Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Ross on November 09, 2021, 06:52:37 am
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In the Amperex spec sheet for the 5AR4 tube, current limiting resistors are called for in capacitor filtered circuits though I've yet to see them in guitar amp schematics. Am I missing something?
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Vintage transformers were designed to incorporate such resistance into the HT winding. With modern transformers, you have to check. It’s perceived as a bad thing for transformers to get warm in use, so manufacturers seem to try to reduce such copper losses where feasible. I’ve seen some modern amp designs with additional resistors.
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Am I missing something?
I take it you read 1/2 way down this page? http://www.valvewizard.co.uk/bridge.html
I think 'traditional' guitar amps didn't have these because tube rectifiers (and PTs) are generally rugged enough to handle abuse. (Plus current limiting resistors on the HT winding steal a bit of B+ voltage)
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Vintage transformers were designed to incorporate such resistance into the HT winding. ...
I think 'traditional' guitar amps didn't have these because tube rectifiers (and PTs) are generally rugged enough to handle abuse. ...
I used to own a 1964 Deluxe Reverb. I measured its power transformer, and it had significantly higher winding resistance than modern replace PTs. I also didn't get the undesired-high-B+ voltage, and found that amp expected 120vac on the primary.
I suspect the higher winding resistance gives a subtly softer attack to the sound, as it would contribute slightly to sag/compression.