I've decided to modify the tone control of my receiver; SAE TWO R9. The schemetics is on attached. The specs indicates tone control operates at 100 and 10kHz for bass and treble, respectively. I wish to modify the tone control to operate at 50 and 15kHz instead. Could anyone help to tell me which parts should I modify? Another question, if the modification was done on tone controls, will the loudness operation also be affected? (From boosting at 100/10kHz to 50/15kHz) Thank you in advance
You already have a built in non-switchable high pass filter ( -3db @ 30Hz) according to the block diagram , a tone control is a type of an audio frequency filter , are you sure you want to modify the frequency response at the low end its going to be bumpy and uneven?
The filter has a switch on the faceplate, though, I've rarely used it. Yes, I'm sure I want to modify the tone control as I found the 50/15kHz was better once the system was connected to the parametric equalizer for an enjoyment.
That last page (which is a duplicate of the 2nd to last I think!) seems to have 4 opamps that
are grouped together vaguely in the centre, with what looks like tone networks in the feedback paths of the top two.
Can't read the component values though.
Normally you'd scale the capacitor values to change response. The high value caps are in the bass section, low value caps would be the treble.
are grouped together vaguely in the centre, with what looks like tone networks in the feedback paths of the top two.
Can't read the component values though.
Normally you'd scale the capacitor values to change response. The high value caps are in the bass section, low value caps would be the treble.
Sorry for the low resolution attached. Here I have attached the new file. This is the pre amp section's PCB layout. Hope this might be helpful.
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Well, the frequencies are determined by the caps connected directly to the tone controls. There are a pair of caps (C229,C230,C231,C232) across the bass pots that sets the bass frequencies and one (per channel) in series with the treble wiper (C221,C222) that sets the treble frequency. Double the cap results in half the frequency (100->50Hz) and 2/3 the treble caps results in 3/2 (= 15/10) the treble frequency.
However 100Hz and 10K are already fairly extreme so I'm not sure that you should move them out. Normally I would expect bass to be set about 150Hz and treble set about 3KHz. The midrange control may have something to do with these choices. I would recommend you leave these tone controls alone and add an equalizer.
However 100Hz and 10K are already fairly extreme so I'm not sure that you should move them out. Normally I would expect bass to be set about 150Hz and treble set about 3KHz. The midrange control may have something to do with these choices. I would recommend you leave these tone controls alone and add an equalizer.
I, yet, thought 100Hz was too much bass punch for me. My other amps' tone controls were all boosting below 100Hz. There were 20 and 50Hz boosts, and I found 50Hz satisfied me most. It is between 20 and 100Hz. (20Hz feels bass too mild, and 100Hz feels bass too punch)
From the schematics provided, would it be possible that someone could derive mathematics or circuit analysis to describe the scheme?
From the schematics provided, would it be possible that someone could derive mathematics or circuit analysis to describe the scheme?
I’m not sure whether it will help, I’ve attached the PCB layout with the component values on post #5.
Those in the business of repairing audio equipment for others require a circuit diagram aka a schematic .
This allows the engineer/technician to judge the design philosophy of the circuit as well as make it a lot easier to trace out faults .
This applies in many areas of engineering including mechanical/electrical , you might be too young to know that very old schematics were called " blueprints " ,I know because I have may radio versions of them as well as "normal " schematics .
Block diagrams give very limited knowledge to somebody repairing electronic equipment , every audio schematic in WW/EW was printed by normal circuit diagram methods so that fellow engineers could scrutinize the circuit and present criticism or agreement with the circuit .
If you do not know the value of circuit diagrams its best to read up on them .
Some companies hide their circuits from other companies to hold exclusive rights to themselves in the design of their products.
That doesn't always work out though as some engineers --"back engineer " an audio product to find out the circuit so some companies make PCB,s that are hard to trace .
This allows the engineer/technician to judge the design philosophy of the circuit as well as make it a lot easier to trace out faults .
This applies in many areas of engineering including mechanical/electrical , you might be too young to know that very old schematics were called " blueprints " ,I know because I have may radio versions of them as well as "normal " schematics .
Block diagrams give very limited knowledge to somebody repairing electronic equipment , every audio schematic in WW/EW was printed by normal circuit diagram methods so that fellow engineers could scrutinize the circuit and present criticism or agreement with the circuit .
If you do not know the value of circuit diagrams its best to read up on them .
Some companies hide their circuits from other companies to hold exclusive rights to themselves in the design of their products.
That doesn't always work out though as some engineers --"back engineer " an audio product to find out the circuit so some companies make PCB,s that are hard to trace .
But find it out yourself - sketch this part of the schematics:
on paper, write the component numbers and their values (readably, taking information also from the parts list and board layout), take a photo or scan it in and upload it here 😉
I got the answers. Thanks for all helps.
However, there’s still a question that is unsolved. With reference to the schematics, if I modify the tone control, by changing cap values, will it affect the loudness?
However, there’s still a question that is unsolved. With reference to the schematics, if I modify the tone control, by changing cap values, will it affect the loudness?
loudness
No. The loudness function comes from a partial low-pass filter that connects half way down the volume control pots. According to the manual the loudness filter caps are on the loudness switch PCB but it is hard to see the details in the pdf you provided.
No. The loudness function comes from a partial low-pass filter that connects half way down the volume control pots. According to the manual the loudness filter caps are on the loudness switch PCB but it is hard to see the details in the pdf you provided.
