Amp Tech Thread / Ask a tech Q

[Hemisaurus]

I'm going to be putting up some foam this week, hopefully that will help. Can't really turn down cymbals much. My amps are only loud enough so that I can hear them over the drums and through my earplugs.
I'm using a borrowed monitor unit so I have to give it back and buy my own at some point.

If you are using earplugs, you probably are already in trouble. If you're using earplugs, either you're already too loud, or your place is too small. Don't know how practical it is for you to get more space, last band I was in that used earplugs, was in the corner of a basement, we just took down the walls and used the whole basement, and that really helped, just having more space. You can simulate it with blankets and foam, but if you can find a bigger space life will be easier. Or have the drummer play with something like lightning rods, or brushes, or dampen the cymbals a bit more.

It's a lot easier than carpetting the walls.

[liquidsmoke]

Can a 600 watt powered floor PA/monitor unit get a lot louder with vocals running into it before it starts feeding back than a similar 200 watt unit?

feedback depends on everything else in the chain feeding back. Watts don't mean anything most of the time, so there is not gonna be any difference if that is the only factor changing, but inevitably other stuff will change with it. Bit of general awareness of the mechanics of feedback helps, sound has to be getting from source to mic, so the pickup pattern of the mic is pretty important, and as said, sound bouncing off a wall is a pretty likely factor.

The monitor is pointed right at the mic which is also right where my head is when I'm singing, no real way around this. Hopefully foam will help. I have some tapestries hung up but they are pretty thin.

[liquidsmoke]

I'm going to be putting up some foam this week, hopefully that will help. Can't really turn down cymbals much. My amps are only loud enough so that I can hear them over the drums and through my earplugs.
I'm using a borrowed monitor unit so I have to give it back and buy my own at some point.

If you are using earplugs, you probably are already in trouble. If you're using earplugs, either you're already too loud, or your place is too small. Don't know how practical it is for you to get more space, last band I was in that used earplugs, was in the corner of a basement, we just took down the walls and used the whole basement, and that really helped, just having more space. You can simulate it with blankets and foam, but if you can find a bigger space life will be easier. Or have the drummer play with something like lightning rods, or brushes, or dampen the cymbals a bit more.

It's a lot easier than carpetting the walls.

There is one wall I could knock out, the room is fairly small right now. Do lightning rods quiet down cymbals? I have some carpet on one wall already and have more I can put up.

Regarding earplugs, I use them because I value my hearing. I wear them at shows too. Even if we practiced in an open field outside and the drummer was 20 feet from me I'd still want to wear plugs because if I didn't my ears would ring after every practice. Brushes for heavy metal? If my amp is above 1 my ears will ring, at practice it's about 2&1/2 or so. Maybe the problem is that I still have some hearing left so my ears ring. I think a lot of more seasoned rockers don't really notice ear ringing anymore because they are so used to it. My dad is rarely around loud sounds and his hearing is already getting somewhat bad at age 61, that has me somewhat concerned about my future.

The bitch is that without earplugs I can hear my vocals just fine... and then my ears are ringing really bad the rest of the day. All I need is a bit more vocal volume and I'll be fine. I hope the foam and more carpet does the trick.

[VOLVO)))]

I wear earplugs, anyways, too.

[cat shepard]

Can a 600 watt powered floor PA/monitor unit get a lot louder with vocals running into it before it starts feeding back than a similar 200 watt unit?

Yes. Provided other changes are made, mainly utilizing the headroom provided by the additional 400 watts. The most efficient means for said headroom utilization would be a reduction in gain on the channel strip at the mixer(?) provided there is one, allowing the same volume or greater to be met with less gain. If the identical gain structure that the 200 watt monitor had going through it is pumped into the 600 watt monitor it could possibly feedback at even less volume. Is there a graphic eq for the signal to pass through before being amplified? If so I would set it flat and find the frequencies that are feeding back and pull them gently until feedback in that range leaves, as that should also obtain further headroom. If you don't have a graphic you can use the eq on the strip to help eliminate the problem frequencies.

[HeavyEar]

wouldn't it depend moreso on the mic, the quality of it to reject feedback, its pattern and placement etc? Honest question so I'm not challenging the headroom issue.

[liquidsmoke]

The setup is- Sure SM-58 > Boss VE-20(digital vocal effects pedal) > Behringer power PA monitor. No mixer or graphic eq. I can try to turn the Behringer's volume up higher and the Boss' lower and see if that helps.

[Mr. Foxen]

Can a 600 watt powered floor PA/monitor unit get a lot louder with vocals running into it before it starts feeding back than a similar 200 watt unit?

feedback depends on everything else in the chain feeding back. Watts don't mean anything most of the time, so there is not gonna be any difference if that is the only factor changing, but inevitably other stuff will change with it. Bit of general awareness of the mechanics of feedback helps, sound has to be getting from source to mic, so the pickup pattern of the mic is pretty important, and as said, sound bouncing off a wall is a pretty likely factor.

The monitor is pointed right at the mic which is also right where my head is when I'm singing, no real way around this. Hopefully foam will help. I have some tapestries hung up but they are pretty thin.

Depends heavily on the pickup pattern of the mic and the angle you ahve it at. Pointing at your head is pretty standard, but you can try Lemmying it if you usually have it pointed up at you.

Also, earplugs, are you using foamies or the rubber christmas tree jobs, some proper musicians earplugs will make a lot of difference as they have a more even response that won't force you to bump highs or overall volume yo hear yourself.

[cat shepard]

The setup is- Sure SM-58 > Boss VE-20(digital vocal effects pedal) > Behringer power PA monitor. No mixer or graphic eq. I can try to turn the Behringer's volume up higher and the Boss' lower and see if that helps.

This should help at least a little. I would try to find a cheap graph, It would help a ton. Somewhere there is to much gain. LESS GAIN, MORE DRIVE

[cat shepard]

wouldn't it depend moreso on the mic, the quality of it to reject feedback, its pattern and placement etc? Honest question so I'm not challenging the headroom issue.

If gain structure is overlooked mic pattern and placement can only help to a certain extent.  To change the mic to a hypercardioid would possibly provide some leniency, but nowhere near the amount if cleaner gain structure were followed with the initial mic. To have a wedge aimed at your head with a mic in front of you is about as standard as you can get. You could move the mic away from that spot and obtain some freedom from feedback but the volume gained  would probably just be enough to compensate for the geographical change and not enough to truly alleviate the problem. By reducing the input gain and increasing the output wattage you can get more clean volume, and keep the mic right where you want it. This is a great topic!

[liquidsmoke]

Depends heavily on the pickup pattern of the mic and the angle you ahve it at. Pointing at your head is pretty standard, but you can try Lemmying it if you usually have it pointed up at you.

Also, earplugs, are you using foamies or the rubber christmas tree jobs, some proper musicians earplugs will make a lot of difference as they have a more even response that won't force you to bump highs or overall volume yo hear yourself.

My voice sounds better with my head pointed slightly down into the mic, can't do the Lemmy thing. This also allows me to easily look at my fretboard when I need to while singing.

I use Hearos, I probably spelled that wrong. They work pretty good. My ears ring a little bit after practice but they are much better than the foam ones.

[Baltar]

Hey folks,
So I'm getting a "pop" in my Bogen CHB50 when I peg it I'm also getting a faint, distant ringing almost like it's a reverb spring, but the amp doesn't have one.  The guy I bought it from told me NOT to set the head on top of the cab.  Of course I did the opposite.  It looks cool, plus I don't have anywhere else to put it 'cept for the floor.  And I'm not putting it on the floor.  The 6L6's are original Bogen's.  It only does this once in a while and only when it's pegged.  The pre-amp tubes are pretty new he said.  I want to switch to EL 34's and see if I need to change caps, resistors, etc. to park it in Plexi-Land permanently.  Supposedly it's a Bassman circuit knock-off.  50 Watts.

Are the power tubes going?

[justinhedrick]

Hey folks,
So I'm getting a "pop" in my Bogen CHB50 when I peg it I'm also getting a faint, distant ringing almost like it's a reverb spring, but the amp doesn't have one.  The guy I bought it from told me NOT to set the head on top of the cab.  Of course I did the opposite.  It looks cool, plus I don't have anywhere else to put it 'cept for the floor.  And I'm not putting it on the floor.  The 6L6's are original Bogen's.  It only does this once in a while and only when it's pegged.  The pre-amp tubes are pretty new he said.  I want to switch to EL 34's and see if I need to change caps, resistors, etc. to park it in Plexi-Land permanently.  Supposedly it's a Bassman circuit knock-off.  50 Watts.

Are the power tubes going?

if it is pegged it could be picking up rattling from the power tubes. you could also have a pre-amp tube going kind of wonky . . .

[Hemisaurus]

Microphonic preamp tubes, try swapping them around, if it get's noisier the 2nd preamp tube is going, if it gets quieter, it's the first. This assuming you know which is the first and which is the second.

[Baltar]

Thanks Hemi, so I'll have to re-bias for the EL 34's when I switch.  Is there anything else I need to know?
Plate voltage?

[justinhedrick]

Thanks Hemi, so I'll have to re-bias for the EL 34's when I switch.  Is there anything else I need to know?
Plate voltage?

isn't there some sort of pin-rewiring that has to happend for EL34s?

[VOLVO)))]

Different screen resistors, eh?

[dunwichamps]

I use 1K 5W wirewounds for all tubes. Pin 1 on EL34s is grounded

[Hemisaurus]

Thanks Hemi, so I'll have to re-bias for the EL 34's when I switch.  Is there anything else I need to know?
Plate voltage?

isn't there some sort of pin-rewiring that has to happend for EL34s?

Only if it's been oddly wired there's an internal connection on one that isn't on the other. Do you happen to know the B+ or plate voltage of the current circuit? Some can be swapped easily, as long as the bias voltage can be adjusted enough, some require more tweaking. For one thing an EL34 draws way more heater current than a 6L6 more than 50% more.

Are you up to sketching the power section? Measure B+ voltage on center of output transformer, all the values of screen resistors, etc. etc.?

Does it have a tube rectifier?

[dunwichamps]

6L6 is 0.9A per tube, EL34s is ~1.5A per tube. Grid bias will need to be changed. Pin 1 grounded

[Baltar]

Thanks guys, it's all tube.  I'll try looking for what pre-amps are in it.  I know fuck all about plate voltage and what not. 

[Hemisaurus]

If schematics aren't your thing several places have layouts and wiring diagrams, more of a connect the dots idea.

[Baltar]

Awesome, there's a guy in town here that I might email about it.  He lives like 5 mins from me.
Here's what's in my pre section:

6C4/EC90, 12AX7/EC83 & 6EU7

[Hemisaurus]

Interesting. The 6C4 is a 7 pin single triode, the other two are nine pin dual triodes. You'll be a triode stage short for a true plexi. You could make a 2 input version, instead of a 4 input, so saving a tube stage.

[Baltar]

It just has 1 input in the back.  I don't need this to be a matching numbers Plexi blah.  I'd just like to get some 34's in there for more mids and a British sound.  If a Bassman is supposedly close to a Plexi, then this can't be an imposible change.