I love well done jobs! Possible having a picture of the inputs/outputs side?
Ah,and please, a mouser code for the poly switch and ferrite? Thanks!
Thanks. Not much to see at the back, just one pair of RCA input, 6mm jack output, a switch to connect the chassis to earth.
For supply power input I used an 3-pins aviation connector GX16 because that is isolated from the chassis.
The poly switch is a RXEF040 type.
All ordered from the far east...
B.t.w. one of the photo's shows the inside/back.
The ferrite ring I got from an old PC power supply. It has a yellow color, possibly an iron powder core, but it seems to work well.
Last edited:
Well spotted Michelag! When I was testing it the circuit was motorboating like crazy and some components became hot. Should not happen, I thought, because I remembered AKSA saying to you 'typically you would use at least 10uF per ma in the supply'.
LTSpice says one circuit draws 93mA at a supply voltage of 12V.
So that needs one capacitor of 2 x 93mA x 10uF = 1860uF. 2200uF should be more than enough using it at 12V supply voltage.
And that was true: after I connected signal ground to the correct, 'clean', side of the inductor, motorboating stopped and everything became normal.
The circuit drew m u c h more current than usual when motorboating. Even 4400uF was not enough.
Yes, this mixed bag of a project of mine is my 'holistic' approach of things 🙂
I got these vintage Wima capacitors from the only classic electronics shop left here in the city where I live, The Hague, Holland.
They are rated at just 10V but they only have to cope with 5.7V, doable.
These are not the only old/vintage components in the circuit. The 1nF capacitors at the input are very old as well, but still good quality. And the resistors are part of the collection that I have, more than 25 years old and part I got at the before mentioned shop.
I take into account that old components like the Wima capacitors fail over time, perhaps more quickly than recently manufactured ones. That is part of the reason I placed them on a separate board. I test and pair all components before I use them and I give the amplifier a burn-in. Yet I have to see a component fail, but time will tell.
Last edited:
@AKSA asking out of curiosity, would a ferrite bead be just as effective as a base stopper resistor?
I have not tried a bead but it would be better at very high frequencies, maybe beyond 1MHz. For audio I would use a carbon resistor, and for RF a ferrite bead.
Hugh
Hugh
Thank you for your answer Hugh. I want to experiment using a D45H11 BJT for Q2 which has a bandwidth of 40 Mhz. Simulation shows a nice second harmonic and hardly anything else (I changed the circuit somewhat to achieve that).
As I understand it, using a faster BJT like a D45H11 increases the chance of oscillation. I will probably use a ferrite bead in series with a 47 ohm carbon resistor at the base of both Q1 and Q2 and see what happens.
Cor
As I understand it, using a faster BJT like a D45H11 increases the chance of oscillation. I will probably use a ferrite bead in series with a 47 ohm carbon resistor at the base of both Q1 and Q2 and see what happens.
Cor