Going to set bit more than 17V (< 18V) on startup because it goes lower when it heats up.
Yes, at start up before its sinks get any significantly hotter than the room's ambient.
Hello DCG3 thread guys.
So I am 90% there but I still have some noise through the speakers. Very very slight...my wife wouldn't hear it generally but us audio sort hear things others dont..!
It plays nice music but there is an underlying noise on musical peaks and transients....and also the popping on moving the volume attenuator
With music playing I measure mere millivolts of DC so I dont think it is that.
Oscillation has been mentioned albeit without anyone else having the problem. Can I test with my OP amp removed....or with a different OP amp. I have an lme49720na to hand.
I am out of know how and patience before I ask very kindly if IDM would take a look but I dont wish to inconvenience anyone.
Best
James
So I am 90% there but I still have some noise through the speakers. Very very slight...my wife wouldn't hear it generally but us audio sort hear things others dont..!
It plays nice music but there is an underlying noise on musical peaks and transients....and also the popping on moving the volume attenuator
With music playing I measure mere millivolts of DC so I dont think it is that.
Oscillation has been mentioned albeit without anyone else having the problem. Can I test with my OP amp removed....or with a different OP amp. I have an lme49720na to hand.
I am out of know how and patience before I ask very kindly if IDM would take a look but I dont wish to inconvenience anyone.
Best
James
Hello James
Did you confirm that R1 C1 C2 values are true to BOM? Did you try another source than the particular mobile phone? Please add 3.3k in series with each pcb level signal input hot (either on the pcb terminals or after the pot between its output pins and outgoing wires) and let me know if and how its affecting the situation.
For servo chips use JFET input type like the AD823 you use or OPA2134 etc. This application wants very low input bias current spec i.e. not bipolar input type. Better not try it on an audio system with the op-amp removed. Why asking? Is it giving much better offset results without the op-amp, just with the trimmer? If yes, the particular chip maybe is damaged.
Did you confirm that R1 C1 C2 values are true to BOM? Did you try another source than the particular mobile phone? Please add 3.3k in series with each pcb level signal input hot (either on the pcb terminals or after the pot between its output pins and outgoing wires) and let me know if and how its affecting the situation.
For servo chips use JFET input type like the AD823 you use or OPA2134 etc. This application wants very low input bias current spec i.e. not bipolar input type. Better not try it on an audio system with the op-amp removed. Why asking? Is it giving much better offset results without the op-amp, just with the trimmer? If yes, the particular chip maybe is damaged.
Hi Salas and thanks
I checked all components are to BOM. Last checks are with Marantz CD67... stock with DC caps still in situ.
I shall get the R3.3k and test thanks.
My query about op amp....that is maybe just my lack of experience and knowledge of what oscillation is.
I can maintain good DC offset with servo in place.
...however as always before if I short the inputs i get 800 to 1100mv....even without servo.
I never got to the bottom of this as everyone else seems to get a low DC figure WITH shorted inputs....I however cannot achieve this
I checked all components are to BOM. Last checks are with Marantz CD67... stock with DC caps still in situ.
I shall get the R3.3k and test thanks.
My query about op amp....that is maybe just my lack of experience and knowledge of what oscillation is.
I can maintain good DC offset with servo in place.
...however as always before if I short the inputs i get 800 to 1100mv....even without servo.
I never got to the bottom of this as everyone else seems to get a low DC figure WITH shorted inputs....I however cannot achieve this
The thing with the shorted to ground inputs higher offset is unusual, we do that to exclude noise interference during the null procedure, its not a basic prerequisite though. Maybe shows something wrong with the uPAs or the opamp but it could also be grounding related. You don't short inputs between channels instead, right? When having the volume pot wired in, fully closed position roughly equals shorted inputs to ground. It also means least insertion resistance so add that 3.3k to test. You got the classic version PCB yes? Not the very last one that has 1.03 printed at the bottom right corner?
Maybe ist is already discussed here but going through approx. 400 pages is quite a task 
How does the Salas SSLV1.3 UltraBib compare to the DCSTB ?
I will need multiple power supplies for other components too so I would prefer to keep it by a single design.
Or does the DCSTB have some benefits for use with DCG3 ?
I will keep the bias current in the DCG3 as low as needed for pre-amp duties only - no headphones ...
How does the Salas SSLV1.3 UltraBib compare to the DCSTB ?
I will need multiple power supplies for other components too so I would prefer to keep it by a single design.
Or does the DCSTB have some benefits for use with DCG3 ?
I will keep the bias current in the DCG3 as low as needed for pre-amp duties only - no headphones ...
I think I have found the answer to my question: (link is to post 3062 from Salas)
Salas DCG3 preamp (line & headphone)
Salas DCG3 preamp (line & headphone)
It's two DCSTBs for dual mono balanced dcg3..
We will aee, will take a little bit longer since girlfriend is pregnant...
Thanks Salas! Its a great design by you. I am using this for attenuation and source selection :
Arduino based LDR volume and source selection controller
The DCG3 then runs into a DIY SONY VFET. My source is a Soekris DAM1021 (raw output) so I needed a bit more gain to drive the VFET.
Speakers are Troels DTQWT.
I am using this for attenuation and source selection :Arduino based LDR volume and source selection controller
The DCG3 then runs into a DIY SONY VFET. My source is a Soekris DAM1021 (raw output) so I needed a bit more gain to drive the VFET.
Speakers are Troels DTQWT.