Educated me on SS power amps and wattage!

[ibanez4life SZ!]

Hey guys!

Looking to try some SS power amps with my Axe FX.

It's obvious that I will need more wattage in the SS power amp than what I used to use in tubes format...thinking about the ART SLA-2, which will be doing over 500 watts in bridged mono.

My question...how does this operation play into speaker wattage for safety? To get the SS power amp to the same volume I was running my 100 watt tube power section at (I play in a HARD hitting metal band right now), do I need the speakers to be able to handle the full 500 watts+? Or since we're looking at the same volume, will they be safe?

I'm running a 280 watt V30 loaded cab....we play LOUD...do I need to worry about blowing out the speakers, or since the SS watts are 'quieter,' will the speakers be ok?

Thanks!

Eric

P.S. Plan B is to get a Fryette 2/90/2...just want to see if I can ditch tubes all together and get most of the way there!

 

[blackba]

First off Watts are Watts, meaning that a 100Watt tube amp is the same power as a 100Watt SS amp. Its just that often the tube amp can be pushed into clipping, which is pleasant and you get more perceived power (sometimes more actual power, as I have read 100Watt amps actually put out more then 100Watts.

For PA the general guide is 1.0-2.0 times the RMS rating for the speakers. So if you have a 280Watt RMS cab, you would get a power amp that can supply 280-560Watts RMS. The 1.5times is generally a good place to shoot for, which in your case is 420Watts. There are 2 main drivers for speaker failure, one is overpowering the speakers. The second is sending too much clipping (Ie sending the speaker a square wave). With the 1.0 times RMS you are more at risk for the clipping. With the 2.0 times RMS, you are more at risk for purely overpowering the speakers.

Another thing to keep in mine with power amps, is that most are stereo, whether they are tube or SS. With a SS power amp the output will depend on a the impedance of the speaker cabinet (like 4ohms, 8ohms, or 16ohms). With a SS power amp you can also run one side of the power amp or run it bridged. Bridged will give you more power, but you have to watch the impedance to make sure it is not too low.

A popular power amp for the Axe-Fx seems to be the Carvin DCM series. the DCM 1500, now replaced by the DCM1540L is a really popular choice.

 

[glpg80]

First off Watts are Watts, meaning that a 100Watt tube amp is the same power as a 100Watt SS amp. Its just that often the tube amp can be pushed into clipping, which is pleasant and you get more perceived power (sometimes more actual power, as I have read 100Watt amps actually put out more then 100Watts.

For PA the general guide is 1.0-2.0 times the RMS rating for the speakers. So if you have a 280Watt RMS cab, you would get a power amp that can supply 280-560Watts RMS. The 1.5times is generally a good place to shoot for, which in your case is 420Watts. There are 2 main drivers for speaker failure, one is overpowering the speakers. The second is sending too much clipping (Ie sending the speaker a square wave). With the 1.0 times RMS you are more at risk for the clipping. With the 2.0 times RMS, you are more at risk for purely overpowering the speakers.

Another thing to keep in mine with power amps, is that most are stereo, whether they are tube or SS. With a SS power amp the output will depend on a the impedance of the speaker cabinet (like 4ohms, 8ohms, or 16ohms). With a SS power amp you can also run one side of the power amp or run it bridged. Bridged will give you more power, but you have to watch the impedance to make sure it is not too low.

A popular power amp for the Axe-Fx seems to be the Carvin DCM series. the DCM 1500, now replaced by the DCM1540L is a really popular choice.

theres so much wrong in this.

first off, do not bridge a power amplifier unless it was specifically designed to do so. if you do this you can damage an amplifier beyond repair without knowing what you are doing. ask me how many times i had to correct car audio nuts connecting their class D cheap power amplifiers bridged when the channels were not designed to do so, popping transistors like the fourth of july.

watts are watts correct. headroom of one and headroom of the other is not. it takes ~300 watts of SS for every 100W dual pair octal-based power tube transistor running class A/B push pull to get the same headroom BEFORE clipping. if you clip the signal of a tube it gives natural distortion that is wanted by some tone chasers. on an oscilloscope it acts like a natural squashing of the sin waves top and bottom. clipping a SS amplifier will clip the original signal and NOT sound pleasant at all - it also overheats the transistors and can cause transient currents (also known as spikes) that can damage speakers or also short transistors base to emitter.

solid state transistors do not run at 400 and 500V, power tubes are much more efficient in high power applications. its why tubes are still used in transmitting radio frequencies for communications. (talking 10kV+ here)

you always want to equally rate both the power amplifier and the speakers for the intended impedance load you want to run for maximum power transfer for each individual channel with enough headroom to operate efficiently - talking about heat dissipation here. power amplifier max output does not matter here, you want the RMS recommended output. rate this in regards to the speaker load, not what sounds good on paper.

let me make this very clear one more time - you do NOT bridge the channels of the power amplifier unless the user manual specifically give instructions on how to do so properly and recommended impedance loads for the total bridged channel design. there are many different classes of bias of operation (A, B, AB, AB+/-, C, D) for amplifying a signal and all classes are not combinable.

onto the impedance to power ratio you mentioned. you are incorrect in stating it how you did. an amplifier gives X ammount of power at all times. you need to know max power transfer laws and their relationships to AC and DC current.

http://www.opamp-electronics.com/tutori ... _10_11.htm

it basically says everything i have mentioned before, except for the fact that the lower the impedance load, the more the load acts like a short to the power amplifier, which stresses the power amplifier more because it is closer to better power transfer of what goes in = 100% goes out. a 0ohm load would be ideal however this is not possible in real world designs due to small resistances in wiring and other variables which just will not happen with component tolerances we have today ( both analog and digital)

 

[glpg80]

Hey guys!

Looking to try some SS power amps with my Axe FX.

It's obvious that I will need more wattage in the SS power amp than what I used to use in tubes format...thinking about the ART SLA-2, which will be doing over 500 watts in bridged mono.

My question...how does this operation play into speaker wattage for safety? To get the SS power amp to the same volume I was running my 100 watt tube power section at (I play in a HARD hitting metal band right now), do I need the speakers to be able to handle the full 500 watts+? Or since we're looking at the same volume, will they be safe?

I'm running a 280 watt V30 loaded cab....we play LOUD...do I need to worry about blowing out the speakers, or since the SS watts are 'quieter,' will the speakers be ok?

Thanks!

Eric

P.S. Plan B is to get a Fryette 2/90/2...just want to see if I can ditch tubes all together and get most of the way there!

QSC and crest audio are the two i would recommend for SS power amplifying. no you wont be needing speakers to handle 500 watts because you wont be running the input signal of the amplifier that hard and an amplifier that puts out this much at RMS is not rated properly to the speakers you are using which will hurt your tone, not improve it.

if your impedance load of the speakers is 16 ohms and 50W RMS, total RMS is 200W, then get an amplifier that can run 300W RMS that is solid state. do not be concerned with max power in solid state amplifiers, that is a useless measurement number and souly based on design purposes. you never want to run a SS amplifier at this number anyway for obvious reasons already mentioned.

AFA the VHT power amp choice - go with either decision bro. if you want tube colouration get a tube amplifier. if you want the best clean power then go SS. both have positives and negatives

 

[ibanez4life SZ!]

Thanks for all the help!

I guess it might help to put things more specifically also...

I'm thinking about running an ART SLA-2 in bridged operation at 8 ohms...it puts out 560 watts this way.

Will it be safe to run with my 4x12 with V30s rated at 280 watts?

Eric

 

[glpg80]

Thanks for all the help!

I guess it might help to put things more specifically also...

I'm thinking about running an ART SLA-2 in bridged operation at 8 ohms...it puts out 560 watts this way.

Will it be safe to run with my 4x12 with V30s rated at 280 watts?

Eric

if it is designed to be bridged or run seperate channels yes.

what is the impedance load of your cabinet? if the cabinet is 16 ohms and the bridged mode needs 8ohms or 4 ohms you will still be in the clear, you will actually have a little loss in power transfer efficiency, so that 560 watts at max power transfer will actually be closer to 480-500W, and keeping in mind ~1.5 the RMS value of the speakers, 280W * 1.5 = 420W so you will not have any problem doing this at all and will come out just right in not stressing or overheating the power amplifier and also getting clean headroom for no signal clipping.

 

[jasonP]

Matt, what book you are you getting this info out of? I would like to read it.

I personally think you should go with plan B. I just think you will be really missing the tube warmth and depth. SS to me if I had to go that way I would go for a mosfet power amp that is warmer on the top end. Of course this is just my opinion.

 

[glpg80]

Matt, what book you are you getting this info out of? I would like to read it.

I personally think you should go with plan B. I just think you will be really missing the tube warmth and depth. SS to me if I had to go that way I would go for a mosfet power amp that is warmer on the top end. Of course this is just my opinion.

its all basic engineering textbook knowledge. alot of this is ground into our heads early on in the degrees. i can tell you a few electronics theory books, but this wont be verbatem inside of them? i dabble in all things sound engineering - specifically car audio power amplifiers, guitar amplifiers, high power PA/vintage, radio communications - RF and LF, and tube high fidelity/linear.

care audio and PA information is where alot of this information has come from, if that is what you are asking. the rest is knowledge i have gained over many textbooks and professors. there isnt anything really im copying and pasting this from - its just knowledge

alot of this information is on the internet, you just have to know where to look. i can PM you a few sites if you would like?

also i forgot to mention the leading cause to speaker failure is not transient spikes, its heat. voice coils that do not get ample time to cool are more prone to shorting.

 

[ibanez4life SZ!]

My cab is wired at 8 ohms, so I'd be getting the full 560 watts put out to the speakers.

Eric

 

[roadifier]

Id buy a mosfet Power amp if your worried about blowing your speakers, and It actually sounds pretty good.

 

[blackba]

theres so much wrong in this.

first off, do not bridge a power amplifier unless it was specifically designed to do so. if you do this you can damage an amplifier beyond repair without knowing what you are doing. ask me how many times i had to correct car audio nuts connecting their class D cheap power amplifiers bridged when the channels were not designed to do so, popping transistors like the fourth of july.

watts are watts correct. headroom of one and headroom of the other is not. it takes ~300 watts of SS for every 100W dual pair octal-based power tube transistor running class A/B push pull to get the same headroom BEFORE clipping. if you clip the signal of a tube it gives natural distortion that is wanted by some tone chasers. on an oscilloscope it acts like a natural squashing of the sin waves top and bottom. clipping a SS amplifier will clip the original signal and NOT sound pleasant at all - it also overheats the transistors and can cause transient currents (also known as spikes) that can damage speakers or also short transistors base to emitter.

solid state transistors do not run at 400 and 500V, power tubes are much more efficient in high power applications. its why tubes are still used in transmitting radio frequencies for communications. (talking 10kV+ here)

you always want to equally rate both the power amplifier and the speakers for the intended impedance load you want to run for maximum power transfer for each individual channel with enough headroom to operate efficiently - talking about heat dissipation here. power amplifier max output does not matter here, you want the RMS recommended output. rate this in regards to the speaker load, not what sounds good on paper.

let me make this very clear one more time - you do NOT bridge the channels of the power amplifier unless the user manual specifically give instructions on how to do so properly and recommended impedance loads for the total bridged channel design. there are many different classes of bias of operation (A, B, AB, AB+/-, C, D) for amplifying a signal and all classes are not combinable.

onto the impedance to power ratio you mentioned. you are incorrect in stating it how you did. an amplifier gives X ammount of power at all times. you need to know max power transfer laws and their relationships to AC and DC current.

http://www.opamp-electronics.com/tutori ... _10_11.htm

it basically says everything i have mentioned before, except for the fact that the lower the impedance load, the more the load acts like a short to the power amplifier, which stresses the power amplifier more because it is closer to better power transfer of what goes in = 100% goes out. a 0ohm load would be ideal however this is not possible in real world designs due to small resistances in wiring and other variables which just will not happen with component tolerances we have today ( both analog and digital)

Here is what I got, that I got wrong, if there is anything else please point it out. Not trying to mislead anyone here, just trying to help. I thought I was helping, so it is disappointing to me that I had things wrong.

- I failed to mention the headroom difference between a SS power amp and tube power amp. I was aware of the difference but did not state is properly.
- I understand max power, I was just trying to point out that SS amps will have different wattage outputs depending on the impedance of the load. But you are right the actual power of the amplifier is not changing with the load.
- I failed to mention that with bridging you need to make sure the amp can handle it. The point I was trying to make is that just cause the amp can run down to 2 ohms a side, does not mean that you should run a 2ohm load from a bridge amps, the manuals will give you a minimum bridged ohm load.
- I thought over powering and clipping both lead to head in the voice coil which fried the speaker, my bad.
- Was I wrong on the 1.0-2.0 RMS? I have seen that posted in the HC Live sound forum. Agedhorse monitors that pretty closely

 

[Anonymous]

a mosvalve 962 or 982 will serve you well. they sound good, are reliable, bulletproof and put out more power than you will EVER need (80 w per side stereo)

ran one for years, never had to turn preamp volume beyond 10oclock.

when i did though, it remained clear, and was LOUD

or, if thats not enough power, they make bigger ones specifically for guitarists.

 

[glpg80]

Here is what I got, that I got wrong, if there is anything else please point it out. Not trying to mislead anyone here, just trying to help. I thought I was helping, so it is disappointing to me that I had things wrong.

- I failed to mention the headroom difference between a SS power amp and tube power amp. I was aware of the difference but did not state is properly.
- I understand max power, I was just trying to point out that SS amps will have different wattage outputs depending on the impedance of the load. But you are right the actual power of the amplifier is not changing with the load.
- I failed to mention that with bridging you need to make sure the amp can handle it. The point I was trying to make is that just cause the amp can run down to 2 ohms a side, does not mean that you should run a 2ohm load from a bridge amps, the manuals will give you a minimum bridged ohm load.
- I thought over powering and clipping both lead to head in the voice coil which fried the speaker, my bad.
- Was I wrong on the 1.0-2.0 RMS? I have seen that posted in the HC Live sound forum. Agedhorse monitors that pretty closely

its cool, we all mean well in the end. but you will have wattage output differences in tubed amplifiers as well. electronic theory does not favor one design over another, it applies to all designs and all circuits from 5V to 5,000,000V.

with bridging it has nothing to do with the amplifier handling it and everything to do with how the amplifier was physically engineered in a manner that the channels can be bridged. there are countless tubed models that dont have this feature, and there are countless SS class A/B and class D amplifiers that dont have this feature. if the amplifier says dont bridge the channels, or does not give instructions for doing so, dont assume otherwise and do it anyway regardless of the impedance load your bridging.

speakers dont care for clipping, they dont care for crossover distortion as well. they are bad for your tone, but the speaker will still work and do its job. what speakers die from are heat. always heat. either pumping too much wattage which melts the coils, or clipping a high output signal which stresses the wire again because of extra movement and stress causing more heat. a speaker is stupid simple and rarely fail due to mechanical failure, most of the time it involves inefficient cooling and the rated wattage of the coils that go right along with this.

think about it for a second in the 1.0 RMS you keep mentioning. 1 * 1 = 1. first off thats not a rule, thats common knowledge and not even worth mentioning. if you do a 1:1 ratio your amplifier will always go before the speakers do - what power goes out, must come in. and if you are stressing a power amp at its max power rating it will give eventually due to heat, only time will tell on that ticking time bomb. 1.5 or 2 is common depending on your knowledge and attention to detail when running bridged loads and knowing how to set up power amplifiers where they are happy with loads; without also blowing or clipping speakers so they are also happy. i always do the lower of the two, 1.5, because you always want to rate the amplifiers to what you are using. otherwise you get high THD or total harmonic distortion tolerances which negatively effect your sound. bigger is not better in this ballgame, and brand names do matter in the SS world because no design is exactly the same. as far as bigger is better - the only difference, is slaving amplifiers off of each other in the SS world, which complicates matters more, but solves THD and max power transfer issues. hence why you never see a single 20,000W power amplifier in a stadium, and always 2,000W's slaved off of one another for better cooling, productivity, THD, and less maintenance.

 

[glpg80]

a mosvalve 962 or 982 will serve you well. they sound good, are reliable, bulletproof and put out more power than you will EVER need (80 w per side stereo)

ran one for years, never had to turn preamp volume beyond 10oclock.

when i did though, it remained clear, and was LOUD

or, if thats not enough power, they make bigger ones specifically for guitarists.

+1, the mosvalve 942 was the 500 stereo model from them. they did a great job in offering a musical tone application and also being road-worthy. i know doug aldrich uses a mosvalve 942 for his wet cabinets live, and has been using one for years. i debated building a clone model from parts since because they are so hard to find. built like tanks.

 

[petejt]

You could try an old H|H power amp.