low frequency occilations on my solo 50

[coppa]

I have a single rectifier and gibson bfg

I like to run the green channel on clean mode but with cranked gain.
output at about 10 o clock and with the solo switch on and at about noon.

What this does is give me a gorgeous clean tone on the neck p90 pickup with the volume rolled off, and a nice high gain sound with the bridge humbucker.

BUT there is one problem. Every time i stop playing especially if i had just played a higher note the amp will start to make this low frequency oscillation sound. it sounds like driving on a flat tire. I can make it stop if i switch to the neck pick up and play a low note and then stop. If i switch to the bridge its uncontrollable.

Turning down the amp helps, but then I don't get the same sounds.

any ideas?.

 

[Anonymous]

I wonder if you're picking up a signal thru your guitar. If you're not sure, when it starts making the noise, unplug the guitar cable from the input jack on the amp. If it still makes the noise, it could be your power supply. Try a different outlet on a different circuit and that might help.

Has this happened for a while or do you think it's a new problem with the amp?

 

[coppa]

I bought the amp used from a place that used to rent it out. snce then the power tubes have been changed. The amp has been this way ever since I had it even with new tubes.

I know rectos can make crazy noises when the gain is too high, but why does it do it when I'm getting a sweet clean tone?.

 

[domct203]

Check your speaker impedence. Too far a mis-match in some amps can cause a 'motor-boat' sound that's very predominent in the low frequencies.

Dom

 

[coppa]

My recto is plugged into this:

http://www.soundperformancelab.com/index.php?id=53

its a dummy load as well as cabinet simulator. Its an 8ohm load and plugged into the 8ohm output of my amp.
would this motor boating thing happen at all settings in the amp.
it seems it happens with my amp when i turn up the output or the solo above noon.

 

[domct203]

That Transducer looks like a real nice unit.

8 ohm to 8 ohm would be correct for the amp to transducer unit.

Can you try the amp with a speaker cabinet? See if it happens with speakers as well. If not, it may just be an artifact of the Transducer and you'll need to deceide if that works for you or not.

If the motor-boating happens with a speaker cabinet as well you'll have to trouble-shoot the amp some. Try turning off the Solo and instead use the output to bring the levels back up and see if it still happens.

How old are the pre-amp tubes? If they are the ones that came with the amp, I would change them also. Do you have any 12AX7's you could trouble-shoot with?

Dom

 

[coppa]

I don't own a speaker cabinet unfortunately.

Would it make any difference to use a 4ohm output on the amp into the 8ohm input on the transducer?.

 

[domct203]

That would be a safe mis-match so it should not hurt the amp, but if this is an impedence issue that mis-match may make it worse. Be ready to shut the amp down quickly incase it does (self-oscillation is not good for the amp).

Can you bring the amp somewhere that has a cab you could use? It could save you a lot of time later, to find out now if it is the Transducer.

Did you try the suggestion posted?

I wonder if you're picking up a signal thru your guitar. If you're not sure, when it starts making the noise, unplug the guitar cable from the input jack on the amp. If it still makes the noise, it could be your power supply. Try a different outlet on a different circuit and that might help.

Again, I recommend that if the pre-amp tubes are the ones that came with the amp, you should change them anyway. At the least have one or two for times like this.

Dom

 

[coppa]

I have turned down the output and the solo a little bit and it has made a huge improvement. The only time I get those oscillations now is on the red channel with the solo turned on, except on the ed channel they are a high pitched oscillation

 

[domct203]

What are your settings (use clock positions) for both the channels?

Unless you are using extreme treble and gain settings this is sounding like a pre-amp tube(s) issue.

Dom

 

[coppa]

my settings are in :O clocks:

solo 1:00
output 11:00

Channel 1: clean

Master 4:00
Presence MAX
Bass 11:00
Mid 11:00
Treble 2:00
Gain MAX

Channel 2: Modern

Master 1:00
Presence 10:00
Bass 7:00
Mid 1:00
Treble 2:00
Gain 9:00

EL34

 

[domct203]

The high presence and gain settings on ch1 could bring out some 'weak tube artifacts' like microphonics and occilations in your clean sounds for sure.

Ch2 settings are fine. If you are getting stranges sounds there I would change those pre-amp tubes.

Dom

 

[coppa]

with mesa tubes or something else?

the onlt things available to me would be mesa or groove tubes

 

[domct203]

That's all a matter of personal taste. The new Mesa's are JJ's, which many either love or hate, and the Doug's Tube (http://www.DougsTubes.com) 'cocktail' is favored by some as well. Groove Tubes has some good offerings also.

What kind of music do you play, and what type of tones are you looking for?

Do you play in a band, or just mostly at home?

Is this your first tube amp?

Dom

 

[coppa]

Im looking for a sound like three days grace or system of a down etc just the recto sound that these amps are known for from the red channel.

The green channel is just about perfect.

Basically the amp sound good it would be nice if I could make it sound the same but better. would replacing my old russian mesa tubes with the new JJ mesa tubes make a big difference?.

 

[domct203]

As far as tube "A" sounding better than tube "B", only your ears can deciede that.

If you do have a bad (or 2) preamp tubes in there IMO any tubes in good working order will be an improvement.

Dom