So why is it some amps take pedals better than others?

Some amps have so much headroom that all a pedal does is sit on top of the sound - it never blends in with it. Nobody likes the sound of an amplified pedal.

 

Not exactly true, what about those Groove Tubes amps that had a ton of headroom that were designed to work with O/D pedals?

I'm no expert, but I think the input impedance has a lot to do with it.

 

I'm surprised about the SLP, though, mine sounds great with pedals. The problem is that you have to have the amp cooking so that it's distorting enough to round off some of the square wave from your fuzz into nice low order harmonics. With an SLP, that means earplugs and no neighbors/wife. Are you trying to run it clean and then distort with pedals? If so, you'll probably have better luck pulling two tubes and using an attenuator to throttle it down just a bit...

 

Input impedance?

The same guitar going through the same cable going through the same pedals at the same settings would have a fixed amount of input impedance. If what you suggest is true, if you plugged that very guitar into a dozen different amps they would all take to pedals in EXACTLY the same way because the input impedance is EXACTLY the same.

Sorry, that just doesn't add up to me.

 

i think he meant the imput impedence of the amp. you were talking about the output impedence of the guitar/pedals.

at least according to the groove tubes info, most amps are designed for a high-impedence input signal, coming straight from a guitar. but since a lot of people use pedals that convert the signal to low impedence to buffer the signal, groove tubes designed their amps for a low-impedence input. see http://www.groovetubes.com/pdfs/S45_Manual.pdf. i don't know the technical reason why/how that makes a difference in how an amp responds to pedals, but i do own a soul-o 45 and can say it takes pedals extremely well.

... also, some pedals like cornish are designed to be run into clean amps.

 

One big factor is in the use of bright caps in the amps. Some amps (blkf fenders) will have them on a switch, but others will have them hard wired in. While they might be adding just a little sparkle to the amp they can really fizz out an overdrive pedal because of the extreme harmonics overdrive produces. The bright cap will just take those harmonics and launch them skyhigh giving a very harsh and fizzy tone. One of the reasons an amp might take a pedal better when turned up a bunch is the fact that the volume control will cancel out the effects of the bright cap when it's turned up there. Then of course there's the whole thing about the amp distorting and blending in with the pedal to thicken things up.

You can have a bright sounding amp that works good with pedals. To me it's about designing an amp that doesn't lose it's high end in the circuit forcing you to artificially create it - which can skew it out of control if you're not carefull.

Later, PaulC

 

Headroom and voicing seem to have a lot to do with it. To me, pedals sound best when you're able to set your amp in it's sweet spot... That is, you've got the amp turned up enough to be creating some sweaty magic of it's own, and then you use a pedal to take it over the top. If you've got the amp turned down to low, most pedals sound transistory and anemic to my ears. If you've got the amp working super hard already and you hit it with a pedal, you get sonic mush, and lack of definition on the lows is the biggest problem here, but that could be just what you're looking for if you want that "amp about to explode" sound.

Voicing also impacts the amps relative pedal-friendliness. As others have said, bright caps can really make pedals running into the amp sound like buzzy noise. If you've got an amp with a midrange hump, and you hit it with a tubescreamer, guess what -- midrange mud. If you hit an already bassy amp with a pedal that has a good amount of low end in it's EQ, that too could be too much.

You can almost always find a pedal to compliment the amp your using if you set it up right.

 

I mean the *input* impedance of the amp.

I think PaulC is onto something there.

 

That's strange. It's my experience that plexi Marshalls take pedals better than any other amp I've played. However, if you are plugged into the bright channel of a Superlead plexi it will be too bright for a lot of pedals, try then Normal channel.

Kelley

 

This would be a conundrum for me, beign that I like the Bright channel of a Marshall better. I couldn't do that, because I wouldn't have the tone I want with the pedal off. Then the question becomes "which is more important to you, the pedal or the amp?"

I've always found Dr Z amps take pedals better than anything else I've tried. Don't know why though ....

 

Yes.

AND

They would all sound different even with
the same settings because EVERY circuit is different even among amps down the same assembly line. Same components, same layout, same assembly, some will sound great, some will be good, and some might have a fault. It is called Variation and every system has it.

AND all the tubes have slight variations too.

Even the taper of the pots are all slightly different.

Oh and the power from the wall is in flux too.

Don't forget your neighbors or businesses,
when their ACs turn on the bias readings
on my amps change too. So do yours.
Not by much, but they do. Sometimes a few mA.

Food for thought.

 

Actually no, I only said to use the normal channel as a quick fix. You can peal back some of the brightness of the bright channel and it will still sound sound like a superlead Marshall, just reduce the value of the treble bleeder cap around the volume pot to 680pF, then insert a 180K resistor in series with it, then locate the resistor/cap right off the wiper of the volume pot, lift one side of that cap and insert a 150K resistor in series with that cap, (I've played around a lot to determine these values), this will reduce the effect of those caps, but not so much that it no longer sounds like a Superlead, pedals will sound better. But before doing this just plug into the normal channel to see what you think, there is really very little difference between the bright and normal channels, tweaking a few components in that area and you can dial in the sweet spot. But if you don't know how to work on amps have a pro tech do it for you.
Kelley