as or louder than other 100wpc amps, tube and transistor.

IMO, the audio industry went in the wrong direction years ago when it moved from peak power (frequently misrepresented by unscrupulous manufacturers) to RMS ratings. The undistorted output of an amp is never determined by its RMS power when playing music. What we really need to know to properly size an amp is what an amp does on the peaks, and that can vary wildly for different amps with the same RMS power spec.

That being said, the clipping characteristics of tubes are relatively benign, so all things being equal, it's often possible to get by with a smaller tube amp than a transistor one, as measured by the onset of clipping -- though the difference isn't anything like a 60 to 400 watt ratio, more like 2:1.

[Hasse]

Where do you guys keep coming up with this "tube watts" vs. "transistor watts" stuff?  Watts are watts.  Non class A transistor amplifiers have different distortion characteristics than a tube amp, and what you're mistaking for "tube watts" is really headroom.

Bring your 60 watt tube amp over and try it next to my 300wpc Burmester amp or 200wpc Pass 200.5 monos, won't even come close.  I've owned 25wpc SS amps from Levinson and Luxman that were full class A with massive power supplies (i.e. more headroom) that sounded like they could play as loud as or louder than other 100wpc amps, tube and transistor.

So much boils down to power supply design and amp/speaker interface, especially with tube amplifiers.

Having tried a LOT of tube amps with Magnepans (of all kinds) over the last 30 years has usually been disappointing.

That doesn't mean don't try it, but don't be surprised if it doesn't rock.  And these are speakers that really don't rock to begin with.

Are you suggesting that the Pass XA100.5´s would be a better match for the MG3.7´s than the (on paper) similarly powered tubed ARC REF150?

[Davey]

Fellas,

You're drifting well off the topic of Nightfall's original query.  It sounds like he was confused on what a bridging adapter is and why you need two amps.  Hopefully this thread has answered his question, but the query would have been much better asked over in the AVA Circle vice this one.

Arguing about "tube-watts" versus "solid-state watts" is a complete waste of time. 

Cheers,

Dave.

[NIGHTFALL1970]

Dave,
thanks for getting things back on topic.  I was wondering if Franks phase inverter option in the new Fet Valve Preamp would make things sound better at lower volume levels.  According to his website you can use it with a single amp.  I called frank on Friday to have him explain this option to me clearly.  He is at a show this weekend and will not be back till Wednesday.  After I talk to Frank I will post his answer.
The reason I posted the subject here was because my main concern was if my 1.7s would be O.K. with high wattage.  I wondered if anyone else on this forum used this setup or had gobs of power running their 1.7s.