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Toshiba RT-SF1 - Microphone Input

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stenzer

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Hi,

I want to record some digital audio files from a PC to an audio-cassette. It seems the only casette recorder I can get hold of at the moment is a Thoshiba RT-SF1, which provides a microphone input using two 3.5 mm jack connectors, one for the Left & one for the Right channel, as can be seen below. The microphone input impedance is stated with 200 Ohm to 2 kOhm. I assume each input is using a mono jack, so I should be able to feed in the audio-signal provided by a PC by a stereo-jack to 2 x mono jack cable. Is this assumption correct?

Unfortunately I was not a able to find a service manual. It would be nice to have a look at the schematics, as I have to change some potentiometers in near future. So I would be happy if someone could share the service manual.

BR

IMG_20220405_000628.jpg


Thoshiba RT-SF1.png
 

Often the patch cable needs to be an attenuating type, when you send a signal to a mic input. The cassette unit expects a very soft (low amplitude), which it amplifies via automatic gain control. As a result your signal is liable to be clipped and distorted.

Of course there is a remote chance that your computer output can be reduced to a soft enough level, and the automatic gain circuitry responds with sufficient attenuation, to record your signal properly.

Even so, a cable tends to introduce mains hum, which becomes audible during soft passages in the music. Therefore you still might want to use a shielded potentiometer to attenuate what goes into the mic input.
 

    stenzer

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Hi,

thank you for the reply. I assume the attenuation can be achived by use series resistors in serises with the audio channel lines. Is there a typical resistor value used?

How does it looks like for the REC/PB connector? Does the record cable also requires an attenuated cable?

BR
 

The 5 pin DIN connector is the dedicated input for line level signals. Attenuation may be still required. Does the recorder provide manual record level control or ALC only?
 

    stenzer

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To my knowledge only ALC. As far as I can remember there are only the TONE, BALANCE and VOLUME (and TUNING) knob.
 

Hi,

my I ask why a casette player? Aren´t there more modern solutions. Smaller, low power, better quality, simpler, ..

Klaus
 

Hi Klaus,

I'm sticked to the physical medium. It's a classic mix-tape, a birthday present for one who grew up in the 80s.

BR
 

Hi,

Ahh, I understand.
I´d go for the REC/PB input. I guess it´s higher ohmic than the MIC input (but maybe they just connected them in parallel)

I´d try a 10k (in your case maybe 1k to 10k) logartihmic pot.

Klaus
 

    stenzer

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I guess it´s higher ohmic than the MIC input (but maybe they just connected them in parallel)
Yes, I would like to have a look on the schematic. But I wasn't able to find a service manual.

I will order a DIN-5 to jack cable and try it with a low volume setting. If this doesn't work, I will have to use a stereo potentiometer, or two resistors.

Thanks
 

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