Not susceptible to psu perturbations caused by the other channel as well. Especially for power amps driving current hungry speakers. Less intermodulation between channels in other words.
Salas, preamp Dcg3 has input potentiometer, but in my case I removed it and instead placed external an LDR volume control, leaving the preamp without that load, I heard disgusting 60Hz. noise that I think is coming from internal input signal wiring (RCA shoket to the pcb) because the noise increases when at touch to that cable (despite this cable is shielded and everything properly wired to ground). Later when the interconnect cable is placed to attach the pre to the potentiometer external unit, the music system improves and performs as expected, although still not completelly noise free.
TIA,
Jordi
TIA,
Jordi
As ground concerns I wired everything properly to the Ground Loop Breaker. Mains ground close to IEC shoket to chassis, transformer ground to dirt side of GLB and signal ground to the clean side of GLB. Mi suceed fixing hum noise my entire system this way. All cables shield to one end. GLB also has improved the sound enough to notice the correct spot to pick un the signal ground is right to the RCA signal out shoket. Also worth to mention in todays fight against hum, I noticed the correct place to wire the signal cable shield ís straight to GLB dirt side (togheter with power transformer internal shield).
Is good sounding pre I am very proud of it. Despite the issue.
Also very proud of my LDR volume control. Now I have it optimised for my system. It allows calibration, I set 250k Ohm input sensivity (same as source, phono pre out) and best setting for DCG3 is 40k Ohm nominal impedance. (Rsnge is 5k to 50k).
My speaker is high sensivity fullrange with field coil instead of magned. Very picky to noise.
So...I am concerned leaving the DCG3 without the pot as input load, don't know what to do...
Now my DCG3 has on input: 3k3 Ohm signal pass, and then 330k Ohm to ground.
Edit: Salas we crossed, now I am going to read your answer above
Is good sounding pre I am very proud of it. Despite the issue.
Also very proud of my LDR volume control. Now I have it optimised for my system. It allows calibration, I set 250k Ohm input sensivity (same as source, phono pre out) and best setting for DCG3 is 40k Ohm nominal impedance. (Rsnge is 5k to 50k).
My speaker is high sensivity fullrange with field coil instead of magned. Very picky to noise.
So...I am concerned leaving the DCG3 without the pot as input load, don't know what to do...
Now my DCG3 has on input: 3k3 Ohm signal pass, and then 330k Ohm to ground.
Edit: Salas we crossed, now I am going to read your answer above
Good day all. My DCG3 still in daily use!
I have been making myself some speakers and also seem to have plenty of power amps now. I am thinking I might like to have a go at biamping the speakers. Seperate amps for bass and mid/hi. I added an extra output to my DCG3 to be able to feed the signal out to a second power amp. Would it be a 'big no no' to attenuate again this second output to level match power amps/speaker drivers. I guess it messes with the impedance. Or even a voltage divider (2 resistors) once some calculations or tests had been made?
Thanks in advance.
Happy weekend!
I have been making myself some speakers and also seem to have plenty of power amps now. I am thinking I might like to have a go at biamping the speakers. Seperate amps for bass and mid/hi. I added an extra output to my DCG3 to be able to feed the signal out to a second power amp. Would it be a 'big no no' to attenuate again this second output to level match power amps/speaker drivers. I guess it messes with the impedance. Or even a voltage divider (2 resistors) once some calculations or tests had been made?
Thanks in advance.
Happy weekend!
Jim hi,
Depends also on how high is the input impedance of the amp you want to attenuate for. If the voltage divider has ten times lower impedance ratio and still is high enough not to overload the DCG3 its worth a try. Remember all outputs are in parallel. Another way is to modify the gain feedback resistors ratio adequately in a power amp itself.
Depends also on how high is the input impedance of the amp you want to attenuate for. If the voltage divider has ten times lower impedance ratio and still is high enough not to overload the DCG3 its worth a try. Remember all outputs are in parallel. Another way is to modify the gain feedback resistors ratio adequately in a power amp itself.
Hi, I have placed 1k + 100k to the RCA input shoket with great success, no more severe oscillation to the DCG3 when detach the pre unit from external volume control. Also very happy to get hum fixed. As an unexpected gift i noticed for some reason, a significant upgrade in sound quality.
I have another DCG3 issue I would like to ask for, that is imbalance on output strenght between HP and Speaker.
At listening throaugh headphones I have plenty smooth steps in volume control to choose from, between step 10 and step 25 are useful for listening different recordings (being 50 last step).
But when use line out, as I usually do, I experience too much gain (efficiency?) and only volume step 2 and step 3 are useful to choose from.
So I can't fine adjust the volume properly.
In my first try to fix it, I turn down the preamp gain from 3x to 2x. But I don't liked, only small decrease in sound pressure and worse, the speaker no more able to project outside the enceinte. Then I placed 2,5X gain , listened again, and liked much more, even more than original 3x setting that turned to be less natural sounding in comparison. Ok., fine for that unexpected gift, but sorry not much progress in reducing the high efficiency issue.
My last attempt to solve the strong efficiency, was increasing the resistivity of R15 (line out resistor) by lowering the 50R original value to half.
Well maybe I am in luck, here again perceived an improvement (increase of detail) not sure if related to the value change, or simply the fact that two Vishay Naked 50R in parallel (and upside down), may somewhat cancel something and perform even better than one resistor only.
All in all, my high effinciency in line out is been lowered a bit, and wonder if a further value decrease on R15 is allowed to enhance the match between both outputs, HP and Line.
TIA,
Jordi
I have another DCG3 issue I would like to ask for, that is imbalance on output strenght between HP and Speaker.
At listening throaugh headphones I have plenty smooth steps in volume control to choose from, between step 10 and step 25 are useful for listening different recordings (being 50 last step).
But when use line out, as I usually do, I experience too much gain (efficiency?) and only volume step 2 and step 3 are useful to choose from.
So I can't fine adjust the volume properly.
In my first try to fix it, I turn down the preamp gain from 3x to 2x. But I don't liked, only small decrease in sound pressure and worse, the speaker no more able to project outside the enceinte. Then I placed 2,5X gain , listened again, and liked much more, even more than original 3x setting that turned to be less natural sounding in comparison. Ok., fine for that unexpected gift, but sorry not much progress in reducing the high efficiency issue.
My last attempt to solve the strong efficiency, was increasing the resistivity of R15 (line out resistor) by lowering the 50R original value to half.
Well maybe I am in luck, here again perceived an improvement (increase of detail) not sure if related to the value change, or simply the fact that two Vishay Naked 50R in parallel (and upside down), may somewhat cancel something and perform even better than one resistor only.
All in all, my high effinciency in line out is been lowered a bit, and wonder if a further value decrease on R15 is allowed to enhance the match between both outputs, HP and Line.
TIA,
Jordi
-Nice to know that my buzz fix proposition for your system configuration worked right away.
-You have very sensitive speakers but normal sensitivity headphones, possibly a high voltage gain zero feedback tube power amp too?
When such is the case there can't be one ideal preamp gain setting for good volume control range in both situations. R15 value is not a fix.
Nonetheless an attenuation attempt can be performed in the power amp. Like add an input potentiometer to it or use a lesser Mu input tube.
Set its voltage gain lower with other Rf Ri resistor values if its a solid state voltage feedback power amp.
-You have very sensitive speakers but normal sensitivity headphones, possibly a high voltage gain zero feedback tube power amp too?
When such is the case there can't be one ideal preamp gain setting for good volume control range in both situations. R15 value is not a fix.
Nonetheless an attenuation attempt can be performed in the power amp. Like add an input potentiometer to it or use a lesser Mu input tube.
Set its voltage gain lower with other Rf Ri resistor values if its a solid state voltage feedback power amp.
Nice to left DCG3 already done. Headphones are planar magnetic and have an uncertain 92-94db. is unbranded chinese. Speakers fullrange units are handcrafted, no provided specs, but I guess around 95-97db. In between is N.Pass Aca amplifier. Measuring 5x voltage gain (driver section is one 2SK170) I think not too much to pay attention. Aca is low feedback design, but a while ago I lowered down even further, sort of enhancement but no LDR volume back then, so I realise now is a must to revisit.
Other than that, I also have room for enhancement in my LDR volume control, I am expecting to receive a matched quad LDR with lowest minimum resistence (30R@20mA), that will achieve a further attenuation to the first steps. Thanks unvaluable and kind attention, Salas
Other than that, I also have room for enhancement in my LDR volume control, I am expecting to receive a matched quad LDR with lowest minimum resistence (30R@20mA), that will achieve a further attenuation to the first steps. Thanks unvaluable and kind attention, Salas
You need more resolution in the first LDR steps as you say because even if with 3X DCG3 + 5X ACA their total 15X or 23.5dB gain isn't so tremendous for a pre + power combo on 95-97dB speakers. I have 28.5dB total on 93-94dB/2.83V/1m speakers using a series 24 step attenuator that still provides satisfactory control on all sources and outputs.
