Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bnwitt on May 21, 2014, 12:19:37 pm
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I'm looking at putting together an 18 watt out of my stash of parts for a friend and one of the things I've always hated about the Ritchie's improved layout is the fact that the tremolo takes it's sweet time turning on and off when you step on the foot pedal. I noticed Sluckey had a tremolo fixing layout of his own and I'm wondering if it improves the on/off problem or just eliminates the ticking. I never had ticking with Ritchie's layout, just the slow on/off. Anyone know?
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The stuff I did to the trem circuit was all about fixing the 'tick'. Just a band aid. That's always been a finicky trem circuit even though it does sound good.
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Steve,
Thanks for the reply. I had a feeling that was the case. Well it is what it is I guess.
Barry
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Barry, FYI, the trem on the AC-15 is also slow to start.
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Merlin shows a position for adding the footswitch (http://www.valvewizard.co.uk/trem1.html) which is supposed to help the oscillator start faster. But others have said here before (http://el34world.com/Forum/index.php?topic=12102.msg112461#msg112461) that this circuit may not start instantly.
What PRR alluded to in the thread was that the Fender amps with fixed bias have a jump-start circuit: rather than grounding the oscillator to turn it off, they un-ground two resistors that are normally grounded. In addition, when those resistors are un-grounded, the oscillator grid gets the full raw fixed-bias voltage. At turn-on, the needed ground is applied to the resistors in the phase-shift circuit, and the tube goes from hard-off to full-on. A serious enough kickstart to insure the oscillator fires right up.
Since the 18w is cathode biased, you'd have to create a negative voltage supply. Maybe voltage-doubler supply off the 6.3v winding? Or a simple bias supply fom the high voltage winding? It would seem like -15 to -30vdc would be more than ample.
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sluckey, will those tremolo caps you added on your 2006 18watt work to stop ticking on any trem circuit?
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no
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I'm looking at putting together an 18 watt out of my stash of parts for a friend and one of the things I've always hated about the Ritchie's improved layout is the fact that the tremolo takes it's sweet time turning on and off when you step on the foot pedal. I noticed Sluckey had a tremolo fixing layout of his own and I'm wondering if it improves the on/off problem or just eliminates the ticking. I never had ticking with Ritchie's layout, just the slow on/off. Anyone know?
Barry,
I have an 18 Watt chassis and iron all wired up. The board can be changed but it is a 1974X faceplate.
Let me know if you are interested.