| Author | Message | ||
     Mike H |
Anyone found a "good" sounding LM1458 or "good" sounding replacement for the LM1458 op amp? What do you like about it? Where did you get it? How much was it? It seems that op amps can flavor tone much the way preamp tubes can. It would be great to compile a list of who's used what and the results. | ||
| Mike H |
In response to my own post, here's what I've found. I tried four different op amps in lieu of the LM1458. I tried a JRC4558, NE5532, TL072, & OPA2228. All were new parts. I have a 112 RP 65 with 7 ops amps. The phaser uses 3, pretty much. All of the op amps were functional in the amp, except in the phase inverter position, IC-7 on my amp. The newer faster chips created funky bad sounds in IC-7. Here's how they did otherwise. OPA2228: worked fine, did sound a hair thin, but not real noticable. NE5532: I had high hopes for this chip, but it overdrove the preamp -- clean sound was not possible. Not a bad overdriven sound however. Might be a good chip for the OD in an RP amp? JRC4558: Maybe a bit punchier -- nominal difference from the LM1458 TL072: Maybe a bit thin -- nominal difference from the LM1458 Lesson I learned: LM1458 op amps are the cheapest around, they work find in my amp -- put them in and forget them. | ||
| Mike H |
I used 2N6488 driver transistors. Could I be hearing slight oscilation from these transistors? | ||
| Steve Kennedy (admin) |
What are the symptoms that would lead you to believe that your driver transistors are oscillating? You might have a leaky or open cap in the output stage that is responsible for your degraded audio quality. Steve | ||
| Mike H |
Thanks for the follow-up, but ignore that last post! My amp's up and running, sounding great! | ||
| Graham Heath (gheath) Username: gheath Registered: 03-2009 |
Hi Mike I've been playing around with my 112RP65 combo for a while with mixed results. I used NE 5532's but got a strange after fuzz on clean notes, the engineers at work had a look and reckoned that one of them was going into HF oscillation and causing the problem. I've just put JRC4558's in and she seems fine, a litlle less noisier, apart from when the reverb's cranked. Had my amp for 29 years now from new, she's looking a little tired but I really can't find anything that sounds that good, at least not in the sub £2k mark. Will have some amp knobs spare soon if anyone needs some too. Regards Graham |