Slimharp
422 posts
Jun 26, 2016
6:56 AM
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I know this has been covered numerous times. One more once. Can you replace the solid state rectifier with the 5U4G tube and not install a bias pot and re-bias. I dont want to fry something !
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Barley Nectar
1233 posts
Jun 26, 2016
8:13 AM
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Yes. A 5U4 has a voltage drop of aprox. 50VDC. An SS recto will drop 2-5VDC. So, with the 5U4, your overall circuit voltage will be lower. This lower voltage on the power tubes will translate into lower current flow and lower wattage dissipated.
I did this to my 95 Bassman RI and by running the 5U4, the amp is now running dead on the voltages speced by Leo Fender for the 59 Tweed Bassman. I also changed V1 to a vintage 12AY7 as per Leo. These are the ONLY changes I made to my Bassman and it sounds wonderfull! Go for it Slim...BN
Last Edited by Barley Nectar on Jun 26, 2016 8:15 AM
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Slimharp
423 posts
Jun 26, 2016
8:56 AM
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Thank you Barley. What is in the pre-amp now is - V1 Sylvania 6072. V2 12AU7 no name visible. V3 GE 5751. Power V4&5 Older Groove Tube ( Marked Glendale Ca. )6L6's
What mid price 5U4G would you suggest ? Are these preamp tubes ok to run. I had Svetlanda Winged C 6L6's in my other RI and it really smoothed it out, but pricey. All in all I dont mind paying for good tubes but not way high end. The amp as is sounds decent but a little harsh and trebbly around the edges. Stock Blue frames in it. Thanks - I appreciate your input.
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Barley Nectar
1235 posts
Jun 26, 2016
9:17 AM
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I would go with NOS, many good ones out there. Last I checked still reasonably priced due to ample availability. I also have the blue frames. Your tubes are fine if you like the tone. Nice amp...BN
Last Edited by Barley Nectar on Jun 26, 2016 9:19 AM
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