I have a quick question. The DCG3 follows a Khozmo shunt attenuator with 51k resistance (to accommodate tube DAC). Is R1= 3.3K optimal for this shunt? The DCG3 is now biased at 122mA, down from 155mA, and with a couple of weeks of playing, the tone is a tad 'hot' or there is a tiny edge to the highs.
Thanks for the lightening quick reply! I am not sure I have that info but can inquire...or measure it.
Got it. Measuring across the input of the DCG3, it ranges from 80 to 6.2K, from min to max listening volume/pleasure. But perhaps I have to disconnect to accurately measure it.
The output impedance of a voltage divider at any setting is the value of two resistors in parallel.
Between input and output pins there is one reading, between output and ground pins there is a second reading for each position/step.
First one is a fixed value resistor for all steps in this case because its a shunt type attenuator.
Fully disconnect the attenuator and measure those resistances for a step, then calculate their parallel value for output Impedance (Zo).
Source impedance of DAC etc. will be in series to the first resistance, and if of relatively significant value it should be added to it for calc.
Between input and output pins there is one reading, between output and ground pins there is a second reading for each position/step.
First one is a fixed value resistor for all steps in this case because its a shunt type attenuator.
Fully disconnect the attenuator and measure those resistances for a step, then calculate their parallel value for output Impedance (Zo).
Source impedance of DAC etc. will be in series to the first resistance, and if of relatively significant value it should be added to it for calc.
Thanks Salas. I will need a minute to get this measured 😉
Maybe, before playing with resistor size/type (if at all), it may be worth trying a couple of lower shunt voltages. It is currently fed 17.5v.
Maybe, before playing with resistor size/type (if at all), it may be worth trying a couple of lower shunt voltages. It is currently fed 17.5v.
Hi guys.
Is it someone here who have used the DCG3 as driver for Nelson Pass F4 ?
If it's,what gain you choose?
What's the values for R6/R7?
Thanks in advance 😃
Is it someone here who have used the DCG3 as driver for Nelson Pass F4 ?
If it's,what gain you choose?
What's the values for R6/R7?
Thanks in advance 😃
Hi,
Try a gain of 10x (20dB). It should be logical with a digital source and F4. G=1+(R6/R7). Thus R6 4.7k & R7 499Ω divide to 9.418+1=10.418x or 20.35dB.
Try a gain of 10x (20dB). It should be logical with a digital source and F4. G=1+(R6/R7). Thus R6 4.7k & R7 499Ω divide to 9.418+1=10.418x or 20.35dB.
No,in this case(+/-19V test conditions).
Now I use another power amplifier to drive the F4.
Laptop line out-Salas DCG3-Bonsai SX ClassA- Pass F4.
Long trace!
PS.standard DCG3? Do you mean standard gain?
Now I use another power amplifier to drive the F4.
Laptop line out-Salas DCG3-Bonsai SX ClassA- Pass F4.
Long trace!
PS.standard DCG3? Do you mean standard gain?
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Its near enough a +/17V preamp for driving a +/-19V buffer power amp. If to max out a higher rails buffer power amp, the preamp must have same rails to fully push it with a strong peak to peak.
Short question 🤔
DCG3 modification for F4 driving.
+/-17V
10X gain?
Or I need to modify the gain for 10X and adjust DCG3 power supply for higher output voltage simultaneously?
DCG3 modification for F4 driving.
+/-17V
10X gain?
Or I need to modify the gain for 10X and adjust DCG3 power supply for higher output voltage simultaneously?
Last edited:
You can't simply adjust it higher. DCG3's output stage takes more, but for the DC servo chip and the relay circuit its safe to use up to +/- 17V. So its about modifying the board, modifying the supplies.
Start with 10x gain to see about sound, stability. Max F4 power isn't a priority now.
Start with 10x gain to see about sound, stability. Max F4 power isn't a priority now.