couple of amp questions...

jeffinwv · June 14th, 2008, 05:00 PM

i gig with 2 amps...and an aby switcher...i have a vibrosonic...that when i turn it up over 4 or so it will blurr a little...thats pretty loud...but it shouldnt blur should ity??is this tubes??? bad..or just overdriven?

my dirty amp is a marshall jcm 2000 triple super lead combo amp 60 watts.. and when i turn it up to a good playing level..when its on the dirty channels it wants to sit and feedback even when the aby box is going into the fender.... i have adjusted the highs and lows...but it seems the only weay it will stop squeeling is to turn it down

how can i solve these problems?

Wally · June 14th, 2008, 05:14 PM

Vibrasonic....what are your tone control levels when you go over 4 on the volume?
Marshall.....you probably have a micorphonic tube that is going into a feedback mode...tap on your tubes o ne at a time to see if you get a high-pitched, loose-sounding reaction. That would be your problem tube.

jeffinwv · June 14th, 2008, 07:19 PM

vibrosonic is set at 8 for higs 4 for mid and 5 for low

and the marshall is brand spankin new...i guess that still a tube could be microphonic right?

on edit: the marshall will get quiet if i switch to the clean channel and of the dirty channels...

Dacious · June 15th, 2008, 01:38 AM

Depending on your guitar and pickups, and any preamps (tubescreamer, distortions, even choruses) over 3 on the bass control on a traditional 6L6 Fender can be too much once volume gets up over mid levels. Part of the reason many of them have a nice early breakup is the power and output transforners are a little short of what they could be. Hot pickups or gain boosters in front make this worse.

Again, your dirty channel on the Marshall is adjustable, and depending on the gain and master volume, you might just be trying to push it too hard. If it does squeal even when not selected, as Wally says, microphonic tube likely. Warranty.

Where are you setting the master volume? Usually the master should be flat out or near to, unless you are trying to induce preamp breakup for recording or something.

jeffinwv · June 15th, 2008, 12:28 PM

so.....are you saying the fender will stop blurring if i turn the bass down on the amp? i have lace sensor pickups in my strat..but there are no chorus or any other pedal between my amp and geetar....i dont use pedals or anything like that.

the marshall will stop squeeling if i turn the volume down low enough....but when i really play loud i have to hit the footswitcher to the clean channel on the marshall to stop the noise.

i have some 7025 tubes here...should i swap the preamp tubes out in there and try?

Wally · June 16th, 2008, 03:40 PM

JEff, on the Vibrasonic, try try lowering the bass control a bit and see if your soncis clear up. those controls are there for a reason. EAch player's approach to playing dictates that each of us learn how to use the guitar and amp control to our individual techniques and taste. There is also the aspect of power tube biasing. If you bias is set to the 'hot' side of things, your distortion will come on earlier. If you can't find a pleasing setting by adjusting the controls, it might be time for a tech to give your amp an inspection jsut to see how the ampl..preamp and power amp sections...are performing. The speaker may not be yielding the soncis you want. there are many possiblities. The controls are the first and easiest approach.
Marshall....I don't have a lot of experience wiht Lace Sensors and high gain, but I have never noticed them giving problems with microphonics. A guitar with microphonic pups will not tolerate high gain situations. However, since in your initial post, you specified that the amp would squeal even when signal was not being sent to and through it, I immmediately suspected the amp.

jeffinwv · June 16th, 2008, 10:16 PM

i dont run any distortion through my vibrosonic...so ill try lowering the bass..like ya said...

that marshall is less than a year old....so it my need a good ole american 12ax7 in it...

thanks guys!!!!

Dacious · June 16th, 2008, 10:37 PM

Not sure whose preamp tubes Marshall is using, but Korg who own Marshall and Vox were using Eis in the Vox, which at one stage had a high microphony/reject rate.

Get yourself a EH or Sovtek 12AX7 (you should have one as a spare anyhow) and sub it in to the various preamp positions - see if it makes a diff.

You are using proper shielded guitar cable?

jeffinwv · June 18th, 2008, 09:50 AM

yea...i think i have good guitar cable...but i am going to try swapping around those 2 preamp tubes....i am going to do that this evening

you guys are great help!!!

thank you for you info and time!!

June 14th, 2008, 05:00 PM	#1 (permalink)
jeffinwv TDPRI Member Join Date: Dec 2007 Location: beckley wv Posts: 58	couple of amp questions... i gig with 2 amps...and an aby switcher...i have a vibrosonic...that when i turn it up over 4 or so it will blurr a little...thats pretty loud...but it shouldnt blur should ity??is this tubes??? bad..or just overdriven? my dirty amp is a marshall jcm 2000 triple super lead combo amp 60 watts.. and when i turn it up to a good playing level..when its on the dirty channels it wants to sit and feedback even when the aby box is going into the fender.... i have adjusted the highs and lows...but it seems the only weay it will stop squeeling is to turn it down how can i solve these problems?

June 15th, 2008, 01:38 AM	#4 (permalink)
Dacious Friend of Leo's Join Date: Mar 2003 Location: Godzone Posts: 2,612 35 Photos	Depending on your guitar and pickups, and any preamps (tubescreamer, distortions, even choruses) over 3 on the bass control on a traditional 6L6 Fender can be too much once volume gets up over mid levels. Part of the reason many of them have a nice early breakup is the power and output transforners are a little short of what they could be. Hot pickups or gain boosters in front make this worse. Again, your dirty channel on the Marshall is adjustable, and depending on the gain and master volume, you might just be trying to push it too hard. If it does squeal even when not selected, as Wally says, microphonic tube likely. Warranty. Where are you setting the master volume? Usually the master should be flat out or near to, unless you are trying to induce preamp breakup for recording or something. __________________ My other Telecaster is a Thinline The Tele Bible, Ch 1, v 10 Love thy Telecaster, covet not thy neighbour's Strat!

June 16th, 2008, 10:37 PM	#8 (permalink)
Dacious Friend of Leo's Join Date: Mar 2003 Location: Godzone Posts: 2,612 35 Photos	Not sure whose preamp tubes Marshall is using, but Korg who own Marshall and Vox were using Eis in the Vox, which at one stage had a high microphony/reject rate. Get yourself a EH or Sovtek 12AX7 (you should have one as a spare anyhow) and sub it in to the various preamp positions - see if it makes a diff. You are using proper shielded guitar cable? __________________ My other Telecaster is a Thinline The Tele Bible, Ch 1, v 10 Love thy Telecaster, covet not thy neighbour's Strat!

June 14th, 2008, 05:14 PM	#2 (permalink)
Wally Friend of Leo's Join Date: Mar 2003 Location: Lubbock, TX Posts: 4,026	Vibrasonic....what are your tone control levels when you go over 4 on the volume? Marshall.....you probably have a micorphonic tube that is going into a feedback mode...tap on your tubes o ne at a time to see if you get a high-pitched, loose-sounding reaction. That would be your problem tube.

June 14th, 2008, 07:19 PM	#3 (permalink)
jeffinwv TDPRI Member Join Date: Dec 2007 Location: beckley wv Posts: 58	vibrosonic is set at 8 for higs 4 for mid and 5 for low and the marshall is brand spankin new...i guess that still a tube could be microphonic right? on edit: the marshall will get quiet if i switch to the clean channel and of the dirty channels...

June 15th, 2008, 12:28 PM	#5 (permalink)
jeffinwv TDPRI Member Join Date: Dec 2007 Location: beckley wv Posts: 58	so.....are you saying the fender will stop blurring if i turn the bass down on the amp? i have lace sensor pickups in my strat..but there are no chorus or any other pedal between my amp and geetar....i dont use pedals or anything like that. the marshall will stop squeeling if i turn the volume down low enough....but when i really play loud i have to hit the footswitcher to the clean channel on the marshall to stop the noise. i have some 7025 tubes here...should i swap the preamp tubes out in there and try?

June 16th, 2008, 03:40 PM	#6 (permalink)
Wally Friend of Leo's Join Date: Mar 2003 Location: Lubbock, TX Posts: 4,026	JEff, on the Vibrasonic, try try lowering the bass control a bit and see if your soncis clear up. those controls are there for a reason. EAch player's approach to playing dictates that each of us learn how to use the guitar and amp control to our individual techniques and taste. There is also the aspect of power tube biasing. If you bias is set to the 'hot' side of things, your distortion will come on earlier. If you can't find a pleasing setting by adjusting the controls, it might be time for a tech to give your amp an inspection jsut to see how the ampl..preamp and power amp sections...are performing. The speaker may not be yielding the soncis you want. there are many possiblities. The controls are the first and easiest approach. Marshall....I don't have a lot of experience wiht Lace Sensors and high gain, but I have never noticed them giving problems with microphonics. A guitar with microphonic pups will not tolerate high gain situations. However, since in your initial post, you specified that the amp would squeal even when signal was not being sent to and through it, I immmediately suspected the amp.

June 16th, 2008, 10:16 PM	#7 (permalink)
jeffinwv TDPRI Member Join Date: Dec 2007 Location: beckley wv Posts: 58	i dont run any distortion through my vibrosonic...so ill try lowering the bass..like ya said... that marshall is less than a year old....so it my need a good ole american 12ax7 in it... thanks guys!!!!

June 18th, 2008, 09:50 AM	#9 (permalink)
jeffinwv TDPRI Member Join Date: Dec 2007 Location: beckley wv Posts: 58	yea...i think i have good guitar cable...but i am going to try swapping around those 2 preamp tubes....i am going to do that this evening you guys are great help!!! thank you for you info and time!!