I recently received from a German friend this tuner escaped through the bow of time as untouched (inside / outside)
I notice that the decoder goes directly out without a buffer to the preamp. and surely there may be impedance misadaptation problems that spoil the deemphasis filter (50 us constant), I'm thinking of adding a valve buffer (lampization).
I ask my advanced and experienced colleagues to suggest something PRACTICAL and easy to adapt to this device
By the way, the interior is quite airy, so it allows interventions without disturbing other circuits.
Regards,
Victor
I notice that the decoder goes directly out without a buffer to the preamp. and surely there may be impedance misadaptation problems that spoil the deemphasis filter (50 us constant), I'm thinking of adding a valve buffer (lampization).
I ask my advanced and experienced colleagues to suggest something PRACTICAL and easy to adapt to this device
By the way, the interior is quite airy, so it allows interventions without disturbing other circuits.
Regards,
Victor
Attachments
Last edited:
The design input of Dual amps in this period is 470K.
The 22K output of the deemphasis will be fine with 470K. As you say, you may wish to load with something else.
The "practical" path is two 10-cent transistors on the existing supply. Snip and remove two caps, replace each with a Q-R-C buffer.
Sure, you can fit a tube in there. The power requirements are very different so you need another transformer(s).
The 22K output of the deemphasis will be fine with 470K. As you say, you may wish to load with something else.
The "practical" path is two 10-cent transistors on the existing supply. Snip and remove two caps, replace each with a Q-R-C buffer.
Sure, you can fit a tube in there. The power requirements are very different so you need another transformer(s).
Attachments
Thanks for your nice and practical answer.
But I want to complicate my life with valves. Do you think a srpp design shall be fine, also do you think subminiature valves can do that job well?
Nevertheless I can asume an aditional psu for the Ua and Uf as there is planty of space inside.
Regards,
Victor
SRPP will probably have too much gain, so you will need to add an attenuator. I thought you were looking for a buffer? A cathode follower is a buffer.
You are right but the tuner was designed for an imput of 300mV/470k and modern preamplifiers have 1V or more, so some amplification shall be needed.
Cathode follower shall lower the signal by 0,8 I suppose.
OK, you want an internal preamp. You have no other lower level sources; if you did, an external preamp would make more sense.
- Status
- Not open for further replies.