monoblock amps, impedance, and why i feel like i'm taking crazy pills while working.

[Miles]

i was always under the impression that whatever ohm load you presented a D Class amp with, that's what it was going to play at. for example, if you wire a DVC sub to 8 ohms, the amp is going to see 8 ohms.

i had a customer come in and, very loudly, proclaim that if you wire it to 8 ohms, you can "bridge" a mono amp to 4 ohms.

i figured i'd just see if this was even in the realm of possibility before i spit on the guy when he comes back into the store.

[relited]

the guy must be retarded you can't bridge a mono amp

[TIM TIM TIM]

how do you bridge one channel? your also correct about the impedance, if the sub is wired to 8 ohms, the amp see's 8 ohms... that guy is an idiot

[Notladstyle]

if the sub is wired to 8 ohms, the amp is gonna see 6 to ~ 100 ohms depending on the frequency its outputting.

Theres nothing to "Set" an amp to as far as resistance. the ohm rating is simply how close to an completely closed circuit the amp can withstand before the fet circuts that actually do the amplifying catch on fire.

An amp rated at .5 ohm can basicly handle a close to straight short circuit without overloading.


now if he was talking about taking two 8ohms subs and presenting a 4ohm load then thats a different story. Hes still an idiot tho.

[Miles]

i was just completely speechless when he told me he was going to bridge his mono amp for more power. i honestly had no idea what to say.

i think i've heard just about every possible ludicrous statement in just 5 months at best buy.

and no, he was just talking about wiring up one dual 4 ohm sub.

[TIM TIM TIM]

i agree, at CC in the 8ish months i have been there im still floored by the stupid stuff i hear.

ie. this guy was a computer engeneer who was running at bazooka 300 rms amp with an infinity reference 12 inch sub (300 rms also). he swore he needed 0awg wire, he sat there with a paper and calculated the amps/wtf ever else and determined he had to have 0awg... i may be the idiot here but every set up similar to that i sell 8awg wire and there is never a problem :lol: we even have charts set up for amps/feet to determine the proper wire size

[Notladstyle]

i agree, at CC in the 8ish months i have been there im still floored by the stupid stuff i hear.

ie. this guy was a computer engeneer who was running at bazooka 300 rms amp with an infinity reference 12 inch sub (300 rms also). he swore he needed 0awg wire, he sat there with a paper and calculated the amps/wtf ever else and determined he had to have 0awg... i may be the idiot here but every set up similar to that i sell 8awg wire and there is never a problem :lol: we even have charts set up for amps/feet to determine the proper wire size


computer engineers dont take courses in electrical resistance and current requirements :D maybe he just wanted the lowest line resistance possible because an 8ga wire can carry more than 100amps (~1500wRMS) at car voltages without getting hot.

[TJElite]

i was always under the impression that whatever ohm load you presented a D Class amp with, that's what it was going to play at. for example, if you wire a DVC sub to 8 ohms, the amp is going to see 8 ohms.

i had a customer come in and, very loudly, proclaim that if you wire it to 8 ohms, you can "bridge" a mono amp to 4 ohms.

i figured i'd just see if this was even in the realm of possibility before i spit on the guy when he comes back into the store.

I think this must be some internet legend, or something. Crossfire mono amps have two + and two - output blocks -+-+...its so you can have more than one pair of speaker leads, or can parallel at the amp, or whatever...still only one set of outputs. Anyway, I've had a couple people tell me that if you use the first neg, and the far end +, you can 'bridge' the amp, and get more power. A couple have even done it, and swear they can hear more bass.

what can you do...

Toby

[samakaballer]

that's kinda what i did to my with my kenwood mono block amp but it's not really bridging

[bigerb6969]

you cant "bridge" a mono amp...its already done inside the amplifier....as far as the dual 4 ohm sub goes.....you can wire the sub by bringing it up to 8 ohms and bring it back to 4 ohms at the amp...say on a mtx thunder they have 2 + and 2 - output speaker lines....it doesnt make any sense though...the best scenario would be a dual 2 ohm sub and having the same thing done with the sub and presenting the amp with a 2 ohm load....you get almost double the power from 4 ohms to 2 ohms...just my .02

[Miles]

you can wire the sub by bringing it up to 8 ohms and bring it back to 4 ohms at the amp...
... explain to me how you got from wiring the 2 voice coils in series to get an 8 ohm load, to having a 4 ohm load again.

[bigerb6969]

my bad...i just realized what i wrote...what i meant was wiring the sub in parallel to get 2 ohms on the amp both + together and both - together....if you wire it in series then you'll get the 8 ohm load....my error

[Notladstyle]

... explain to me how you got from wiring the 2 voice coils in series to get an 8 ohm load, to having a 4 ohm load again.



magic. silly.

[Eclipse99RS]

You hear this one yet? I had a guy come in to BB today and ask me for a "100a" fuse. I told him we don't carry "100 amp" fuses. Then he goes on and tells me "its not a 100 amp fuse, its a 100a fuse. I'm talking about the model number on the top of the fuse." So i try again to tell him yeah that is a "100 amp" fuse the "A" stands for amp. But then he just started getting all pissed off and saying how big of an idiot i was and how he didn't understand how BB could hire someone like me and not know anything about fuses. So i started laughing at him and walked away... Some people are just clueless.

[Notladstyle]

You hear this one yet? I had a guy come in to BB today and ask me for a "100a" fuse. I told him we don't carry "100 amp" fuses. Then he goes on and tells me "its not a 100 amp fuse, its a 100a fuse. I'm talking about the model number on the top of the fuse." So i try again to tell him yeah that is a "100 amp" fuse the "A" stands for amp. But then he just started getting all pissed off and saying how big of an idiot i was and how he didn't understand how BB could hire someone like me and not know anything about fuses. So i started laughing at him and walked away... Some people are just clueless.

you idiot, that was me and I dont appreciate your lack of knowlege. theres 100a fuses and then theres the SC-100-A fuse from my walmart scoshe power kit and the manual says that its a high performance fuse and I cant just use any regular 100 amp fuse in there. So please, until you have installed the high current power kit from walmart dont talk to me about fuses.



lmao just kidding ;)

[passfan]

Transistor amplifiers are load dependant, they amplify to what they see. If you want to change the impedence you do it at the speaker terminations and not through a switch on the amp, correct? That being said, you can bridge two mono amplifiers together, but you must have two. They don't have to be in the same case but you better know what your doing.


Tube amplifiers can be setup to amplify with impedence mismatches because they have transformer outputs. It's bad for the tubes depending on how you set it up but it will run. Anyone who quotes specs IMHO is an idiot simply because the way ALL manufacturures write them up is tantamount to lying.

[Notladstyle]

Transistor amplifiers are load dependant, they amplify to what they see. If you want to change the impedence you do it at the speaker terminations and not through a switch on the amp, correct? That being said, you can bridge two mono amplifiers together, but you must have two. They don't have to be in the same case but you better know what your doing.


Tube amplifiers can be setup to amplify with impedence mismatches because they have transformer outputs. It's bad for the tubes depending on how you set it up but it will run. Anyone who quotes specs IMHO is an idiot simply because the way ALL manufacturures write them up is tantamount to lying.

:serious: