My active preamp/tone-control and TL074 - diyAudio
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Old 23rd November 2005, 04:22 AM   #1
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Default My active preamp/tone-control and TL074

I have built several DIY projects including STK 4192II power amp, STK 6238A equalizer and several other power supply projects. I am still in the early stage of the learning curve of designing the circuits but I am determined to learn it.
For STK amp I have built the preamp-tone control module based on a circuit published in a magazine using LM 349 Quad-op-amps! After visiting this wonderful forum I learnt that for buffer stages the better op-amp options are NE5532, TL072 and some OPA/BB modules. As TL074 is pin compatible with LM349, I am wondering whether I can replace the LM349 in my Preamp module with them. I am planning to build better regulated, discrete PSU for the preamp too.
Can one of the experts here advice me whether I can replace the LM349 with TL074 in the following circuit without any change in the passive components? If passive component are to be changed, what should I change?

Thanks in advance
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Old 23rd November 2005, 04:43 AM   #2
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if these opamps r pin compatible then u can safely replace them.
no need to change any passive components

remember::::do not forget to put decoupling caps with each chip!they r absolutely essential.
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Old 24th November 2005, 05:59 PM   #3
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Thanks it works and a significant improvement of sound! I think I can find other alternatives too in the local market. What about OPA4134, OPA4132 and OPA4228? Will they work in the circuit without any change in the passive components?
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Old 24th November 2005, 09:28 PM   #4
DcibeL is offline DcibeL  Canada
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TL074 is a yucky op-amp IMO. OPA4134 and OPA3142 should work out quite well. Also, replacing the coupling caps with high quality polypropylene or polyester caps (if they are poor parts like electrolytic) will also help. Might as well make sure all the caps aren't electrolytic, since they aren't very large sizes.
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Old 1st December 2005, 08:15 PM   #5
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OPA packages are not available in quad configuration! OPA 4134 is available only in SOIC package. The local distributor for the Farnell only gives me few options.
As NE5532 seems to be a good cost effective option can somebody help me to find whether quad configuration available with NE series an in TL074 [TL072 series]

I really think tone controls is a must though recent audiophile thinking is otherwise.

http://zero-distortion.com/views/ton...econtroles.htm

Can I implement active volume control after the circuit given above shown in the following link?

http://sound.westhost.com/project01.htm
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Old 2nd December 2005, 03:50 AM   #6
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if u getting opa4134,use it.its a wonderful ic.far better than 074,ne etc.

even if its a surface mount,modify it as something given here

http://www.soundodyssey.com/AudioParts/OpAmps.html

the sonic benifits of opa far outweigh the little extra effort.
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Old 2nd December 2005, 10:23 AM   #7
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some alternates suggestions that are pin to pin compatible with TL074 are
OPA4134,LM324(crappy though), LM348, TL084, LM349
BTW OPA4134 is available in PDIP package with retailers u have to find the right one
BUt do remeber my experince suggests usage of single OP AMP as dual or quad amps do have some cross talk between channels.
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Old 3rd December 2005, 12:01 PM   #8
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Thanks for all the infomation. I have built with separate opamps for each channel for better seapration. I am going to add following circuit from ESP projects after the above preamp circuit. Will it give some problems?
I would love to have links regarding proper earth(ground) techniques and proper routing techniques for building circuits.
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Old 3rd December 2005, 12:28 PM   #9
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visit analog devices website, there u could find articles about grounding techniques and star ground atheories.
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Old 3rd December 2005, 01:48 PM   #10
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t.i also has good articles

moreover esp site's articles section also has good article.
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