| fossil2k |
| Hey guys, I'm trying to modify my pre-amp using TI084CN to AD731. Except from comparing the specifications, I'm not sure if the AD731 will fit as a direct replacement to TI084CN without any modifications to other components or values used. Can anybody enlighten me please? |
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| x-pro |
What is AD731?
Cheers
Alex |
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| janneman |
Maybe he means AD713. The 713 and the TL084 are both fet-input quads several decades old. They were two companies' answer to each other, and are very similar. If you want to update, take something a few generations more recent ;)
Jan Didden |
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| Leolabs |
| In the datasheet stated that:"Enhanced Replacement for LF347 and TLO84." |
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| fossil2k |
| Thanks for the reply. It is indeed AD713 and I'm still unsure if I should change to AD713. I mean, do I need to do any other modifications to the circuitry or just do a direct replacement to TL084CN?? Any better idea on what chips to use? |
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| djk |
"OPA4134"
No longer available in a DIP. |
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| janneman |
| quote: | Originally posted by Leolabs
In the datasheet stated that:"Enhanced Replacement for LF347 and TLO84." |
Of course it said, this is marketing of course.
The 713 is also decades old, and that recommendation is probably from the 80's?
Get something really better.
Jan Didden |
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| fossil2k |
| Thanks djk..OP3134 is only available in SMD..now have to think of the problem of sourcing a PCB that allow me to convert SMD into DIP. |
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| djk |
I suggest two dual SMD types, one on either side of an adaptor board.
http://www.futurlec.com/PCBService.shtml
will do a good price on a small order, the only thing left to find is pins to go from the adaptor board to the original 14 pin DIP holes. |
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| fossil2k |
| djk, thanks for the info. |
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| fossil2k |
| Is it worth to change LM339N to CMP04? Will there be any sonic improvement? I've recently replaced my CDP NJM2114 to AD8065 and is very satisfy with the result. I'm now thinking of changing the NE5534N to AD8065 as well. Is there any better suggestion? |
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| QSerraTico_Tico |
OPA2134 better???
Hahaha just as LM4562........... better than all |
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| fossil2k |
| So guys, any advise to change to CMP04?? |
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| fossil2k |
| Look at LME49740 which is a quad op-amp and its designed specifically for hifi..worth a try?? |
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| fossil2k |
| Basic to some basics..OPA2134 is a dual op-amp and if I were to use only one of them..do I need to shunt a resistor across its inputs & output or I just leave them floating?? |
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| djk |
| It's not an FET input, but depending on the application it may work (input bias is much lower than previous BJT input opamps). |
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| carlmart |
Sorry guys. Everything will depend on the source level to find a difference between any quad IC designed in the '80s or '90s.
The AD713 comes from the late '80s, and it's still considered one of the best there is. So I think it will all depend of the implementation.
The AD713 is better than the TLO84 though, and certainly more modern.
Now if you will compare a quad with single chips or even some dual ones, then that's different. You will find many chips around, DIP or SMD that will certainly improve on any quad. |
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| circuitscc |
How about using OPA4227? Very low noise and distortion.
Regards. |
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| fossil2k |
| Should I shunt the inputs & output with resistors is 1 op-amp is not used in a dual op-amp package?? |
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| AndrewT |
| quote: | Originally posted by fossil2k
Should I shunt the inputs & output with resistors is 1 op-amp is not used in a dual op-amp package?? |
We cannot advise until you post the schematic. |
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| djk |
"Should I shunt the inputs & output with resistors is 1 op-amp is not used in a dual op-amp package??"
On unused opamp sections I ground the non-inverting input and hook the inverting input to the output, no resistors required. |
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| fossil2k |
Sorry guys, in the earlier post I've asked for suitable replacement for LM339 but after obtaining the schematic of my amplifier a few days ago, I've found that it is used in the protection circuit. Anyhow, I have made some modifications to my amplifier.
1. Bypass the selector switch by connecting directly the RCA socket to the volume control and to the amplifier circuit using silver wire.
2. Changing the aged capacitors in the circuit with those from WIMA & Panasonic.
3. Changing NE5534 with OPA2134/NJM2114 with BG caps across its supply.
After comparing both chips, 2134 gives solid image but I find that the bass a bit too much. Whereas the 2114 gives more balance sound but not solid. Anymore chips that I could use? As my CD63 is upgraded before with AD8065 & BG caps, I was thinking of using the same chip as well.
Somewhere in the forum, I have read that there is some low noise transistors. Is it true?? I have attached the schematic and maybe you guys can give some comments. Thanks. |
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| dpuopolo |
TI has come out with an enhanced replacement to the TLO-84.
It is the TLE-2074. This opamp part of their Excalibur series, possessing lower noise and distortion and higher gain bandwidth product and slew rate. They are VERY good sounding opamps.
They also make singles (TLE2071) and duals (TLE2072).
Also, National Semiconductor now has a quad high performance audio opamp-the LME49740. It is essentially a second generation quad version of the LM4562 dual. They also have singles (LME49710) and duals (LME49720). If you use these opamps, make sure that you have sufficient power supply bypass capacitors installed, as these units have the ability to become great oscillators without them. |
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| fossil2k |
If you use these opamps, make sure that you have sufficient power supply bypass capacitors installed, as these units have the ability to become great oscillators without them. (dpuopolo)
Can you explain the power supply bypass capacitor? Mine have a 0.47uF NP across its supply and sitting on top of the op-amp. |
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| carlmart |
| quote: | Originally posted by fossil2k
Can you explain the power supply bypass capacitor? Mine have a 0.47uF NP across its supply and sitting on top of the op-amp. |
Local bypass, very close to the power pins, with something like 47uF or so, with good quality caps, may be necessary too, besides the film type bypass. I must confess I am not too much a fan of ceramics, even if some types seem to work quite well in audio projects. |
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| fossil2k |
The 0.47uF BG cap is recommended by a local DIY shop that claims to improve the sound. My next problem if you look at the schematic is what type of cap to replace at the input of the op-amp.
My next project would be building a KWAK clock for my CD63 but not sure if the schematic I got is correct. |
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| dpuopolo |
You have to have caps from each power supply pin to ground.
I usually use .1's, but .47's should also be fine. It's not necessary to put a capacitor between the two power supply pins; in fact it might be detrimental. |
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| fossil2k |
| You mean to say that both + & - supply rail to the op-amp need to have a cap grounded? |
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| fossil2k |
| Also, can you guys recommend the brand for each type of caps that is good??polyester?electrolytic?ceramic?etc? |
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| dpuopolo |
Yes, a cap from each power supply pin (+ -) to ground. Make the leads as short as possible.
Cap preference in this order:
Polycarbonate, mylar, ceramic disk, tantalum, electrolytic.
The best value for a bypass is mylar. They work fine and are cheap. Even Radio Shack will sell you two .22 50 volt mylars for $1.49. These are completely suitable and I use them frequently.
http://www.radioshack.com/product/i...rentPage=family |
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| fossil2k |
I have got some Mylar from Panasonic. Maybe will try this during the weekend.
Another question on the op-amp, it is running at half of its rated voltage but it becomes hot after 1hr. Could it cause by the 2nd internal op-amp not being grounded? |
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| djk |
| Could be oscillating and running hot (if not grounded). |
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| fossil2k |
| Thanks. Will ground it and test again. |
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| carlmart |
| Which quad chip are you using after all? |
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| dpuopolo |
| You need to 'turn off' unused amplifiers by connecting their output to their inverting input and then connecting their non inverting input to ground. This is ESSENTIAL! |
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| djk |
Post #22
"Should I shunt the inputs & output with resistors is 1 op-amp is not used in a dual op-amp package??"
On unused opamp sections I ground the non-inverting input and hook the inverting input to the output, no resistors required.
__________________ |
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| fossil2k |
Thanks for the advise. For the quad chip, I did not change them. As said earlier, I finally get a copy of the amp schematic and found that it is used for protection circuit, therefore I did not bother to change them. I will try the grounding of the op-amp and see if it will become hot..
I'm still looking at changing the op-amp. I have tried AD8065 on my CDP and find that the sound is good. I was recommended LME49710 but the price USD25 compare to USD6 for AD8065.. |
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| fossil2k |
| What is the best replacement for polystrene & stack foil capacitors?? |
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| AndrewT |
| quote: | Originally posted by fossil2k
What is the best replacement for polystrene & stack foil capacitors?? |
Hi,
what do you want to use either of these for??? |
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| fossil2k |
| Its mostly for signal path..I read in Creek catalog that they use stack foil..but most of the time I seen is polystrene?? |
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| fossil2k |
| Sorry...and polyester... |
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| AndrewT |
Polypropylene and polystyrene are both good for passing audio signal.
The big disadvantage of both is size and cost.
Polycarbonate was almost as good, but the film went out of production.
Poly everything else are the next step down but are usually smaller and cheaper. |
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| fossil2k |
| Sorry, it should be stack film capacitor..and not stack foil..Last few days was going through Farnell book and came across Panasonic ECA series capacitor which claim to be good in audio circuit. Anyone have use this before? |
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| carlmart |
| quote: | Originally posted by fossil2k
Sorry, it should be stack film capacitor..and not stack foil..Last few days was going through Farnell book and came across Panasonic ECA series capacitor which claim to be good in audio circuit. Anyone have use this before? |
I think stacked film and stacked foil are the same thing, but I maybe wrong with all these new nominations. Both are very good for audio. ;) |
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| AndrewT |
Hi,
the use of the descriptors film and foil sometimes get swapped by various manufacturers.
The generally accepted definition is foil is a separate metal foil alternately layered with an insulating di-electric.
Film is usually accepted as meaning a metallised surface applied directly to the surface of the insulating di-electric. |
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| fossil2k |
| On which section should i use them? Or to be precise, what type of application? For stack film, I can't find the values that I need from Farnell. Its 220pF. |
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| carlmart |
| quote: | Originally posted by fossil2k
For stack film, I can't find the values that I need from Farnell. Its 220pF. |
For that value use polystyrene. In fact always use polystyrene for any values you can get for, at least for audio applications. They are better than polyester, polypropylene and polycarbonate. |
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| fossil2k |
Another question on the op-amp, it is running at half of its rated voltage but it becomes hot after 1hr. Could it cause by the 2nd internal op-amp not being grounded?
I have grounded the op-amp and it is still hot..the op-amp is rated 18V max and the power supplied is 18V as well. Most probably it is operating at its max?? |
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| carlmart |
| quote: | Originally posted by fossil2k
Another question on the op-amp, it is running at half of its rated voltage but it becomes hot after 1hr. Could it cause by the 2nd internal op-amp not being grounded?
I have grounded the op-amp and it is still hot..the op-amp is rated 18V max and the power supplied is 18V as well. Most probably it is operating at its max?? |
Yes, it might be. Lower the voltage to +/- 15v.
Heat might be due to oscillation as well.
Can you please tell me which quad chip are you using after all? |
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| fossil2k |
How about these caps from the link below??
http://www.octave-electronics.com/Parts/mundorf.shtml
Based on the schematic attached, I've planned to change the caps from the input, 0.47uF, 220pF & 220uF. I have plannedto use 0.47uF from the above, 220uF will be BG and 220pF is an option left open. Any suggestions?
I have wanted to changed the capacitors as recently I've just tested a Creek CAS4040 and it sounded so open. In the catalog from Creek, it is written that they have used "valuable" polystrene & stack film capacitors. I'm really wondering if these are really making the amp sounded better?? |
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| carlmart |
The caps should be nice, even if a bit expensive. Put your big money on the input cap.
| quote: | Based on the schematic attached, I've planned to change the caps from the input, 0.47uF, 220pF & 220uF. I have plannedto use 0.47uF from the above, 220uF will be BG and 220pF is an option left open. Any suggestions?
I have wanted to changed the capacitors as recently I've just tested a Creek CAS4040 and it sounded so open. In the catalog from Creek, it is written that they have used "valuable" polystrene & stack film capacitors. I'm really wondering if these are really making the amp sounded better?? |
The Creek sound may not be only due to the caps, but to whole design.
Best film caps are usually polystyrene, bettered only by teflon caps. The only problem with polystyrenes are values availability.
It wouldn't be a bad idea using a .47uF polystyrene at the input, either by parallelling smaller values or finding one.
The 220pF should definitely be polystyrene. |
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| fossil2k |
| Thanks for the advise. I can't find stack film for the 220pF. I think I will just stick to the original polystrene or maybe those M Cap if they have this value. In Farnell catalog, Panasonic ECA series is used specifically for audio purpose. Anyone have used those? I'm trying to upgrade a CD52mkII and contemplating to use BG or Panasonic. |
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| carlmart |
| quote: | Originally posted by fossil2k
Thanks for the advise. I can't find stack film for the 220pF. I think I will just stick to the original polystrene or maybe those M Cap if they have this value. |
If the original is polystyrene, don't replace it. Polystyrenes only have two things against them mostly: larger size which may make them inductive in certain situations, magnetic terminals in some cases. But they have the lowest dissipation factor around, except maybe for teflon caps, which are too expensive.
| quote: | | In Farnell catalog, Panasonic ECA series is used specifically for audio purpose. Anyone have used those? I'm trying to upgrade a CD52mkII and contemplating to use BG or Panasonic. |
What are you trying to upgrade? The output cap? Just wire-bypass it.
There are some articles on the web on how to mod a Marantz CD52. |
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| carlmart |
BTW: also use polystyrenes for those small pF values you have. Try to avoid ceramics there.
If you can't find them try silver mica. |
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| jcx |
polystyrene has a few more issues:
extremely low temperature tolerance - you need to heatsink the leads while soldering, limit bake out, operating temps to <70 C
solvent sensitivity - incompatable with some pcb "flux cleaners"
and as far as anyone knows cap grade polystyrene isn't made any more - but with low demand and existing stocks this hasn't been a probelm yet |
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| carlmart |
| quote: | Originally posted by jcx
polystyrene has a few more issues:
extremely low temperature tolerance - you need to heatsink the leads while soldering, limit bake out, operating temps to <70 C
solvent sensitivity - incompatable with some pcb "flux cleaners"
and as far as anyone knows cap grade polystyrene isn't made any more - but with low demand and existing stocks this hasn't been a probelm yet |
Good points. You should be careful with these caps indeed. |
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| AndrewT |
Hi,
Polystryrene is reputed to have excellent sound quality.
That 220pF and the 6k8 input certainly will have an effect on the sound quality since the roll-off fequency is lowish in comparason to most other amplifiers. Significant phase angle change starting just above 10kHz with a 1.5uS filter vs 30kHz with a 0.5uS filter.
However, I must ask, if the 6k8 were reduced to around 1k to reduce the input time constant to operate solely as an RF filter rather than an top frequency filter, will polystyrene be the best choice any longer?
Would a lower inductance cap perform as a better RF filter that keeps attenuating the unwanted RF signal way beyond the frequencies that I think the polystyrene is beginning to flatten out? Would the benefit endowed by polystyrene still be audible if the RF filter were moved up and octave or two?
I would suggest that this amp will sound different if the two input filters were moved more towards a wide passband, but I suspect it would no longer sound like the original. My final question becomes:- which version sounds better? |
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| fossil2k |
It will only take a jiffy to solder these caps on and will take good care of them during soldering.
Andrew - What do you suggest I do with the resistor values? This is quite interesting to try.. |
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| AndrewT |
Hi,
these suggestions WILL change the sound of the amplifier and may also upset it's operation, but probably worth trying. Be prepared to revert to the original values.
Set the two input filter time constants to about 80mS to 100mS and to 0.75uS to 0.3uS.
This could be done retaining the 220pF and the series resistor reduced to 1k5 to 3k. Alternatively parallel the 220pF with a 330pF polypropylene and use ~1k0 as the series resistor. This works best with a low source resistance (Rs) unit preceeding the amplifier, certainly <=300r and preferably ~50r.
The bass/DC block could use the original 20k and a new 4.7uF film cap.
If the source also has a DC blocking capacitor then the pair of capacitors work in series and the usual formula has to be applied to the combination to then calculate the time constant.
The NFB DC blocking time constant does not need altering to match these input modifications. It can remain as 1k0 & 220uF giving 220mS. If you wanted to experiment with a better capacitor here, then do not drop it (or a parallel combination) below 150uF. |
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| fossil2k |
| First thing to do is to use original values with good quality caps. After some listening test, will try some new values. |
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| fossil2k |
| I have replaced the original Philips 0.47uF with M-Cap and 220uF Elna with BGs. It sounded more open but the bass sound subdue . I will let it run for few more days and see how it will sound then. |
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| fossil2k |
| quote: | Originally posted by AndrewT
Hi,
these suggestions WILL change the sound of the amplifier and may also upset it's operation, but probably worth trying. Be prepared to revert to the original values.
Set the two input filter time constants to about 80mS to 100mS and to 0.75uS to 0.3uS.
This could be done retaining the 220pF and the series resistor reduced to 1k5 to 3k. Alternatively parallel the 220pF with a 330pF polypropylene and use ~1k0 as the series resistor. This works best with a low source resistance (Rs) unit preceeding the amplifier, certainly <=300r and preferably ~50r.
The bass/DC block could use the original 20k and a new 4.7uF film cap.
If the source also has a DC blocking capacitor then the pair of capacitors work in series and the usual formula has to be applied to the combination to then calculate the time constant.
The NFB DC blocking time constant does not need altering to match these input modifications. It can remain as 1k0 & 220uF giving 220mS. If you wanted to experiment with a better capacitor here, then do not drop it (or a parallel combination) below 150uF. |
Hi Andrew, been busy for sometime and couldn't test out the recommendations you suggested. Will try once it out soon. |
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