fizzy sound in amp?

[tt0511]

I've been playing my amp more this week and the past two nights I've noticed a subtle, ...well not so subtle to my ears since it's annoying me, fizzy sound on the lead channel.  My amp is a Classic 30 that I bought new around a year and a half to two years ago.  The store was out of them so I bought the display model at a good price.  When I got it home, later on I did notice that it had JJ tubes in it.  Let's see, the amp has four EL84s and three 12AX7s.  The four larger ones are JJ's.  I remember one of the 12AX7's being sovtek when I changed out the speaker last year, and I think the other two didn't have a label on them?  Can't remember exactly.

I'm wondering if this amp was used and sold to me as a new display.  But, ...it didn't have a scratch on it!  It still doesn't.  I didn't think the Classic 30's came with JJ's and that most people upgraded to those so I was happy to see them in there.  But, I'm wondering if this fizz I'm hearing in the mid to high frequency range might be a tube or tubes going sour?  It's my first tube amp so I don't know.  I just know I don't remember that fizzy sound being there before.  I haven't played it much since I bought it, so it's hard to believe the tubes need replacing at this point, ...unless they were run hard before I got it.

Ideas?

 

[jackthehack]

"Fizzy" does not compute; is what you're hearing a "hiss" around above 2000 Hz or higher? Is it present if you turn the volume on your guitar all the way down? If you roll the treble control all the way to 0 does it go away? Does it happen of you plug the guitar directly into the amp? Anything new and electronic or with an electric motor in the room since it started happening?

 

[-CB-]

The lead channel ... isn't that 'posed to get fuzzied up a bit?

I wouldn't worry about the tubes.  Peavey is a turn on a dime company.  They can switch things in a moment to fit the situation - they're VERY responsive.  Of all the folks I've dealt with, Peavey was by far the easiest and most accommodating when it came to buying parts and getting tech help over the phone.

 

[tt0511]

The clean channel sounds great.  It's just the lead channel and I hear it the worst when playing single notes.  It's not the amp's normal hum when the volume on the amp or guitar is all the way down.  That noise level is actually very quiet as long as the guitar isn't right up to the amp.  The fizzy sound only occurs during playing.  I tried adjusting the amp EQ and with treble and mids rolled way, way back the problem began sinking into the background.  

The only one thing I did think of after posting the thread is that recently I turned the amp's boost off to experiment.  Most threads and reviews I've read for the Classic 30 have most people saying they leave it off.  I've always left mine on.  Perhaps this is a function of relatively low amp volume on the lead distorted channel and the boost that I have always had on pushed the tubes a bit more causing the distortion to smooth out?

I did a google search on amps with this fizz and found several possible answers.  The ones involving tearing into the chassis are likely not for me.  I can't imagine this problem is that serious.  I did however find a few threads where people had the same problem and it sounded like they were playing at bedroom volumes.  Some folks were telling them that what they were experiencing was playing a large rig at too low a volume and were probably only getting preamp distortion because they weren't pushing the lead channel tubes at all at such a low volume.  This sounds like a reasonable possibility to me.  I generally play at bedroom volumes, ...have always left the boost on until recently.  Seems to add up.  

I don't have time tonight to try it again with the boost on and I won't be around the amp for the next couple of days.  I'll have to try it with the boost on and see if that eliminates the problem.  I can say that I noticed it last night and it was bothering me.  So, to investigate I cranked it on up to about 4 or 5 with the boost off and it seemed to clean up and sound like it should.  Now, the same problem tonight but I didn't crank it up.  At first I thought I was just imagining things, but I don't think so.  I have a fairly discriminating ear.

 

[tt0511]

The lead channel ... isn't that 'posed to get fuzzied up a bit?

Yes sir.  But this is an unpleasant sound.

 

[jackthehack]

Have played through a Classic 30 occasionally when jamming/sitting in with a friend's blues band, but always at bar/club volume....

I will always defer to C.B.'s expertise, but if you look at the schematic:

http://www.freeinfosociety.com/electronics/schematics/audio/peaveyclassic30.pdf?phpMyAdmin=af0f6b4465fe3f904426eaeb3dc0e3fa&phpMyAdmin=Kb2XHnhmhTctZwPmOqks7zD3-sc

The V1 preamp tube is split and 1/2 used in that Boost circuit.

If you play at volume, does the issue go away? If so, could be an idiosyncrasy of the amp design, BUT if you have some mis-matched tubes in that pre-amp circuit swapping them out with ones that match may make the amp sound better, even if it doesn't fix the low volume problem and only cost $20-25 bucks at most... Sovtek 12AX7WC's will give you a little "darker" sound; JJ or Groove Tube ECC83's will be a bit cleaner/brighter; search through the Rig section on this site and there are a number of posts about tube swapping...

 

[Superlizard]

The clean channel sounds great.  It's just the lead channel and I hear it the worst when playing single notes.  It's not the amp's normal hum when the volume on the amp or guitar is all the way down.  That noise level is actually very quiet as long as the guitar isn't right up to the amp.  The fizzy sound only occurs during playing.  I tried adjusting the amp EQ and with treble and mids rolled way, way back the problem began sinking into the background.  

The only one thing I did think of after posting the thread is that recently I turned the amp's boost off to experiment.  Most threads and reviews I've read for the Classic 30 have most people saying they leave it off.  I've always left mine on.  Perhaps this is a function of relatively low amp volume on the lead distorted channel and the boost that I have always had on pushed the tubes a bit more causing the distortion to smooth out?

I did a google search on amps with this fizz and found several possible answers.  The ones involving tearing into the chassis are likely not for me.  I can't imagine this problem is that serious.  I did however find a few threads where people had the same problem and it sounded like they were playing at bedroom volumes.  Some folks were telling them that what they were experiencing was playing a large rig at too low a volume and were probably only getting preamp distortion because they weren't pushing the lead channel tubes at all at such a low volume.  This sounds like a reasonable possibility to me.  I generally play at bedroom volumes, ...have always left the boost on until recently.  Seems to add up.  

I don't have time tonight to try it again with the boost on and I won't be around the amp for the next couple of days.  I'll have to try it with the boost on and see if that eliminates the problem.  I can say that I noticed it last night and it was bothering me.  So, to investigate I cranked it on up to about 4 or 5 with the boost off and it seemed to clean up and sound like it should.  Now, the same problem tonight but I didn't crank it up.  At first I thought I was just imagining things, but I don't think so.  I have a fairly discriminating ear.

If the lead channel tone is all fizzy, then yes, sounds like the symptom of a typical Master Volume
circuit - thin, buzzy/fizzy tone.  You have to get those powert00bs sweating to get any balls out
of a t00b amp.  What you're hearing (judging by your description of how you set the amp) *is*
mostly preamp gain (BZZZ!).  I suggest (as I always do in these cases) getting a power
attenuator so you can crank the damn thing and not suffer so much tone-wise.

 

[tt0511]

If the lead channel tone is all fizzy, then yes, sounds like the symptom of a typical Master Volume
circuit - thin, buzzy/fizzy tone.  You have to get those powert00bs sweating to get any balls out
of a t00b amp.  What you're hearing (judging by your description of how you set the amp) *is*
mostly preamp gain (BZZZ!).  I suggest (as I always do in these cases) getting a power
attenuator so you can crank the damn thing and not suffer so much tone-wise.

I looked up the THD Hot Plate.  Hot DANG those things are expensive!  If I can pick up a used one on evilbay I will.  Hard to justify spending that kind of dough for a new one.  May be that the 5watt Blackheart would be much better suited to home playing if that's the case.  I bet with an overdrive pedal in front of the 5watt, I could eliminate the problem.  And, it would be about the same price for a high quality overdrive pedal (which I currently lack) and a Blackheart head as it would for that Hot Plate.  

I do think this volume thing is the problem though.  The other thing that has changed recently is that I used to have the amp on the floor beside the extension cab.  Having gotten married this year and having to consolidate for space, I stacked the Classic 30 on top of the extension cab, so it is much closer to the ears now.  I bet it's been doing that the whole time but I didn't pick up on it because it sounds bassier on the floor.

 

[tt0511]

Have played through a Classic 30 occasionally when jamming/sitting in with a friend's blues band, but always at bar/club volume....

I will always defer to C.B.'s expertise, but if you look at the schematic:

http://www.freeinfosociety.com/electronics/schematics/audio/peaveyclassic30.pdf?phpMyAdmin=af0f6b4465fe3f904426eaeb3dc0e3fa&phpMyAdmin=Kb2XHnhmhTctZwPmOqks7zD3-sc

The V1 preamp tube is split and 1/2 used in that Boost circuit.

If you play at volume, does the issue go away? If so, could be an idiosyncrasy of the amp design, BUT if you have some mis-matched tubes in that pre-amp circuit swapping them out with ones that match may make the amp sound better, even if it doesn't fix the low volume problem and only cost $20-25 bucks at most... Sovtek 12AX7WC's will give you a little "darker" sound; JJ or Groove Tube ECC83's will be a bit cleaner/brighter; search through the Rig section on this site and there are a number of posts about tube swapping...

Ha ha.  I did have electronics one year in High School.  ....But, ...that schematic is a little beyond, ..no, a lot beyond my current level of knowledge and ability to understand, lol.

 

[Superlizard]

If the lead channel tone is all fizzy, then yes, sounds like the symptom of a typical Master Volume
circuit - thin, buzzy/fizzy tone.  You have to get those powert00bs sweating to get any balls out
of a t00b amp.  What you're hearing (judging by your description of how you set the amp) *is*
mostly preamp gain (BZZZ!).  I suggest (as I always do in these cases) getting a power
attenuator so you can crank the damn thing and not suffer so much tone-wise.

I looked up the THD Hot Plate.  Hot DANG those things are expensive!  If I can pick up a used one on evilbay I will.  Hard to justify spending that kind of dough for a new one.  May be that the 5watt Blackheart would be much better suited to home playing if that's the case.  I bet with an overdrive pedal in front of the 5watt, I could eliminate the problem.  And, it would be about the same price for a high quality overdrive pedal (which I currently lack) and a Blackheart head as it would for that Hot Plate.  

I do think this volume thing is the problem though.  The other thing that has changed recently is that I used to have the amp on the floor beside the extension cab.  Having gotten married this year and having to consolidate for space, I stacked the Classic 30 on top of the extension cab, so it is much closer to the ears now.  I bet it's been doing that the whole time but I didn't pick up on it because it sounds bassier on the floor.

Truth is, even 5 watts is too loud for bedroom-levels playing... once, I had a Z-Vex Nanohead 1/2 watt t00b amp, and it was as loud cranked as say a loud TV... something to consider.

 

[Patrick from Davis]

This could actually be something a lot simpler.  If you look at the rectifier in the circuit, the diodes are 1n4007.  It doesn't always rear its head, but the switching rate in the diodes is slow enough to be heard, but not as a pitch.  It is more of a clicking thing that gets to sounding fizzy, especially with distortion.  The quick fix is to get UF4007 diodes (high speed recovery diodes) and swap the 1n4007's out with them.  The two diodes perform identically except the recovery rate of the UF's is about 100 times faster, so you no longer hear the switching, and no more fizzy.  I had this exact prob with my little homebrew amp.
Patrick

 

[tt0511]

Truth is, even 5 watts is too loud for bedroom-levels playing... once, I had a Z-Vex Nanohead 1/2 watt t00b amp, and it was as loud cranked as say a loud TV... something to consider.

Well, I like the Killer Ant, but there is zero clean headroom.  Wouldn't the Little Giant that is 3w/5w switchable sound great at say, half volume and using an overdrive pedal to push it on into the harder tube breakup?  Seems like it would HAVE to sound much better than the 30W pv Classic at home volumes.  I live in my own house, not a condo or apartment so I have "some" liberty.  I don't know if the goal is to absolutely hit max on the amp volume is it?

Heck, maybe I should just get a Killer Ant for the sweet overdriven tones and the Little Giant for good clean tones at bedroom volumes.  I think someone probably makes a switch to allow me to split my guitar signal going to the amp to have it go to both amps.  Then I could have the 1w for overdrives and the 3w for cleans, both amps set at the same volumes and use them like a 2-channel amp (like my PV).

 

[-CB-]

If you're getting weird fuzzy - unpleasant - look for the obvious.  Is there something VIBRATING in the cabinet.  Rearrange the tubes of the same type.  Switch around your 12AX7's and see if the problem goes away or moves or gets worse.  Could be a microphonic tube.  Tape on the tubes like yer flickin' a booger into the next county... see if it makes a difference in the noise.  Try a new cable.  Try a different guitar.  Does it happen when you move the cable in the jack.  All that sort of stuff.

 

[Superlizard]

A consideration, although not necessarily the case here (at least that's what my spidey-sense tells me):

Playing at very low volumes, an amp's volume bright cap (no different electronically or function-wise than a guitar vol knob bright cap) comes into play much more than when the amp's volume is turned up... this can also help perpetrate the thin, buzzy/fuzzy tone.

Although, admittedly, the schematic Jack posted doesn't show a bright cap on the volume... this doesn't necessarily prove
the lack of one, though.

It is however a common mod for Marshall reissue modders to remove the gawd-awful, non-vintage-spec stock super-bright cap
(or put in a period-correct one)... they do this to alleviate the thin buzzy/fuzzy tone at low volume and as well to get rid of the
"on/off" feel (i.e. turn volume to "1" and the amp's volume level is waaay too loud for being on "1") of the volume knob.

 

[tt0511]

I tried the amp again and the problem was still there.  But, I when I turned the Boost feature on again (as it has always been up until a couple of weeks ago) the problem disappeared.  The amp manual says this boost is an overall system gain boost.  I am finding that I prefer the tone when the Boost feature is disabled.  The amp does sound "honkey" with the Boost on and more balanced with it off.  At least, that's the way some people who have reviewed the amp described it.  That tells me that a Hot Plate would probably make me happy.  I'm not so sure the amp would sound "honkey" with the boost enabled at gig volumes though.  A little work with the amp's EQ may help this out at bedroom volumes too.  I'll work on that.  I know lot's of people complain about their amp's tone, and they won't even adjust the EQ but will get rid of the amp for another one.  They are too accustomed to Microsoft Windows Plug and Play features, ha ha.

Thanks for all of the great info guys!

 

[Superlizard]

I tried the amp again and the problem was still there.  But, I when I turned the Boost feature on again (as it has always been up until a couple of weeks ago) the problem disappeared.  The amp manual says this boost is an overall system gain boost.  I am finding that I prefer the tone when the Boost feature is disabled.  The amp does sound "honkey" with the Boost on and more balanced with it off.  At least, that's the way some people who have reviewed the amp described it.  That tells me that a Hot Plate would probably make me happy.  I'm not so sure the amp would sound "honkey" with the boost enabled at gig volumes though.  A little work with the amp's EQ may help this out at bedroom volumes too.  I'll work on that.  I know lot's of people complain about their amp's tone, and they won't even adjust the EQ but will get rid of the amp for another one.  They are too accustomed to Microsoft Windows Plug and Play features, ha ha.

Thanks for all of the great info guys!

Before you go out spending all yer clams on a Hot Plate or whatever, does the amp have that "fizz":

1)  with boost off

2)  with volume above "bedroom" levels  (like, try "5" or higher or as you say "gigging" volume)

 

[tt0511]

Yes, the fizz is there with the boost off, as mentioned in one of my earlier posts.  The first night I had the boost off I cranked the amp on up and it did seem to go away.  I will try that again tonight.  If it does go away with volume, I'm back in the dilemna of paying the money for a hot plate, or like I said, a 1 or 3-5watt amp.  I've heard that the Blackstar sounds fantastic at bedroom volumes.  Before I shell out the dough for a hot plate, I'll be checking out a couple of smaller amps like that. 

 

[jimh]

Blackstar HT5 combo is amazing value.  I speak from personal experience.  Red McMannus ( a part time Warmother forumite has one), and he's my bestest mate from home.

 

[tt0511]

Okay, the fizzy quality diminishes as the amp is turned up.  I don't know if anything is "off" or "wrong" but I definitely know there is a distinct difference between the boost being on and being off.  I recorded some random chords in the linked mp3.  I played my Gibson SG Std on the bridge pup.  The first half is the lead channel at about 5.5 or 6 on the volume, gain at 8.5.  Bass at 12 o'clock, Mid and treble at about 11 o'clock.  The second half of the track is with the boost on and the only setting change was dialing the volume back about 1 or 1.5 to keep the output volume approximately equal.  I did this on the fly, it's total noodling so don't fuss at me for that. It's total a-la-carte improvised on the fly as I went along.  Haven't been playing for around a year until the past few weeks.

Anyway, let me know what you think of the amp's sound.  At first when I listen to the first half of the recording, it doesn't sound bad.  But the tone is much fuller with the boost on.  I guess they are just different sounds altogether but with the boost off the amp kinda sounds a little thin or wirey to my ears.  It's probably just the amp's sound with the Celestion Vintage 30 in it.  I put the V30 in because when I got the amp it just sounded a little muffled.  The V30 made it sound more like it was breathing.  I'll say one thing, this amp is damn loud.  I'm about deaf and probably have a couple of gaps to seal around the window now, ha ha.

http://soundclick.com/share?songid=8073590

 

[tt0511]

oh yeah, the mic used is a MXL V69 Mogami Edition tube mic.  The only one I have.