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Old 13th May 2013, 07:11 AM   #3691
Ceglar is offline Ceglar  Australia
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Default Input impedance of B1 Buffer without volume pot

I'm needing a buffer with high input impedance, no volume control required.

If I were to build a B1 without the pot, would the input impedance then be simply the 1M resistor across the input?


(schematic found at Enjoy the Music.com - High End Audiophile Audio Equipment and Music Reviews. The Absolute Sound, Superior Audio, hi-fi+ and Review Magazine)


Thanks,
Shane
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Old 13th May 2013, 07:55 AM   #3692
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Very close to 1M0.
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Old 13th May 2013, 08:02 AM   #3693
tinitus is offline tinitus  Europe
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I suppose the ground resistor can only lower and fix the input Z
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Old 13th May 2013, 10:36 AM   #3694
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The grounding resistor before the blocking cap could be another 1M, giving Zin~500k, or use a 2M2 giving Zin~680k
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Old 13th May 2013, 11:54 AM   #3695
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Thanks guys, ~1M it is then and I'm off to the races !
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Old 14th May 2013, 11:45 AM   #3696
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I should have asked.. is there a practical limit to how high the value the resistor across the input can be. Application is for 20Hz - 100Hz only, need it as high as possible..

2.2M
10M ?

Thanks,
Shane
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Old 14th May 2013, 12:05 PM   #3697
AndrewT is online now AndrewT  Scotland
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when the interconnects are fitted at both ends, the grounding resistors at both the Source end and the Receiver end have virtually no effect. On this basis while listening to Audio the grounding resistors can be ANY High value. 10M if they are available cheap would do.

When one or other end of the interconnect is open then the game changes. If you do this hot (power on) then lower values would probably be better.
If you ALWAYS make or break connections when powered down, then high values are not a problem.
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Old 15th May 2013, 06:58 AM   #3698
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Thanks Andrew.
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Old 21st May 2013, 06:56 PM   #3699
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Guys, I'm puzzled

Been rolling caps on my b1, everything was fine.
Recently I ve turned it on and had massive hum- had to switch off immediately.
Next day I did check everything, reconnected wires. Everything was fine . Used it for some time.
Few days ago I put my system on and notices weak music goes along with much louder hum. If I increase volume- hum increases.

Strange, cause everything seems to be normal.

10uf caps placed outboard- russian mbgo 2. 1uf is russian 71-4...

What can be the cause of the problem.

P.S. device running off the battery.
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Old 21st May 2013, 08:23 PM   #3700
udailey is offline udailey  United States
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purchase LDRs anytime Also try my Resistor Replacers or LDR based Input Selector Email me. diyldr@gmail.com
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