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In Reply to: RE: TDM crossover - opamps upgrade? posted by KanedaK on May 24, 2018 at 00:54:53
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Follow Ups:
OPA2132 is excellent IMO. Highly recommended.
"Without followers, evil cannot spread." Spock
I'm no fan of oPA2134, is 2132 much better?
The new OPA1642 seems very interesting. Only available as SMD part, but they are sold on DIP8 adapters on the bay. Has anybody already tried it?
While it's not as completely different like a bi polar device I would say it's much better. I prefer fets from my experience. I went from the 2704 which people like a lot to love and found it too warm and bloated, and that's saying something since I lean in at least the warmish, "musical" direction and am always looking for more and deeper bass. The 2134 I thought was significantly better but it didn't make me stop looking. The 2132 made me stop looking. It is a pretty high end device IMO. It's still in the fet family. It is not super duper fast or etched but very musical, ballanced and clean. This rolling was done in a dac. YMMV T456
"Without followers, evil cannot spread." Spock
Thanks tweaker, I will keep it in mind.
Still hesitating on leaving the NE5532, but tL072 have to go for sure!
If the TLO72 has to go so does the 5532!!!!!!!!!!!!!!!!! IMHO
"Without followers, evil cannot spread." Spock
I'm sure - for having tried it myself - that the lM4562 n the right circuit sounds better than NE5532.
what's I'm scared of is the likely inadequacy of the local decoupling for the faster LM4562. I remember having to try different decoupling schemes using 0,1uF MLCC capacitors close to each opamp. In my cD player (where NO local decoupling was originally present! no kidding) I settled for one 0,1uF from V+ to V- pin under each chip, and one 0,1uF from V- to ground, almost ON the pin.
Here I have 0,1uF close to each pin (V- and V+) for each input and output buffers (about 0,2 inch close) but the other opamps on the circuit share a couple of 0,1uF wich are located on the power rails between 1inch (closest opamp) and 2inches (fartest opamp) of the chips, wich I think won't be good enough for LM4562. I wonder, if I add local decoupling 0,1uF under each chip, if I should leave the original 0,1uF on the power rails, or if the redundance might prove detrimental and I'd better clip them off?... power rails also have, for each channel, a bunch of 100uF electrolytics (Nichicon KZ): two are located about 2inches aways from the input/output buffers, and two are located about 2inches from the filter opamps. I guess those are well located and will stay there. I don't think I need to add more capacitance with electrolytics closer to each opamp?...
It's all very complicated because I'm completely sure the crossover WILL sound better with better opamps BUT I'm scared of oscillations or bad behaviour and I don't wanna ruin the circuit. I don't know much but i do know opamps aren't "plug and play"...
I'm also planning to use machined, gold-plated sockets; not because I wanna be able to "roll" different opamps in the future, but because I don't own a temperature-controlled soldering iron, and I'd rather overheat the sockets instead of the chips themselves; but i've read sockets can be detrimental for the performance (even tho everybody seems to use them nowadays)...
You change out the pamphlet for a different one. Most circuits are tune just for that opamp in that circuit, so you need make sure.
Even if the new opamp looks fine you really won't know how it will act until it's connected with load/s it will be driving and then the load may cause oscillation.
I changed out an OPA 2134 for a OPA 2604. It looked great and was not oscillating on the scope. I connected it to the load it would be driving and that 2604 opamp was ringing like a bell! I tried everything to stop it from rising but nothing helped. So I couldn't use it for that application.
Be careful with sockets, some opamps have trouble with sockets and it can cause oscillation too. Saw this first hand too so I'm not going off what someone said or what I read somewhere else.
Try it use a scope and then try all the tuning process to try to make the opamp work. From rail bypassing techniques to compensation in the feedback loop to isolation resistor on the output. Then if all fails move on to a different opamp. Try to match the opamps as best you can spec wise and then go from there.
Hope this helps.
I'm 99% sure I can replace the TL072 with OPA2132 without problems.
For the LM4562... I might wait a little. Maybe I'll be happy with just the TL072 out of the way for a while. I will proceed step by step, in any case.
Some op amps are plug in and play and some aren't.
"Without followers, evil cannot spread." Spock
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