Dating vintage jbl d130f speaker
The main focus of this article will be speakers found in Fender amps, but before we get into that topic let’s go over a few other areas first.Early silver face amps: Part 2 went into this topic in some detail, but since that article was printed, I have been asked a of questions about this subject.The amps during this period could have the earliest style silverface grill cloth or the more familiar silverface grill cloth.
Bad because cathode biased amps run very hot especially those with four power tubes (witness the Vox AC-30).
Also, the different component values could be due to a necessary substitution on the production line when a particular value was out of stock. These changes have been observed on tweed, brown/blonde, and blackface models.
Often the differences are minor such as small changes in resistor or capacitor values.
These amps have AB763 tube charts and normally any silverface amp made prior to May 1968 will have the AB763 (a.k.a. After April 1968, most of the big Fender amps received the AC568 circuit, which is a semi-cathode biased design.
However, these two Showman amps have a fully cathode biased design that is factory stock!!!