best choice for upgrade from LF353P OP AMP - diyAudio
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Old 20th August 2008, 07:03 PM   #1
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Default best choice for upgrade from LF353P OP AMP

My Parasound power amp model 2125 two channel had LF353P op amps at the input board I removed those and installed opa 2132pa chips to try. are these considered an upgrade to the LF353 chips? They seem to produce more detail, and smoother all around sound. I also have some opa 2134, and opa 2604 would either of these be a better choice to try? Thanks!
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Old 20th August 2008, 08:58 PM   #2
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Default Found some opa 2132P Amps also!

I don't know the difference between the opa 2132pa and the 2132P versions soundwise, but any way I have found a couple of those also. I think it may boil down to either the 2134's or, the 2132P any opinions before I change out the 2132pa's with the 2132P's? Thanks!
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Old 21st August 2008, 02:45 AM   #3
Bonsai is offline Bonsai  Taiwan
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Quote

"Parasound power amp model 2125 two channel had LF353P op amps at the input board"

John (Curl) are these used in the signal path or are they doing some other function?
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Old 23rd August 2008, 06:32 PM   #4
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I got to thinking, maybe the two LF353P op amps might be for the 12v. trigger turn on circuit which, I will never use. could I safely unplug one of the chips from it's socket to verify whether or not it is in the signal path? Thanks!
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Old 23rd August 2008, 06:51 PM   #5
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Old 23rd August 2008, 06:52 PM   #6
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Unless it's performing a DC servo task there is no problem with unplugging an op-amp.
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Old 23rd August 2008, 07:18 PM   #7
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Quote:
Originally posted by richie00boy
Unless it's performing a DC servo task there is no problem with unplugging an op-amp.
Thanks richie00boy! I might try removing the top chip since I can reach it with no problem.


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Old 23rd August 2008, 08:23 PM   #8
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Well, I removed the top chip (opa2132P) and had no left channel output so I assume, the bottom chip is for the right channel. now, I guess I need to decide on which op amps I want to use for replacement of the LF353P (original amps). on hand I have opa2604, opa2134, AD826, LM6172, OPA2132pa although, the AD826, and the LM6172 may be too fast, and also have much higher dc offset levels than the other chips. any suggestions on op amps, decoupling, bypassing etc? Thanks!
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Old 26th August 2008, 08:23 PM   #9
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My B&K AVP1000 also has 11 of LF353N (not 'P') together with 4 of OP249G, and I was thinking of swapping them all out for LM4562 based on their low cost (~$3) and overall good reviews here on DIYAudio. I believe my other low-cost choices are OPA275 (~$2.50), OPA2134 (~$2.50, which I have read are 'dull'), and AD823 (~$6.50, so not exactly 'low-cost').

I don't have the schematic, but based on a quick peek inside, it appears the LF353 does tone control and surround stuff, while the OP249 is more 'important.' Either way, I would just swap them all out. Was the OP249 an 'audiophile-approved' choice back in the day when this preamp was made? Any other thoughts on a simple swap?
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Old 27th August 2008, 10:40 AM   #10
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Originally posted by Tosh
I would just swap them all out. Was the OP249 an 'audiophile-approved' choice back in the day when this preamp was made? Any other thoughts on a simple swap?
re do all the decoupling and compensation.
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