Amplifier question

kn505

My 5-channel amp has 500 wpc at 8 ohms. I use 2 of the 5 channels to test a pair of 6 ohms SDA CRS+. I did not play it too loud and it appears to be OK.

I would like to use both the CRS+ as center channel (to be connected to one of the 5 channels). If they are connected parallel, the impedance would be 3 ohms. Would I get any problem with the amp?

(The amp is California Audio Labs CL-2500 MCA and the manual only specifies the rating for 8 ohms.)

danz1906

kn505 wrote: »

My 5-channel amp has 500 wpc at 8 ohms. I use 2 of the 5 channels to test a pair of 6 ohms SDA CRS+. I did not play it too loud and it appears to be OK.

I would like to use both the CRS+ as center channel (to be connected to one of the 5 channels). If they are connected parallel, the impedance would be 3 ohms. Would I get any problem with the amp?

(The amp is California Audio Labs CL-2500 MCA and the manual only specifies the rating for 8 ohms.)

I dont think so, what brand of Amp is it?

kn505

danz1906 wrote: »

I dont think so, what brand of Amp is it?

It is California Audio Labs.

seeclear

kn505 wrote: »

It is California Audio Labs.

Have you tried contacting them and asking that question?

kn505

Keiko wrote: »

I'm not a technical guru by any means, but if the amp is only rated for 8 ohm loads I wouldn't advise it. You may be risking damage to the amp and/or speakers.

Would it safe to run only one single speaker at 6 ohm?

kn505

seeclear wrote: »

Have you tried contacting them and asking that question?

They are no longer existed.

treitz3

The amp is only rated for 8 ohm speakers. Driving a different load may work but it will damage the amp over the long term.

Systems

kn505 wrote: »

Would it safe to run only one single speaker at 6 ohm?

Sure, but with the 3 ohm load you will likely run into heat related issues.That channels thermal protection will likely engage and or the fuse may open due to excess current draw.The content of the program material and loudness levels will play a big part in how it can cope with the more difficult load.

megasat16

It is 5 channel amps with 500wpc into 8 ohms load. It can drive 4 ohms load speaker but not too sure about anything lower than 4 ohms. It's the fore-runner of the BIG Adcom multi-channel amps (GFA-7x0x series) since Adcom seems to have hired most of the Engineers from the CAL when they closed their door.

Systems

megasat16 wrote: »

It is 5 channel amps with 500wpc into 8 ohms load. It can drive 4 ohms load speaker but not too sure about anything lower than 4 ohms.

Yeah It's power rating would indicate a beefy output stage with the current capability to drive lower impedances.However being as it's a 5 ch unit that lessens the amount of room alotted for adequate heatsinking which I'm guessing is the reason for the manufacturer specifying it for use with 8 ohms only. Operating it into lower impedances at high levels with bass heavy content will push it to it's thermal limits quicker than if the content was mostly movie dialog found normally in the center channel.

TNRabbit

I seriously doubt the ability to drive 500 watts into 5 channels; that's 2500 watts, and most electrical circuits are only 1800 watts (15 amp)....

Systems

TNRabbit wrote: »

I seriously doubt the ability to drive 500 watts into 5 channels; that's 2500 watts, and most electrical circuits are only 1800 watts (15 amp)....

I guess they spec it on a per ch. basis unless it has dual power cords:).Anyway it would be a very rare occurance to have conent that would require the full output from each of the 5 channels at the same time.

ViperZ

TNRabbit wrote: »

I seriously doubt the ability to drive 500 watts into 5 channels; that's 2500 watts, and most electrical circuits are only 1800 watts (15 amp)....

This type of rating has been discussed to death on this and carver forums, and I am sure on multiple other sites...
The manufacturers are allowed to do the measurements with only 2 channels driven. How often would you push 5 x 500 Watts continuously anyway?

I would not recommend even trying 3-Ohm load on the amp, which is not designed for loads below 8 Ohms per channel. Best case, your thermal protection will kick in. Worst case, you'll blow the output transistors.

kn505

Thanks every one for your inputs and advices. Maybe I should had included the amp's specs earlier (see attachment). I don't understand the technical specs and hope you can give some guidances.

megasat16

GV#27 wrote: »

Yeah It's power rating would indicate a beefy output stage with the current capability to drive lower impedances.However being as it's a 5 ch unit that lessens the amount of room alotted for adequate heatsinking which I'm guessing is the reason for the manufacturer specifying it for use with 8 ohms only. Operating it into lower impedances at high levels with bass heavy content will push it to it's thermal limits quicker than if the content was mostly movie dialog found normally in the center channel.

Yep! They did not specify the power output for the lower impedance. This one is 109LBs amp. I remember reading something like if it's driven at 500wpc for all 5 channels for more than 20s, the amp will blow the internal fuse (said it's designed this way to protect itself).

I almost bought one before I bought the adcom GFA-7807 amp.

TNRabbit wrote: »

I seriously doubt the ability to drive 500 watts into 5 channels; that's 2500 watts, and most electrical circuits are only 1800 watts (15 amp)....

Yes, I think you need dedicated 20 amps outlet for this one.

GV#27 wrote: »

I guess they spec it on a per ch. basis unless it has dual power cords:).Anyway it would be a very rare occurance to have conent that would require the full output from each of the 5 channels at the same time.

I think it has dual power cords too. So the owner can plug into two separate 15 amps outlet. I guess running 20amps dedicated line is preferable. It said it can run Class A up to 50W and all the way to 500WPC @ 8ohms with 0.05THD.

ViperZ wrote: »

This type of rating has been discussed to death on this and carver forums, and I am sure on multiple other sites...
The manufacturers are allowed to do the measurements with only 2 channels driven. How often would you push 5 x 500 Watts continuously anyway?

I would not recommend even trying 3-Ohm load on the amp, which is not designed for loads below 8 Ohms per channel. Best case, your thermal protection will kick in. Worst case, you'll blow the output transistors.

It has internal fuse that will blow if you run all 5 channels at full power for more than a short period of time. This rating is not for 2 channels measurement. It's for all 5 channels measurement since each channel has it's own heatsinks and discrete outputs.

But I agree that it should not be used with anything lower than 4 ohms. Even though there is no indication of how much power in can push into 4 ohms safely, I think there are owners who seems to have used it with lower load impedance than 8 ohms. But anything less than 4 ohms could be problematic.

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1127397572&openflup&1&4#1

megasat16

Ok! the spec said it'll blow internal fuse if 500wpc x 5 is used for more than 15s. I thought it was 20s. Oh well, it's better to blow it's own fuse than blowing your fuse when it let the smokes out.

kn505

megasat16 wrote: »

Yes, I think you need dedicated 20 amps outlet for this one.

I will have a dedicated 20 amps outlet installed later. Right now, it is plugged into a power surge center.

megasat16 wrote: »

I think it has dual power cords too.

It has only one power cord.

megasat16 wrote: »

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1127397572&openflup&1&4#1

Thanks for the link to additional information.

There is a place in New Jersey that can service them. I don't want to have to send it in for service because the shipping is very expensive. It costed the ebay seller more than $300 to ship from Maryland to Nebraska. It weights more than 140 lbs with its crate, and therefore it could not be shipped with ups or fedex.

ViperZ

It has internal fuse that will blow if you run all 5 channels at full power for more than a short period of time. This rating is not for 2 channels measurement. It's for all 5 channels measurement since each channel has it's own heatsinks and discrete outputs.

You are joking, right? "each channel has its own heatsinks and discrete outputs" - so what? In any good amp, each channel has its own heatsinks and discrete output transistors. LOL. It doesn't mean that you can drive all channels simultaneously at 500 Watts per channel *continuously*.

Also:
- Nowhere does that spec mention impedance lower than 8 Ohms.
- 2500 Watts will let you run around 21 Amps of current... You really need to be plugged into some industrial crazy receptacle. Otherwise, the breaker on your main panel will just flip.

It's a great amp, but it is NOT designed to run 5x500 continuously.

megasat16

ViperZ wrote: »

You are joking, right? "each channel has its own heatsinks and discrete outputs" - so what? In any good amp, each channel has its own heatsinks and discrete output transistors. LOL. It doesn't mean that you can drive all channels simultaneously at 500 Watts per channel *continuously*.

Also:
- Nowhere does that spec mention impedance lower than 8 Ohms.
- 2500 Watts will let you run around 21 Amps of current... You really need to be plugged into some industrial crazy receptacle. Otherwise, the breaker on your main panel will just flip.

It's a great amp, but it is NOT designed to run 5x500 continuously.

You do not seem to know or read about this amp. Read the SPEC. It is 500wpc x 5 rated (continuous) but if you used the continuous rating for more than 15s, the internal fuse will blow. It is designed to run 5x500w continuously but it has fuse protection to avoid potential disaster. If you are so inclined to know, buy one and bypass the fuse and try to see what's the continuous power from all 5 channels simultaneously.

About power rating for anything less than 4 ohms, I already said there is no indication from the CAL about it. I only said I've heard from other owners who said it can run lower impedance load than 8 ohms (down to 4 ohms) but using anything less than 4 ohms is not a good idea.

megasat16

kn505 wrote: »

I will have a dedicated 20 amps outlet installed later. Right now, it is plugged into a power surge center.

It has only one power cord.

Thanks for the link to additional information.

There is a place in New Jersey that can service them. I don't want to have to send it in for service because the shipping is very expensive. It costed the ebay seller more than $300 to ship from Maryland to Nebraska. It weights more than 140 lbs with its crate, and therefore it could not be shipped with ups or fedex.

I don't know what kind of power surge center you used but I would make sure it can handle up to 20amps. Otherwise, you'll likely trip the power center protection when you crank up this amp.

About the power cord, there seems to have a few variations. Some owner of the Adcom GFA-7807 said it has two power cords but mine has only one too. But the manual said it must be plugged into 20amps outlet.

Yep, it's heavy amp. I would avoid UPS / FedEx and use only freight for something this heavy. I wish you luck that you won't be needing any kind of service soon.

kn505

I have read the manual, but dont recall that it requires a dedicated 20 amps outlet. But I am planning to install one anyway.

I tested the amp with a pair of 2.3TL speakers at reasonable loud volume (my wife and kids told me to turn it down) for about an hour; and there was no problem with the amp. I also tested the amp with the CRS+ (in stereo with the interconnect cable) with lower volume and it was also OK. So I think the amp can handle speakers below 8 ohms load.

I called Polk and talked to a very nice guy named Ken. Ken thinks that it is probably OK to connect the CRS+ in parallel into one channel IF the interconnect cable is NOT used. The CRS+ is rated at 6 ohms WITH the use of the interconnect cable. WITHOUT the interconnect cable, the rating is actually at 8 ohms.

ViperZ

megasat16 wrote: »

You do not seem to know or read about this amp. Read the SPEC. It is 500wpc x 5 rated (continuous) but if you used the continuous rating for more than 15s, the internal fuse will blow. It is designed to run 5x500w continuously but it has fuse protection to avoid potential disaster. If you are so inclined to know, buy one and bypass the fuse and try to see what's the continuous power from all 5 channels simultaneously.

I'd do that if I wanted to burn my house down. Thanks. I will also run a dedicated 40A line just to make sure.

megasat16

kn505 wrote: »

I have read the manual, but dont recall that it requires a dedicated 20 amps outlet. But I am planning to install one anyway.

I don't have the full manual so I don't know exactly is said there. But I think it's recommended it to use with 20 amps outlet since it can draw a lot of current at time. You can still use regular 15A outlets without much problem if you are not using it at full power.

I would say, most people uses 10-50W of continuous power and 250-300W dynamic power most of the time. But my experience with power amps such as this indicate that the amp sounds a lot cleaner and better when it is put on a dedicated line (circuit) on it's own. It's very noticeable during heavy bass movies or music.

megasat16

ViperZ wrote: »

I'd do that if I wanted to burn my house down. Thanks. I will also run a dedicated 40A line just to make sure.

Yes, you should run dedicated lines if you are seriously talking about power amplifiers! I ran 4 x 20Amps dedicated lines for my HT. I guess you are missing the advantages of running dedicated lines for power amps such as this. I got 3 x Parasound HCA-2205AT and 2 x Pioneer M91 doing HT duties. Plus 2 x SVS PB13 Ultra and 2 x ED A7s-450 and 4 Polk PSW1000 subs. I could dim the street lights if I wanted to but no, my house is not under the threat of fire hazard. Fire Hazard is when you over use the power lines that is not rated for.

Oh...Wait, I also have 2 x 20amps circuits (before adding 4 x 20 amps circuits) in that room so make it 6 x 20 amps in one room for all the subs and TV and Amplifiers.

kawizx9r

Sorry to thread jack but this is aimed at the tube-gurus here.

Like many of you know, this hobby knows no bounds and it's an absolute must to experience more and more gear to see what ultimately 'satisfies' you before you find something even better.

I love the sound tubes reproduce and would like to stick with it regarding 2 channel listening. Question is, when selecting am amp (yes this is pretty vague), how do I know whether or not its power is enough to run my SDA 1C's or something just as power hungry in the future?

I know there are different class-type amplifiers, but how do you know it'll be enough if it doesn't state what class type it is? Don't get me wrong, I love my Moscode hybrid but curiousity is nudging me and I want to get my ears on other said amps such as these things -
http://www.audiogon.com/cgi-bin/cls.pl?ampstube&1255743754&/Jolida-JD-502P-60-watt/ch-Powe

http://www.audiogon.com/cgi-bin/cls.pl?ampstube&1256159487&/Dynaco-Triode-St-70-Maroom-and

I don't plan on getting another amp just yet, and yes I know that for my SDA's I'd need a common ground amp I'm just a bit worried about choosing something that'll work well. This purchase won't be done for another few months, but it'll come thats for sure.

zingo

kawizx9r wrote: »

Sorry to thread jack but this is aimed at the tube-gurus here.

Like many of you know, this hobby knows no bounds and it's an absolute must to experience more and more gear to see what ultimately 'satisfies' you before you find something even better.

I love the sound tubes reproduce and would like to stick with it regarding 2 channel listening. Question is, when selecting am amp (yes this is pretty vague), how do I know whether or not its power is enough to run my SDA 1C's or something just as power hungry in the future?

I know there are different class-type amplifiers, but how do you know it'll be enough if it doesn't state what class type it is? Don't get me wrong, I love my Moscode hybrid but curiousity is nudging me and I want to get my ears on other said amps such as these things -
http://www.audiogon.com/cgi-bin/cls.pl?ampstube&1255743754&/Jolida-JD-502P-60-watt/ch-Powe

http://www.audiogon.com/cgi-bin/cls.pl?ampstube&1256159487&/Dynaco-Triode-St-70-Maroom-and

I don't plan on getting another amp just yet, and yes I know that for my SDA's I'd need a common ground amp I'm just a bit worried about choosing something that'll work well. This purchase won't be done for another few months, but it'll come thats for sure.

You're right, it is a thread-jack; so start your own thread. It's rude toward the original poster and contributors.

nguyendot

ViperZ wrote: »

You are joking, right? "each channel has its own heatsinks and discrete outputs" - so what? In any good amp, each channel has its own heatsinks and discrete output transistors. LOL. It doesn't mean that you can drive all channels simultaneously at 500 Watts per channel *continuously*.

Also:
- Nowhere does that spec mention impedance lower than 8 Ohms.
- 2500 Watts will let you run around 21 Amps of current... You really need to be plugged into some industrial crazy receptacle. Otherwise, the breaker on your main panel will just flip.

It's a great amp, but it is NOT designed to run 5x500 continuously.

Where did you get the 2500 watts = 21 amps of current? Is this amplifier 100% efficient?

What's the fuse rated for inside? That will tell you what this thing can continuously pull, regardless if the hardware is capable.

As far as running a 40A circuit? That's ludicrous. Are you even going to find a power cable capable of 40A? With the correct connector? Even better, is the receptacle on the amp capable of the current draw?

Assuming this amp is even 80% efficient, that'd be 26 amps. I'm guessing it's not even close to 80%.

Specs mean nothing, you can see they're obviously bloated.

ViperZ

nguyendot wrote: »

Where did you get the 2500 watts = 21 amps of current? Is this amplifier 100% efficient?

What's the fuse rated for inside? That will tell you what this thing can continuously pull, regardless if the hardware is capable.

As far as running a 40A circuit? That's ludicrous. Are you even going to find a power cable capable of 40A? With the correct connector? Even better, is the receptacle on the amp capable of the current draw?

Assuming this amp is even 80% efficient, that'd be 26 amps. I'm guessing it's not even close to 80%.

Specs mean nothing, you can see they're obviously bloated.

Umm... what you wrote in your last sentence is what I meant. I am just making fun of the guy who is claiming that this amp can push 5x500 continuous.
I'll get out of this thread now. Too much fun.

(these guys did mention that the fuse is 20A, which would give you approx. 2400 Watts consumption (max), so with average efficiency of MOSFET based amps of around say 70%, you'd get about 336 Watts per channel, which is still ridiculously good... but but... the guy has TWO dedicated 20A circuits, woohoo! for the amp with a single power cord... must help... and see, the dedicated heatsinks and FETs on each channel mean that all channels can pull 500W simultaneously... what do I know??? sorry for the rant... lol)

megasat16

nguyendot wrote: »

Where did you get the 2500 watts = 21 amps of current? Is this amplifier 100% efficient?

What's the fuse rated for inside? That will tell you what this thing can continuously pull, regardless if the hardware is capable.

As far as running a 40A circuit? That's ludicrous. Are you even going to find a power cable capable of 40A? With the correct connector? Even better, is the receptacle on the amp capable of the current draw?

Assuming this amp is even 80% efficient, that'd be 26 amps. I'm guessing it's not even close to 80%.

Specs mean nothing, you can see they're obviously bloated.

Hey, you sounds like a smart guy to me. You must be the prof. and Viper must be the expert in this field.

What do EE knows about electronics and amplifiers?

Obviously, you haven't read what the manufucture said in the SPEC and what is capable is doing.

Viper was saying the 500W rating is for 2 channels only. I say you are a tad smarter him since you can divide 2500W / 120V! And you know the amplifiers are not 100% efficient. But you fail to understand the internal fuse will blow in 15s if you use it at 2500W. The 20A circuit breaker will withstand 25A-40A of current draw for a few seconds before it trips. Also, there are internal reservoir capacitors that stores energy and still supply quite a bit for current even when the breaker trips. It may give you a second or two at 2500W depending on what much energy it has stored in it.

ViperZ wrote: »

Umm... what you wrote in your last sentence is what I meant. I am just making fun of the guy who is claiming that this amp can push 5x500 continuous.
I'll get out of this thread now. Too much fun.

(these guys did mention that the fuse is 20A, which would give you approx. 2400 Watts consumption (max), so with average efficiency of MOSFET based amps of around say 70%, you'd get about 336 Watts per channel, which is still ridiculously good... but but... the guy has TWO dedicated 20A circuits, woohoo! for the amp with a single power cord... must help... and see, the dedicated heatsinks and FETs on each channel mean that all channels can pull 500W simultaneously... what do I know??? sorry for the rant... lol)

I am a little amazed that you could figure a way out that the single cord amplifier don't need two dedicated outlets! Real Smart!

I guess I need to go back to school and learns Electronics Engineering again.

FYI for both Nguyendot and Viper, you need to understand what the SPEC said and how it was measured and tested. Without fully understanding what the amp can do or can't do and saying what you think it can it can't do is a real joke! The real funny thing is that you guys are guessing and estimating efficiency when you don't even know what kind of topology the amp used in it's power supply regulation and in the output switching.

I suggest you don't provide answers to the questions that you can't fully understand in the first place. Or read the manual and use Google to learn more about the topics under discussion.

http://www.soundstagelive.com/factorytours/calaudio/

nguyendot

ViperZ wrote: »

Umm... what you wrote in your last sentence is what I meant. I am just making fun of the guy who is claiming that this amp can push 5x500 continuous.
I'll get out of this thread now. Too much fun.

(these guys did mention that the fuse is 20A, which would give you approx. 2400 Watts consumption (max), so with average efficiency of MOSFET based amps of around say 70%, you'd get about 336 Watts per channel, which is still ridiculously good... but but... the guy has TWO dedicated 20A circuits, woohoo! for the amp with a single power cord... must help... and see, the dedicated heatsinks and FETs on each channel mean that all channels can pull 500W simultaneously... what do I know??? sorry for the rant... lol)

Not all of my post was meant for you - I was just too lazy to multi-quote

I saw what your point was.

nguyendot

I don't have to assume what the efficiency is, the fact is no amp is 100% efficient. You don't have to assume that, it's a given.

Either way, go get the amp benched. Until you do, you can't come in saying it puts out X watts because you honestly don't know, do you?