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Brian Scherzer
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Could use help understanding bridging an amp

Pardon my lack of knowledge, but I could use some help trying to understand something due to conflicting information. I currently use an old Wadia 6 that goes straight into a Rowland Model 1 via balanced interconnects, and then to a pair of Aerial 10T speakers. I have enjoyed this setup for about 8 years, with no changes being made. Reading more about the 10T speakers, I know that they aren't efficient and, although the Wadia/Roland/Aerials system sounds "good", I am told that the 10Ts would sound even better with more power. Hang in there, because this is a 2 part question.......

I have also been told that, by using the Wadia at about 1/2 volume on its internal preamp, I am likely not getting all of the audio information that I could. It was suggested that I get a preamp so that I can have the Wadia set to its full volume, controlling the actual volume with the preamp, and that I consider buying a second Rowland Model 1 to use as bridged mono amps.

I have mentioned this to a couple of people and got very mixed messages. On the negative side, I am told that I should NOT bridge the Model 1, but don't understand why. Another person stated that this would be ideal. Based on the current price of used Model 1s, buying a second one would be an inexpensive venture. If needed, I can certainly find a used nice stereo preamp. Right now I lack the info that might help me understand the plusses and minuses of what good (if any) it might do to put a preamp in the path, or to purchase another Model 1 to increase the power going to the Aerial speakers. Any help in understanding this would be most appreciated!

Monty
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Re: Could use help understanding bridging an amp

This is a tough call. I would be surprised that running the Wadia at half throttle is leaving much on the table by way of dynamics. It is possible that the Wadia has better channel separation at a particular setting, but half throttle is usually in the optimum zone for most preamps.

Amps can sound different bridged, but separate power supplies is usually a good thing and effortless power reserves would be achieved with mucho current.

If it wouldn't kill ya to buy right and eat a little cash if you have to resell the amp...give it a try, especially if you like your music loud.

I'm not familiar with the Wadia, but if the Wadia is your CD source and you are running it half throttle, it is possible that you would benefit quite a bit from running it full throttle. However, Wadia does have a good reputation with their attenuators. If you were using most anyone elses, it would be a lot more likely that you could benefit from not using the CD source's output adjustment.

Jeff Wong
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Re: Could use help understanding bridging an amp

I suspect the reason people are recommending you use the Wadia at full volume is that you may be losing bit resolution; with a digital volume control, for every 6dB you attenuate, you lose 1 bit of resolution. If you lower by 12dB, you've got the equivalent of a 14 bit source (assuming you've got 16dB playback to start with... if it's higher, it might be less of an issue.)

ampnut
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Re: Could use help understanding bridging an amp

Jeff is correct, A didgital Volume control looses 1 bit of res, for every 6 dB attenuation.

To quote from Fi Magazine's review of the 860 on the Wadia site :

Mitigating the disadvantages of digital domain volume control Trust that helps....

ampnut
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Re: Could use help understanding bridging an amp

On Bridging .....

1. Check Out the detailed tech review of the Aerial 10T speakers on the S'phile site. JA provides a wealth of info.

http://www.stereophile.com/floorloudspeakers/466/index4.html

These speakers are a Nasty 3 Ohm load at some frequencies, and Suck a lot of power from the amplifier trying to drive it. Yes, JA mentions that they are power hungry, and need power to sing.

2. In general, most amps will not be happy driving ANY 4 Ohm speakers in Bridge mode, because the bridged amp 'sees' half that as the impedance it is driving. Given that the Aerial 10Ts dip down to 3 Ohms, that too at a nasty phase angle ( current and voltage are out of sync, making it even more difficult for the amp ) the bridged amp will effectively be called on to drive a nasty 1.5 Ohms load.

The Rowland 1 is a High Current Amp, with a Huge ( 55 Amperes ) peak current capability. If any amp can do duty to this application, I guess the Rowland 1 will. But still, you would probably be pushing the Rowland 1 also to its extreme, in terms of current demands, in bridge mode, driving yr speakers. Sound may suffer, particularly in the mid-range where the speaker load is particularly nasty....

Maybe Rowland can advise you ?

Unless advised by the amp manufacturer to the contrary, don't drive the Aerial 10T speakers with ANY Bridged amp...

3.

Quote:

Could use help understanding bridging an amp

A 'normal' amplifier drives the speaker between its Output and ground. Hence, when the Output voltage swings to say 8 Volts positive, across a 4 Ohm speaker load, the speaker will draw 2 amperes of current.

Connecting 2 amplifiers in Bridge mode means that you configure the 2 power amps such that when 1 of them receives a rising signal, the other receives a mirror opposite falling signal.

Hence when 1 of the 2 bridged amps provides an output of +8 Volts, the other amp swings to -8 Volts.

The Speaker is connected between the 2 'Live' outputs of the 2 amplifiers. So the speaker sees a voltage of +8 V & -8V across it, ie 16 Volts. A 4 ohm speaker connected such, will demand a current of 16/4 = 4 Amperes from Each of the bridged amps....

Double the current is hence delivered, this implies 4 times the power ( Power = Current x Current x Voltage ) into the speakers by the bridged amplifiers.

Brian Scherzer
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Re: Could use help understanding bridging an amp

My thanks to all who responded. I won't pretend that I understand every word written, but I certainly get the gist of the responses. I appear to be left with some decision trees and a better understanding of what those decisions might entail:

1. My Wadia is one of the much older models, so I would assume 16 bits, probably losing 1.5 bits (roughly) of info by not opening up the Wadia to full throttle and using a good preamp. On the other hand, I have a purer pathway by not using a preamp.

2. Adding a second Rowland Model 1 in bridged mode may not be a good idea.

Summary........I should either stick to my present setup or should consider a more powerful amp, which would then make buying a preamp more important, since the internal preamp of the Wadia would need to be attenuated even more due to the increased power of a new amp.

Thanks folks!

Jim Tavegia
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Re: Could use help understanding bridging an amp

I think an interesting test for you would be to see if you could get a JR Concerto preamp on loan and insert in in YOUR system, bypassing the Wadia varable output control and see if you can hear an improvement.

Your system has great resolving power and it may be very hard to discern the difference between the Wadia digital control and the Concerto. These are the kinds of "work" that needs to be done when you reach the level of your gear. It should be considered fun and your next science project.

It did not take WP long to realize the sonic loss in the Quad CD-P out of the varable output vs. the fixed out. It is the same reason I was using a Creek OBH to adjust input levels for inputing my LPs into my computer. The OBH affected the sound quality in a discernable way. I took it out, sold in on Audiogon with one hour of posting.

I lowered the selectable output of my phono stage to keep levels below zero. The same issues happen with amps with input attenuators. And most, if not all, of these are not the quality of the Wadia at all.

We soon realize as did ST a few issues back that PVCs do color the sound and that is why great preamps cost what they do to keep the signal unharmed...the proverbial straigh wire with gain.

Good luck.

gkc
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Re: Could use help understanding bridging an amp

Hi, Brian --

A few years ago I heard the Rowland intgrated amp driving the Aerial 10 T's at Ambrosia Audio in Brentwood (Los Angeles), with mid-priced Synergistic cabling, a Levinson one-piece CD player, and the cheapest Basis Turntable (Rega RB-300 arm + Grado "Sonata" cartridge). It was one of the best-sounding systems I had ever heard. Since the amp was rated around 150 watts (Rowland watts, as you no doubt know, are "big" because there is a lot of current available), lack of power might not be your problem. This system clearly outperformed another, in the same room (about 25' X 35' X 9'), with the $20,000 Revel Ultima Salon speakers, the $16,000 Levinson preamp, the top-of-the-line (at the time) Levinson power amp, about ten grand worth of wire, and about thirty grand worth of Levinson transport + separate DAC...not to mention a $5,000 Burmester line conditioner. I was amazed. You might want to check out that Rowland integrated. Or get a Rowland preamp to go with your present power amp. Just a thought, because this system had a synergy you seldom hear at ANY price. Cheers, Clifton

Brian Scherzer
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Re: Could use help understanding bridging an amp

I should emphasize that I have used this same gear with pleasure for a number of years. I could go on enjoying it for the remainder of my life, or for as long as my hearing holds out (I was a bass player in the '70s during the "Wall of Sound" rock music period, so my hearing is not assured!). It took a number of gear changes before I found what made me happy. For that reason, I am being cautious in changing anything! For my taste, the Wadia, the Rowland, and the Aerials just match up very well. The "weakness" could be due to my room, but the soundstage isn't as wide as it could be or as deep as I "think" it should be. My system would be defined as being on the "dark side", but I prefer it that way since violins no longer fatigue me like they did on brighter, more detailed, systems. Aerial tells me that putting a more powerful amp in the system would "open up" the speakers more, which I assume means that the soundstage would be wider and deeper. I plan on borrowing a more powerful amp (of good quality) just to see if it really makes a difference in my room. If it does, I'll know that I simply need more power....easy enough to find at a reasonable cost with used gear.

ampnut
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Re: Could use help understanding bridging an amp

Hello Brian,

Though its probably awefully obvious, have you tried re-orienting your speakers to get a better sound stage ?

A good starting point is to have the speakers and the listner in an isosolese or equilateral triangle.... speakers toed in approx 55 degs each, towards the listner.

Now gradually toe out the speakers so that they almost face the wall straight ahead, with little to no toe-in.

Usually this will produce a deeper & wider soundstage, though there will be a loss of treble, since the tweeters dont point at the listner's ears....

Cheers !

Monty
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Re: Could use help understanding bridging an amp

According to the article linked earlier, the Wadia can be impedence matched with his amp via an internal switch. That would seem to be the first place to start.

His description of a somewhat constricted soundfield is certainly one of the things that I have found to be a trade-off for using a passive preamp, though you are right on with the importance of speaker toe to balance soundstage characteristics with high frequency extension.

Even though the math suggests that a source output should be able to drive an amplifier without the use of a gain stage, an active preamp has always produced better sound to my ears. The purity of signal may have some sonic advantages in some areas, but I've yet to hear a passive preamp that didn't put a wrinkle in my nose when it came to low level dynamics and staging.

Harley noted in the article his preference for the Wadia directly running the amp and I've always heard Wadia did this better than anyone else. The article seems to explain why this is the case.

ampnut
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Re: Could use help understanding bridging an amp

I concurr with you, Monty.

I too am an 'Active Pre-amp' person.


Quote:

Harley noted in the article his preference for the Wadia directly running the amp and I've always heard Wadia did this better than anyone else.

That is why I refrained fro recommending an active pre.

The Valve amplification that I have seems to sound stage better than any solid state that I have heard in my set up. Hence maybe a Valve Pre ..... :-)

Brian Scherzer
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Re: Could use help understanding bridging an amp

I will spend some serious time this weekend working with speaker placement. Fortunately, the Aerial 10Ts have that head with the midrange speaker and tweeter that swivels, which can certainly help movement tweaking. It appears that there is some argument as to whether it is better to have the Wadia go direct into the Rowland, or to have a preamp between them. Rowland made a preamp called the Consonance during the time period that my amp was being produced, and it seems to sell used for about $1k. It may be worth it to buy one, just to see what the effect of adding it into the system is.

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