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Muddy sounding amp Electric Guitar Amplification
Old 10th December 2012
  #1
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Muddy sounding amp

I just bought a Vox ac15 tube amp. It is my first tube amp and to be honest I'm not really sure how they are "supposed" to sound (I don't play with a whole lot of other people or anything like that.) When my tubes are really being overdriven I am getting a very muddy sound. I'm using a strat and I only really have this problem when the distortion is past 2 o clock and it gets worse as my pickup switch gets closer to the up position. I'm not using any pedals or anything....

Is this normal for tube amps?....
Old 10th December 2012
  #2
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Quote:
Originally Posted by TheEscapist View Post
I just bought a Vox ac15 tube amp. It is my first tube amp and to be honest I'm not really sure how they are "supposed" to sound (I don't play with a whole lot of other people or anything like that.) When my tubes are really being overdriven I am getting a very muddy sound. I'm using a strat and I only really have this problem when the distortion is past 2 o clock and it gets worse as my pickup switch gets closer to the up position. I'm not using any pedals or anything....

Is this normal for tube amps?....
No.

Are you playing a ****ty guitar?
Old 10th December 2012
  #3
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Originally Posted by isawsasquatch View Post
No.

Are you playing a ****ty guitar?
Nahh. 2012 American Standard Strat
Old 10th December 2012
  #4
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Some amps will get bassier as you increase the gain (Mesas in particular). Using the neck pickup will add to this as well. Try turning the bass down a bit and see if that helps.
Old 10th December 2012
  #5
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Originally Posted by Frodebro View Post
Some amps will get bassier as you increase the gain (Mesas in particular). Using the neck pickup will add to this as well. Try turning the bass down a bit and see if that helps.
nopee that didn't help
Old 10th December 2012
  #6
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Welcome to the world of using and educating your ears.

I can't tell you how many times over the last 40 years I've bought something that initially impressed me but soon left me feeling less than happy.

I have over 20 guitars and a dozen amps (seven are Mesa's). There's no one amp that does everything. I have several Strats, Tele's and many Gibson electrics with humbuckers.

When I play live, I'm happy playing a single Mesa dual Rectifier through a 4x12 cab, I can easily and happily do a bar gig with that and my Flying V and feel totally satisfied but I could never be happy with that as my only rig for recording.

From what you're describing I'd say your ears are coming to life and guiding you. I don't have a fast fix for you, ultimately it's probably going to require a different amplifier for you because it sounds like you're manipulating the controls right.

Guitar distortion is a very personal taste thing, you're just defining yours. I bet you will spend more time evaluating tones on the next amp you buy or maybe you'll do what I did, just buy everthing, play with them all and find the tones you like.

Wishing you all the best in your quest, good luck and good music to all.
Old 10th December 2012
  #7
Your sound gets bassier as you move the pickup switch higher towards the neck pickup. I've never found Vox amps to be tubby. Is it bassy on the bridge pickup too? Where is your bass knob on the amp? How are your tone knobs set on your guitar?
Old 10th December 2012
  #8
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abaga129's Avatar
 

You could try a different preamp tube and see if you like he sound better, or perhaps a decent overdrive pedal. I'm not a fan of the sound of my tube amp's distortion on it's own but with my my Direct Drive I can get some nice crunchy rock tones.
Old 10th December 2012
  #9
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Speakers also play a critical role in amp distortion. What's in the amp? A bulldog? A Blue? The watt rating for your speaker determines when and how it breaks up signal from the amp. Higher-rated speakers are stiffer and can get tubby when driven. Lower-rated speakers break-up sooner, tend to have a softer quality to their distortion.

Tubes and how long they've been broken in also play a part.

You might experiment with running your amp at a moderate, just breaking-up level and using OD or other drive pedals to achieve your grittier textures.
Old 11th December 2012
  #10
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Thank you all for replying.. So basically what I'm getting is that this is pretty much just the sound of my amp?

I would know if the amp was defective right?
Old 11th December 2012
  #11
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It's ONE possible sound of your amp. There are a lot of factors that affect what you get out of it. In general, the AC15 is a pretty bright amp, lots of upper mids. It's not known for muddiness. It's generally known for pretty outstanding, benchmark pop guitar sounds.

The guitars you jack into it, the kinds of effects you use, the tubes currently in the amp, the speaker you're running it through--all these things can contribute to the tone you're hearing.

If there are facets of the amp that you like, you can start playing with some of these elements to see if the sound gets closer to what you desire. Otherwise, you might want to think about swapping amps.

Maybe the Vox isn't your thing? Lower-watt Fenders like the Princeton Reverb or the Deluxe Reverb have a lot of clear low end and nice chimey high-end. Muddiness tends to come from mids, something that the Fender amps downplay.
Old 11th December 2012
  #12
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Quote:
Originally Posted by godotzilla View Post
It's ONE possible sound of your amp. There are a lot of factors that affect what you get out of it. In general, the AC15 is a pretty bright amp, lots of upper mids. It's not known for muddiness. It's generally known for pretty outstanding, benchmark pop guitar sounds.

The guitars you jack into it, the kinds of effects you use, the tubes currently in the amp, the speaker you're running it through--all these things can contribute to the tone you're hearing.

If there are facets of the amp that you like, you can start playing with some of these elements to see if the sound gets closer to what you desire. Otherwise, you might want to think about swapping amps.

Maybe the Vox isn't your thing? Lower-watt Fenders like the Princeton Reverb or the Deluxe Reverb have a lot of clear low end and nice chimey high-end. Muddiness tends to come from mids, something that the Fender amps downplay.
I only get muddiness from the low end when I apply heavy distortion.
Old 11th December 2012
  #13
Where are you getting the heavy distortion from?
Old 11th December 2012
  #14
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JonMiller's Avatar
I own two of these amps and use them a lot for studio work.

In reality, this is an amp for clean tones and not distorted. It will distort as you turn up the input, but that's not really it's thing. There is no diode clipping circuit like there is in a Mesa, Marshall, Blackstar or any other 2 channel amp that has distorted / hi-gain channel.
The AC15 is just a single channel(the top boost channel of an AC30) in a combo with either a 1x12 or 2x12 speaker configuration.
Old 11th December 2012
  #15
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JonMiller's Avatar
I guess a should reiterate my point. Most tube amps (99%) that have 2 switchable (from a foot switch) channels have a diode clipping circuit. The AC 15 does not, which is why it sounds like that way it does when it is distorting.
Old 11th December 2012
  #16
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Quote:
Originally Posted by JonMiller View Post
I guess a should reiterate my point. Most tube amps (99%) that have 2 switchable (from a foot switch) channels have a diode clipping circuit. The AC 15 does not, which is why it sounds like that way it does when it is distorting.
Thank you sir.
Old 11th December 2012
  #17
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Quote:
Originally Posted by JonMiller View Post
In reality, this is an amp for clean tones and not distorted. It will distort as you turn up the input, but that's not really it's thing. There is no diode clipping circuit like there is in a Mesa, Marshall, Blackstar or any other 2 channel amp that has distorted / hi-gain channel.
Where do you get that clipping is done with diodes in these amps? I've never seen a diode in the signal path on the schematics of any Mesa or Marshall that I've seen.
Old 11th December 2012
  #18
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It's clearly labeled on JCM 900s and up. You can actually increase or decrease the amount of gain by adding in series or replacing resistors. Typically in JCM 900 and 2000, this is the "High Gain" Marshall mod. If memory servers me right, it's d4 and d5 on the JCM 900s


I also know that the JCM 800 2025 model uses diode clipping as well as the Jubilee amps. On the Marshall's there is also a driver tube. Same with Mesa and Fender Devilles. How else do you get that amount of distortion even when the gain is on 1 on the drive channel? Black Magic?

This will explain how to bybass it on some JCM amps.
Marshall JCM diode clipping bypass mod

I'm not an amp tech so I don't know Mesa's in and out, but I had to have it replaced in a Mesa before. Also Mesa uses diodes in the rectifying circuit.

Blackstar and Bogner are an assumption, but since they are made by ex-Marshall research and development leads, one would assume the same practice continues. It's not a bad concept in reality.

Compress the wave before sending it to the tube for more distortion.
Old 11th December 2012
  #19
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Quote:
Originally Posted by TheEscapist View Post
I just bought a Vox ac15 tube amp. It is my first tube amp and to be honest I'm not really sure how they are "supposed" to sound (I don't play with a whole lot of other people or anything like that.) When my tubes are really being overdriven I am getting a very muddy sound. I'm using a strat and I only really have this problem when the distortion is past 2 o clock and it gets worse as my pickup switch gets closer to the up position. I'm not using any pedals or anything....

Is this normal for tube amps?....
This is the way many vox amps sound, they are very muddy with lots of overdrive.
Old 11th December 2012
  #20
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kafka's Avatar
Quote:
Originally Posted by JonMiller View Post
It's clearly labeled on JCM 900s and up. You can actually increase or decrease the amount of gain by adding in series or replacing resistors. Typically in JCM 900 and 2000, this is the "High Gain" Marshall mod. If memory servers me right, it's d4 and d5 on the JCM 900s


I also know that the JCM 800 2025 model uses diode clipping as well as the Jubilee amps. On the Marshall's there is also a driver tube. Same with Mesa and Fender Devilles. How else do you get that amount of distortion even when the gain is on 1 on the drive channel? Black Magic?

This will explain how to bybass it on some JCM amps.
Marshall JCM diode clipping bypass mod

I'm not an amp tech so I don't know Mesa's in and out, but I had to have it replaced in a Mesa before. Also Mesa uses diodes in the rectifying circuit.

Blackstar and Bogner are an assumption, but since they are made by ex-Marshall research and development leads, one would assume the same practice continues. It's not a bad concept in reality.

Compress the wave before sending it to the tube for more distortion.
No black magic is needed. High gain is exactly that - one gain stage feeding another. The original JCM 800s definitely didn't use a diode in the signal path. Mesa doesn't use any diodes in the signal path on any amp I've ever seen, including the Rectifier series. The rectifier isn't part of the signal path. It just rectifies AC power so you can get a DC voltage out of it. A diode doesn't compress anything. It's a switch that turns off when the voltage goes below (actually, gets close to) zero.
Old 12th December 2012
  #21
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foldback's Avatar
Fender has put some cheesy sounding clipper diode circuits in amps like the Hot Rod series.

Mesa has never used diodes in any of the circuit to create distortion, it's pure cascaded preamp tubes running into each other. I've OWNED over 20 Boogies since 1979, currently have seven, three of which are Dual Rectifiers, never been a diode clipper in any of them.

I've never seen a REAL tube Marshall head that relies on any clipping diodes in the audio path (ala fuzz box technology).

In some of the cheaper Marshall stuff that's out there to compete with other low end brands there could be anything in there but the classic Marshall preamp is cascaded gain stages too.

Good music to all!
Old 12th December 2012
  #22
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Quote:
Originally Posted by foldback View Post
I've never seen a REAL tube Marshall head that relies on any clipping diodes in the audio path (ala fuzz box technology).
JCM 800 2205 2210 heads & 42xx combos, all have clipping diodes. I can't think of a better guitar tone that those amps just listen to RATM

Randy Rhodes, Zakk and many others played 2203 JCM 800s. They used MXR or BOSS pedals in front
which have clipping diodes. It's a great sound. Even the Tube screamers that SRV used had a similar technology
it used an opamp in addition to some IC based distortion circuitry.

I like boogies but they don't sound necessary any better than a Marshall with a fuzz box. It's just a different kind of distortion. It's preference. Hendrix used fuzz pedals so did 100s of other guitarists with great tone.
Old 12th December 2012
  #23
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JonMiller's Avatar
Quote:
Originally Posted by kafka View Post
No black magic is needed. High gain is exactly that - one gain stage feeding another. The original JCM 800s definitely didn't use a diode in the signal path. Mesa doesn't use any diodes in the signal path on any amp I've ever seen, including the Rectifier series. The rectifier isn't part of the signal path. It just rectifies AC power so you can get a DC voltage out of it. A diode doesn't compress anything. It's a switch that turns off when the voltage goes below (actually, gets close to) zero.
Audio compression occurs at multiple stages inside of a guitar amp. What do you think distortion is? What is actually happening to the wave when distortion occurs, extreme compression?
Old 12th December 2012
  #24
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JonMiller's Avatar
I'm pretty sure my Mesa's and Marshalls got tubes and diode clipping circuits. If you're a betting man, I'll pull them apart.

Name the wager.

Quote:
Originally Posted by foldback View Post
Fender has put some cheesy sounding clipper diode circuits in amps like the Hot Rod series.

Mesa has never used diodes in any of the circuit to create distortion, it's pure cascaded preamp tubes running into each other. I've OWNED over 20 Boogies since 1979, currently have seven, three of which are Dual Rectifiers, never been a diode clipper in any of them.

I've never seen a REAL tube Marshall head that relies on any clipping diodes in the audio path (ala fuzz box technology).

In some of the cheaper Marshall stuff that's out there to compete with other low end brands there could be anything in there but the classic Marshall preamp is cascaded gain stages too.

Good music to all!
Old 1 week ago
  #25
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Old 1 week ago
  #26
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You're replying to a 6 year old thread. And a quick google search shows that model 2205 was the first to use the clipping diodes, the 2203 that you linked never used them.
Old 1 week ago
  #27
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Old 1 week ago
  #28
Quote:
Originally Posted by kafka View Post
Where do you get that clipping is done with diodes in these amps? I've never seen a diode in the signal path on the schematics of any Mesa or Marshall that I've seen.
"Modern" Marshalls (The ones I hate - JCM 900s, etc.) and the cheap models have diode clipping. I've never seen a Mesa with it but I have not seen the schematics to every one of the more recent models. None of the "classic" designs do.
Old 1 week ago
  #29
Quote:
Originally Posted by JonMiller View Post
It's clearly labeled on JCM 900s and up. You can actually increase or decrease the amount of gain by adding in series or replacing resistors. Typically in JCM 900 and 2000, this is the "High Gain" Marshall mod. If memory servers me right, it's d4 and d5 on the JCM 900s
Do you know the difference between a diode and a resistor?

(EDIT: evidently not.)

Quote:

I also know that the JCM 800 2025 model uses diode clipping as well as the Jubilee amps. On the Marshall's there is also a driver tube.

All push-pull tube amps use a driver tube, also known as a phase inverter. It has nothing to do with preamp overdrive and has nothing to do with distortion unless you turn the master all the way up and drive the amp really hard. Its function is to drive the output tubes. And the extra preamp gain tube in Mesas and some Marshalls (NOT a driver tube) has nothing whatsoever to do with diode clipping circuits.

Technically a diode clipping circuit is not an overdrive - it works by lopping off the top and bottom portions of the waveform (clipping), which produces high harmonics while reducing the level of the signal (the opposite of overdrive), which then requires makeup gain from another amplifying stage to get your level back. In essence it's nothing more that a built-in fuzz tone.


Quote:
Same with Mesa and Fender Devilles. How else do you get that amount of distortion even when the gain is on 1 on the drive channel? Black Magic?
Since you ask, you do it by running the output of one high gain preamp state into the output of another high gain preamp stage, so that the output of the first state exceeds the input that the second stage is able to handle without distortion. Then you put a volume control after the output of that second stage to control the level. Usually there will also be a level control between the two to control the amount of overdrive/distortion. How these controls are labelled varies from manufacturer to manufacturer.

Quote:
I'm not an amp tech so I don't know Mesa's in and out, but I had to have it replaced in a Mesa before. Also Mesa uses diodes in the rectifying circuit.
Damn straight you're not an amp tech. And all amps use diodes (either tube or solid state) in the rectifying circuit of the power supply. Rectifier diodes are what change the AC off the power line into DC to power the amp. They have NOTHING to do with distortion circuits. Or with amplification, for that matter.
Old 1 week ago
  #30
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Originally Posted by teleharmonium View Post
You're replying to a 6 year old thread.
Damn, you're right.
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