Guess I should have seen that coming. I think streaming is a great tool for discovering new (to you) music... but listening to "my" music like that? Nah. I have some custom EQ for my speakers and headphones, and when travelling some routes I regularly pass areas where I can't even get a connection for a call, not to mention all the power and cost overhead involved over a plain Rockbox'd Clip+ with a big µSD card. I dread thinking about having to replace that one, as much as I would appreciate a display bigger than a postage stamp - good players suitable for Rockbox just aren't growing on trees.
Not that strange. This seems to be the way Windows handles it by default, presumably to aid using multiple of the same kind of device. I've had to tell one of our users that they had to use the correct USB port for their printer to work, too. (It was a retirement gig for a little old Brother laser with some life left in it.)
All very much correct.
It's just that this is not the only consideration. Output impedance by itself says fairly little about the output's ability to deliver current and do so without excessive nonlinear distortion, and it's generally specified midband (~1 kHz).
You could still have output coupling capacitors rolling off the bottom end - the time constant is (R_out + R_load) * C_coupling - or a super wimpy output amplifier. TL072 opamps for example are quite notorious for preferring loads as high as 10k or even 20k if you want to avoid performance degradation, and 4558s aren't an awful lot better.
First off, you can blame this guy:
Thevenin's theorem - Wikipedia
"||" is a shorthand for a parallel circuit.
R1 || R2 = R1 * R2 / (R1 + R2)
This works quite the same for complex impedances Z. Should somebody be lazy enough to write "R || C", what they actually mean is "R || Z(C)", with Z(C) = 1 / (j 2 π f C).
Hi and sorry to jump in.
Another case here of preamp with too much gain.
dac Zout = 50 ohm
preamp Zin = 12.5 kohm
Referring to the image below i was thinking to R1= 2kohm and R2= 1kohm
Another case here of preamp with too much gain.
dac Zout = 50 ohm
preamp Zin = 12.5 kohm
Referring to the image below i was thinking to R1= 2kohm and R2= 1kohm
Hi let me explain better the situation. Now i get too high SPL in my room with the volume pot of the preamp even below 9 o'clock position
I would like to have the same situation with pot at 12 o'clock or around that position
I do not really know how many dBs of decrease this would mean ... the idea is to start with reducing the signal coming from the dac of 2/3 ...
Yes the Zin of the preamp is 12.5k from the specifications.
I would like to add that this situation is very common for me ... i really do not understant why the preamps have not a variabile gain control made maybe with high quality resistors
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i am attaching the only info i have .. i see a line input overload of 20dB ... could this be the gain of the line stage ? 10 times ??? 😱😱😱
Thanks a lot for your support 🙂
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can't find an email for tech support on discontinued products 🙁
Thanks ! i have already seen some very interesting advice
Hi i have found the Service Manual on the HiFi Engine site.
I wonder if i can upload it here without creating any copyright issues ...
I wonder if i can upload it here without creating any copyright issues ...
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This is a small gain value surely don't need to attenuate unless he is using high sensitivity speakers.
You have the right idea.
Don't over-compute when you don't know "how much" you need (you don't).
Buy a bunch of 470r 1k 2k2 3k3 4k7 resistors, twist into an RCA-RCA cable, and TRY it. 2k:1k may work for "a little too much gain". If you have a lot too much ("9" seems like a lot of empty gain) then 4k7:470r may be more what you want. Resistors are cheaper than hurting your brain
looking-up specs and computing numbers.Thank you so much for your very kind and valuable advice.
I hope this will not cause impedance issues ... at least with amp of 10K and up
Thanks again. The alternative would be a small value pot (2.5k ?) placed directly at the power amp inputs. Then measure the wiper to ground resistance for the position of the pot that gives a good compromise ?If you have a lot too much ("9" seems like a lot of empty gain) then 4k7:470r may be more what you want.
Resistors are cheaper than hurting your brain
Hi Actually i do not know for sure I cannot find the specs
I wonder if i can measure it with a simple tester 😕
I only know that the line input impedance of the preamp is 12.5kohm/100 pF