| Reducing amp volume [message #27264] |
Wed, 12 April 2006 11:02  |
Shane
Messages: 1117
Registered: May 2009
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Illuminati (3rd Degree) |
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I've got a Peavey 5150 combo that I used to use when gigging that I seldom use anymore. About once a month I turn it on for 2-3 hours, maybe playing through it for 1/2 hour or so to keep the caps in shape. Problem is that this amp is soooo loud and has tremendous gain that it just can't be played at low volumes and sound right (even at a setting of 2 on the volume this dude is loud and doesn't really "sing" until you hit 5). I seem to remember years ago that Marshall made a unit you could put between the output and speakers to drop the volume levels, but still be able to use all the gain of the amp to keep that nice, saturated distortion you get when cranked up. Anyone have any suggestions on how to accomplish this?
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| Re: Reducing amp volume [message #27265 is a reply to message #27264] |
Thu, 13 April 2006 06:31  |
Damir
Messages: 1005
Registered: May 2009
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Illuminati (2nd Degree) |
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Reduced volume can be obtained in various ways - switching output tubes to triode operation, switching off one pair of output tubes (when amp has 4 tubes), reducing anode/g2 voltages (by some kind of autotransformer, or switching trafo taps) while keeping heater voltage the same, etc.
Some manufacturers have "speaker emulators/attenuator" units, but we have different opinions about safe use of them, especially with simple, resistive units.
The simplest method for reducing output power is resistive attenuator. For example, your speaker cabinet is 8 Ohms (check it), and amp "gives" 50W to it. It means 20V/2,5A on the 8-Ohms speaker. We can connect the power resistor of 8 Ohms/25W in parallel with speaker, and another resistor of 4 Ohms / 50W in series with this combination (between the amp, and speaker + 8-Ohms resistor in parallel). Now, amp "sees" 8-Ohms load as before, but only 12,5W reaches the speaker. We dissipated 25W in 4-Ohms resistor, and another 12,5W in 8-Ohms resistor. You can build a small metal case with two jacks (one to the amp, another to the speaker) and resistors inside, connected on the chasis (heatsink).
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| Re: Reducing amp volume [message #27310 is a reply to message #27290] |
Wed, 26 July 2006 19:13 |
Shane
Messages: 1117
Registered: May 2009
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Illuminati (3rd Degree) |
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Is your reply to everything completely IDIOTIC? I've been using tube guitar amps for 20 years. I think I know how the damn volume control works, and the gain control. Anyone who knows anything about tube amps and distortion realizes that the best sounding saturated distortion when playing full on rock (ie. Megadeth, etc...) happens when the tubes are pushed hard. Can't do that at a low volume and get the correct "tone", especially with this amp. And unless you own a 5150 combo or similar high gain amp don't make any more stupid suggestions.
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| Re: Reducing amp volume [message #27315 is a reply to message #27313] |
Thu, 27 July 2006 21:41 |
Shane
Messages: 1117
Registered: May 2009
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Illuminati (3rd Degree) |
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Exactly. The trick is to be able to do it without burning the amp up. Blowing out the trafo's and power tubes. It must have something to do with keeping the impedance right.
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