If you deduct the cost of the volume knobs I've specified (knobs weren't included in the original kit) the amplifier project can be built for about half the adjusted cost of the project kit offered by Radio Shack in 1969. The economic value of $9 in 1969 is equivalent to around $61 today. To put that cost in perspective, the 8 Transistor Stereo Amplifier kit was introduced in 1969 at a retail price of $8.95. Total cost for all new parts in small quantities is around $40 not including tax and shipping.
![old graymark radio old graymark radio](https://www.smecc.org/rest_of_images/grayma1.gif)
All components are available from Mouser or Digikey, or can be obtained from other suppliers that may be more convenient to your geography. Review the parts list and obtain the components indicated. Obtaining parts for the Stereo Amplifier project You might want to include some of the suggested modifications during construction or dream up your own before you start. If you are familiar with breadboard construction techniques, you can probably complete the project in a single evening.īe sure to read through the "Tweaks and Hacks" section before you order parts and start building. I built the kit in two evenings, taking my time, and double-checking my progress while following the manual. The specifications I obtained from the amplifier I built were: 00000001% THD to fill a room with good tunes. As you can tell from the video demonstration at the beginning of this article, you don't need 1000W at. I was very pleased to have ended up with a nice little "vintage" amplifier that produces room filling sound when connected to an efficient speaker system. The result of that work is the subject of this article. All I needed to do was redesign the kit for silicon transistors, improve the push-pull bias circuit, and limit high frequency response to something reasonable. The Radio Shack kit used a push-pull direct coupled design, found only in "serious" Hi-Fi equipment at the time which eliminated the transformers. These transformers simplified the amplifier circuit but they added weight and limited low and high frequency response. Most cheap amplifiers in 1969 used at least two coupling transformers.
![old graymark radio old graymark radio](https://i.ebayimg.com/images/g/jAcAAOSwEAtdCjNr/s-l800.jpg)
In addition, the amplifier kit was one of the most complex in the catalog and probably didn't work very well which would have been disappointing given it's cost.Īfter reading the transistorized Hi-Fi article referred to earlier and reviewing the available documentation on the 8 Transistor Stereo Amplifier kit, I wanted to build one. The reasons are unclear, but I suspect the germanium "matched pair" transistors were expensive and hard to source. In 1969, an 8 Transistor Stereo Amplifier kit was released but withdrawn in 1972. The first P-Box kits released in 1968 looked suspiciously like those sold by Eico under the Eicocraft brand but quickly expanded (Radio Shack sold experimenter kits from Eico, Knight, and Allied Radio until 1973). These were great kits containing all the electronic components, wire, and perfboard needed to build a useful electronic device. In 1968, Radio Shack introduced it's first P-Box kits marketed to the electronics experimenter. But we still have vacuum tubes in our microwave ovens.
#Old graymark radio full#
The CRT display, a giant glass vacuum bottle filled with tin, copper, zinc, cesium, silver, and lead didn't leave the scene until the first decade of the 21st century, replaced by a flat glass screen full of transistors. Far from an explosion, the shift to transistors and the obsolescence of the vacuum tube required decades. The transistor had to pick it's battles against the vacuum tube while new materials and manufacturing processes were being developed.
#Old graymark radio portable#
Except when you needed thousands of them for a computer, then they weren't so great.īy the 1960s, the transistor had finally found it's niche in portable and mobile AM radios, Hi-Fi stereo systems, computers, and telephone repeaters while vacuum tubes continued to carry the day in high frequency radios, RF power amplifiers, and high voltage switches. Sure the vacuum tube was large and inefficient, but it could do just about anything that needed doing at the time. Many engineers were struggling to figure out what the transistor was good for outside of miniature hearing aids or signal conditioning in diode logic circuits. Transistors in the 50s were hard to manufacture, noisy and unreliable, and when they worked it was only at low frequency and very low power. Often, success depends on convincing your boss that a certain idea or process is worthwhile.
![old graymark radio old graymark radio](https://i.etsystatic.com/22602312/d/il/75ac0d/3177443547/il_340x270.3177443547_2x34.jpg)
This article provides a nice back-stage view on how electronic design is carried out. While doing some research on the transition to solid state devices I encountered a really interesting article on the worlds first Transistorized Hi-Fi System.