Randall RG75 G3 sound sample - any opinions?

[Mick Bailey]

Rather than continue under Schematic Requests, I thought I'd post this separately.

I did a repair on this amp in September last year. The owner was really happy with the work, which amounted to nothing other than replacing a noisy 12AT7. The amp hummed loudly originally, and a tube swap fixed it. The amp has changed hands since and the new owner contacted me regarding a perceived fault - "When I turn the treble up and the overdrive channel level control is anywhere above 3 it sounds weird. Like a filter or wah is on and it distorts strangely "

The clean channel is fine. He sent me a sound clip, with the note "Can you hear it? Its like a quack." (the artifact at the end is string noise).

I'm listening to the clip but can't arrive at any conclusion. The amp does have a filter as part of the power amp, consisting of 4 simulated inductors. I wonder what other people think?

randall.mp3

[nosaj]

Rather than continue under Schematic Requests, I thought I'd post this separately.

I did a repair on this amp in September last year. The owner was really happy with the work, which amounted to nothing other than replacing a noisy 12AT7. The amp hummed loudly originally, and a tube swap fixed it. The amp has changed hands since and the new owner contacted me regarding a perceived fault - "When I turn the treble up and the overdrive channel level control is anywhere above 3 it sounds weird. Like a filter or wah is on and it distorts strangely "

The clean channel is fine. He sent me a sound clip, with the note "Can you hear it? Its like a quack." (the artifact at the end is string noise).

I'm listening to the clip but can't arrive at any conclusion. The amp does have a filter as part of the power amp, consisting of 4 simulated inductors. I wonder what other people think?

[ATTACH]43778[/ATTACH]

What if you took Duncans tonestack and set it with the parameters for the randall Would it give you a visual on what it could be?(granted I'm not familar with it.)

Thanks,
nosaj

[Mick Bailey]

Duncan's tone stack has fixed tonestack circuits with variable parameters and can't be configured for anything else. The amp is complex, having additional tone shaping in the power amp - like a pre-set 4 band EQ. Spice or Proteus would model it, but the whole amp needs to be considered.

I 'm just canvassing opinion on the sound clip right now - really to determine whether the owner is hearing a characteristic of the amp. Trying to help the guy out - it's not under any obligation or warranty, but he bought the amp in England and he lives in Ireland so I can't get to hear it first-hand.

[MarkusBass]

I think that instead of recording this riff, he should rather play one single note. Otherwise, one could think that he plays additional notes, or the amp sounds exactly like this and there is no problem with it.
Based on the customer's description the amp may oscillate.

PS: I can help with simulation of the output filter but if the amp oscillates, it won't help much.

Mark

[Mick Bailey]

Here's a scale clip.

Any views? To me, this doesn't sound broken and needs the EQ tweaking - maybe the Matt Schofield trick would get a better sound.

randall2.mp3

[MarkusBass]

What is "Matt Schofield trick"?
I was hoping for something else - for long, single notes that decay (because he said that the endings of notes sound strange). For me there is nothing wrong with the amp. The sound is heavily distorted but this may be due to gain settings and strong signal from guitar. Can you suggest him to turn the gain down in the preamp?

Mark

[Mick Bailey]

Matt Schofield uses a lot of hired gear and his method to get the best sound (though he says someone else taught him this) is to rotate each control and notice where the sound changes most dramatically through the rotation. This is the 'sweet spot' and he sets each control to that position. Someone referred it as the "bite point". I've done this many times since reading the interview in Guitarist magazine and it's worked really well.

He said it distorted strangely, but no specific mention of note decay. The gain level is turning the note to fizz. The power amp EQ is probably more prominent under high-gain conditions. Less gain and a more balanced preamp EQ setting would give a better sound. It also may be that he has a guitar with high-output pickups (though I haven't checked).

[MarkusBass]

What about comparing it with some demo recording, eg. like this one: https://www.youtube.com/watch?v=QCr1gsaQIRA ?

[Mick Bailey]

I listened to a few comparative clips. The amps all sound overly-compressed anyhow, similar to a metal pedal with the gain turned up through transistor amp. I still can't hear anything in the guy's clips that suggests a fault. There is a characteristic squeaky sound immediately after the pick attack that comes through, but that's about it. I've also heard this with some of Tony Iommi's early recordings.