Bridged Amp Power?

AsSiMiLaTeD · May 2004

I'm looking at the parasound HCA 1000A. It has 125 WPC into 8 ohms x 2 chanels. But in bridged mode, it delivers 400 WPC into the 1 channel and I guess I don't understand why.

I've seen this with almost every amp I look at.

I figured that if you take two 125 chanels and bridge them, you get 250 into 1 channel. That seem the most logical to me. However, there's obviously some other factor that I'm missing.

What is it???

lonwa · May 2004

The reason its 400 and not 250, is because when the unit is run in mono mode, it only sees half the ohms of the speaker, so your 8 ohm speaker will be seen as 4, and will get the 200 X 2 = 400 watts in mono mode @ 4 ohms.

Here is the FAQ link for that unit, with the relevant q and a pasted below:

http://www.parasound.com/products/amplifiers/stereoampfaq.html

_______________
Will these amps handle a four ohm speaker while the two channels are bridged to MONO?

No. Remember amps bridged to mono will "see" half the impedance the speaker is actually presenting. Sustained 2 Ohm loads are not advisable with any Parasound amplifier.
_______________

Hope this helps

Lonwa

AsSiMiLaTeD · May 2004

Thanks. So will I get as good sound quality in bridged mode as I would in stereo mode?

dorokusai · May 2004

Yes.

PolkWannabie · May 2004

Doro,

Really ? ... I thought in bridged mode most amps usually had some additional THD or IMD ... whether or not this is significant enough to be noticeable I suppose is academic.

AsSiMiLaTeD · May 2004

Originally posted by dorokusai
Yes.

Mark, I know you've had some experience with the Parasound stuff and seem to like it. Can you characterize the difference in sound between the Parasound and HK stuff?

Would you say the Parasound is higher end than the HK or on about the same level?

dorokusai · May 2004

It will add a little increase in THD, but you need to start buying some test equipment to actually hear it.

I cannot offer a direct A vs B comparison to HK, although I have heard both manufacturers. I think HK is a nice AVR(Etc.), but the Parasound will outclass them on the individual component level.

The Parasound is more high end than the HK. Parasound uses better components, and is Class A active, depending on which model you ultimately choose. The HCA-1500A is a real **** kicker.

I-SIG · May 2004

If you find a HCA-2200 do it! <hehe!>

Wes

AsSiMiLaTeD · May 2004

You had any experience with the HCA 1000A? I was thinking of running four of those.

I'd run two in bridged mode on the 150s, giving each speaker 400 WPC.

I'd run the third on the center bi-amping the center.

I'd run the fourth for the surrounds...

Any thoughts on this setup?

PolkWannabie · May 2004

Hope you got some beefy power goin to the outlets ...

Then again ... http://cls.audiogon.com/cgi-bin/cls.pl?ampsmult&1090510897

I don't agree with everything the seller has to say, but these are very good components.

AsSiMiLaTeD · May 2004

Originally posted by PolkWannabie
Hope you got some beefy power goin to the outlets ...

Would I have issues running four of those HCA1000A amps on one socket? I didn't think about that, glad you mentioned it...

Also I noticed the 1000A amps don't use a MOSFET driver stage like the 1500 does, how much of a difference will that make?

AsSiMiLaTeD · May 2004

Also I noticed that the 1000A has 45 amperes per channel, will that double to 90 when run in bridged mode?

Thanks for all the info so far, keep it coming...

lonwa · May 2004

No sorry. The 45 amperes is PEAK per channel. Its actually a ratio of ohms and volts. Sinces the ohms are stable, and so is the power consumption, amperes physically cannot increase.

I'm no physics buff (for those of you who are), so if I screwed that explanation up, please let me know.

EDIT: Actually now that I think about it, the Parasounds can handle 2 ohms for periods of time, just not sustained for long periods. So in theory, you could get more than the 45 amperes in MONO mode, but more than likely the unit will shut itself off pretty quickly (because you are pushing the power consumption and output beyond designed limits (hence the 45 amperes)).

Lonwa

jdhdiggs · May 2004

Originally posted by lonwa
No sorry. The 45 amperes is PEAK per channel. Its actually a ratio of ohms and volts. Sinces the ohms are stable, and so is the power consumption, amperes physically cannot increase.

I'm no physics buff (for those of you who are), so if I screwed that explanation up, please let me know.

EDIT: Actually now that I think about it, the Parasounds can handle 2 ohms for periods of time, just not sustained for long periods. So in theory, you could get more than the 45 amperes in MONO mode, but more than likely the unit will shut itself off pretty quickly (because you are pushing the power consumption and output beyond designed limits (hence the 45 amperes)).

Lonwa

You are correct and not... Most likely the amplifier is acting as a voltage source up to a point, that being once 45 amps is reached, two things can happen:the power supply goes into failure, or the output circuitry fries. From the description of the amp, the latter is far more likely. To handle two ohm loads for short period of time, the circuits are proabably going to just overheat. Ok for short time periods, not good over the long all...

As far as constants:
Voltage is constantly fluxuating (This drives the up and down motion of the cone) and the resistance (ohms) is changing depending on the frequency of the voltage.

AsSiMiLaTeD · May 2004

So if it can give 45 amps to each of two channels (albeit in peak bursts), isn't it logical to conclud ethat it can give 90 to one channel.

I'm not educated on electronics at a very advanced level, so feel free to help me out here...

F1nut · May 2004

Let's not forget that when bridged you shouldn't run a speaker with less than a 8 ohm rating.

dorokusai · May 2004

PW - Is it better than Krell or Sunfire? Who knows, it's opinion and subjective. It's just advertisement hype so he can sell his amp....common Audiogon practice. You know how it is with that place sometimes.

PM - Can you run 4 of them on one outlet? Yes. The CTC amp is 240+ amp(peak), and 2400 watts power consumption.....run off the same outlet, along with other gear and no problems noted to date. I don't listen to music like old people either...and surely haven't hit those figures at any time.

EDIT: The value is a combined figure simply for an example of potential draw and load, not a per channel value. Actual value is 120+a/1200w per channel roughly.

As mentioned above, the spec's are for peak transients, and/or heavy load values.

Could it trip the breaker given crazy high volume media, and a couple subwoofers on the same outlet? Sure. If that is the case, you should be bumping up your outlets and breaker panel anyways....I would suggest this especially in your future "HT" room that you have planned. 20amp dedicated lines will have you set for many futures.

F1nut · May 2004

Bro, the figures of 240 amps peak and 2400 watts of power consumption are not possible given the output rating of 300 or so wpc @ 8 ohms. Figures of 120 amps peak and 1200 watts of power consumption would be inline with the rated power.

For example the JC-1 Halo is rated at 400 wpc @ 8 ohms with 135 amps peak and 1280 watts of power consumption. The Musical Fidelity kW is rated at 1000 wpc @ 8 ohms with 200+ amps peak and 3000 watts of power consumption.

PolkWannabie · May 2004

Doro,

Agreed ... At this price point and quality it's all about personal preference.

dorokusai · May 2004

Bro - That's spec's per the Parasound 3500. Here is the link for your reading pleasure.

I just combined them as an example, not as a per channel value.....read before posting.

Parasound HCA-3500

F1nut · May 2004

I'm not 100% sure about the peak amps, but the power consumption is always listed as a total. You don't double that.

dorokusai · May 2004

It's per channel Jesse, check out the HCA-3500 owners manual.

It was as an example freakshow, and here's the link for you to read more.

Owners Manual

EDIT: Actually this has turned interesting, as some spec's are listed as per channel and some are not. I will just edit the original post, it was only for example purposes anyhow. The likelyhood of reaching any of these values anyways is far from easy.

HBombToo · May 2004

Originally posted by jdhdiggs
You are correct and not... Most likely the amplifier is acting as a voltage source up to a point,

I think that an amp should be characterized more so as a current source... and its all about the power supply at that point which imho is the true gate. A preamp is a voltage source...
HBomb

F1nut · May 2004

I got your freakshow.......lol.

AsSiMiLaTeD · May 2004

Ok guys so help me out here. I've got two scenarios, trying to decide which would be better.

Scenario 1:

I buy 3 Parasound HCA 1000A's. Two will be used in bridged mode providing 400 WPC to each of the RTi150s. The third amp will be used in stereo, but be used to bi-amp the CSi40 at 125 WPC on each terminal. I could run that one in bridged mode also but I think 400 WPC may be a little much for the center - yes I know overpowering is not as bad as underpowering and all that...

This gives me 400 WPC on the 150s and 250 on the CSi40 and will cost me around $1K, maybe a bit more...

Scenario 2:

I buy 1 HCA 1500A to use to power the lows on the 150s. This provides 205 WPC to the lows on each front.

I buy 1 HCA 1203A, which is a three channel amp doing 140 WPC. I'd use two of the three channels to power the mids and highs on the 150s and the third to power the center.

This Scenario gives 345 WPC on the 150s and 140 on the center. This will also cost around $1K, maybe a bit less.

Based on power alone, scenario 1 appears to be my best choice. However, I believe the 1500A to be the superior amp with the MOFSET driver stage (not on the 1000A). I'm wondering if the 1500 is superior enough to force me to go with scenario 2.

By the way, in either scenario above you won't notive power for the surrounds. I'm just going to use the receiver for that right now and then add another amp back there when I can afford it later, really not a big deal since I use only for movies and not much MC music...

I've listened to Parasound and I think it's obvious at this point that that's my choice. However, I've not been able to compare the amps in question and am buying used and unfortunately will not have that option, so I'm going to be depending on you guys to help me out here.

Thanks guys, you've been a big help thus far...

F1nut · May 2004

I'll let the HT experts help you out with those questions.

HBombToo · May 2004

I have the Outlaw 770 and Doc has the mono blocks... either way gets you to a level thats great from a quality and quantity standpoint. Perhaps you should take a hard look IMHO.

HBomb

Early B. · May 2004

Yeah, I was gonna suggest you get a couple of Outlaw monoblocks for your fronts and let your receiver power the center channel, as you mentioned. Later on, get a 5-channel Outlaw amp for the remaining channels, including the center. Then after that, get an Outlaw pre/pro, and you're in HT nirvana.

HBombToo · May 2004

Originally posted by Early B.
Then after that, get an Outlaw pre/pro, and you're in HT nirvana.

The Outlaw prepro is second on my list. I'm seriously considering MSB Tech for my prepro.

HBomb

PolkWannabie · May 2004

I still like my original recommendation of the 2205 in the Parasound line the best ... Did you check the Audiogon link ?

Make yourself a good set of jumpers and forget the biamping ...

This should be the best of all worlds and will provide more than adequate power in HT as well as Stereo to all speakers in a 5.1 set up.

Once you get to preamp land, if you decide you want to go to 7.1 you can then either add a lesser 2 channel amp for the rears or a better 2 channel amp for the mains depending on your experience up to that point.

AsSiMiLaTeD · May 2004

Henry and Early B, I know the Outlaw stuff is excellent and I've had a chance to listen to their gear, I just like the Parasound sound a bit better, just suits my taste better I guess. I'm decided on the sound I want and parasound does that for me, just trying to figure out which amps at this point.

Rick, that 2205 is a nice amp, but not best for my situation for a couple of reasons:

1 - It's a bit more than I wanted to pay at $1350

2 - It only gives me 220 WPC on the 150s and I think they need more than that, so I'd still have to buy another Parasound to bi-amp those, bringing me well over my budget.

3 - It gives 220 WPC to the surrounds also which is great, but right now I've got small speakers back there and taht is way overkill, although I do know that this would be great someday.

basically, that's an awesome amp and will likely be an addition to my system someday, but I don't think it's right for phase 1.

Thanks for the suggestions guys. I'm not trying to be closed-minded, but I think I've pretty much narrowed it down to the two scenarios I proposed...just trying to determine which way to go.

Bridged Amp Power?

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