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potentiometers) and those used in the original amplifiers (Vishay/Dale RN65 precision metal film resistors, 1W
carbon film resistors, SBE 6PS polyester film capacitors, high-quality ceramic disc capacitors, Belton tube
sockets, Alpha potentiometers). We prefer high-quality enclosed Cliff (built in the UK) jacks to the open-style
Switchcraft jacks used in the originals and many clones. Finally, we occasionally use NOS components from
our vast surplus parts collection in locations they work well and complement the voicing or enhance the
performance of the amplifier.
I’ve read about something called a PI trimmer inside of the amp. Does the Tweedle Dee have it, and what does it do?
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Yes, the Tweedle Dee amplifier has a PI (short for phase inverter) trimmer. This is part of the original design
that controls the balance of the signal sent to each of the power tubes. Different settings on this control are
very subtle, and are typically monitored with an oscilloscope and not ears.
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We highly recommend the use of a non-conductive rubber screwdriver, and only adjust the trimpot when the
amplifier is not powered and disconnected from the wall outlet. DO NOT ADJUST THE PI TRIMMER WHILE
THE AMPLIFIER IS ON! Note that the power supply capacitors in the amplifier can/will still store charge, and
you can still be bitten by 450VDC even though the amp isn’t connected to the wall! Adjust the PI TRIMMER
only at your own risk!
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On the next page, there is a picture with an arrow. The BLUE arrow is the PI trimmer. If you are so inclined,
this is where you make your adjustment.
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Adjust this with a non-conductive screwdriver ONLY!
Adjusting that PI trimmer sounds intimidating. Am I missing anything if I don’t experiment with them?
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Absolutely not. We adjust each trimmer to ensure the best results for each amplifier leaving our shop.