Roender's FC-100 prototype and builder's thread

Status
Not open for further replies.
What is the best option for the input DC blocking cap? It should be 3.3 to 3.9uF according to Andrew? I haven't been able to find any quality polypropylene caps that would fit 15mm lead spacing on Rudi's board.

I was trying 4.7uF polypropilene capacitor from Arcotronics in my project and I can get down the THD 1khz at almost 0.0001%. I was changing 4.7uF with 22uF bipolar elcap fromt Fischer & Tausche ATBI serie and the result are ... the same 😉 In the negative feedback again it is a ....bipolar elcap.
 
I am a bit late to this party but I have finished 2 shunts and they both worked perfectly on first power up. 2 more to go... Then the main boards,
 

Attachments

  • IMAG2313.jpg
    IMAG2313.jpg
    532.9 KB · Views: 474
Why don't you put the SS relay under the negative feedback ? 🙂

Interesting suggestion, but here's my reasons

a) My first SS relay was on a separate board and you don't want long wires as part of your feedback loop. My 2nd SS relay was on-board (search for my TGM8 amplifier) so I could have done it there
b) Sometimes you want a delayed turn-on which means the SS relay is open and you don't want to break the feedback loop when the power supply / amplifier is just warming up at turn-on
c) Perhaps having the feedback loop open will produce some undesirable things which I didn't think about yet
d) I find there is no impact on sound quality so why do I need to include it inside the feedback loop ?

Rgds
 
Until you does the real measurements you don't know if the SS relay is transparent. You can put the relay under the NFB for lower distortions and for high damping factor. Of sure, you must to have all time the closed feedback loop. For that u can put a parallel resistor on the relay, 1k ohm for example ?
 
Until you does the real measurements you don't know if the SS relay is transparent.

I don't have the measurement equipment to do this. But since it's for my personal listening pleasure - if I don't hear a difference between SS relay or a wire then I'm content to have the SS relay in the circuit in series with the speaker.

Perhaps SS relays aren't yet as popular so there isn't very much information about them - but I've never read a report where somebody was unhappy with having a SS relay in their speaker circuit. Until this thread.
 
Congratulations, Paul! Go ahead!

Best regards - Rudi

P.S.: Paul: remove the light-bulb, please. There is a small amount of voltage dropping across it, so the transformer's secondaries will not reach their designated value, and re-adjust again!
 
Last edited:
Thanks Rudi! It sings. This is wonderful. I have been playing Kraftwerk all afternoon in your honour. But what should I play for Mihai? Mihai this is a truly exceptional amplifier. Thank you for sharing it with us sir!
 

Attachments

  • IMAG2361.jpg
    IMAG2361.jpg
    462.1 KB · Views: 432
Status
Not open for further replies.