Archive for the ‘Audio’ Category:

2019-04-29 Center Tapped Voice Coil And OTL Circuit

from FB group Vintage Transistor Radios Apr 29 Robert Abend Yeah, thanks for bringing that up. Many of the GE radios have a center tapped coil in their armature speakers. I never really thought about the unusual CT voice coil. The most important reason why is that a voice coil moves and has to be

(Read More…)

2019-04-08 Output Transformers Construction

from FB group Regenerative Receiver… Apr 8 庄议翔 The power transformers have the laminations interleaved. The first lamination has an E then I, the next one has I then E. So the transformer core does not have any air gaps, because it does not have any DC flowing through the windings. The transformers for single

(Read More…)

2019-04-06 HP Transmission Test Set

from FB group Bell Telephone of… Apr 6 (I bought a transmission test set, TTS-4, photo at bottom.) Glenn Peters We had a HP 493something transmission test set for testing up to 56 kb/s lines. I remember seeing the symbols on the green screen, like a carriage return would look like a little ‘CR’. The

(Read More…)


from FB group Vintage Transistor Radios April 6 I clicked on the link and I looked at the schematic. I’m surprised that in 1959 they had a radio that used the OTL amplifier to drive the spkr. I remember OTL was used in the early ’60s for Hi Fi amps, but I didn’t think that

(Read More…)

2019-03-15 The Tape Recorder 6V6 Making Crackling Noise

from FB group Building Transistor Radios Tuck Choy I was a reel to reel tape recorder fanatic when I was a kid, and had a recorder with a 6V6 output to the spkr. The first thing I did was modify the recorder to add an external spkr. One time I plugged in a clip leads

(Read More…)

2019-03-05 The Low Frequency Audio Uses A Lot Of Power

from FB group Vintage Transistor Radios 2019 Mar 5 The ear is not as sensitive to low ‘bass’ frequencies so they use a lot of power. If the speaker is large enough to reproduce them, they will use quite a bit of power. With pocket radios, the audio amplifiers are limited in low frequency response

(Read More…)

2019-01-09 Bootstrap Principle In Audio Amps

FB group Building transistor radios 2018-01-09 Willie Barnett That is one deficiency of your circuit: the output transistors do not have the ‘bootstrapped’ bias resistor. I’ll explain why it’s needed. In your circuit, the signal turns the driver transistor as close to off as possible. The current through the base bias resistor causes the top

(Read More…)

2018-12-22 European Electronics In 1969

from FB group Building Transistor Radios 2018-12-22 Mike van Kleeff Most of the European radios sold in the US were probably brought in by GIs who came back from their military deployment in foreign countries. I was in Germany in ’69 and saw some European electronics and I was impressed by the performance. But what

(Read More…)

2018-12-14 Voice Filter For Telecom And Radio Comm

from FB group Building Transistor Radios 2018-12-14 A voice band filter for telecomm or radio comm. The .068 or .0068 uF caps can be made by putting a 0.1 and 0.22 or .01 and .022 uF capacitors in series. The opamp can be a 1458 ‘dual 741’ opamp.

2018-11-29 Fixing Badly Worn Volume Controls

from FB group Building Transistor Radios 2018-11-30 I’ve done some experimenting on volume controls that are badly worn and noisy. The idea is to substitute some resistance for the badly worn spot. The loud crackling will be reduced and the normal volume point will be moved to a higher point on the control. For a

(Read More…)

© RustyBolt.Info/wordpress