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Old 12th March 2015, 03:13 PM   #1
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Default Need help for Suddenly drop and increased volume issue

Hi all,

Recently i bought Marantz Cd5005 cdp instead of existing source Philips Dvp (Normal Player) to my ref rev c amp.

But, i connect the mz cdp to my amp, it sounds very high volume and cant able to control volume in consistent level. When i touch my volume control knob its suddenly increase and decrease and also closed volume to zero level, amp is singing very low noise. Just for information, i used china made 25k dual volume control from ebay and DAC make RCA interconnect...

I check all my solder point and connector joints respectively. but this issue does not happen previously used philps dvp.

Anybody advice to rectify this problem.

Thanks in advance
Ramesh:
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Old 12th March 2015, 03:27 PM   #2
rayma is offline rayma  United States
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Quote:
Originally Posted by rameshaudio View Post
it sounds very high volume and cant able to control volume in consistent level.
When i touch my volume control knob its suddenly increase and decrease and also closed volume to zero level,
amp is singing very low noise. Just for information, i used china made 25k dual volume control from ebay and
DAC make RCA interconnect...I check all my solder point and connector joints respectively. but this issue does
not happen previously used philps dvp.
It almost certainly is the volume control circuit and not the CD player. Try the old CD player again to verify.
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Old 12th March 2015, 05:51 PM   #3
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The old DVD player may have had very low output for some reason. I would expect the standard ~2V @ 0 dBFS for the Marantz. Pre + power amp may have too much gain now.

A quick search shows that MyRef rev C should have a voltage gain of 31.7 or 30 dB. With the levels on CDs these days, people routinely run into trouble with touchy volume pots at a typical 45 dB total, so no more than 15 dB voltage gain in the preamp would be needed to get into that kind of territory. If it's more like 20 dB, things would become rather touchy indeed.

Hence I would advise finding out what the preamp's gain is, by reverse-engineering if need be.
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Old 13th March 2015, 05:17 AM   #4
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You have used a linear pot, it looks like. Use an audio/log taper pot.

Gajanan Phadte
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Old 13th March 2015, 05:45 AM   #5
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Quote:
Originally Posted by gmphadte View Post
You have used a linear pot, it looks like. Use an audio/log taper pot.

Gajanan Phadte
Thanks to all of your Replies and Gajanan Phadte, i uesd this v.pot.

1pc B 25K Potentiometer Rotary 6mm Split 20mm Shaft B25 | eBay
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Old 13th March 2015, 06:44 AM   #6
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Quote:
Originally Posted by rayma View Post
It almost certainly is the volume control circuit and not the CD player. Try the old CD player again to verify.
Oh..yes... after verify.. problem continued slightly in old cdp also.
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Old 13th March 2015, 10:15 AM   #7
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Go down the page...and read, it's a linear pot. It is written in red.

Gajanan Phadte
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Old 14th March 2015, 09:15 AM   #8
AndrewT is offline AndrewT  Scotland
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Linear pots are very useful where one requires a "calibrated" input, or sensitivity adjustment.

Many "professional" power amps have a sensitivity control on the input.
It can be set easily to 20%, or 50%, or 75%, or any other.

Volume control is required to match our hearing. This is closely met with a log law pot.

Some of the log law can be added to a linear pot.
Look up log faking resistor.
The resistor value can be from ~5% to 25% of the pot value to be reasonably effective over SOME of the rotation range of the linear pot.
For a 25k linear I suggest you try adding a pair of 3k6 or 3k9 from wiper to bottom pin of both tracks. See if it meets your requirements for volume adjustment.
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Last edited by AndrewT; 14th March 2015 at 09:20 AM.
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Old 14th March 2015, 12:30 PM   #9
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just get a log pot.
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Old 21st March 2015, 02:20 PM   #10
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Thank your friends. Problem solved after changing the Log audio Pot.
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