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  1. B

    The "$250" Amp? - 6LU8 Compactron SE, UL

    When you switch your power switch on you get no voltage after the switch? I suspect you are not measuring correctly. Since your filaments all seem to be working you must be getting ac to the transformer. If you are getting no DC to the capacitors you probably have the rectifier wired...
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    The "$250" Amp? - 6LU8 Compactron SE, UL

    DC is what makes the tubes work and enables them to amplify. The purpose of the PS is to convert the house current (120 VAC) into the B+ (300 VDC). In layman's terms, the DC goes out through the part of the PS schematic marked B+ to the output transformer and the tubes, through the tubes and...
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    The "$250" Amp? - 6LU8 Compactron SE, UL

    The ground and B+ can never connect with each other directly, but only through a load of some type like a tube, resistors, capacitors (sort of, they are not actually a load) etc. In this PS schematic the capacitors are the only thing between B+ and ground. Note that capacitors block DC, which...
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    The "$250" Amp? - 6LU8 Compactron SE, UL

    I've since taken mine apart so no pics. Even if I had some I'm not sure it would help. The pin numbers on the sockets are always hard to read in person let alone from a picture. Building an amplifier is all about unifying 2 documents - the schematic and the tube diagram (pin-out). On my very...
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    The "$250" Amp? - 6LU8 Compactron SE, UL

    Adding volume control There are a couple ways to do it. One simple way is to install a 100k audio taper pot between the input RCA jacks and the first section of the tube. I suggest you search the web for single ended amp schematics that use a volume pot to see how the volume control is...
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    The "$250" Amp? - 6LU8 Compactron SE, UL

    Has anyone implemented a volume control? I'm using your basic 100k pot to ground as a volume control on this project, but I get a high level of distortion at anything but full volume. Anyone experience similar? Also, what is the sensitivity of the amp when built as drawn? Is it somewhat low...
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    The "$250" Amp? - 6LU8 Compactron SE, UL

    Thanks both for the comments. I'll admit to wondering if it is worth the trouble. I do plan to hook up per the drawing before I start experimenting. I need to get a baseline even if it won't be A/B back to back. Unfortunately I'm working with the Hammond 124ESE, so can't easily duplicate...
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    The "$250" Amp? - 6LU8 Compactron SE, UL

    OK, new topic: Direct coupled design Glad to see there has been a little action on this thread. Very cool. I'm thinking this tube offers good possibilities for a direct coupled design. I've never built one before but I think i'm going to have a go. With both tube sections on the same...
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