chasmo Posted April 5 Posted April 5 Hi. I have a tri-amplified system using 5" wide band paper cones for the mid bass/lower midrange(125-500Hz), 3" full range cones for the midrange (500-3,000hz) and planar tweeters for the treble(>3khz). The amplifiers have sockets to allow for changing the (dual) op-amps. I have 4 pairs of op-amps to select from: OPA2134, OPA2604, OPA1656 and LM4564's. Anyone have experience with these op-amps and suggestions for which frequency range each one works better(best)? I appreciate your kind comments coming from actual experience with these op-amps. -Chuck
mbz Posted April 5 Posted April 5 What opamp is originally installed? Are the replacements compatible (current draw, +/-V,,,). I've used LM4564's and OPA2134 in preamps but not as you are intending. The OPA2134 performed well in the midrange warmth/presence/"air" area so as a first attempt I'd try that. The LM4564 was VERY slightly more clinical and I'd be using it for the tweeter duties. Since you have sockets you will eventually try "all" combinations so let us know what worked best.
chasmo Posted April 6 Author Posted April 6 Thanks for your comments. My amps are: Douk Audio A5 (low mids), needed here for its adjustable high-pass filter. Aiyima A07 (upper mids) Aiyima A07 ((treble) The above amps all came with NE5532's, and my replacement op-amps have similar current draw plus they are pin- compatible. The only one I'm worried about is the LM4562, which I've heard can oscillate if used improperly.
chasmo Posted April 6 Author Posted April 6 I forgot to add that I also have available two other fresh op amps: OPA1642 OPA1612 I haven't received them yet, but I hear they are cutting edge.
aussievintage Posted April 6 Posted April 6 On 06/04/2025 at 4:19 AM, chasmo said: Anyone have experience with these op-amps and suggestions for which frequency range each one works better(best)? Opamps are designed for any frequency from 0 hertz (DC) to frequencies many many times the frequencies you are dealing with. Over the small sub-range you need, performance will remain consistant, so pick the one you like and use it for all three.
chasmo Posted April 6 Author Posted April 6 Thanks for the info. Since it is often stated that some op-amps have a brighter presentation while others have better midrange, I've decided to "hedge my bets" and place the slightly more bright one in the treble amp. My tweeter is very smooth and I'd like a little more twinkle in the high frequencies. Furthermore, If all the reviews are imaginings of the deluded, then still I've lost nothing by putting two different comparable op amps in their respective amps. Thx again
aussievintage Posted April 6 Posted April 6 40 minutes ago, chasmo said: often stated 40 minutes ago, chasmo said: all the reviews You seem to think the majority think this way, but I think you have just sampled audiophile sources of information, not the wider electronics community. I have experimented with opamp rolling and heard nothing reliably different, say, between the NE5532 your stuff came with, and the OP2134. 41 minutes ago, chasmo said: I've lost nothing I agree, well, nothing but the cost, which is likely to be insignificant for most opamps.
chasmo Posted April 26 Author Posted April 26 Well, I had an opportunity to try each Op amp in the various amplifiers and find I prefer the following: Low mids: OPA2134 Upper mids: OPA1656 Tweeter: OPA1612 The 2134 has just the right upper bass/low midrange warmth, the 1656 has the cleanest midrange and treble, with a broad soundstage. The 1612 has the best upper treble with nice "bite" on trumpet and cymbals. Of course this wasn't a controlled, double-blind test, but merely careful listening with familiar material. Of course, YMMV. 1
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