#1
Just a quick and simple question...

I have a Carvin BX500 amp. On the back, it has a 2 Ohm button that when pushed in allows you to drop your overall load down to 2 ohms (for example, if you're running two 4 ohm cabinets). While the amp has this option, I just want to know if it's healthy for it. I've heard a couple different times that running an amp that low for too long can possibly harm it.

Thanks for the help all!
#2
I'm not the foremost expert on these types of things; however, I don't believe that dropping your load to 2 ohms on an amp like that will harm it. Its a feature that is supposed to be used. And a pretty darn useful one at that. If I ever sell my Eden combo, that head is taking a serious bit of consideration from me. How are you liking it?
...it was bright as the sun, but with ten times the heat
#3
Quote by c3powil
I'm not the foremost expert on these types of things; however, I don't believe that dropping your load to 2 ohms on an amp like that will harm it. Its a feature that is supposed to be used. And a pretty darn useful one at that. If I ever sell my Eden combo, that head is taking a serious bit of consideration from me. How are you liking it?


Thank you for the input.

I'm very, very please with the head. The built in-overdrive doesn't give you a distorted sound, but it gives a mean growl instead. It's VERY powerful, reliable and sounds good live, and it's given me a multitude of tones (given, I can't dial a bass tone in quite as well as a guitar tone, lol). My only complaint is that the frequency sweep for the low and high mids has a bit of a learning curve cause the gain effects the way the frequency works.
#4
Now I am only throwing out what I head when a guy was talking to me about my Peavey Mark IV head. He said it was a 8-4 ohm head and the 2 ohm level was a way to get 300 watts but the head was not meant to run at length at that level. I guess to him the option was for you showing up to a huge venue and needing a boost, not a every day at practice, every gig and leaving it on to go pee/get a drink/smoke.

I could be misinformed, but I think it's still best until proven otherwise to treat it like a nun... it can put out, but that doesn't mean it wants to.
#5
My Mark VIII runs at 4 ohms and 2 ohms, and Im sure that itll be fine. As said before, it was meant to be used.
pinga
#7
Quote by SMB13
Just a quick and simple question...

I have a Carvin BX500 amp. On the back, it has a 2 Ohm button that when pushed in allows you to drop your overall load down to 2 ohms (for example, if you're running two 4 ohm cabinets). While the amp has this option, I just want to know if it's healthy for it. I've heard a couple different times that running an amp that low for too long can possibly harm it.

Thanks for the help all!
First of all, if you're running two 4 ohm cabinets wired in
parallel (Red to red & black to black), it presents a 2 ohm load to the amp anyway.

If you run them in series, (black (from amp, 1st cab)) then its red wire to black in the second cab and its red wire going back to the amp, you're wired in series, and the load would be 8 ohms.

If I didn't explain that so you get it, post back and I'll try again.

The current draw is much higher @ 2 ohms. Higher current equals higher heat. That said, most really big transistor power amps are designed to run at 2 ohms.

With lower load resistance, the amplifier power is actually higher than @ 4 ohms.
#8
Quote by Captaincranky
First of all, if you're running two 4 ohm cabinets wired in
parallel (Red to red & black to black), it presents a 2 ohm load to the amp anyway.

If you run them in series, (black (from amp, 1st cab)) then its red wire to black in the second cab and its red wire going back to the amp, you're wired in series, and the load would be 8 ohms.

If I didn't explain that so you get it, post back and I'll try again.

The current draw is much higher @ 2 ohms. Higher current equals higher heat. That said, most really big transistor power amps are designed to run at 2 ohms.

With lower load resistance, the amplifier power is actually higher than @ 4 ohms.


Well, I have this cabinet, and I'm looking at getting this to go with it. I'm just running my first cab with a speaker cable and then I'll daisy chain it to the second. It should be running at 2ohms if both cabs are 4ohms, correct?

In a Carvin manual I had awhile ago it said you could also run a 4ohm and an 8ohm cabinet (their cabs, of course), and it would equal out to 2.66ohms.
#9
It's possible for most amps to run down to 2 ohms nowadays anyway, but amp companies don't really advertise it because it's unhealthy for the amp over long periods of time.
Quote by skater dan0
Damn you and your ninja-like modding
#10
If you halve the impedance then you double the power demand on the amp. This means drawing more current. 100W into 4 ohms is 5A and 7A into 2 ohms. If the amp is designed for 7A then you are unlikely to blow the output transistors. The extra current has to come from the power supply and this may not deliver the extra current. It may heat up and it's resistance will increase reducing the power available. It is not uncommon for amps to produce the same power through 2 ohms and 4 for this reason.

Most components heat up more as more current goes through them and heat is a major contributor to their ageing and eventual breakdown.

The small resistances of the cables and jack plugs/sockets etc are not worth worrying about into 8 ohms but they become a considerable fraction of the resistances in a 2 ohm circuit leading to loss of power and loss of damping (the control the amp has over the speaker).

If the amp is rated at 2 ohms it may well be that the designer has allowed for all of these things but it is pushing the boundaries a little and I would avoid it personally.

An analogy might be that your car will rev at 5.500 rpm but if you revved it alike this all day you wouldn't be surprised if the engine died prematurely.
#11
Quote by Phil Starr
If you halve the impedance then you double the power demand on the amp. This means drawing more current. 100W into 4 ohms is 5A and 7A into 2 ohms. If the amp is designed for 7A then you are unlikely to blow the output transistors. The extra current has to come from the power supply and this may not deliver the extra current. It may heat up and it's resistance will increase reducing the power available. It is not uncommon for amps to produce the same power through 2 ohms and 4 for this reason.

Most components heat up more as more current goes through them and heat is a major contributor to their ageing and eventual breakdown.

The small resistances of the cables and jack plugs/sockets etc are not worth worrying about into 8 ohms but they become a considerable fraction of the resistances in a 2 ohm circuit leading to loss of power and loss of damping (the control the amp has over the speaker).

If the amp is rated at 2 ohms it may well be that the designer has allowed for all of these things but it is pushing the boundaries a little and I would avoid it personally.

An analogy might be that your car will rev at 5.500 rpm but if you revved it alike this all day you wouldn't be surprised if the engine died prematurely.


This is what I was trying to say, just without all the educated answers

Watch for heat, especially in a close environment like a rack, if you need to consider putting a fan by it. Or just don't do it.


On the subject, would it be beneficial on amps that run hot, tube amps etc, to cut a hole on either side and add PC size silent fans so they suck air across all the tubes and chassis?
#12
Seems we have a split opinion this subject lol. My amp gets slightly warm when it's on, but nothing more than that. I'll try and see if it runs warmer when the 2ohms is activated or not. Even so, if the general consensus of people say that it's not healthy for the amp, I may just only use one cab at practice and just switch it to 2ohms and plug in the second cab just for shows.

I'll try looking for some amp schematics and see what I can't find.
#13
Quote by askrere

On the subject, would it be beneficial on amps that run hot, tube amps etc, to cut a hole on either side and add PC size silent fans so they suck air across all the tubes and chassis?


Certainly! Lots and lots of amps come with them built in, and it's not an uncommon mod to hot passively-cooled amps by any means.
#14
Quote by SMB13
Seems we have a split opinion this subject lol. My amp gets slightly warm when it's on, but nothing more than that. I'll try and see if it runs warmer when the 2ohms is activated or not. Even so, if the general consensus of people say that it's not healthy for the amp, I may just only use one cab at practice and just switch it to 2ohms and plug in the second cab just for shows.

I'll try looking for some amp schematics and see what I can't find.


How many watts is your amp at 4 and 2 ohms? And do you have PA access at shows?

Now I have no real idea what you are doing or what cabs and ohms they run at, but it seems to me if your trying to run this at the limit you are also pushing the volume way up there. If you are having volume issues there are ways to fix it.

I'd probably get the most efficient cabs with the most speakers two in the 8 ohm range. Or if your trying to maintain a clean sound get a amp with more existing wattage to increase headroom. If your amp only seems to do what you need on the edge of the comfort zone maybe it's not the right amp.
#15
Quote by askrere
How many watts is your amp at 4 and 2 ohms? And do you have PA access at shows?

Now I have no real idea what you are doing or what cabs and ohms they run at, but it seems to me if your trying to run this at the limit you are also pushing the volume way up there. If you are having volume issues there are ways to fix it.

I'd probably get the most efficient cabs with the most speakers two in the 8 ohm range. Or if your trying to maintain a clean sound get a amp with more existing wattage to increase headroom. If your amp only seems to do what you need on the edge of the comfort zone maybe it's not the right amp.


500 for both, and yes. I'm not having volume issues, it's just a question of whether the load will hurt the amp. I have one 4 ohm cab (2x10), and I'm looking at adding another cab. Carvin's site says that if you run one of there 4 ohm and 8 ohm cab that it equals 2.66 ohms, while two 4 ohm cabs would be 2 ohm. Since the amp can be dropped down to 2 ohms, I'm wanting to know if could harm the amp.
#16
Quote by SMB13
500 for both, and yes. I'm not having volume issues, it's just a question of whether the load will hurt the amp. I have one 4 ohm cab (2x10), and I'm looking at adding another cab. Carvin's site says that if you run one of there 4 ohm and 8 ohm cab that it equals 2.66 ohms, while two 4 ohm cabs would be 2 ohm. Since the amp can be dropped down to 2 ohms, I'm wanting to know if could harm the amp.


Seems like you don't actually need it. But Phil did say it's not going to blow it up, just add stress, so it's up to you.