Tech question

[stanjanssen]

Hi,

Does anybody know the usual input impedance on a guitar amp / combo? I'm not talking about an extension cabinet, but just the thing you plug your guitar into...

I use a valvetronix ad30vt amp by the way, but I guess the impedance should be quite standard?

Thanks,
Stan.

[ggunn]

Originally Posted by stanjanssen

Hi,

Does anybody know the usual input impedance on a guitar amp / combo? I'm not talking about an extension cabinet, but just the thing you plug your guitar into...

I use a valvetronix ad30vt amp by the way, but I guess the impedance should be quite standard?

Thanks,
Stan.

It's high, on the order of 100K or a megohm.

[Light]

Originally Posted by ggunn

It's high, on the order of 100K or a megohm.

Good lord, no. It is high, but more like 5,000-10,000 ohms. Piezo pickups (without a preamp) are on the order of 100,000 ohms.



Light

"Cowards can never be moral."
M.K. Gandhi

[ggunn]

Originally Posted by Light

Good lord, no. It is high, but more like 5,000-10,000 ohms. Piezo pickups (without a preamp) are on the order of 100,000 ohms.

You would know; I stand corrected.

[Ed Dixon]

The input impedance of amps varies from a few thousand ohms to 50K to 100K depending on brand and model. All of these are considered high impendance. The ones I own vary from 10K to 50K (based on product specs)

The inpedance of the input device is separate. Most guitars are high. Other devices vary.

Ed

[stanjanssen]

Thanks

Stan.

[demosthenes]

Originally Posted by Light

Good lord, no. It is high, but more like 5,000-10,000 ohms. Piezo pickups (without a preamp) are on the order of 100,000 ohms.



Light

"Cowards can never be moral."
M.K. Gandhi

I think you may be thinking of the output impedance of a pickup. Many tube guitar amps do have input impedance approaching 1 megohm. Solid states tend to be a bit lower, but certainly at least 100kohm, to bridge the output impedance of guitar pickups and keep good tone. A guitar amp with input impedance much lower than that would start to have high-end loss.

[Levinin]

Should be somewhere between 50k and 1M ohm - the higher the better.

To maintain a good signal the 'ideal' is to have no output impedence and infinite input impedence. Because guitars have output impedence in the 10k's you need a very high input impedence to even pretend to have a good ratio.

[bongolation]

Originally Posted by demosthenes

I think you may be thinking of the output impedance of a pickup. Many tube guitar amps do have input impedance approaching 1 megohm.

You're correct.

[Light]

Originally Posted by demosthenes

I think you may be thinking of the output impedance of a pickup. Many tube guitar amps do have input impedance approaching 1 megohm. Solid states tend to be a bit lower, but certainly at least 100kohm, to bridge the output impedance of guitar pickups and keep good tone. A guitar amp with input impedance much lower than that would start to have high-end loss.

Could be. I don't really work on amps, but I guess I assumed they would be about the same.


Light

"Cowards can never be moral."
M.K. Gandhi