I have been tinkering lately with the 12V germanium amplifiers found in extremely affordable 8-track automotive decks from the late 60's and early 70's that can be found at yard sales or on Ebay for under $30 including shipping. While 8-track tape is generally a dismal source, don't let that turn you off- the amplifiers present a great opportunity to study and experiment with vintage designs that use these early transistors. Easily restored and modified, the result can sound unique, amazing, different, and surprisingly good quality. These really are hidden gems- because for a pittance they include all of the impossible to find parts (the interstage transformers, thermistors, and matching sets of germanium pre and power transistors) all in one functional package, usually working fine even if the tape deck is dead.
These amplifiers are typically designed and built in Japan, so are often high quality in a compact package- Usually stripped down to the most basic elements to save cost and area, but using high quality components. They are, however, pretty low power- With only 12-14V car battery voltage to work with, a class AB can only generate about 4-5 Watts per channel even into 4 Ohm speakers. This is not enough for full-room listening, but it is perfect for near-field listening on a desk top or bookshelf, headphone amplifier, or a little test amp.
I reworked one of these as a learning exercise into a small stand-alone amplifier that I detailed in my "Germanium Bake King" project:
https://classichificare.com/viewtopic.php?t=2984
- Kraco 8-track Reborn as Germanium Bake King
You can find FREE service literature for many such auto radio designs at the World Radio History website. Just search for "SAMS" at the main site, (or see the SAMS listings link below ) and you will find a great many volumes of the SAM's "Auto Radio Series" included there among the SAMS bookshelf. The Auto Radio Series was a long series of periodic books, each volume of which included service literature for a dozen or so various recent models. These books alone are a treasure trove of free service literature and design examples worthy of study.
World Radio History: https://www.worldradiohistory.com/index.htm
SAMS Listings: https://www.worldradiohistory.com/BOOKS ... f_Sams.htm
You can look up your desired make and model using the free SAMS Annual Index Volume 1:
https://www.samswebsite.com/downloads/A ... 1_2002.pdf
which covers all SAMS models from 1946 through 2001. If the SAMS number starts with "AR-", it is in one of these Auto Radio Series books and =MAY= be there for free at the World Radio History library.
Here is the eBay search string I usually use to find good cheap automotive 8-track players:
https://www.ebay.com/sch/i.html?_nkw=8+ ... =1&_sop=15
ranked lowest cost first. For a germanium amplifier you will want to look for a deck that is 8-track only, usually an earlier looking design, the more chrome the better.
It should be from the late 60's or early 70's, with a boxy rectangular "under the dash" design (Not the two-shaft through the dash design). You should see only volume, tone, and balance, with no radio dial. Once you get into the late 70's with AM or AM/FM designs they have moved on to silicon transistors or integrated circuits- also fun, but not my focus here. If you want to be really sure, find the ones where you can see the power transistors mounted on the outside of the rear panel like this Kraco:- Rear of original Kraco KS-408A 8-track (w/Transistors)
You might even be able to see a transistor number and look it up. Even if you can't see the transistors on the outside, if it's 8-track only, you stand a good chance, and it is worth finding one with the transistors inside, as they will likely be fresh and clean looking like new, unlike the external ones that are often corroded.
Anyway, happy hunting, and please share you results or thoughts. -Warren
