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alexclaber

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

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[quote name='28mistertee' timestamp='1373265588' post='2135327']
...
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?
[/quote]

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

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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.

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[quote name='mikhay77' timestamp='1272918549' post='826852']
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.
[/quote]
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.

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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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[quote name='omikin' timestamp='1389436750' post='2334086']
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?
[/quote]

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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[quote name='alexclaber' timestamp='1185902620' post='39654']

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........

[/quote]

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.

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[quote name='The Dark Lord' timestamp='1394575639' post='2393008']
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.
[/quote]
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. :)

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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.

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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

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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

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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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[quote name='Safetyman' timestamp='1439409203' post='2842669']
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
[/quote]

Just in case anyone reads this, the following bit is 100% incorrect:

"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."

NOT TRUE AT ALL!!!

However, this is kind of correct: "As the cone is a piston, moving vast amounts of air which keep it cool, it loses the ability to move air."

It isn't actually the air that the cone moves which keeps it cools, it's the smaller amount of air which is pumped through the motor (the bit at the back with the magnet structure etc) that helps cool the voice coil. But as soon as the woofer cone stops pistoning back and forth whilst still making loud sound (i.e lots of mids and treble, no low frequencies) then the air pump cooling the voice coil stops and things overheat quickly.

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Alex, Duke le Jeune places his ports to enable chimney effect cooling. Have you tried this, and is there any evidence that is works? If it does of course, the benefit would be that the heat itself causes the movement of air not the low notes.

Edited by Chienmortbb

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After reading the whole thread I am still confused. It seems even the people with relevant qualifications cant agree on what constitute "Gain, Power and Volume".

There again I dont really care. If I like the sound of an amp, and I need it, I buy it.

The way I look at it, leaving all manufacturers nonsense aside, you plug the bass into the amp. There is a volume control next to the input, lets call it the pre amp, for want of a better name. If you leave that at 0 you get nowt out of the amp, regardless of what setting the power amp volume is set at, and vice versa. The way seems to me to get a nice clean sound, regardless of the amps power, is to balance the so called pre and power amps outputs, a little of each. I am using layman's terms throughout this rant so bare with me.

I hear two distinct types of warmth or distortion, call it what you like. Pushing the pre amp means warmth at lower volume, dialing back the pre amp and pushing the power amp stage means a much more fluid and warmer sound at much higher volume. The type that valve amp guitarists love. So you can have two types of nice distortion, quiet and thin, by driving the input stage, and loud and thick by driving the output stage. Weather my names for the amp sections are correct or not its what most none techies call them.

I feel it would make things much easier if cabinet manufacturers would include sensitivity ratings so we had a starting point regarding how much volume any given cabinet and speaker configuration would produce. Power handling is nice to know but If its a really sensitive cab you would know you could get good volume results with a lower wattage amp. Powered cabs have DB ratings on them but surely thats a different thing as they also include the power amp?

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[quote name='mikel' timestamp='1480677815' post='3186291']


I feel it would make things much easier if cabinet manufacturers would include sensitivity ratings so we had a starting point regarding how much volume any given cabinet and speaker configuration would produce. Power handling is nice to know but If its a really sensitive cab you would know you could get good volume results with a lower wattage amp. Powered cabs have DB ratings on them but surely thats a different thing as they also include the power amp?
[/quote]

I think most cab makers give an SPL @ 1watt @ 1m figure. It would be nice if they gave this to us with the source frequency or type of noise (pink/white) ...

For instance my Tecamp 810 has a sensitivity of 105db/1w\1m but it appears to be pretty much identical to my Super12T with 102db/1w/1m. Theoretically the S12 should need twice as much power to sound the same as the 810, but it doesn't

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[quote name='markstuk' timestamp='1480679113' post='3186310']
I think most cab makers give an SPL @ 1watt @ 1m figure. It would be nice if they gave this to us with the source frequency or type of noise (pink/white) ...[/quote]That would constitute truth in advertising, which is an oxymoron of the first degree. Many manufacturers quote sensitivity either in the midrange or at the highest point, which isn't Kosher. Ampeg is one manufacturer that posts accurate sensitivity figures. Since the physics that apply to Ampeg apply to everyone it's a pretty safe assumption that any manufacturer making sensitivity claims substantially different from Ampeg for the same driver configuration are yanking your chain.

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[quote name='markstuk' timestamp='1480679113' post='3186310']
I think most cab makers give an SPL @ 1watt @ 1m figure. It would be nice if they gave this to us with the source frequency or type of noise (pink/white) ...

For instance my Tecamp 810 has a sensitivity of 105db/1w\1m but it appears to be pretty much identical to my Super12T with 102db/1w/1m. Theoretically the S12 should need twice as much power to sound the same as the 810, but it doesn't
[/quote]

But they are pretty meaningless figures to the layman. 105 db at 1 watt at 1 mtr????? So assuming I have a 100 watt amp I will be pushing 105 db in my bedroom using next to nothing of the amps power, less than 1 on the volume control. Crank it up to half way and the windows will blow out??? Possibly even the walls.

Edited by mikel

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[quote name='mikel' timestamp='1480689792' post='3186454']
But they are pretty meaningless figures to the layman. 105 db at 1 watt at 1 mtr????? So assuming I have a 100 watt amp I will be pushing 105 db in my bedroom using next to nothing of the amps power, less than 1 on the volume control. Crank it up to half way and the windows w

ll blow out??? Possibly even the walls.
[/quote]

Not really.,.You 're aware that things are quieter the further away they are.. So 1m is a good standardised distance.. And it's pretty easy to calculate what the SPL would be a 10/50/100w. Basically everytime you double the power you add 3dB .. So your 100W amp will do about 125 dB at 1m. It will do very small amounts of dB at 1 km ..

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[quote name='mikel' timestamp='1480689792' post='3186454']
But they are pretty meaningless figures to the layman.[/quote]True, but if you're here you're not a layman, you're a bassplayer, probably semi-professional, if not a full fledged professional. That makes your gear tools of your trade, tools which you should have a pretty good understanding of. There's no shortage of resources that you can use to improve upon that understanding.

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[quote name='Bill Fitzmaurice' timestamp='1480697337' post='3186562']
True, but if you're here you're not a layman, you're a bassplayer, probably semi-professional, if not a full fledged professional. That makes your gear tools of your trade, tools which you should have a pretty good understanding of. There's no shortage of resources that you can use to improve upon that understanding.
[/quote]

I do have a perfect grasp of what I like to hear and what equipment I like to play, its the willfully misleading and needlessly complicated jargon used by amp manufacturers that baffles me, even the qualified on here cant agree. You seem well versed in amp and cab technology so perhaps you can explain to me the difference between valve watts and solid state watts?

I also like to spend my free time actually playing the bass, rather than trawling through technical papers regarding amplifier technology.

Edited by mikel

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[quote name='mikel' timestamp='1480713976' post='3186733']
You seem well versed in amp and cab technology so perhaps you can explain to me the difference between valve watts and solid state watts?
[/quote]A watt is a watt, 1 joule per second. What makes valve and SS amps different is how they process the signal. At the limits of their output capability valves naturally compress the signal, SS does not. 6dB of compression can subjectively sound the same as a 4x increase in power output. That's why they sound different. You can use processing with SS to emulate what valves do. That's what TC does with their RH 450 and RH 750 amps, which they falsely rated in output based not on how they measured, but how they were perceived. They were rather famously outed for having their thumb on the scale, and while they never quite admitted to the deed, they did put up this:
http://service.tcgroup.tc/media/tc-electronic-power-rating-and-active-power-management.pdf

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[quote name='Bill Fitzmaurice' timestamp='1480716958' post='3186765']
A watt is a watt, 1 joule per second. What makes valve and SS amps different is how they process the signal. At the limits of their output capability valves naturally compress the signal, SS does not. 6dB of compression can subjectively sound the same as a 4x increase in power output. That's why they sound different. You can use processing with SS to emulate what valves do. That's what TC does with their RH 450 and RH 750 amps, which they falsely rated in output based not on how they measured, but how they were perceived. They were rather famously outed for having their thumb on the scale, and while they never quite admitted to the deed, they did put up this:
[url="http://service.tcgroup.tc/media/tc-electronic-power-rating-and-active-power-management.pdf"]http://service.tcgro...-management.pdf[/url]
[/quote]

Cheers mate, but it still seems from your post that a 100 watt valve amp and a 100 watt SS amp, played through the same cab, would produce vastly different DB levels.

Most consumers buy an amp at least partly based on how many watt's it produces. If the DBs it is capable of producing is governed by how it processes said watt's it would appear to be fairly pointless stating wattage

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[quote name='mikel' timestamp='1480777010' post='3187066']
Cheers mate, but it still seems from your post that a 100 watt valve amp and a 100 watt SS amp, played through the same cab, would produce vastly different DB levels.
[/quote]With DSP processing the SS will deliver the same dB levels, at far less cost, size and weight than valves.

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