Jim,
Beautiful implementation!
Did you drill holes or cutout the wood under the heatsink?
It looks like you will have no air flow through the heatsink, otherwise.
Rush
I am having strange issue with one channel being much more silent than other. I haven't started troubleshooting yet, just that I switched cables to identify the issue in DCG3 and not in power amp.
Anyone had this issue and maybe some suggestions where to start debugging?
Thanks in advance !
Anyone had this issue and maybe some suggestions where to start debugging?
Thanks in advance !
On headphones with just one source or interconnected to a full system including various sources and a power amp? Includes a selector board? What version DCG3 board you got? Has 1.3 printed at the right front corner or nothing there?
Was it alright before until you added something, or it acted up without any system changes or tweaks?
Was it alright before until you added something, or it acted up without any system changes or tweaks?
Headphone out does not seem to be affected. Only speakers when headphones are disconnected (not sure if connecting headphones would make a difference). Just one source from external DAC.
No, just regular selector switch.
V1.03 as far as I see now.
I did mess a little with front panel, dact stepped attenuator might have been affected? I will double check all wiring, but I would not expect it to lower the volume for one channel..
Yes and no.
I noticed few things:
- that when i wiggle the wires close to attenuator for the channel that plays louder sometimes the volume would go super loud as if on 0 resistance
- this happens not on all levels, on lower volumes it would be fine
- the wire connections appears to be fine, nothing suspicious
I think the attenuator might be broken because I did bend it few times during last time I removed and added front panel.. do you think it is easy to physically break that chinese dact type attenuator? Should I try to bridge the GND left to right?
First ground the pot's metal can with a wire. Then try bridge its GND pins in case a ground point inside has been compromised. So to estimate if something's going wrong with the ground of the pot from those two experiments. Normally it shouldn't need bridging as it was playing fine before. Yes easy to break pots, they are good sounding for their little price, but naturally flimsy. A signal connection inside could have gone bad.
Get any 20k-25k log carbon pot from the nearest shop or fastest local online retailer to change it and see what happens. Like those found in dj mixers etc. Good enough for fault finding and even sweet sounding sometimes. To replace with and find if the problem remains or not before looking further into the preamp
Get any 20k-25k log carbon pot from the nearest shop or fastest local online retailer to change it and see what happens. Like those found in dj mixers etc. Good enough for fault finding and even sweet sounding sometimes. To replace with and find if the problem remains or not before looking further into the preamp
Tried it, still same issue when wiggling the wire.
Will do that though I am sure that the issue is the pot.
Unfortunately it will be hard to find proper pot in local shops as very few options are available. I see that Alps blue is quite popular around diyaudio forums - do you think it's worth the money? I could try ordering from hificollective.
Alps Blue is a great pot mechanically. Can be bit more opaque than fixed resistor attenuators due to their superior channel matching but with smoother handling because continuous log. At least much smoother than the 24 position ones. If not a final choice, always handy to have one around for testing projects. Not too expensive and virtually lifetime reliable.
Thanks Jim ! I'm bit worried I'll break it as well
What do you use for your final build? Did you have a chance to compare with dact type?Guess it's worth considering, less likely to break anyways
Thanks Salas for helping to troubleshoot 
Almost there! Need to tidy up some cables with ties, L/R leads from the Rpi to the iSelect and a once over to make sure I've not made any mistakes ....
I have a question though - I was checking I didn't have a short between left/right/ground on the inputs and when I checked with a meter I have :
Between L and R (measured on the DCG3 L/R in terminals) varies from 1.7 ohm to 35k ohm as I turn the pot from min to max.
Between L or R to ground varies from 2.3 ohm to 17.5k ohm
If I disconnect the pot, on the DCG3 terminals I have:
L or R to ground 333k ohm
L to R 670k ohm
Measuring the pot disconnected it appears fine.
Is this some wacky reading caused by the iSelect board?
I have a question though - I was checking I didn't have a short between left/right/ground on the inputs and when I checked with a meter I have :
Between L and R (measured on the DCG3 L/R in terminals) varies from 1.7 ohm to 35k ohm as I turn the pot from min to max.
Between L or R to ground varies from 2.3 ohm to 17.5k ohm
If I disconnect the pot, on the DCG3 terminals I have:
L or R to ground 333k ohm
L to R 670k ohm
Measuring the pot disconnected it appears fine.
Is this some wacky reading caused by the iSelect board?
A pot (wired as volume control) when at minimum shorts the signal to ground to mute it. Gradually develops resistance across hot and ground in a logarithmic fashion as we turn it up for the input signal to grow stronger across it. Consequently across the preamp's input too. The preamp's fixed input resistance lays in parallel to the pot's at any position.
Thanks Jim ! I'm bit worried I'll break it as well
Sorry I missed this. My final dcg3 build isn't finished yet but the seller sent me correct 20k dact type...so the 10k is spare.
It's yours if you want it.. dont worry about breaking it