View single post by Toeffelholm
 Posted: Sun Apr 28th, 2019 06:55 pm
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Joined: Sun Sep 21st, 2008
Location: Germany
Posts: 513
I'm on the sound route again! 

I modified my loco sound test setup, and the "Sound Transmitter Box" looks like this now:

Top left is the DelTang Rx (plastic box), that controls the Phoenix sound device, bottom left.

The Rx runs in parallel with the Rx in the loco,
and the esc output delivers the velocity dependent control signal for the Phoenix sound card.

Bell and whistle are controlled via 2 function outputs of the Rx. 

Left hand of the Rx is a relay as a kind of inductive load for the motor exit of the Rx.
The  Phoenix doesn't work if there isn't a consumer. 

The speaker wires of the Phoenix sound are connected to the impedance converter,
and from there the sound signal is fed to a Bluetooth transmitter (the black box in the lid),
that transmits the signal to the loco and the under layout speaker at the same time. 

Above the impedance converter there is an audio potentiometer for volume control.
It's connected inbetween the Phoenix speaker output and the impedance converter.
It is so big, because this is a motor-driven potentiometer.
So I can control volume with my DelTang transmitter
And can also fade in and out the sound when the loco enters or leaves the scene.
The Connection to the Rx will be explained later if there’s any interest for this aplication.

Power supply is given by a 10Ah (nominal) power bank with a additional 12V output,
via the connector at the rear side of the chest.

The under layout speaker with the test setup for the "Low Frequency Receiver Box",
recently looks like this:

On the right you see this low pass filter device.
The little black-box above is the Bluetooth receiver,
receiving the sound signal from the transmitter box.

The signal is fed to the low-pass filter, and from there to an amplifier that drives the speaker.
It's an old subwoofer speaker but without any electronics inside.
So speaker and box only.

With this arrangement the low-frequency part sounds much better now.
I can turn the frequency control down to the lower limit of the low-pass filter now,
that is 22Hz, and can still hear it. 

Only the amplifier is a bit noisy, so have to look for something else. 

For completion, the "Loco Sound Receiver Unit",
still looks like this at the moment:

With speaker, Bluetooth receiver and 5V fixed voltage-regulator.


modelling in 1:22.5 on 32mm and 16.5mm track
Actual project: 7/8" scale on 45 mm track
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