Gainclone kit passive pre configuration

sharpi31 · 14th October 2006, 02:25 PM

I am going to build a compact system by integrating a Monica2 dac, stepped attenuator and lm3875 kit into one box.

I currently have a 100K attenuator that I'd like to use. Couple of questions:

1. Will 100K with >10cm connections to the amp board be ok? The capacitance of the short run will be minimal.....

2. Will the Monica2 be happy driving 100K? I think the dacs low output should prefer a higher attenuator input impedance.

3. Do I need the 22K resistor from input signal to ground on the ampboard if the 100K attenuator is hard wired and very close? This may be a stupid question, but it seems like we have two resistors doing a similar job... Put it another way, is 22K optimal after a 100K attenuator?

Leolabs · 15th October 2006, 05:01 AM

Is the attenuator a log type???

sharpi31 · 15th October 2006, 11:27 AM

yes - 100k log attenuator

Nuuk · 16th October 2006, 02:52 PM

The best answer is to try it. You could also buy one of those 50K (and or 20K) 9mm Alps pots from Farnell or Jaycar and try that to see if you hear any difference.

I would personally want an active stage between pot and GC.

Peter Daniel · 16th October 2006, 02:59 PM

Quote:

Originally posted by sharpi31
3. Do I need the 22K resistor from input signal to ground on the ampboard if the 100K attenuator is hard wired and very close? This may be a stupid question, but it seems like we have two resistors doing a similar job... Put it another way, is 22K optimal after a 100K attenuator?

If you are using minimized GC configuration, you need 22k shunt resistor, otherwise, with only a 100k pot you will get high DC offset at lower volume settings (shunt resistance >22k)

50k or 25k pot works better than 100k.

I obtained very good results with a pot directly at amp's input (you don't need an additional active stage here) and an active buffer at DAC's output.

keps · 16th October 2006, 07:05 PM

Does it mean 10k pot works better than 50k or 25k pots?

Nuuk · 16th October 2006, 07:13 PM

Quote:

Does it mean 10k pot works better than 50k or 25k pots?

No! Remember that you must match the impedance right the way through the chain!

Try Googling the subject.

keps · 16th October 2006, 07:15 PM

roger that.

14th October 2006, 02:25 PM	#1
sharpi31 diyAudio Member Join Date: Oct 2005	Gainclone kit passive pre configuration I am going to build a compact system by integrating a Monica2 dac, stepped attenuator and lm3875 kit into one box. I currently have a 100K attenuator that I'd like to use. Couple of questions: 1. Will 100K with >10cm connections to the amp board be ok? The capacitance of the short run will be minimal..... 2. Will the Monica2 be happy driving 100K? I think the dacs low output should prefer a higher attenuator input impedance. 3. Do I need the 22K resistor from input signal to ground on the ampboard if the 100K attenuator is hard wired and very close? This may be a stupid question, but it seems like we have two resistors doing a similar job... Put it another way, is 22K optimal after a 100K attenuator?

16th October 2006, 02:52 PM	#4
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	The best answer is to try it. You could also buy one of those 50K (and or 20K) 9mm Alps pots from Farnell or Jaycar and try that to see if you hear any difference. I would personally want an active stage between pot and GC. __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

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15th October 2006, 05:01 AM	#2
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	Is the attenuator a log type???

15th October 2006, 11:27 AM	#3
sharpi31 diyAudio Member Join Date: Oct 2005	yes - 100k log attenuator

16th October 2006, 07:05 PM	#6
keps diyAudio Member Join Date: Sep 2006	Does it mean 10k pot works better than 50k or 25k pots?

16th October 2006, 07:15 PM	#8
keps diyAudio Member Join Date: Sep 2006	roger that.