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ampage archive
Vintage threads from the first ten years
weak trem on silverface princeton
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 9/27/1997 7:59 PM |
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robert hinson |
weak trem on silverface princeton hey guys, i got a silverface princeton that a very weak trem intensity. all the parts are ok and a change in driver tube did not help. as you know, these amps modulated the power tube to get this effect as opposed to the deluxes, etc. which used the LDR. as i said all parts appear ok and voltages are ok too. any ideas? |
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| 9/28/1997 6:45 PM |
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| J Fletcher | The weak trem is inherent in the design.The oscillator is directly coupled to the output grids and it doesn't have enough power to produce a very deep trem.If you added another triode stage after the osc , set up as a cathode follower,you could get a nice deep effect.You could change all the coupling caps in the osc cct and see if there is any improvement,but normally the intensity is on 10 to get a moderate effect....no deep trem on these babies |
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| 10/3/1997 7:06 PM |
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| moocow | The Princeton uses a 1M resistor to feed the LFO signal to the depth control. Change this to a 470K or even 220K resistor, which is used in the brown Vibroverb and other amps. You can also increase the amount of tremolo drive by increasing the .1 uF coupling cap to .47 uF, but the resistor should be sufficient (and cheaper). Even without a cathode follower this circuit will properly modulate the output tubes of a 6L6 amp. This circuit works very well in my much-modified ’72 Twin Reverb. When the tremolo is activated, it is an impressive sight to see all four output tubes flashing blue in unison ! Gibson, Ampeg, and many other amps use bias modulation tremolo. Study those circuits and see how it is applied to fixed-bias as well as cathode-bias designs. |
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