I don't see a lot of posts on Germanium transistor amplifiers, and wanted to throw a shout out to a really cheap, fun, area ready for learning and experimentation-
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 a dismal source, don't let that turn you off- the amplifiers present a great opportunity to study vintage designs that use these early transistors. Easily restored and modified, the result can sound unique, amazing, different, whatever you are in the mood for. These really are hidden gems- because 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 fairly high quality in a compact package- Generally 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.
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 directly here ) 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 design examples worthy of study.
You can look up your desired make and model using the free SAMS Annual Index Volume 1, 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, ranked lowest cost first. Generally 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 maybe balance, with no radio. 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:
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.
Anyway, happy hunting, and please share you results or thoughts.
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 a dismal source, don't let that turn you off- the amplifiers present a great opportunity to study vintage designs that use these early transistors. Easily restored and modified, the result can sound unique, amazing, different, whatever you are in the mood for. These really are hidden gems- because 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 fairly high quality in a compact package- Generally 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.
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 directly here ) 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 design examples worthy of study.
You can look up your desired make and model using the free SAMS Annual Index Volume 1, 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, ranked lowest cost first. Generally 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 maybe balance, with no radio. 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:
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.
Anyway, happy hunting, and please share you results or thoughts.
Sure a LOT of cheap 70's 8-track players with fun working class-AB germanium transistor amplifiers inside available on ebay right now.