TI's Tone control

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JhonDoe

Member
Joined 2004
hi!

I would like to build the conplete tone control from aplication bulletin of TI (http://focus.ti.com/lit/an/sboa082/sboa082.pdf) for my computer and need some help for getting the values of the pot(the Bass and Treable). What will be the best values for this pot's?

I will connect this tone control in my GC(inverted vertion) the application show's for non-inverted do I need R11(1meg) and R12(22k)?

my plan is to remove the balance pot and the two limitting res. just a volume pot. do u tink 50k will be sufficient for this?

one more thing. the schematics shows in page 1 figure 1 the 2 resistors R6 are 11k whch have the same value but in page 2 figure3 R6 have a different value 11k and 22k. which is correct for the figure?



:confused: :confused:
 
B

BC

Member
Joined 2004
I contacted TI a few months ago about that app. information. If you study the schematic there are errors. If you read the information, there are errors. TI told me that the author no longer works for BB/TI. Your Math isn't necessarily bad. Sorry for negative information.:whazzat:
 
J

JhonDoe

Member
Joined 2004
thanks guys!...

JojoD818 said:
Hi,

I have built that one and based on the app note, I used a 100K linear pot. It sound is worth building, but be smart in choosing your opamps. Read their corresponding datasheets for further references.

HTH,
JojoD
Click to expand...

did u mean 100k for both(treble and bass)?


BC said:
I contacted TI a few months ago about that app. information. If you study the schematic there are errors. If you read the information, there are errors. TI told me that the author no longer works for BB/TI. Your Math isn't necessarily bad. Sorry for negative information.:whazzat:
Click to expand...

I thought it was me who have not undestand the figures in that app.
:D

I got another question guys.. in power amp stage I'm running the chip in inverted topology, the app. shows the power amp in non inverted, can i remove the two input res before and after the input cap???
 
TonyTecson

TonyTecson

Member
Joined 2003
hi,

you may want to try dual 250k linear taper for the bass, and 50k for the treble, also linear taper....

you can not remove the resistor after the input cap to the opa549 amp. it is meant to bias the input on the op amp...the 1meg is high enough and is better to leave it as is....
 
B

BC

Member
Joined 2004
Hi once again,
Just a little more followup. Speaking with TI, they suggested not to use the OPA544, or OPA548, or OPA549 for the power amp if you want quality audio. They said that those ICs were biased Class B. I suggest using the National Semi. opamps Lm3875, or LM3886 or LM4780. These are designed specifically for audio and Nat. Semi states in data sheets that they are biased "quasi Class AB". They are also a lot cheaper. Also in the TI app. bulletin the Zoebel network filter R14 and C6 is wrong. R14 should be 1ohm NOT 1k ohm. More info about the LM 3875 etc. chips can be found throughout the ChipAmp section of DIY Audio Forum. Enjoy.;)
 
TonyTecson

TonyTecson

Member
Joined 2003
hi,

ti parts are general purpose power op amps, dataheet lists applications for motor driver, servo amp, synchro-exiter, audio amps, programable power supply, in that order...

unlike ns parts which states that the chips were made specifically for audio use....

but i see no reason not to use ti parts for audio if one wishes to...
 
J

JhonDoe

Member
Joined 2004
joan2 said:
hi,

you may want to try dual 250k linear taper for the bass, and 50k for the treble, also linear taper....

you can not remove the resistor after the input cap to the opa549 amp. it is meant to bias the input on the op amp...the 1meg is high enough and is better to leave it as is....
Click to expand...

As i mention in my past post, the power amp is running in an Inverted topology I believed that in this set up i dont need the ground reference input resistor R12 in the that application.. pls correct me if i'm wrong.. but if the resistor R11 and R12 is really needed I will include it in my final set-up
thanks bro..

BC said:
Hi once again,
Just a little more followup. Speaking with TI, they suggested not to use the OPA544, or OPA548, or OPA549 for the power amp if you want quality audio. They said that those ICs were biased Class B. I suggest using the National Semi. opamps Lm3875, or LM3886 or LM4780. These are designed specifically for audio and Nat. Semi states in data sheets that they are biased "quasi Class AB". They are also a lot cheaper. Also in the TI app. bulletin the Zoebel network filter R14 and C6 is wrong. R14 should be 1ohm NOT 1k ohm. More info about the LM 3875 etc. chips can be found throughout the ChipAmp section of DIY Audio Forum. Enjoy.;)
Click to expand...

I know most of the people in this forum prefer the LM chips, I hope national will send sample here in the philippines, I would like to try those LM3875, 3886 too but there are not available in my location.. I got a lot of TI's chips (544,548,541,549 even the opamp opa132,134,627,2134,4227,buf627) I got all those chips for free. i'm using it with every project i made and i dont see any problem...:D :D
 
JojoD818

JojoD818

Staff Emeritus
Joined 2003
geocities.com/jojod818/index.html
Hi JohnDoe,

I completely understand your point about TI chips being free and all, but for just a few hundred pesos, I suggest that you try the "Overture" series of NS including the LM3875 and you'll probably understand why a lot of guys here (foreign and domestic) prefer them.

I have personally tried the TI chips (541-544-548-549) with excellent results though, so go ahead. Still, try the Overtures, or you'll be missing a lot. ;)

JojoD
 
TonyTecson

TonyTecson

Member
Joined 2003
hi,

As i mention in my past post, the power amp is running in an Inverted topology I believed that in this set up i dont need the ground reference input resistor R12 in the that application.. pls correct me if i'm wrong.. but if the resistor R11 and R12 is really needed I will include it in my final set-up
Click to expand...

in this case you can drop the resitor after the coupling cap....

i have a bunch of lm3875, lm3875fp, lm3886, lm3886fp i got as samples, i m willing to give you a pair, but you have to get it from my place....

offer is good while i am still here in pinas, i am going overseas for a job i a months' time...

tony
 
J

JhonDoe

Member
Joined 2004
JojoD818 said:
Hi JohnDoe,

I completely understand your point about TI chips being free and all, but for just a few hundred pesos, I suggest that you try the "Overture" series of NS including the LM3875 and you'll probably understand why a lot of guys here (foreign and domestic) prefer them.

I have personally tried the TI chips (541-544-548-549) with excellent results though, so go ahead. Still, try the Overtures, or you'll be missing a lot. ;)

JojoD
Click to expand...

I'm not closing my mind to try the LM chips but as of this time money is too tight for me, you know what i mean.. almost all basic needs are getting higher but the salary still the same. Last month I found an LM3875 for the price of 400p in one of the electronics store in san fernando but 400 for me is too much and i cant spend that kind of money just for my hobby. i sould buy my little daughter's milk and i'm sure my wife will be happy for me!..

joan2 said:
hi,


in this case you can drop the resitor after the coupling cap....

i have a bunch of lm3875, lm3875fp, lm3886, lm3886fp i got as samples, i m willing to give you a pair, but you have to get it from my place....

offer is good while i am still here in pinas, i am going overseas for a job i a months' time...

tony
Click to expand...

thanks tony! bu i cant go there, need to work hard here!..
Good luck! dnt forget my pasalubong..hahaha... I hope u where not going to Iraq...
 
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