can I add and extra set of rca's for out to sub , either jumping them from the imput rca's or going out from volume pot (50K), one set of wires to the board and the other to the out rca's? looking for the lowest degradation in sound vs. going out from d/a with a Y splitter to tpa 3116 amp and to sub line level input. Any recommendations will be appreciated! Thanks!
As far as I understand yes, in standard equipment conditions.
That is, you need to mind input and output impedances of the connected circuits.
You can split source output to two amps.
I would also like to know what is the basic rule here and what are the minimum/maximum in/out impedances between attenuated source and two amps.
Any easy to read info about that is welcome.
TIA
That is, you need to mind input and output impedances of the connected circuits.
You can split source output to two amps.
I would also like to know what is the basic rule here and what are the minimum/maximum in/out impedances between attenuated source and two amps.
Any easy to read info about that is welcome.
TIA
I've been skipping around in this thread to find something like this, but I havent found it yet... so maybe someone will happen to know or know where to direct me.
I got a 2.1 3116 board and it has a lot of hiss when the LR VOL knob is halfway. If it is less than halfway, or almost all the way up, then the noise is much less, but still noticeable. The noise is present with or without a source, and with or without any main vol at all. So I can have a source playing with no volume, so you cant even hear it from my speakers, but still a loud hiss and even some oddball noise (the bleeps the creeps and the sweeps)
The way the noise only shows up at half volume is sortof like this youtube
any suggestions?
The board is stock other than the input cap, run with 24v power brick and 4ohm speakers.
I got a 2.1 3116 board and it has a lot of hiss when the LR VOL knob is halfway. If it is less than halfway, or almost all the way up, then the noise is much less, but still noticeable. The noise is present with or without a source, and with or without any main vol at all. So I can have a source playing with no volume, so you cant even hear it from my speakers, but still a loud hiss and even some oddball noise (the bleeps the creeps and the sweeps)
The way the noise only shows up at half volume is sortof like this youtube
any suggestions?
The board is stock other than the input cap, run with 24v power brick and 4ohm speakers.
I don't mind difficult, and if I mess it up I will leave it on some spark-e's desk to fix and buy lunch
I see this mod described earlier, 3.3ohm resistor and 10uf to ground right?
I'm trying to read up also on this input impedance vs pot value thing. I'll get there someday. So far I'm not understanding the relationships between source impedance, input impedance, and pot selection... But there's a lot of reading around
thanks for the help so far!
Well I put that filter on pin17 of my LR amp chip and it looks as though I escaped without destroying anything. I'll never know if I can hear improvements from the change, the 'before' sound was trash because the hiss drives me
I'm not understanding where noise comes from if the pot impedance is too high for the input impedance. Also I noticed that I can hear noise even when all the knobs are at min, its just very very quiet.
I'm not understanding where noise comes from if the pot impedance is too high for the input impedance. Also I noticed that I can hear noise even when all the knobs are at min, its just very very quiet.
smacksfrog, I tried the 10r+1u but I think I put on a bigger value capacitor. This was last year so I don't remember excactly what the values were...
But you did manage to separate the pin 17 leg (in the corner) from the the 2 nearby power pins? Just checking cause that mod really lowered the hiss when a source is connected and the volume is high. With no music playing there was a big difference.. I use this card as amp for my pc speakers and I still hear some hiss from 70cm away.
I think I'll try doctormord's advice and try something like a 5k pot? If anyone could comment if that would work I'd appreciate it The source is my pc which can drive 40ohm headphones, so I think it has fairly low output impedance. The tpa3116 input impedance is currently at ca 10k with a slight amount of hiss.
But you did manage to separate the pin 17 leg (in the corner) from the the 2 nearby power pins? Just checking cause that mod really lowered the hiss when a source is connected and the volume is high. With no music playing there was a big difference.. I use this card as amp for my pc speakers and I still hear some hiss from 70cm away.
I think I'll try doctormord's advice and try something like a 5k pot? If anyone could comment if that would work I'd appreciate it
The source is my pc which can drive 40ohm headphones, so I think it has fairly low output impedance. The tpa3116 input impedance is currently at ca 10k with a slight amount of hiss.
Last edited:
well I used 10r 2.2u, its what I could find at work. It may have made a big difference, but it is masked by the problem i am trying to solve. I can probably jumper across my resistor later to see if there was an improvement, but the more iron I put on that pin the worse, so I will probably just leave it
Ok so I get that the low amperage is prone to noise. I think the pots on there are 50k, not 100% on that, and my amplifier is 15k... so 10k makes sense based on the rules-of-thumb I've read elsewhere. I've got a couple related questions, for my understanding:
1) I still hear the hiss even with my LR vol knob all the way up (the main vol knob works correctly so I'm ignoring it's effect for now). If the high impedance is the issue here, my amp is set from the manufacturer at the 32db setting which should be 15k input impedance, which is still too high if I'm picking up noise like that. Can I lower that by shunting a resistor? (I know I can also swap resistors so the amp latches at 36db.. would make for 9k input impedance)
2) I still hear the same-sounding noise, though really quiet, when the vol knobs are all the way down. If impedance is the issue, which means I'm picking up noise pre volume pot, why isn't that noise just going to ground in the pot?
3) The volume pots are between the pre amps and amps, right? I'm new here and I'm only guessing they're between the pre amp and amp based on intuition. >.>
He wrote input impedance.
Don't know where you picked up he was talking about output impedance.