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04-02-2010, 12:14 AM
| | Registered User
Bass player | | Join Date: Dec 2009 Location: Downunder Oz | | | Poweramp Ohms
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G`day bassists,
I need a simple question answered....
What ohms does a Poweramp see when two 8ohm cabs are connected in Parrallel mode ??
What about Bridge mode using two 8ohm cabs, does it half the ohms to 4ohms?
I have this amp called ` E-SysytemsPro-Power 3000`
The amp has Stereo-Parrallel & Bridge mode selector.
Maybe its not a simple question.
Growly.
Last edited by Growly Lytes : 04-02-2010 at 12:17 AM.
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04-02-2010, 12:29 AM
|  | vintage bass nut
John K Custom Basses | | Join Date: Feb 2008 Location: Thousand Oaks, CA | | Quote:
Originally Posted by Growly Lytes  What ohms does a Poweramp see when two 8ohm cabs are connected in Parrallel mode ?? | 4 ohms Quote:
Originally Posted by Growly Lytes What about Bridge mode using two 8ohm cabs, does it half the ohms to 4ohms? | yes. |
04-02-2010, 12:32 AM
| | Registered User
Bass player | | Join Date: Dec 2009 Location: Downunder Oz | | | God that was quick mate.
Thanks my bass brother. |
04-02-2010, 05:16 AM
|  | Keepin' the Groove Alive ! | | Join Date: Aug 2006 Location: Stax 1966 | | | I never really understood what " parallel " mode was, and why you would use it? In what situations would you prefer that mode over stereo or bridge ?
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R.I.P Duck Dunn, 2012.
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04-02-2010, 05:30 AM
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Originally Posted by jnewmark I never really understood what " parallel " mode was, and why you would use it? In what situations would you prefer that mode over stereo or bridge ? | I just looked it up.. wasn't familiar with the term 'parallel' and power amps. It looks like it is the mirror image of 'bridging'... so parallel mode would result in each side of the amp running at 8ohms in parallel mode instead of 2ohms when bridged with a 4ohm cab (or two 8ohm cabs connected in parallel). According to the couple of things I just read, you would only use parallel mode in a situation where you had a speaker impedance that was too low for the amp to be bridged into (i.e., a 4ohm cab, but the amp rated safe at only 8ohm minimum bridging).
That's the way I understand it... kind of like hooking speakers up in series (parallel amp mode... doubling each side's impedance relative to the actual speaker impedance) versus parallel (bridged amp mode... halving each side's impedance relative to the actual speaker impedance).
I think that is it, if I'm understanding the white papers I just skimmed.
Last edited by KJung : 04-02-2010 at 05:35 AM.
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04-02-2010, 05:37 AM
| | Registered User | | Join Date: Jun 2005 Location: Mississippi Coast | | | hmmm..Googling the power amp listed, I come up with nothing related to audio or musical instruments, so not sure what they're calling "parallel mode".
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ERIC WATKINS
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04-02-2010, 05:55 AM
|  | Registered User | | Join Date: Dec 2002 Location: Virginia Beach, VA | | | Parallel - essentially a mono set-up. A single signal is sent to power amp's input A but, internally or via jumper cable, also sent to input B. The (2) internal amps "see" the same source signal but are capable of independent adjustment and immune to differences in speaker closure ohmage (man, I love that word!). Case in point: let's say I have a PLX 3102, a 4 ohm Acme B-2, and an Acme 8 ohm B-4. I plug my preamp into the PLX's input A, set the mode switch to "Parallel", and then run the A channel output to the B-2 and the B channel output to the B-4. Adjust attenuators as necessary and you're good to go.
Riis
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"20% of the money will buy you 90% of the sound..another 30% of the money will buy you another 5% of the sound..you can't buy the remaining 5% of the sound because nobody can agree about what it is." |
04-02-2010, 06:01 AM
| | | Quote:
Originally Posted by Zooberwerx Parallel - essentially a mono set-up. A single signal is sent to power amp's input A but, internally or via jumper cable, also sent to input B. The (2) internal amps "see" the same source signal but are capable of independent adjustment and immune to differences in speaker closure ohmage (man, I love that word!). Case in point: let's say I have a PLX 3102, a 4 ohm Acme B-2, and an Acme 8 ohm B-4. I plug my preamp into the PLX's input A, set the mode switch to "Parallel", and then run the A channel output to the B-2 and the B channel output to the B-4. Adjust attenuators as necessary and you're good to go.
Riis | I think you are describing 'dual mono' operation, not parallel. |
04-02-2010, 06:15 AM
| | Keepin' the Groove Alive ! | | Join Date: Aug 2006 Location: Stax 1966 | | Quote:
Originally Posted by KJung I think you are describing 'dual mono' operation, not parallel. | Is'nt that the same as using a " Y " cable?
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04-02-2010, 06:33 AM
| | Registered User | | Join Date: Dec 2002 Location: Virginia Beach, VA | | Quote:
Originally Posted by KJung I think you are describing 'dual mono' operation, not parallel. | Nope, not according to my manual. The inputs are wired in parallel...what one input "sees", so does the other. Most modern amps I've encountered do this internally without the need for a Y cable. Even my RMX 1450's have this feature via the rear DIP switches. Comes in handy when running a single monitor signal from the board but needing to push 4 monitor enclosures.
Yes, in theory it is "dual mono", just not labeled as such so you are right, KJ. Matter of terminology. Last time I encountered "dual mono" was on my DriveRack's EQ program (you can select dual mono or stereo-linked).
Riis
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"20% of the money will buy you 90% of the sound..another 30% of the money will buy you another 5% of the sound..you can't buy the remaining 5% of the sound because nobody can agree about what it is." |
04-02-2010, 06:36 AM
| | | Quote:
Originally Posted by Zooberwerx Nope, not according to my manual. The inputs are wired in parallel...what one input "sees", so does the other. Most modern amps I've encountered do this internally without the need for a Y cable. Even my RMX 1450's have this feature via the rear DIP switches. Comes in handy when running a single monitor signal from the board but needing to push 4 monitor enclosures.
Yes, in theory it is "dual mono", just not labeled as such so you are right, KJ. Matter of terminology. Last time I encountered "dual mono" was on my DriveRack's EQ program (you can select dual mono or stereo-linked).
Riis | +1 Semantics. However, I guess there is an actual 'parallel' mode of combining two amps that works just like bridging (i.e., allowing both amps to power a single cab), but results in the each side of the amp seeing double the impedance of the cab rating versus half the impedance of the cab rating when in bridge mode.
I was not aware of that, and I guess, as you point out, different amp manufacturers use these terms in different ways. |
04-02-2010, 06:40 AM
| | Registered User | | Join Date: Dec 2002 Location: Virginia Beach, VA | | http://media.qscaudio.com/pdfs/manua...anual_revE.pdf
Here's a link to the manual page, guys....the reference is about 1/4 of the way down.
Riis
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"20% of the money will buy you 90% of the sound..another 30% of the money will buy you another 5% of the sound..you can't buy the remaining 5% of the sound because nobody can agree about what it is." |
04-02-2010, 06:41 AM
| | | Quote:
Originally Posted by jnewmark Is'nt that the same as using a " Y " cable? | If you are talking about 'dual mono', then yes. With all in one heads with dual power amps, 'dual mono' is achieved internally. I assume some (many?) power amps have a 'dual mono' input built in (which from the above, I guess is called 'parallel' by some companies) which would eliminate the need for a Y cable from a mono preamp. |
04-02-2010, 06:44 AM
| | | Quote:
Originally Posted by Zooberwerx | +1 They are using 'parallel' as you stated, which I guess I always called dual mono. Again, it does seem like there is also a 'parallel' mode that describes something different also, and that is a different method of actually combining the two sides to run a single cab.
I love learning about this stuff! |
04-02-2010, 06:45 AM
| | Registered User | | Join Date: Dec 2002 Location: Virginia Beach, VA | | Quote:
Originally Posted by KJung +1 Semantics. However, I guess there is an actual 'parallel' mode of combining two amps that works just like bridging (i.e., allowing both amps to power a single cab), but results in the each side of the amp seeing double the impedance of the cab rating versus half the impedance of the cab rating when in bridge mode.
I was not aware of that, and I guess, as you point out, different amp manufacturers use these terms in different ways. | Negative, this is is not bridging. Parallel mode allows the two amps to work independently. There would be no need or rationale to use it if only powering a single cab. It does have its applications like the aforementioned monitor set-up and mixing / matching of different cab config's. Its simply two internal amps sharing a single signal source.
Riis
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"20% of the money will buy you 90% of the sound..another 30% of the money will buy you another 5% of the sound..you can't buy the remaining 5% of the sound because nobody can agree about what it is." |
04-02-2010, 06:46 AM
| | Registered User | | Join Date: Jan 2008 Location: Westfield, MA, USA | | | In stereo mode input A goes to output A and input B goes to output B. This is for using both sides of the amp to drive two different speaker systems, each with different input signals.
In parallel mode input A goes to both output A and output B. This is for using both sides of the amp to drive two different speaker systems, each with the same input signal. This is functionally identical to running in stereo mode and splitting the input signal with a Y cable.
In bridge mode input A goes to output A and input B has it's polarity inverted and then goes to output B. This is for using both sides of the amp to drive a single speaker system.
If you are driving two 8 ohm loads, one off of each side of the amp in parallel or stereo mode, each side of the amp sees an 8 ohm load.
If you are driving two 8 ohm loads, both off of one side of the amp, that side sees a 4 ohm load and the other side sees nothing.
If you are driving two 8 ohm loads off of both sides of the amp together in bridged mode, each side of the amp sees a 2 ohm load.
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04-02-2010, 06:50 AM
| | Registered User | | Join Date: Dec 2002 Location: Virginia Beach, VA | | Quote:
Originally Posted by KJung +1 They are using 'parallel' as you stated, which I guess I always called dual mono. Again, it does seem like there is also a 'parallel' mode that describes something different also, and that is a different method of actually combining the two sides to run a single cab.
I love learning about this stuff! | KJ,
Sorry but I'm running about one post behind you. I've never run across "parallel" used to describe two amps tied together to run a single enclosure. If you run across a reference, let me know.
Yep, I never stop learning on this site!
And a joyful Good Friday to all!
Riis
__________________
"20% of the money will buy you 90% of the sound..another 30% of the money will buy you another 5% of the sound..you can't buy the remaining 5% of the sound because nobody can agree about what it is." |
04-02-2010, 06:54 AM
| | | Quote:
Originally Posted by Zooberwerx KJ,
Sorry but I'm running about one post behind you. I've never run across "parallel" used to describe two amps tied together to run a single enclosure. If you run across a reference, let me know.
Yep, I never stop learning on this site!
And a joyful Good Friday to all!
Riis |  No problem (I type too quickly sometimes!! I again think your definition of parallel is the one that is most commonly used, and describes the OP's questions.
Here is one of the 'other' definitions I found for 'parallel' mode:
A paralleled amplifier configuration uses multiple amplifiers in parallel, i.e., two or more amplifiers operating in-phase into a common load. The image shows two identical amplifiers A1 and A2 connected in parallel configuration. This configuration is often used when a single amplifier is incapable of being operated into a low impedance load or dissipation per amplifier is to be reduced without increasing the load impedance or reducing power delivered to the load. For example, if two identical amplifiers (each rated for operation into 4 Ω) are paralleled into a 4 Ω load, each amplifier sees an equivalent of 8 Ω since the output current is now shared by both amplifiers — each amplifier supplies half the load current, and the dissipation per amplifier is halved. This configuration (ideally or theoretically) requires each amplifier to be exactly identical to the other(s), or they will appear as loads to each other. Practically, each amplifier must satisfy the following...... |
04-02-2010, 07:04 AM
| | Registered User | | Join Date: Jan 2006 Location: Brookfield, CT | | | I had a Crown Power Base amp that had this feature. Never used it. You'd connect the two red binding posts together with a jumper then connect the load to one of them, and a black post. Doubles the current capability, whereas bridging doubles the voltage. Still not clear on why you'd prefer it over bridging. |
04-02-2010, 07:04 AM
| | Registered User | | Join Date: Dec 2002 Location: Virginia Beach, VA | | Quote:
Originally Posted by KJung No problem (I type too quickly sometimes!! I again think your definition of parallel is the one that is most commonly used, and describes the OP's questions.
Here is one of the 'other' definitions I found for 'parallel' mode:
A paralleled amplifier configuration uses multiple amplifiers in parallel, i.e., two or more amplifiers operating in-phase into a common load. The image shows two identical amplifiers A1 and A2 connected in parallel configuration. This configuration is often used when a single amplifier is incapable of being operated into a low impedance load or dissipation per amplifier is to be reduced without increasing the load impedance or reducing power delivered to the load. For example, if two identical amplifiers (each rated for operation into 4 Ω) are paralleled into a 4 Ω load, each amplifier sees an equivalent of 8 Ω since the output current is now shared by both amplifiers — each amplifier supplies half the load current, and the dissipation per amplifier is halved. This configuration (ideally or theoretically) requires each amplifier to be exactly identical to the other(s), or they will appear as loads to each other. Practically, each amplifier must satisfy the following...... | Okay....has anybody out there ever pulled this off or had need to? Kinda curious as to what practical applications would arise in our arena of sound reinforcement.
Doesn't sound as if a screw-up or mismatch would be too forgiving. Do you smell smoke?!?
Riis
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