Bypassing Tone Controls (STK4141-II)

Zoodle · 28th June 2009, 01:31 AM

Hi,
I have a Sansui receiver that I've simplified into a poweramp. I'd like to by-pass the tone controls, but when I disconnect that board something begins to overheat (in the P/S I think). I assumed the tone controls were at line level, but it seems they are hooked into the power amp board.

The tone control board has multiple components + the pots themselves. Six wires connect to the combined P.supply/PowerAmp board. Is there a way I can replace the tone control section with some sort of dummy load?

sangram · 28th June 2009, 01:33 PM

The tone controls may be part of the feedback network, something that lazy receiver manufacturers did to drop costs. Removing it may be causing the amplifier to become unstable.

The STK4141 datasheet is easily available, you'd be best advised to trace the circuitry on the boards and redo it according to the reference. This may be as simple as adding a single resistor for each channel.

Are there any active components on the Tone board, or is it all caps and resistors and pots?

And can you procure a service manual for the receiver? Looking at a schematic would be pretty helpful for something like this.

Zoodle · 29th June 2009, 03:15 AM

Quote:

Originally posted by sangram

Are there any active components on the Tone board, or is it all caps and resistors and pots?

Hi Sangram,

Just resistors, caps and the two pots.

sangram · 29th June 2009, 05:57 AM

Is it possible for you to post a circuit trace of just the tone board (it might be easier to just look at the manual, though)?

Zoodle · 29th June 2009, 08:07 AM

Thanks for the reply. The parent product is 'Sansui DA-T550,' but I don't have a schematic for it. I do have the application notes for the chip - perhaps I can figure it out from there.

28th June 2009, 01:31 AM	#1
Zoodle diyAudio Member Join Date: Jun 2009	Bypassing Tone Controls (STK4141-II) Hi, I have a Sansui receiver that I've simplified into a poweramp. I'd like to by-pass the tone controls, but when I disconnect that board something begins to overheat (in the P/S I think). I assumed the tone controls were at line level, but it seems they are hooked into the power amp board. The tone control board has multiple components + the pots themselves. Six wires connect to the combined P.supply/PowerAmp board. Is there a way I can replace the tone control section with some sort of dummy load?

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28th June 2009, 01:33 PM	#2
sangram diyAudio Member Join Date: Sep 2002 Location: Calcutta, India	The tone controls may be part of the feedback network, something that lazy receiver manufacturers did to drop costs. Removing it may be causing the amplifier to become unstable. The STK4141 datasheet is easily available, you'd be best advised to trace the circuitry on the boards and redo it according to the reference. This may be as simple as adding a single resistor for each channel. Are there any active components on the Tone board, or is it all caps and resistors and pots? And can you procure a service manual for the receiver? Looking at a schematic would be pretty helpful for something like this.

29th June 2009, 05:57 AM	#4
sangram diyAudio Member Join Date: Sep 2002 Location: Calcutta, India	Is it possible for you to post a circuit trace of just the tone board (it might be easier to just look at the manual, though)?

29th June 2009, 08:07 AM	#5
Zoodle diyAudio Member Join Date: Jun 2009	Thanks for the reply. The parent product is 'Sansui DA-T550,' but I don't have a schematic for it. I do have the application notes for the chip - perhaps I can figure it out from there.

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