I tested this part because I was curious whether the higher winding ratio has an effect: As fas as I can judge it (direct comparison is difficult because changing the connection takes about halve a minute) the output feels same but is a little bit weaker with the same series resistor (10 Ω) and at the amplifier volume compared to the Reichelt part.mantrid wrote: Mon Sep 23, 2019 11:04 am Example 2 (Digikey part)[/b]:
Part number 237-1146-ND is the only transformer I found on Digikey that may work. The 2.9 Ω side should be connected to amplifier with an series resistor. I probably will try out this part because it has a higher winding ratio compared to my part. But it is possible the this part becomes to inefficient due to the high output resistance.
Winding ration is 25, i.e. load dependent part of X_T is the output load divided by 625
R = 10 Ω
X_T = 3 Ω
C = 100 µF
f = 500 Hz
==> X_C = 3.18 Ω
==> Transmittance factor A=0.80
You see for feasible transformers R is the dominating part in the formula for A. A simple rule is therefore C=100µF for R=10Ω and C=47µF for R=20Ω.
Digikey part numbers for capacitors: 493-17272-ND and 493-6080-ND
I used a 0.6W series resistor which became hot, i.e. recommended power rating for this part is at least 1W. The tiny transformer became a little bit warm but it's also possible that the heat came from the resistor. If the signal is to weak (I don't think) you also can chose a lower resistor value.
I made a photo of one output circuit before I isolated it with shrink tubings:
