Does Anyone Use The -15 db Button?

[bolophonic]

No.

 

[j0616bass]

Never had the need.

 

[Hopkins]

I have a couple active basses with 18v preamps that put out a *really* hot signal. It usually enough to just either roll off some input gain at the amp or dial back the master volume on the bass itself.

They still sound a little hairy on my trusty old Mesa Walkabout, so I just use the pad on them.

Not doubting that your basses produce a hot signal, but it has nothing to do with them being 18v. Increasing voltage does not increase output, it only increases head room

 

[EdwardofHuncote]

Not doubting that your basses produce a hot signal, but it has nothing to do with them being 18v. Increasing voltage does not increase output, it only increases head room

Thanks for clarification. The only reason I included that 18v comment was because those two basses (Turner Electrolines) are the only ones I ever pad down. There's a way to trim the output internally, but I don't mess around in there too much.

 

[agedhorse]

Not doubting that your basses produce a hot signal, but it has nothing to do with them being 18v. Increasing voltage does not increase output, it only increases head room

Increasing the supply voltage can certainly result in an increased output voltage if the design utilizes it as such.

 

[Hopkins]

Thanks for clarification. The only reason I included that 18v comment was because those two basses (Turner Electrolines) are the only ones I ever pad down. There's a way to trim the output internally, but I don't mess around in there too much.

If there is a trim pot on the preamp, I would set it to match your other basses and play through the normal input instead of the pad.

 

[Hopkins]

Increasing the supply voltage can certainly result in an increased output voltage if the design utilizes it as such.

I have yet to come across an on board preamp that was designed in such a way.

 

[agedhorse]

I have yet to come across an on board preamp that was designed in such a way.

Most are, and many of these also have an output level control or a loop gain control for better matching of the electronics to the pickups and the load.

 

[Hopkins]

Most are, and many of these also have an output level control or a loop gain control for better matching of the electronics to the pickups and the load.

You know more about it than I do, so I would be a fool to argue with you. But I have used Aggie, Bart, Duncan, EMG and Kent Armstrong Preamps so far and have never come across the situation when output was increased with voltage.

 

[agedhorse]

You know more about it than I do, so I would be a fool to argue with you. But I have used Aggie, Bart, Duncan, EMG and Kent Armstrong Preamps so far and have never come across the situation when output was increased with voltage.

If you JUST increase the supply voltage then it won't increase the output voltage, but that's just one parameter in isolation. Other parameters come into play within a design, and these parameters take advantage of the increased supply voltage to result in an increase output voltage. I think you are confusing or missing the gain term of the overall output level equation.

Let's look at it another way. Say you have a pickup with an output voltage of 0.2 volt (RMS for all measurement) for a "standard pluck 'o the string", and a closed loop voltage gain of 20dB. This will result in an output level of 2 volt RMS or 5.6 volts peak-peak. Now, say the closed loop gain is 26 dB, the resulting voltage would try to be 11.2 volts peak-peak, which is beyond the capabilities of a single 9 volt supply. By using an 18 volt supply, the output voltage would be in fact 11.2 volts, higher than in the 9 volt scenario.

This is one factor when considering the design of active electronics, balancing the gain and operating (playing) dynamics within the available dynamics window of the electronics. In general, you will see some increased gain capability when using a dedicated higher voltage design, which is also why you see output level trims on the electronics and even one reason input pads are included on many bass amps.

One minor disadvantage of higher voltage amps is a possibly slight increase in noise floor, though with higher signal levels this would probably be negated. More is not always better.

 

[Hopkins]

If you JUST increase the supply voltage then it won't increase the output voltage, but that's just one parameter in isolation. Other parameters come into play within a design, and these parameters take advantage of the increased supply voltage to result in an increase output voltage. I think you are confusing or missing the gain term of the overall output level equation.

Let's look at it another way. Say you have a pickup with an output voltage of 0.2 volt (RMS for all measurement) for a "standard pluck 'o the string", and a closed loop voltage gain of 20dB. This will result in an output level of 2 volt RMS or 5.6 volts peak-peak. Now, say the closed loop gain is 26 dB, the resulting voltage would try to be 11.2 volts peak-peak, which is beyond the capabilities of a single 9 volt supply. By using an 18 volt supply, the output voltage would be in fact 11.2 volts, higher than in the 9 volt scenario.

This is one factor when considering the design of active electronics, balancing the gain and operating (playing) dynamics within the available dynamics window of the electronics. In general, you will see some increased gain capability when using a dedicated higher voltage design, which is also why you see output level trims on the electronics and even one reason input pads are included on many bass amps.

One minor disadvantage of higher voltage amps is a possibly slight increase in noise floor, though with higher signal levels this would probably be negated. More is not always better.

I thought that what you were describing was basically headroom. When the voltage tried to be 11.2v it would drive the 9v preamp into clipping where the 18v would stay clean. Am I wrong in my terminology, or am I just oversimplifying?

 

[twinjet]

My understanding is it's supposed to be used for Active Basses; at least that's how it's advertised. Any thoughts about that in TB Land?

I depress the button so the amp doesn't scream if the knobs twist in transit. It also makes volume adjustment inside my apartment easier and I don't have to worry about suddenly rocking my floor. I don't use it for anything else.

 

[agedhorse]

I thought that what you were describing was basically headroom. When the voltage tried to be 11.2v it would drive the 9v preamp into clipping where the 18v would stay clean. Am I wrong in my terminology, or am I just oversimplifying?

Maybe a little of both, because in the big picture none of this exists without considering all of the other factors. Just increasing the supply voltage without any other changes, and assuming that the signal wasn't clipping with 9 volts would result in increased headroom. As soon at that headroom is actually used (with increased gain or harder playing) then it's no longer headroom but serves to increase the output voltage.

This is not a simple concept, even though it might appear to be on the surface. In fact, balancing these variables within a design takes a lot of time and understanding of all input and output parameters. For example, the output level will change with the position of the pickups, so the electronics must be designed with the range of levels in mind rather than a single level.

 

[Hopkins]

Maybe a little of both, because in the big picture none of this exists without considering all of the other factors. Just increasing the supply voltage without any other changes, and assuming that the signal wasn't clipping with 9 volts would result in increased headroom. As soon at that headroom is actually used (with increased gain or harder playing) then it's no longer headroom but serves to increase the output voltage.

This is not a simple concept, even though it might appear to be on the surface. In fact, balancing these variables within a design takes a lot of time and understanding of all input and output parameters. For example, the output level will change with the position of the pickups, so the electronics must be designed with the range of levels in mind rather than a single level.

Thank you for the information.

 

[agedhorse]

Thank you for the information.

I think your questions highlight how difficult and also how important the details are when you strive for higher and higher performance products. What used to be acceptable suddenly is no longer a good solution because of the evolution of other components within the signal path. For example line level effects loops, they weren't necessary until bass players discovered the DBX-160 compressor. Suddenly, there was a need to interface instrument levels (and impedances) with line levels (and impedances). This was the beginning of the line level (specifically the +4dBu) effects loop, because the 160 operated at a much higher level than instrument level. Before then, loops were not really necessary (other than perhaps to slave out to another power amp).

 

[Burwabit]

This is a festival feature. If you have 2 guys using same rig and one has a much hotter bass (like my old G&L L-2500), it's useful. Otherwise never would consider it.

 

[Ffreddy]

Yep. I have a GK400rb and use it when I run cranked pedals into it, or when I want to run the preamp really loud for break up purposes. Haven't noticed any tone difference at all when engaged.

 

[blastoff99]

For home use, I use an Ampeg BA-210v2 with a Fender Elite Jazz and a Kubicki. Both basses are 18v with active/passive switch. I engage the -15db switch when using active and disengaged in passive mode. If I don't use the -15db while in active the volume is way too sensitive and I can only go up to 2-3 on the volume before it gets too loud. So I have more volume adjustment/range if I use the -15db.

Pretty much this with my Godin A4 and BA-108. It's only 9V but holy cats, that bass is loud. Even so, I'm running about 30% on the volume slider on the bass, and in the 4 -5 range on the amp (home use, no insulation in walls). When out and about, there might be more options. I played through a FOH desk once that had both a PAD and a mic/line level switch (in addition to the gain knob). We went with line level and still gained it down.

 

[bikeplate]

Hell no

 

[madmanmerc]

Never have used it, never will. Tends to be more of a tone suck than anything else IMO/IME.

+1