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Gain, power and volume - a confusing ménage à trois...


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#61 BOD2

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Posted 17 December 2012 - 04:33 PM

On the MB Fusion you effectively have two independent channels - A and B - selected using the button on the front panel, or the footswitch. The two channels don't interact with each other - controls marked "A" have no effect when channel "B" is selected and vice versa. It gives you the option of two different sounds, selectable at the flick of a switch.

You shouldn't be able to "break anything" on the MB Fusion no matter what control settings you use, so you can experiment with the controls as much as you like. The only time you need to be cautious is when using lots of volume through speakers. If its starts to sound horribly distorted then back off any of the volume or gain controls to reduce the volume and start again.

When setting up, treat it as two separate amps - amp A and amp B. To setup amp A, the A/B switch should be off (out) then use only the controls marked "A". To setup amp B push the A/B switch in then use only the controls marked "B". The tone controls affect BOTH amp A and B settings.

Setting the Masters at 3 o'clock should allow you to hear what is happening at the input stage as you adjust Gain A or B. The 3 o'clock setting is a sort of "average" setting to use as a starting point. Without hearing how loud this it's difficult to say exactly how to go about setting this up. But start at this Master setting, select channel A then bring up "Gain A" until you like what you're hearing.

If "Gain A" has to be set very high to get the desired volume and is starting to distort a little, then you might want to turn UP "Master A" and turn DOWN "Gain A" to get the right balance of volume and distortion (or lack of distortion). Fine tune the two controls to get what you like.

Then do the same for channel B - bearing in mind that you might get some warm valve distortion earlier since this is what it's meant to do.

Once you have both channels sounding the way you want, leave "Gain A" and "Gain B" as they are. Now only adjust "Master A" and "Master B" to get the correct relative volumes from each channel so that when you switch from one to the other there isn't a huge change in overall volume (unless that's the effect you want).

That's how I would go about setting it up.
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#62 Si600

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Posted 18 December 2012 - 08:44 AM

Cheers chap.

I suspect that this is hijacking the OP somewhat, but are those Gain and Master controls a ratio or something? If it sounds nice at home will it still sound the same but louder once it gets into rehearsal or rocking it out at the Dog 'n' Duck if I leave the Gain where it is and just turn the Master up?

If that makes sense :)

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#63 Mr. Foxen

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Posted 18 December 2012 - 06:18 PM

Stuff doesn't sound the same louder due to Fletcher-Munson curves.

#64 BOD2

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Posted 18 December 2012 - 06:58 PM

+1 to what Mr. Foxen says, unfortunately.

Stuff doesn't even sound the same when you leave all the controls untouched but play in a different room sometimes !

But it'll give you a starting point for setting it up at a gig or rehearsal.
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#65 iceonaboy

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Posted 09 January 2013 - 10:52 AM

View PostSteveO, on 22 May 2008 - 06:15 AM, said:

Mmmmmmm flashing lights and shiny knobs. Yup, that's pretty much all I look for when buying gear ;)

What else is there when you are standing at the back bored?

#66 iceonaboy

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Posted 13 January 2013 - 02:17 PM

View PostSteveO, on 22 May 2008 - 06:15 AM, said:

Mmmmmmm flashing lights and shiny knobs. Yup, that's pretty much all I look for when buying gear ;)

Agreed and if you are worried about your speaker not being up to the job, buy a bigger speaker :rolleyes:

#67 iceonaboy

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Posted 13 January 2013 - 02:37 PM

View Post4 Strings, on 28 October 2009 - 11:25 AM, said:

Just a quickie about matching speakers and amp power. Consider them like the chassis and engine of a car.

A 10W amp going into 500W speakers would be like running a 10bhp go-kart engine in a 500bhp Le Mans racer. It will hardly move it.

The other way round, a 500W amp into a 10W speaker will, like a 500bhp Le Mans racer engine in a go-kart, blow the thing to pieces at anything above tick-over. 10W into a 10-20W speaker gives enough headroom for safety without too heavy a burden and it will go like a go-kart. 500W into 500-1000W of speakers will fly like a Le Mans racer.

Nice analogy mate!

#68 Mr. Foxen

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Posted 13 January 2013 - 03:00 PM

I thought analogies have to work to be nice, and that one doesn't.

#69 Mikey R

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Posted 19 January 2013 - 01:41 AM

As musicians, we are used to calling the attenuation on the input "gain" and the output "master" or "volume" - we've been calling them that for 40 years, we all know what they mean so lets keep on calling them that.

There are good technical reasons for this, but they really dont matter since theres no need to redefine a language that works.

Edited by Mikey R, 19 January 2013 - 08:11 AM.


#70 Mr. Foxen

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Posted 19 January 2013 - 01:54 AM

Too many people think gain means distortion and that is a pain in the nuts.

#71 Mikey R

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Posted 04 May 2013 - 06:17 AM

Rather than start a new topic, thought I'd post this in here. Ive been reading through some threads in Amps and Cabs, and there seems to be a trend.

In the late 90s, I used to play with quite a loud rock rap band. We had a hard hitting drummer and the guitarist used a 4 x 12. Because of the hip hop influence, most of our songs were driven by the rhythm section so were kinda bass heavy.

All of this, and I kept up with my old (new at the time) Trace Elliot GP7SM 150 watt combo. This had the slotted front port and the smaller (10 inch maybe?) driver, so was probably far less efficient than a modern Neo loaded cab. Since I wasnt using an extension speaker, this was probably putting out around 80 watts.

So why, as bassplayers, are we feeling the need for a half kilowatt stack for the low end? Are we competing with guitarists with terrible scoopy tone? Do we just like the headroom?

Edited by Mikey R, 04 May 2013 - 06:18 AM.


#72 Mr. Foxen

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Posted 04 May 2013 - 11:43 AM

Lower tuned cabs, instead of a high tuned one for a midbass hump, now the trend is actual low end extension.

#73 Bill Fitzmaurice

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Posted 04 May 2013 - 11:59 AM

View PostMikey R, on 04 May 2013 - 06:17 AM, said:

So why, as bassplayers, are we feeling the need for a half kilowatt stack for the low end?
To paraphrase Sir Edmund Hillary, "because they're there". In 1965 I bought a 50 watt Fender Bassman because it was what was available. If I could have bought a 500w ten pound Class D micro-amp instead, I would have.
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#74 Mr. Foxen

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Posted 04 May 2013 - 12:01 PM

Mate of mine was gigging his 1964 50w bassman with original cab until 10 years ago.

#75 28mistertee

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Posted 08 July 2013 - 06:39 AM

Apologies for re opening an old thread again. Im a newbie to heads and cabs so just to clarify it wouldn't matter if I had a 300w head driving a 300w or a 1000w cab it wouldn't damage it or be detrimental to the sound in anyway?
Also what has been baffling me is how is the power distributed when you daisy chain 2 8ohm cabs together to run at the amps 4ohm recommendation. In other words how is the wattage distributed between the two cabs?

#76 chris_b

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Posted 08 July 2013 - 09:26 AM

You cannot damage a cab or amp by under powering either and you will only run the risk of getting a less than perfect sound and causing damage if you are running either flat out.

The amp will see the speakers evenly. 2 8 ohm cabs will look like 1 4 ohm cab to the amp and it will send the same signal to both.

If you are running an amp flat out, IMO you need a more powerful amp. I usually run my amps between 11 o'clock and 12 o'clock on both volume controls and I aim to have more rated watts in the cabs than the amp.
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#77 28mistertee

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Posted 08 July 2013 - 11:31 AM

View Postchris_b, on 08 July 2013 - 09:26 AM, said:

You cannot damage a cab or amp by under powering either and you will only run the risk of getting a less than perfect sound and causing damage if you are running either flat out.
Makes sense, so I could hook up a cab if its rated at 800w to my 350w? Cheers :)

The amp will see the speakers evenly. 2 8 ohm cabs will look like 1 4 ohm cab to the amp and it will send the same signal to both.

If you are running an amp flat out, IMO you need a more powerful amp. I usually run my amps between 11 o'clock and 12 o'clock on both volume controls and I aim to have more rated watts in the cabs than the amp.


#78 Mr. Foxen

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Posted 08 July 2013 - 01:14 PM

Yes.

#79 TimR

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Posted 10 July 2013 - 11:41 PM

View Post28mistertee, on 08 July 2013 - 06:39 AM, said:

...
Also what has been baffling me is how is the power distributed when you daisy chain 2 8ohm cabs together to run at the amps 4ohm recommendation. In other words how is the wattage distributed between the two cabs?

Beware of using the term 'daisy chaining'.

Daisy chaining implies running the speakers in series. You're actually connecting them in parallel. The current splits, half goes down to one speaker, the other half goes down the other speaker.

Although because of the way the cables are run it does look like the speakers are daisy chained. The first cable takes all the current for both speakers, half the current goes through the first speaker, while the second cable takes the other half of the current to the next speaker.

Edited by TimR, 10 July 2013 - 11:46 PM.

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#80 Mr. Foxen

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Posted 11 July 2013 - 02:09 PM

I think its more that people assume daisy chaining means connecting in series, and it doesn't, because the connectors on most cabs allowing you to go from one to the other are in parallel.

#81 Handwired

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Posted 31 December 2013 - 08:25 PM

View Postmikhay77, on 03 May 2010 - 08:29 PM, said:

I have used trace gear for years and unless I have missed something(its like and idiots guide for me) the red knob to the left is labeled input gain,I suppose its what I have been conditioned to look for.With a flashing light or a thumbs up to tell you when its about right,go above that and the output signal distorts no matter how low my volume control is or whatever speaker cab is connected so I would have thought it is gaining the input stage.Also playing through 4x10s they sound better when being pushed a bit,if really low volumes they are a little thinner,or is that just me? I do understand about sensitivity etc but played through some new neo cab and even though the output seemed higher at lower output settings they came to life more when pushed.Sort of fuller.Thats my ears telling me I know its not really science.
Well put, this is an interesting thread but I think most Bass players don't fully understand the internal workings of an amplifier, but what they do understand is what a gain control and a master volume control does to the sound irrespective of the true technical function of the component.

#82 omikin

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Posted 11 January 2014 - 10:39 AM

This might be a really stupid question, but am I right in thinking that if I run my Fender Bassman 100 into my Barefaced Super 12 then I can pretty much turn the amp as loud as I like without fear of damaging the cab?

As in will my hearing be destroyed before the cab is, or do I still need to listen out for tell-tale farting noises or something?
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#83 Roland Rock

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Posted 10 March 2014 - 09:08 AM

View Postomikin, on 11 January 2014 - 10:39 AM, said:

This might be a really stupid question, but am I right in thinking that if I run my Fender Bassman 100 into my Barefaced Super 12 then I can pretty much turn the amp as loud as I like without fear of damaging the cab?

As in will my hearing be destroyed before the cab is, or do I still need to listen out for tell-tale farting noises or something?

Are you talking the Bassman 100 valve head, or the SS Combo?

If it's the valve head, you'll be absolutely fine putting it through the Super 12, as it can take a silly amounts of power.

If it's the solid state combo, you will not be able to add the Super 12. The minimum impedance for that amp is 4ohms, and it's already paired with a 4ohm speaker. Adding the Super 12 would make 2ohms, which would be a bad thing.
If, however, you could bypass the internal combo speaker, and plug into the Super 12 instead, you should be fine. And loud.

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#84 The Dark Lord

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Posted 11 March 2014 - 10:07 PM

View Postalexclaber, on 31 July 2007 - 05:23 PM, said:


If you put a preamp or booster in front of the amp you might be able to put 10V into the preamp but you still won't be able to get more than 28V out of the power amp.

If an amp is not loud enough, no amount of louder effects pedals, outboard preamps, pickups, will make it louder........


Not sure about this bit. I paired by MiBass up to a single Mi12 8 Ohm cab the other day, to see if I could get away with using just one instead of two. I tweaked my bass and the amp gain and volume knob to give me as much volume as I could possibly get out of it. I thought wasn't quite loud enough. Then, I stick a Line 6 X3 in front of it - and I get more volume. It sounded noticeably louder with the X3 ..... or let's call that a preamp .... in front of it.

This does not tally with some of the OP's comments.

PS: Turns out, when I got to the gig, the guitarist and drummer told me to turn waaaay down. It's amazing how carried away you get at home.

#85 Musky

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Posted 12 March 2014 - 12:11 AM

View PostThe Dark Lord, on 11 March 2014 - 10:07 PM, said:

Not sure about this bit. I paired by MiBass up to a single Mi12 8 Ohm cab the other day, to see if I could get away with using just one instead of two. I tweaked my bass and the amp gain and volume knob to give me as much volume as I could possibly get out of it. I thought wasn't quite loud enough. Then, I stick a Line 6 X3 in front of it - and I get more volume. It sounded noticeably louder with the X3 ..... or let's call that a preamp .... in front of it.

This does not tally with some of the OP's comments.

PS: Turns out, when I got to the gig, the guitarist and drummer told me to turn waaaay down. It's amazing how carried away you get at home.
Ashdown's previous class D range, the Little Giants, were reputed to have quite a low output from the preamp, which could be raised by adding in a booster in the effects loop. So if the Mi's power amp isn't receiving a high enough input to make maximum power...

Just a thought. :)

#86 tonewheels

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Posted 11 May 2015 - 05:21 PM

This business of power amp clipping destroying your speakers comes from the hi-fi world where usually amp outputs and speaker handling are pretty well matched. The warnings about clipping come from a concern about the clipped audio having substantially increased HF content and thus sending more power via the crossover to the tweeter which then melts. Perfectly reasonable argument IMHO.

The gain issue which really gets my goat is in the guitar world where poodle rockers are sold "high gain" amps. Actually the (dreadful) sound of these monstrosities usually comes from a low gain stage before the master volume. This has a high value cathode resistor to drive the valve into a very non-linear low gain regime which generates lots of harmonics. I guess you need some high gain to recover from the damage wrought by such an abomination but the sound of these amps is decidedly "low gain". I guess it would be difficult to sell to the neanderthals who use them using such an unmanly term though.

#87 Safetyman

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Posted 12 August 2015 - 10:49 AM

I hope I can be of help here, though I am a newby to bass guitars , cabs etc.


In the pa area that I deal in,'Gain' means the input level volume of the channel on the mixer and 'Volume' means the level of output from the mixer to the amp/power amp etc. Some mixers have fixed input gain to each channel, which are not adjustable, which can lead to a lack of sufficient signal strength to the mixer if the source has a low output ( such as guitars/basses etc ).

In the pa world, anyway, you can use any amplifier into any speaker. So, 1,000 watt amp into 100 watt speaker will go. However, 100 watt amp into 1,000 watt speaker might ( if you do not know the rule of thumb ) lead to both'blowing'. The rule of thumb, assuming that both amp and cab are of good quality, is to increase the output of the amp into the speaker(s) until the sound starts to distort or under stress. Then back-off the amp by a couple of clicks/notches or ,say, 1 hour on the clock. That should bring the sound back to'sweet' and allow both to play for the whole gig without blowing either. If it still sounds distorted or stressed, then back-off a bit more until it sounds sweet again. The reason for this is that the soundwaves go into'clipping', or 'distortion'. A clipped or distorted signal to the cab means that ,say, the woofer ( driver) in a bass cab gets a signal to move the cone forward & another signal to move it back before the cone has had a chance to reach it's maximum excursion. The result is that the cone heats-up( very rapidly) and melts or distorts so much that it starts to litterally break-up, and eventually fails. In this scenario, the amp will fail too, as the cone draws more and more power out of the amp which eventually melts or one of the components fails, resulting in failure of the amp.

Ok, so you can shoot me down now ! Not trying to teach anyone to 'suck eggs', though.

Cheers

#88 chris_b

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Posted 12 August 2015 - 11:00 AM

How can 100 watt amp into a 1000 watt cab cause either to blow?
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#89 Safetyman

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Posted 12 August 2015 - 07:53 PM

Chris b,

Distortion of the signal ( clipping )means ,effectively, that the speaker cone gets not one, but two commands from the amp at nearly the same time. This causes heat to build-up as the cone ends up not moving in either direction, due to the two opposing signals it receives all the time it's in clipping mode. As the cone is a piston, moving vast amounts of air which keep it cool, it loses the ability to move air. This makes it overheat, leading to it's destruction. If you like, effectively like a short-circuit in electrical wiring.

Cheers

#90 Chienmortbb

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Posted 19 September 2015 - 12:40 PM

I doubt whether a 100W amp will blow a 1000W Speaker.

On the Gain issue. It s simple. Gain is the control of the amount of gain a circuit has and has nothing to do with Overdive (WTF is that). Volume is more woolly but in general is an attenuator at the end of a stage or pre-amp. A gain control is part of the circuit and a volume control is after a circuit.

The trouble is that these are semantics for the people and for marketing department, just the job for fooling the punters.





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