Voltage and current distortion point of steel amp inputs?

Keith Hilton · From: 248 Laurel Road Ozark, Missouri 65721

Nowdays, the majority of players have one or more effect units between their amp and their guitar. Every powered device in a signal chain, even battery powered devices, create signal gain. With powered devices in a signal chain, it is easy to overdrive the input of an amplifier. You don't have to know anything about electronics to understand the old story about the straw that broke the camel's back. What happens, at some point, when adding, or turning up,powered devices in the signal chain? Easy answer--distortion. The more gas you pour on a fire, the bigger the fire gets. The more signal you feed to the amp at the distortion point, the more intense the distortion gets. Many of you have, and know how to use, a multi-meter. At what point of voltage and current readings on a multi-meter does your amp's input start to distort? Voltage reading? Current reading? I would say that would be a GOOD thing to know. Of course the high impedance input, and low impedance input, on amps will distort at different levels. If you guys knew at what level your amp would start to distort, you could measure the end of your signal chain. Then you could see how close you were to the point of distortion. I would like to know the voltage and current readings on a multi-meter that makes all the different amps distort? Peavey Amps, Fender Amps, Evans Amps, ETC. Of course, the amount of voltage and current at the end of your signal chain would depend on how high you had the signal strength set on each device in the signal chain. For example: A Peavey Pro Fex II has a input and output signal strength control. Some cheap floor effect units have no way to control either the input or output signal strength. Get out your multi-meters and give me some readings? I am interested in knowing how close you are to over driving your signal in terms of voltage and current. Should be pretty easy to measure, since most muli-meters will give a read out in mili-volts and mili-amps.

David Doggett · Posted 25 Feb 2008 8:53 am

Pedal steel players and many lap steel players use a volume pedal. That would seem to have a major effect on your question. I think most of us attack notes with the VP backed off halfway or more. We only approach the full throw of the VP when the string vibration is dying out, and there is very little signal coming out of the pickup. So to get a realistic reading of what is going to the amp, you would have to have the VP set approximately where it usually is set when notes are attacked. I have been puzzled when some people have complained that pedal steel pickups are too strong and overdrive some amps. Are they taking into consideration the volume pedal effect?

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Really good devices that aren't meant as preamplifiers or overdrives should posess a near unity gain. Still, even with only 1 db gain, if you keep multiplying it through 5 or 6 EFX, it can cause problems. Some amps have an input control ahead of the first stage, but if one doesn't, it's no big deal to add one. As to coming up with useful voltage readings, it's very difficult due to the many dynamics involved. Line voltage and regulation, how hard you pick (dynamically), and also what kind of programming you're generating (Chords? Expanded chords? Highs? Lows?) all have an effect.

Also, I feel that measuring voltages to determine whether or not you're getting distortion is rather pointless...you either hear distortion, or you don't. If your signal sounds fine, but the reading says "you're distorting", then what 'ya gonna do? If the signal sounds distorted, but your voltage reading is in spec, what do you do then?

At some point, we should forget test equipment and just use our ears.

Keith Hilton · From: 248 Laurel Road Ozark, Missouri 65721

Donny, I think you are right. I couldn't get what I wanted to measure just picking my guitar. I wound up hooking up a sine wave generator to get a constant signal. I could then slowly turn up the amplitude of the sine wave generator, and measure the voltage at the end of the signal chain. As you say Donny, it is pointless. There are so many variables involved it won't work. As you say Donny, your ears work best.

Jim Sliff · From: Lawndale California, USA

Yeah, it's very hard to match a 'scope output to what you actually hear when using devices....and "gain" doesn't necessarily mean distortion; there are too many other factors involved. So yes - ears are the best guide.

One thing most players DON'T know is that any. many effects devices have trimpots inside - some for other reasons, but quite a few for gain adjustment. You can completely alter the sound of your guitar coming through a bunch of effects by tweaking one "swirly" pedal so it has unity gain.
_________________
No chops, but great tone
1930's/40's Rickenbacher/Rickenbacker 6&8 string lap steels
1921 Weissenborn Style 2; Hilo&Schireson hollownecks
Appalachian, Regal & Dobro squarenecks
1959 Fender 400 9+2 B6;1960's Fender 800 3+3+2; 1948 Fender Dual-8 Professional

Bo Legg · Posted 29 Feb 2008 4:32 pm

Old PSG proverb: Stick all your F/X rack and pedals up your as and you will know how your amp feels.

Jim Sliff · From: Lawndale California, USA

Bo, what in the heck was that supposed to mean?
_________________
No chops, but great tone
1930's/40's Rickenbacher/Rickenbacker 6&8 string lap steels
1921 Weissenborn Style 2; Hilo&Schireson hollownecks
Appalachian, Regal & Dobro squarenecks
1959 Fender 400 9+2 B6;1960's Fender 800 3+3+2; 1948 Fender Dual-8 Professional

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Keith, for what it's worth, I can get a signal of around 3/4 of a volt (750mv) by just strumming my guitar. That's a lot more than I expected!

Lotta variables, yes. But Drake's equation has a lot of variables too, and many still think it's valuable.

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