The Cleanest Boost Circuit ??

[HOTTUBES]

I'm looking for a super clean boost circuit ....

I have tried the AMZ boost & the SHO boost , both sound very good but still add a good amount of gain when pushed ...

Is there one that stays clean right to the top ?

[Lurco]

Opamps offer heaps of clean gain!

[HOTTUBES]

Opamps offer heaps of clean gain!

Any suggestions for a circuit or op amp ?


thanks

[FiveseveN]

still add a good amount of gain when pushed

I think you mean saturation. But are you sure it's the boosters themselves distorting and not the next stage?
An opamp gain stage could indeed give you more headroom for a given supply voltage (especially rail-to-rail opamps).

Have you read this? http://www.muzique.com/lab/boost.htm

[HOTTUBES]

What do you mean by" next stage" ?

I will give a read of your link ....thanks

[CynicalMan]

Op amp boost with a MAX1044 voltage doubler or tripler.

[Mark Hammer]

Um, they are all "clean", if used properly.  The dirt comes about by either:

a) applying more gain that the supply voltage can manage,given the input signal amplitude, or
b) using them to feed subsequent stages, like the amp's input, with a bigger signal amplitude than the amp can handle.

Any single one of them - whether bipolar circuit, MosFET or FET, or opamp -  is clean as a whistle if you keep the gain modest (e.g., less than 10x), and set the gain on the amp near minimum with amp master volume up full.

The only exceptins would be those circuits deliberately intended to provide overdrive tone themselves that you may have grouped together with simple non-colouring gain circuits.

[Gurner]

I'm looking for a super clean boost circuit ....

I have tried the AMZ boost & the SHO boost , both sound very good but still add a good amount of gain when pushed ...

Is there one that stays clean right to the top ?

If you want a clean signal at high volume, then you really want only a little gain from your preamplifier - but then whack the master volume up on your main amp.

If using a fresh 9V battery & a rail to rail opamps, you should be able to get about 7x or 8x voltage gain without any clipping whatsoever in the preamplifier (assuming a std passive mag pickup as the input).....but then you'd be outputing a signal of about 8V peak to peak onwards to your amp...which will likely clip there! So consider carefully how much gain you need from a preamplifier.

[HOTTUBES]

I'm trying to get the S.O.S OD circuit & the SHO circuit to play well together , and it's not working as well as I imagined etc.

Its got alot better with some changes to the SOS but , when you turn on the Boost ( SHO ) it all gets  a bit to " Hairy"

Now , i could be wrong , but i have been blaming the SHO circuit for this problem .....I'm looking for a larger volume increase

rather than more gain or Drive etc





I'm kinda new at this stuff , i'm still learning .....


Thanks for your help !

[oliphaunt]

Sounds like you just need to put the boost after the OD rather than in front of it?

[R.G.]

Let's think a minute about fundamentals.

Imagine an amplifier. It has an input point, an output point (at least one), some power supply voltages, and some gain. The exact numbers are not important for the moment.

The output stage cannot in general create a signal bigger than the power supply. There are exceptions, but they are very unusual; rare enough to think this way until proved different. If you feed the input a signal big enough to make the output try to go outside the power supply, **it will distort**. It can't not distort because it physically can't go any bigger. For most amplifiers, they can't even get to the power supply voltages on the output, but can only come within a few volts of the most positive or most negative

=>So there is a limitation on output swing, and it's tied closely to the size of the power supply voltages.<=

There is some gain. It may be 1, or much more than one. Gain is defined as the amount bigger the output is than the input, so we can also think of it as the amount smaller the input is than the output. If the output can only go to X volts, and the gain is G, then the biggest input that it can stand without clipping and distortion on the output is X divided by G. If the amp can swing 10 volts on the output and it has a gain of ten, then the biggest input that does not cause distortion is 1V.

=>So there is a biggest input that can be accepted without causing distortion on the output.<=

In fact, the input itself has some limitations on it. Many amplifier inputs can accept DC as a signal. If you try to force it outside the range the input can handle linearly, the INPUT will distort.

=>So there are limits on the DC offset at the input that can be accepted without causing distortion on the output.<=

You probably think I've been talking about a pedal effect amplifier. But this applies to your guitar amp too. Let's think about your guitar amp for a minute.

There is a biggest input you can feed it without it distorting too. When you hit the limits of the output voltages it won't put out more power or volume than it's already doing. It *can't*. So to get more power/loudness on a real basis out of an amplifier, you have to rebuild the power supply and output stages to make it able to put out more power. Overdriving the input may make it sound louder, but that's largely a psychoacoustic effect.

=>So if you want your amp to be louder, you have to get or build a bigger amplifier and/or speakers.<=

Notice that we're not down to effects output yet. This is a limit on the guitar amplifier itself. For a tube guitar amp with a DC coupled input, the biggest input the front end tube can withstand is about 1V peak, as that's about the linear range of a 12AX7 tube. Signals bigger than that will be clipped in the input tube grid circuit, even if the volume control is turned down. This is the fundamental basis of "master volume" controls on amps, clipping in preamp tube stages.

Now let's look at pedal outputs. A pedal powered by 9V can swing about 5-6 of those 9 volts if it's an opamp output, and maybe 8 of them if it's designed to swing wider. This is enough to exceed the input ability of a common tube amp. That is, for most situations, you can't drive the input of a tube amp to make more loudness without also causing massive distortion at the input or output of the amp itself.

If the amp can't put out that much clean power, there is no pedal that can drive it to greater clean loudness.

As a sidelight, "gain" is not the same as distortion, although guitarists say it like it is.

[HOTTUBES]

I have changed the order and its got better , but i'm still looking for more Volume .........if possible

[HOTTUBES]

Let's think a minute about fundamentals.

Imagine an amplifier. It has an input point, an output point (at least one), some power supply voltages, and some gain. The exact numbers are not important for the moment.

The output stage cannot in general create a signal bigger than the power supply. There are exceptions, but they are very unusual; rare enough to think this way until proved different. If you feed the input a signal big enough to make the output try to go outside the power supply, **it will distort**. It can't not distort because it physically can't go any bigger. For most amplifiers, they can't even get to the power supply voltages on the output, but can only come within a few volts of the most positive or most negative

=>So there is a limitation on output swing, and it's tied closely to the size of the power supply voltages.<=

There is some gain. It may be 1, or much more than one. Gain is defined as the amount bigger the output is than the input, so we can also think of it as the amount smaller the input is than the output. If the output can only go to X volts, and the gain is G, then the biggest input that it can stand without clipping and distortion on the output is X divided by G. If the amp can swing 10 volts on the output and it has a gain of ten, then the biggest input that does not cause distortion is 1V.

=>So there is a biggest input that can be accepted without causing distortion on the output.<=

In fact, the input itself has some limitations on it. Many amplifier inputs can accept DC as a signal. If you try to force it outside the range the input can handle linearly, the INPUT will distort.

=>So there are limits on the DC offset at the input that can be accepted without causing distortion on the output.<=

You probably think I've been talking about a pedal effect amplifier. But this applies to your guitar amp too. Let's think about your guitar amp for a minute.

There is a biggest input you can feed it without it distorting too. When you hit the limits of the output voltages it won't put out more power or volume than it's already doing. It *can't*. So to get more power/loudness on a real basis out of an amplifier, you have to rebuild the power supply and output stages to make it able to put out more power. Overdriving the input may make it sound louder, but that's largely a psychoacoustic effect.

=>So if you want your amp to be louder, you have to get or build a bigger amplifier and/or speakers.<=

Notice that we're not down to effects output yet. This is a limit on the guitar amplifier itself. For a tube guitar amp with a DC coupled input, the biggest input the front end tube can withstand is about 1V peak, as that's about the linear range of a 12AX7 tube. Signals bigger than that will be clipped in the input tube grid circuit, even if the volume control is turned down. This is the fundamental basis of "master volume" controls on amps, clipping in preamp tube stages.

Now let's look at pedal outputs. A pedal powered by 9V can swing about 5-6 of those 9 volts if it's an opamp output, and maybe 8 of them if it's designed to swing wider. This is enough to exceed the input ability of a common tube amp. That is, for most situations, you can't drive the input of a tube amp to make more loudness without also causing massive distortion at the input or output of the amp itself.

If the amp can't put out that much clean power, there is no pedal that can drive it to greater clean loudness.

As a sidelight, "gain" is not the same as distortion, although guitarists say it like it is.

Thanks R.G. , this is good info to know for a noob like me   !!!

[HOTTUBES]

Has anyone got a link to a op amp boost layout ??

[Xavier]

I use an AMZ mosfet booster and it doesn't distort AT ALL. It is really a clean pure booster.

Are you sure that the distortion is coming from the booster ? I could be the actual amp distorting when being pushed and making you think it's the booster.........

I suggest you lower the gain in your amp to have more headroom and try again...........