Smartphone to hifi amp : do I need anything?

Started by snk, December 04, 2021, 03:54:14 PM

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Rob Strand

QuoteBy the way, this is the schematic I drawn (and then built) after Rob's explanations : could you confirm it is correct?
Looks good.

FWIW,  some cheaper headphone amps have quite small output caps so the load can cut some of the bass - it actually cuts the bass with the headphones as well, lower impedance more cut.    So if you find that circuit works, and isn't so fussy about the dummy load, if want to choose a load resistor go for the higher value as that will cut the bass less.
Send:     . .- .-. - .... / - --- / --. --- .-. -
According to the water analogy of electricity, transistor leakage is caused by holes.

snk

Hello,
It's me again, still trying to figure out the best way to wire my hifi amp...
I have another question, but didn't feel like I needed to start a new thread (correct me if i'm wrong) :

The Revox amp i am using features a stereo MIC input (2.7mV, 100k omh). I don't need any mic, but I would like to use it either for a CD player or a cassette deck (or for my smartphone, like the thread started).
I guess I'd just need to make a simple voltage divider with a couple resistors in order to build a pad attenuator (a bit like a DI box, but without the need of a trafo), right ?

1- First question : for a phones out (or cd/cassette player out) to mic level, which ratio of attenuation and which impedance should I aim for (I am trying to figure out the resistor values) ?

2- second question : I was going to use the classic "T design" (like found in the links below), but this video seems to use a different design (involving a capacitor) : which design would be the best in my case?

https://www.guitarandbeyond.com/40-db-pad/
http://www.uneeda-audio.com/pads/
https://www.sonelec-musique.com/electronique_realisations_att_bf.html
https://gearspace.com/board/low-end-theory/879645-help-diy-pad.html

Thank you in advance!

PRR

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snk

As simple as that? Perfect, thank you PRR :)

(I think I understand that in the video linked above, which used a cap in the circuit, the cap was here because his device may be designed to use an electret condenser mic, right?)