Which is cleaner: mosfet booster or opamp?

[Sage]

I'm looking to build a clean booster to go into my guitar amp's effects loop just to bump the volume of my leads, and I'm debating whether to build Jack Orman's Mosfet Booster or a simple opamp booster instead.  I'm hearing that an opamp booster will provide a cleaner, flatter response, but I'm also hearing that an opamp may not cover the frequency response that the mosfet booster will.  Anyone have an informed opinion on which one will provide a cleaner, truer boost?

[PRR]

> an opamp may not cover the frequency response that the mosfet booster will.

Baloney.

You can find an opamp to boost 3X (much louder) with frequency response to 1 GHz. Which is 300,000 times or 18 Octaves above any guitar tone.

The 13-cent TL072 will do 3X boost out past 1Mhz, 100X what you need from guitar.

Even antiquated '741 and '308 opamps will do 3X beyond the audio range.

That's utter non-issue.

[PRR]

Anyway, don't always think "boost".

Is your amplifier maxed-out? If not, set it for your Lead gain, then use a cut-back box to set a lesser gain for non-Lead times. This can be a passive pot with a bypass switch. No battery to go dead just when you need it.

[Clips]

Not to hijack the thread  (), but while we're on the subject, is there a benefit to using mosfets instead of other options when amplifying a signal? I ask because after stripping a couple of junk boards i have a nice selection of mosfets.

[Buzz]

Not to hijack the thread  (), but while we're on the subject, is there a benefit to using mosfets instead of other options when amplifying a signal? I ask because after stripping a couple of junk boards i have a nice selection of mosfets.

I can see two benefits in your case. 1. You already have them in your possession. 2. They were free.

To the OP, Depends what you like the sound of best , which you can only judge with your ears when working with your gear. My 2c.

[bool]

...b.s.

a MOSFET booster will sound like this:



and an OPAMP booster will sound like this:


so take your pick..

[allesz]

Both

[digi2t]

...b.s.

a MOSFET booster will sound like this:



and an OPAMP booster will sound like this:


so take your pick..

Funniest thing I've seen in a long while. Thank you. 

[seadi123]

What about JFet boosters ?

[samhay]

^What about JFet boosters ?
They look rubbish in leather.

[GibsonGM]

I love Jack's Mosfet Booster. 

I use it to bump up for leads.  I don't do the opposite (cut for rhythm, take the brake off for leads) because I like to hit my pre tubes with the booster, which makes my leads more distorted.  6 of one, 1/2 dozen of another - I like it this way, tho...   Tons of gain there, IF your amp has the headroom.

As for what sounds like "more authentic tube-like tone": honestly, I can also use an LPB that has had its freq. response adjusted to do the same thing.

[Mark Hammer]

1) The typical guitar amp speaker starts to roll off above 5-6khz, so bandwidth is a nonissue when deciding between boosters.  As long as the input impedance is sufficient to retain whatever the pickups can deliver, you're fine.  Chips and trannies will both do that for you.

2) The input stage of most amps is designed to anticipate a certain range of input signal amplitude.  Push beyond that and things start to break up.  Unless one is playing with lipstick pickups whose magnets have been partially degaussed, applying more than 4-6x gain (roughly 12-15db) will virtually eliminate any "cleanliness" from your sound, because no matter how clean the booster is, the amp won't be, at that point.

3) If one is aiming for a degree of boost that allows the amp to remain clean, and one wants the signal it receives to arrive clean, then supply voltage of the booster matters as much, if not more, than the specific technology used to produce the boost.  Guitar signals have a wide swing, with big initial peaks, and a rapid simmering down.  The post-peak period is no big deal, but the peaks can be where the sound breaks up.  An op-amp running off a 9v supply is more than likely going to have not much more than a +/-3.5v swing capability, before it runs out of headroom.  If one is applying a gain of 5x to the signal, then we're looking at whether it can do that to a guitar signal with initial peaks of +/-700mv, which is not that unrealistic in today's pickup world.  If one uses a higher supply voltage, whether by means of a charge pump or simply a different adapter, successfully managing peaks becomes a different matter.

[amptramp]

The difference I would care about is that I can design an op-amp booster and build it and know that if I build another one, the characteristics will be the same.  With a FET, the Vgs and gain can be all over the place and if I build a second one, I may have to tweak some resistor values.  You may be able to get lower noise with a FET, but the noise of a TL071 is low enough to not be an issue.

[garcho]

"What about JFet boosters"

TL07x is FET technology anyway. MOSFET and FET will have very high input impedance, which is why they're popular buffers in guitar pedals. Jack Orman's MOSFET buffer will make your guitar sound 'cleaner' or 'crisper' (impedance) and give it extra output, if you need it. A 'booster' is a different story: do you want dirt, filtering, etc.?

[Sage]

The 13-cent TL072 will do 3X boost out past 1Mhz, 100X what you need from guitar.

Awesome, that's exactly the information I needed.  Is there any limit on the lower frequencies with either solution?

The input stage of most amps is designed to anticipate a certain range of input signal amplitude.  Push beyond that and things start to break up.  Unless one is playing with lipstick pickups whose magnets have been partially degaussed, applying more than 4-6x gain (roughly 12-15db) will virtually eliminate any "cleanliness" from your sound, because no matter how clean the booster is, the amp won't be, at that point.

Understood.  This will happen in the effects loop *after* the preamp, and I'm not looking for a huge boost, just a slight volume bump for leads.

An op-amp running off a 9v supply is more than likely going to have not much more than a +/-3.5v swing capability, before it runs out of headroom.  If one is applying a gain of 5x to the signal, then we're looking at whether it can do that to a guitar signal with initial peaks of +/-700mv, which is not that unrealistic in today's pickup world.  If one uses a higher supply voltage, whether by means of a charge pump or simply a different adapter, successfully managing peaks becomes a different matter.

Yeah, I'm already planning to run this at 18v just for the headroom.  It's a combination input buffer/effects loop booster/parallel loop switch.

Anyway, don't always think "boost".

Is your amplifier maxed-out? If not, set it for your Lead gain, then use a cut-back box to set a lesser gain for non-Lead times. This can be a passive pot with a bypass switch. No battery to go dead just when you need it.

That's a very interesting solution I hadn't thought of.  I could potentially just crank up the master volume and do this.  Thanks for the tip!

[JerS]

...b.s.

a MOSFET booster will sound like this:



and an OPAMP booster will sound like this:


so take your pick..

Nailed it! This is the perfect description.

[JustinFun]

I think half the trouble is that a completely flat boost might not sound the most 'transparent', depending on how you are using it. If you're pushing an overdriven amp in to all-out distortion, a bit of treble roll-off and mid hump might give a clarity that makes it sound 'cleaner' than a flat boost. When using a booster you're not usually just after a volume control.