Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: VintageAmps on September 25, 2020, 02:05:31 pm
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Ok , you experienced guys, I still have the original 65 deluxe reverb on the bench. I have it hooked up to its speaker using guitar cable out of the speaker jack and clip leads from other end of guitar cable to amp speaker. With all controls turned down , and no input to amp , amp is quiet when advancing volume controls to 10 on normal or vibrato channel. With volume control (one at a time) to 10 and then advancing treble control for that channel, I hear an increasing amount of what I describe as white noise. Does this sound like normal operation. I believe it is but wanted to double check with others.
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You should never use a guitar cable for driving speaker. Wire are too small and guitar cable have some impedance speaker cable have not.
Use right cable .
White noise ....What amount ? Amp may be normal or some 12XX7 plate resistors are noisy.
It's happened sometimes on old amp.
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I suspect it's "normal", not much chance your "cable" is a cause since it's long way from pre stuff
Like Latole says, could be hissy plate R, I'd evaluate it with guitar, if you don't hear the noise with amp n guitar on 10 it's not a problem :icon_biggrin:
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Thank you both for the reply. When I got home this evening I moved the chassis off the bench and put it on top of the DR cabinet. Plugged the speaker directly into speaker output and noise is virtually non existent with no input to amp. Plugged my old Gibson es 335 (1974) in and with guitar volume up to 7 very quiet , start getting some hum after that which can be partially cancelled by turning guitar to different angle. which is actually fairly normal for this guitar.
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Everything hisses if Gain is high enough. With Treble full-down, you can hardly hear it. So this part makes perfect sense. And is meaningless. Put the knobs AT the expected normal positions. (Which may mean a guitar and a large room, not "nothing" in a bedroom, to learn what 'normal' is.)
Some hi-fi amps will go banana driving more than a few feet of coax. Radio-frequency, you hear nothing, but may smell burning parts. "Most" tube guitar amps are not that high-strung, but I'd be real careful on some Sunns, and any transistor amp. I used to keep a 1/4 plug on zip-cord dedicated to hay-wire speaker experiments.
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Realizing I may not always have access to the cabinet and speaker what do you recommend as a shop setup. Do you have a couple of speakers say a 16 and a 4 ohm impedance that can be matched down to an 8 or 2 ohm impedance?
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just thought a couple of 8 ohm speakers and you could wire them in series for 16 ohm or in parallel for 4 ohm.
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Personally, I have an 8 ohm speaker in a small cab, and a 4 ohm in a bass amp cab, that's generally what I use for testing.
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AmberB , thanks for sharing your setup. The majority of my past electronic experience has been in 800 MHz trunked radio. Did not worry to much about delivering anything but voice and data in that field.