Bring down noiselevel in amz mosfet boost

[Jay Doyle]

Pete makes a good point, it may be something we are completely overlooking, like a cold solder joint.

Bilbi? You still out there?

[hilbi]

Poor hilbli, asks a question and gets a bunch of dorks swinging our EE (or in my case non-EE) weiners around while completely avoiding an answer to his question:

no problem  . I will be trying the metal fim for R3 and R4 tomorrow.

Have you tried replacing the 2nd MB for the 1rst MB in that position?

yes exactly the same result.

I'm not certain this is a problem inherent with other Mosfet Boosts into Overdrives scenarios [ie maybe there is something 'unique' to this 2nd Mosfet Boost or the OD...]...er, I think we agree it 'shouldn't do that'...and taking it one step further, maybe it doesn't do it except under the exact conditions in your bandmates case.

We tried the mb infront of the boss OD-3 and barber direct drive. I tested it also on my board infront of the blue magic. Same result.

I will do some tests tomorrow when i have the materials and update you on this.

[Jay Doyle]

Hilbi,

I would first try reflowing all of the solder joints, if that doesn't work, go ahead with the resistor changes...

[hilbi]

i prety sure it is not the solder joints, i build two mb and both are causing this. When used stand alone the mb is dead quit and perfectly working.

[puretube]

2 cascaded: = bad impedance mismatch...

[WGTP]

If I had known there was wiener swinging going on, I would have read this thread sooner.   I sure appreciate you swingers helping us non-swingers out with this stuff. 

[petemoore]

  I think it could be a 'before / Mosfet Boost /After' anomoly...
  Ie exactly what's before and after it may have something to do with the noise. Wierd noise [not unheard of, considering these hilbi reports]...in that the MB's been around the block a number of times, plenty of reports...most all are problem free.
 

[amz-fx]

Noise? Hum? or Distortion?  I'm always unsure about the exact nature of this type of problem that people are having with a circuit when they post asking for help...  the problem could be:

1. The very high impedance of the circuit in effect increases the bandwidth of the signal by not loading it down and rolling off the highs...  you may be hearing noise that was there all along but attenuated by the other circuits.

2. The Mosfet Boost puts out a lot of gain so maybe it is overdriving some other part of the signal chain.

3.  The mosfet is misbiased...  measure the dc voltage from the drain to ground and it should be 4 - 5v.  If it is not then we can adjust it.

4. Two of them cascaded are almost certainly overdriving...

5. Some wiring problem we have not detected yet...

6.  The mosfet has been damaged by handling...  put in a new BS170P.

This circuit has been repeatedly tested  and should not be the source of the problem.   

regards, Jack

ps: Turn up the guitar volume to preserve the S/N ratio.

[hilbi]

Noise? Hum? or Distortion?  I'm always unsure about the exact nature of this type of problem that people are having with a circuit when they post asking for help...  the problem could be:

1. The very high impedance of the circuit in effect increases the bandwidth of the signal by not loading it down and rolling off the highs...  you may be hearing noise that was there all along but attenuated by the other circuits.

2. The Mosfet Boost puts out a lot of gain so maybe it is overdriving some other part of the signal chain.

3.  The mosfet is misbiased...  measure the dc voltage from the drain to ground and it should be 4 - 5v.  If it is not then we can adjust it.

4. Two of them cascaded are almost certainly overdriving...

5. Some wiring problem we have not detected yet...

6.  The mosfet has been damaged by handling...  put in a new BS170P.

This circuit has been repeatedly tested  and should not be the source of the problem.   

regards, Jack

ps: Turn up the guitar volume to preserve the S/N ratio.

The noise is certanly no distortion. It is the noise you hear when you turn up an overdrive pedal to its max settings and don't play, guitar volume completely open.

1: could be the issue.

2: The mb is turned open just to amplify a strat to les paul volume. There is no distortion in sound, so i don't think it is overdriving something.

3: The mosfet is biased at 5,5 volt.

4: the mb is used in front of a barber direct drive (it is doing the same on boss od-3). the noise is there when you don't play anything, guitar volume completely open.

5: i built two mb's both work fine stand alone or after an od. both are acting the same way infront of an od. so i don't think it is a wiring issue.

6: several bs170 tested, all same issue.

This circuit has been repeatedly tested  and should not be the source of the problem. The mb used stand alone is very quit, only when used infront of an od i'm having issues. Has anyone already tried an mb infront of an od, i would like to know what your experience is with that.

I use the vero layout from torchy, the version where the mb is also used as buffer.

[davebungo]

Shot in the dark but easy enough to try out:

connect a 100K resistor on the output of the Mosfet Boost to gnd (after the output cap).  See if that makes any difference.  I'm just thinking that perhaps the OD's expect some DC resistance across the input i.e. normally it would be from the guitar itself or the output Z of another effect.

[Jay Doyle]

Do you have the OD on? If so, you are going to get more noise.

In re-reading the whole post, you may want to check the strat's wiring, there may be a ground loop, and using an mb only boosts the noise that was already there.

A strat is going to be noisier than a les paul because of single coils...

[bwanasonic]

When I first built my AMZ Mosfet Boost, I was getting some hiss when I used a DC adapter. A 100 ohm resistor in series with the +9v input fixed that problem.

Code Select Expand


>>+9v-----------^^^^----------O------------| |---------GND
                100           |            100uf
                              |
                              |


Kerry M

[hilbi]

Do you have the OD on? If so, you are going to get more noise.

In re-reading the whole post, you may want to check the strat's wiring, there may be a ground loop, and using an mb only boosts the noise that was already there.

A strat is going to be noisier than a les paul because of single coils...

yes the od is on. yes i'm expecting more noise, the mb is only much noisier then a boss ge-7 and I would like to get down to that level of noise.

the strat wiring is ok, i tested with another strat, a tele and a jazzmaster, same thing on all guitars, les paul is indeed ( as expected) much cleaner noise wise.

[mountainking]

Before everybody starts redesigning the circuit, first try using a pair of decent shielded cables. You'll be amazed at the difference they can make. Also, always use shielded hookup wire for all the connections to the input of the circuit when building any high gain booster, in addition to various other contruction techniques that will help to eliminate or at least lessen the level of unwanted noise. Of course, as everyone has already pointed out, its gonna amplify whatever signal goes into it, so if theres even a small amount of noise coming from your pickups, its gonna make it much more noticeable. Many of the big brand name pedals like Boss have filtering in the circuit to help get rid of some the noise from pickups, cheap cables etc., but because of this filtering, they tend color your guitar's tone and end up sounding artificial.

[hilbi]

Tonight i changed R3 and R4 to metal film. The 10M resistor is now down to 1M. It helps a little bit, but i'm not down to boss levels off noise.

Any ideas? Did anyone already try an mb infront of an od?

[zachary vex]

you may just have to accept that you've got too much gain going, perhaps significantly more than your EQ was providing before.

[petemoore]

  Did anyone already try an mb infront of an od?
  Oh yes................................................................................................................................................................................................................................................................I'ts been tried once or twice at least.

[hilbi]

what were the results?

[Ben N]

Not to sound too dumb, but has anyone here ever heard of a quiet GE-7?!?  Were your guy's settings on the Boss flat, or was he cutting certain (noisy) frequencies?
Ben

[petemoore]

what were the results
  I Read: 'works great'.