Randall RG100G3 power amp help

[Roly]

that is more like blocking distortion,, nothing to do with microphonics.

Totally agree, that's not "microphonics" in any sense I understand the term.  In fact it sounds almost like a beat note because it changes it's period depending on what note is being played.

[belleraphon88]

that is more like blocking distortion,, nothing to do with microphonics.

Totally agree, that's not "microphonics" in any sense I understand the term.  In fact it sounds almost like a beat note because it changes it's period depending on what note is being played.

When i play chords, especially when palm muting, it like farts out.

[J M Fahey]

You have no *tube*, nor even *amp* problem.
You are using way too much gain and your *guitar* is feeding back in an uncontrolled way.

1) you pluck your guitar 13 times.
Count them because it's more precise than referring so such and such second, the video is short, but enough.

2) video can be divided in:
silence/7 plucks/silence/4 plucks/silence/2 plucks/silence

"silence" is a joke, your guitar is howling all the time, in an uncontrolled way, normally at a relatively low frequency, more precisely what the open strings are tuned to.

When you push a string against the fretboard, it will howl at a different, higher frequency.

That higher frequency produced  an unplucked but howling/oscillating string will beat with the frequency of the actual plucked one, and since the amp is *heavily* distorting, it will produce 2 beat frequencies, one the sum (it will sound as a dissonant octave) and one at the difference, which will be a low frequency which to boot will modulate volume, like a crazy tremolo.

That's what you hear as "chirps" or "bursts" because thanks to the unstability the howling string starts and stops at random.

You can hear it *clearly* on plucks nº:

end of 2 , beginning of 3, low frequency modulation, sounds similar to a tremolo/vibrato/phaser/chorus

8/9/10 : higher frequency modulation, sounds like "chirping"

That it's a guitar feedback problem and not an amp one (and even less a *tube* problem, as confirmed by:

Its only the dirty channel that gets effected, the clean channel is fine, but if i use a OD infront of the clean channel it does the same thing.

Solutions?

a) use somewhat less gain

b) play further away from the amp
It will drive you crazy in the bedroom or garage, won't bother you onstage at an open air festival.

c) keep playing a long time and apparently "it willl disappear on its own" , which really means that it won't "disappear" but when you become an experienced guy instintively you'll avoid it, one way or the other.

d) don't waste time or money on substi-tubes (specially in *this* amp), use the prescribed 12AT7.
That's not a "gain stage" which offers some flexibility but a current buffered speaker driver.

[belleraphon88]

You have no *tube*, nor even *amp* problem.
You are using way too much gain and your *guitar* is feeding back in an uncontrolled way.

1) you pluck your guitar 13 times.
Count them because it's more precise than referring so such and such second, the video is short, but enough.

2) video can be divided in:
silence/7 plucks/silence/4 plucks/silence/2 plucks/silence

"silence" is a joke, your guitar is howling all the time, in an uncontrolled way, normally at a relatively low frequency, more precisely what the open strings are tuned to.

When you push a string against the fretboard, it will howl at a different, higher frequency.

That higher frequency produced  an unplucked but howling/oscillating string will beat with the frequency of the actual plucked one, and since the amp is *heavily* distorting, it will produce 2 beat frequencies, one the sum (it will sound as a dissonant octave) and one at the difference, which will be a low frequency which to boot will modulate volume, like a crazy tremolo.

That's what you hear as "chirps" or "bursts" because thanks to the unstability the howling string starts and stops at random.

You can hear it *clearly* on plucks nº:

end of 2 , beginning of 3, low frequency modulation, sounds similar to a tremolo/vibrato/phaser/chorus

8/9/10 : higher frequency modulation, sounds like "chirping"

That it's a guitar feedback problem and not an amp one (and even less a *tube* problem, as confirmed by:

Its only the dirty channel that gets effected, the clean channel is fine, but if i use a OD infront of the clean channel it does the same thing.

Solutions?

a) use somewhat less gain

b) play further away from the amp
It will drive you crazy in the bedroom or garage, won't bother you onstage at an open air festival.

c) keep playing a long time and apparently "it willl disappear on its own" , which really means that it won't "disappear" but when you become an experienced guy instintively you'll avoid it, one way or the other.

d) don't waste time or money on substi-tubes (specially in *this* amp), use the prescribed 12AT7.
That's not a "gain stage" which offers some flexibility but a current buffered speaker driver.

ill make another vid with the gain on 1, it does the same thing.
Ive been playing guitar for a few years. My problem is definitively not feedback and too much gain.

[J M Fahey]

My problem is definitively not feedback and too much gain.

Both go hand in hand.

What would you call the permanent howling between plucked notes?

Please reread my comments while listening to the video, time and again.

Plus, others are noticing the same as I do, maybe using different words but the general meaning is the same.

[belleraphon88]

My problem is definitively not feedback and too much gain.

Both go hand in hand.

What would you call the permanent howling between plucked notes?

Please reread my comments while listening to the video, time and again.

Plus, others are noticing the same as I do, maybe using different words but the general meaning is the same.

Phatt said it could be blocking distortion. what ive read about blocking distortion sounds more like what im experiencing. Ill record a better vid in the morning, i usually use a boss ns-2 and a boss sd-1, i put the amp gain on 5 and boost it with the boss sd-1.
The howling betwenn notes, do you mean that repeated notes?
what that is do not know. This is the first amp i have that does this when the gain channels level gets turned up.

[stormbringer]

What are your settings on the sd-1? Normally to boost, you go with lowest possible gain, and max volume. if you run drive full on the pedal and then distort again through the preamp, squealing is more or less inevitable.

If you bypass the sd-1, does it still sound that way?

[Enzo]

Here is a simple experiment.  Stand away from the amp, and have it set up to play, and presumably the noise will result.   Now turn 90 degrees and face to the side.  ANy change?   Now another 90 degrees, and face away from the amp (well the speakers really).  Any change, and finally another 90 degrees so you are facing the other side.  ANy change?    If the direction you aim the guitar changes the sound in any way, it is feedback.   Feedback in a high gain amp can happen even at low volumes you can talk over.

[belleraphon88]

What are your settings on the sd-1? Normally to boost, you go with lowest possible gain, and max volume. if you run drive full on the pedal and then distort again through the preamp, squealing is more or less inevitable.

If you bypass the sd-1, does it still sound that way?

Hi
My settings on the sd-1 are, drive: 2 and level on 8. sometimes ill max the the level to 10.
If i dont use this method, it sounds the same, just with lots of noise and feedback.

[belleraphon88]

Here is a simple experiment.  Stand away from the amp, and have it set up to play, and presumably the noise will result.   Now turn 90 degrees and face to the side.  ANy change?   Now another 90 degrees, and face away from the amp (well the speakers really).  Any change, and finally another 90 degrees so you are facing the other side.  ANy change?    If the direction you aim the guitar changes the sound in any way, it is feedback.   Feedback in a high gain amp can happen even at low volumes you can talk over.

That only changes the feedback to some degree. But the amp still makes those extra notes. What i found was that chords on the Low strings sound fine, only the high strings are making that ping crackling noise. I tested it with 2 different guitars just to make sure its not my guitar.

[stormbringer]

What i found was that chords on the Low strings sound fine, only the high strings are making that ping crackling noise. I tested it with 2 different guitars just to make sure its not my guitar.

Yeah, that's a good idea, the high E string tends to "oscillate" when it gets worn.

edit:
Never mind, i was listening through lousy speakers at work, i hear the problem properly now at home. you still need to change that string though

[J M Fahey]

This is the first amp i have that does this when the gain channels level gets turned up.

Agree.
That amp has **incredible** gain, way above anything you used before.

To put it in perspective:

a classic Overdrive pedal (Tube Screamer) has gain 100X (500K/4K7) before hitting the diodes.

a classic Distortion pedal (MXR Dist+) has gain 200X (1M/4K7).
Your DS1 is also around 200X gain.

a classic Randall amps (RG100) had 2 20X Fet gain stages cascaded in the Red channel, for a gain of 20x20=400

This was Dimebag's amp, you won't call his sound "puny" or similar.

Your amplifier, in the "Gain 1" channel has (cascaded) the following stages:
IC1A (3X) + IC1B (367X) for a whopping 1100X gain before hitting clipping diodes D5/D6 .
And that's the "mild" channel . :loco

In the "hot" Gain 2 channel, gain stages are again IC1A (3X) + IC2A (41X) + IC2B (142X).  Do the Math.

Ok, to save some time, here it is: 3*41*142=17466 X  xP :duh
With that amount of gain, squealing is guaranteed, with any guitar on this Planet, specially if you are within the same room.

As I said before, such a monstrous amount of gain is somewhat controllable on a big , Rock Festival stage, because you are:
a) typically 10/15/20 yards away from the speakers.
Or more: you'll probably use a wireless transmitter .
b) you are in open air, or if "inside", the roof will probably be 25 yards above and the Stadium walls will be 30 to 80 yards away, same thing.

to which I should add :
c) usually the amps shown onstage are off or just props, and the actual amp miked is **backstage** .

For one real example from a Forum member here, look at this:

http://youtu.be/3QEjiJ56Zac

You'll see our friend onebaldbloke there (I guess you'll recognize him from his nickname), playing in a big stadium, with excellent sustain.
Oh, the wall of Marshalls?  Look nice, huh?

He was *actually* using a little Squire SS amp, plus a Rat or Big Muff pedal:

I've always had a fondness for SS stuff. The biggest selling album I ever recorded (multi Platinum here in Oz) was done with a $50 SS Squire with an 8" speaker, though everyone seems to think I used valve big stacks - ah well.

That live stuff is the same little Squire out the back in a road case with a Sennheiser 421 mic on it.
Fun setup!

All those Marshalls on stage and what we're hearing is a miked up Fender Squier 15 hidden in back of a road case! I love it. Sounds good;

The full thread:
http://www.ssguitar.com/index.php?topic=2560.0

PS: in a nutshell: at those gain levels, *any* guitar will squeal, unless you get far away from the speakers.

EDIT: I forgot to mention (although it should be real evident): they are Australians !!!!

[phatt]

@ belleraphon88,
Re blocking distortion.
Some insight into this can be found here at Roly's wonderful Site. :tu:

http://www.ozvalveamps.org/choking.htm

This may or may not be the exact same thing but I have experienced this effect with both Valves and SS Builds.

FWIW I've just spent over a year trying to get it through to a young lad's passionate but vain attempt to extract a million watts from a 10 watt amp that gain does not go on forever and sky hooks just don't exist. :lmao:

Even the simple opamp Odrive pedals I build can suffer from this sort of spitting problem if you over do it.

In my limited understanding the signal is getting way too big to fast and the next stage may well momentarily cut off on big peaks.

Either way the end result is *Exactly* as J M Fahey has already explained.

It's possible it may just need to be backed off at some point in the signal path but wait and see.
Food for thought;
If you have trouble understanding what these chaps are saying then my advice is to throw out what you think is wrong and let these clever minds help you and guide you through the issue. They are well versed in fault finding.

Do the tests that are asked of you and reply to best of your ability.
Once you go off on tangents then it becomes so much harder to help.

As JMF has noted already,,Your Amp is super high gain and like a lot of them won't take pedals well.

So when you read a mag review of the latest BS mega uber hyper drive bragg rig and the writer says it does not take pedals well,,, It simply means it's got way too much inbuilt gain and if you use pedals then expect problems like you are experiencing.
Phil.

[belleraphon88]

This is the first amp i have that does this when the gain channels level gets turned up.

Agree.
That amp has **incredible** gain, way above anything you used before.

To put it in perspective:

a classic Overdrive pedal (Tube Screamer) has gain 100X (500K/4K7) before hitting the diodes.

a classic Distortion pedal (MXR Dist+) has gain 200X (1M/4K7).
Your DS1 is also around 200X gain.

a classic Randall amps (RG100) had 2 20X Fet gain stages cascaded in the Red channel, for a gain of 20x20=400

This was Dimebag's amp, you won't call his sound "puny" or similar.

Your amplifier, in the "Gain 1" channel has (cascaded) the following stages:
IC1A (3X) + IC1B (367X) for a whopping 1100X gain before hitting clipping diodes D5/D6 .
And that's the "mild" channel . :loco

In the "hot" Gain 2 channel, gain stages are again IC1A (3X) + IC2A (41X) + IC2B (142X).  Do the Math.

Ok, to save some time, here it is: 3*41*142=17466 X  xP :duh
With that amount of gain, squealing is guaranteed, with any guitar on this Planet, specially if you are within the same room.

As I said before, such a monstrous amount of gain is somewhat controllable on a big , Rock Festival stage, because you are:
a) typically 10/15/20 yards away from the speakers.
Or more: you'll probably use a wireless transmitter .
b) you are in open air, or if "inside", the roof will probably be 25 yards above and the Stadium walls will be 30 to 80 yards away, same thing.

to which I should add :
c) usually the amps shown onstage are off or just props, and the actual amp miked is **backstage** .

For one real example from a Forum member here, look at this:

http://youtu.be/3QEjiJ56Zac

You'll see our friend onebaldbloke there (I guess you'll recognize him from his nickname), playing in a big stadium, with excellent sustain.
Oh, the wall of Marshalls?  Look nice, huh?

He was *actually* using a little Squire SS amp, plus a Rat or Big Muff pedal:

I've always had a fondness for SS stuff. The biggest selling album I ever recorded (multi Platinum here in Oz) was done with a $50 SS Squire with an 8" speaker, though everyone seems to think I used valve big stacks - ah well.

That live stuff is the same little Squire out the back in a road case with a Sennheiser 421 mic on it.
Fun setup!

All those Marshalls on stage and what we're hearing is a miked up Fender Squier 15 hidden in back of a road case! I love it. Sounds good;

The full thread:
http://www.ssguitar.com/index.php?topic=2560.0

PS: in a nutshell: at those gain levels, *any* guitar will squeal, unless you get far away from the speakers.

EDIT: I forgot to mention (although it should be real evident): they are Australians !!!!

I did another vid, with less gain, you should hear it better now, especially at 00:14. no pedals, just the amp
http://www.youtube.com/watch?v=Hd14djOlLu4

[stormbringer]

I'm really no expert here. Experienced player, kinda new builder. so better wait for the "big guys" here to come with more qualified analysis. (mr Fahey, Roly, hint hint).

But just a thought.. are you sure that the speaker itself is ok? any chance to test the send out to Another amp? and Another preamp or hell even the DS-1 into the return? or disconnect the speaker, and connect to an external cab (Watch the impedance). As somewhat of an amateur, that's what i would try just to find which of those 3 is causing the issue, and move on from there.

Edit: By the way, wasnt that the amp that was modded by some Tech to get cooler? If that is the case, it would really help knowing exactly what was done. Maybe the mod has something to do with your problem? Did it behave like this Before the mod?