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Old 4th September 2005, 12:03 AM   #1
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Default Tone ctrl bypass reduces volume?

In my cheapo-vintage-Toshiba-integrated-amplifier, I decided to bypass the tone control board. I removed the ground wire and connected Lin with Lout and Rin with Rout together.

Since I've done this, the gain turned lower than before : I have to put volume pot on 2 instead of . Also, now, the gain and tone greatly depends of the source. The tuner sounds crappy with tons of bass, and the CD player is clear, loud and practically bass free.

Does someone knows how can this happen? Impedance?
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Old 4th September 2005, 01:55 AM   #2
Leolabs is offline Leolabs  Malaysia
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Did u actually bypass the tone-control,ie leave the board no connection at all or just loop the I/Os???
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Old 4th September 2005, 02:06 AM   #3
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I've connected the source selector directly to the preamp instead of source selector ->tone control ->preamp
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Old 4th September 2005, 02:09 AM   #4
Leolabs is offline Leolabs  Malaysia
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Is your tone control active or passive???
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Old 4th September 2005, 02:32 AM   #5
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Passive, that's what I find strange.
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Old 5th September 2005, 01:57 AM   #6
anatech is offline anatech  Canada
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Hi DragonMaster,
Is it possible that your tone control circuit is in the feedback loop of the amplifer stage?. To test, put a 22K resistor between the in and out. If the tone controls were in the feedback network the gain will go up. Install an equivalent resistance to the impedance of the tone control circuit. Trial and error with on channel will get you there.
-Chris
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Old 5th September 2005, 03:46 AM   #7
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I'll try. I'll post you the results.
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Old 7th September 2005, 03:42 AM   #8
Enzo is offline Enzo  United States
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But like leo asks, did you DISconnect the tone circuit or just leave it in place with the bypass installed?
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Old 7th September 2005, 03:28 PM   #9
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I've disconnected it and connected the inputs and outputs together.

Should I try disconnecting them?
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Old 7th September 2005, 08:45 PM   #10
anatech is offline anatech  Canada
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Don't do that. If it's part of the feedback network you will breal the loop partially. Normally there is a DC path of very high resistance.

Connect a resistor between those points as I suggested to see if the gain goes up.

-Chris
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