mrarroyo
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Post by mrarroyo on Mar 4, 2011 23:38:07 GMT
I received the op amp LME49720HA very fast even though it had to travel across the pond! Thanks mate. I fitted it to an adaptor including a heat sink and proceeded to replace the NE5532 in Solo SRGII. For the record I have liked the sound from this op-amp and its predecessor the LM4562 for a long time, however I am not sold on how it sounds in the Solo SRGII. Specifically I believe I hear a bit a harshness and shrillness regardless of the can I use. I have allowed the op-amp to burn-in for about 25 hours and will try another 25 before making my final determination. Attachments:
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Post by Deleted on Mar 4, 2011 23:46:58 GMT
I received the op amp LME49720HA very fast even though it had to travel across the pond! Thanks mate. I fitted it to an adaptor including a heat sink and proceeded to replace the NE5532 in Solo SRGII. For the record I have liked the sound from this op-amp and its predecessor the LM4562 for a long time, however I am not sold on how it sounds in the Solo SRGII. Specifically I believe I hear a bit a harshness and shrillness regardless of the can I use. I have allowed the op-amp to burn-in for about 25 hours and will try another 25 before making my final determination. Miguel That would be more than likely due to inadequacies in the PSU area .(bypass caps etc.) The LM4562 is very fussy about it's power supply. Does the SRG2 use a SMPS plugpack ? Alex
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mrarroyo
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Our man in Miami!
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Post by mrarroyo on Mar 5, 2011 8:47:33 GMT
Actually I am using an special edition of the Little Pinkie that Mike made for me. It is a 24 VDC unit.
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Post by Deleted on Mar 5, 2011 20:00:09 GMT
Miguel, There is a (small ?) chance the IC's are oscillating ! In some amps you simply cannot take out slower opamps, 5532 with 10MHz is not superfast, and substitute for higher frequency devices (55MHz for 49720) without proper decoupling of it's power pins. In some amps there is not even any decoupling present or it is done at the wrong place some distance from the IC itself or simply at the wrong point. Decoupling caps MUST be mounted as close as possible to the powersupply pins (pin 4 and 8 dual opamp and 4 and 7 single opamp) and both power pins should be bypassed to ground or at least 1 cap between both power pins. Once you have done that evaluate again. This has nothing to do with 'voicing' but pure technical proper decoupling of IC's which NOT all manufacturers do. before passing judgement you should better check this aspect. Perhaps Alex can be of assistance or you could ask me.
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Post by Deleted on Mar 5, 2011 21:37:00 GMT
Miguel, There is a (small ?) chance the IC's are oscillating ! In some amps you simply cannot take out slower opamps, 5532 with 10MHz is not superfast, and substitute for higher frequency devices (55MHz for 49720) without proper decoupling of it's power pins. In some amps there is not even any decoupling present or it is done at the wrong place some distance from the IC itself or simply at the wrong point. Decoupling caps MUST be mounted as close as possible to the powersupply pins (pin 4 and 8 dual opamp and 4 and 7 single opamp) and both power pins should be bypassed to ground or at least 1 cap between both power pins. Once you have done that evaluate again. This has nothing to do with 'voicing' but pure technical proper decoupling of IC's which NOT all manufacturers do. before passing judgement you should better check this aspect. Perhaps Alex can be of assistance or you could ask me. Miguel Frans is spot on again, as usual when it comes to purely technical matters. The actual solution may not be so straightforward with this amplifier, without having access to the schematic. Many of Graham Slee's amplifiers use "rail splitter" tecniques to run the amplifier off a single +VE supply rail, instead of using dual + and - power supply rails. If a member has access to this schematic, then perhaps they could forward a copy to Frans without posting it ? Frans (or myself) could then provide what will be a very simple and easy to perform modification using perhaps a couple of tantalum capacitors ? Alex
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Post by Deleted on Mar 5, 2011 23:02:17 GMT
Instructed by Frans (can't thank him enough) I decoupled the LM4562 as described above in my X-Cans and there is absolutely no trace of harshness or sibilance. Only sweet incrdebly detailed sound with a huge sound stage and astounding separation between instruments.
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mrarroyo
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Our man in Miami!
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Post by mrarroyo on Mar 6, 2011 0:29:29 GMT
Funny you mention oscillation, a while back I received a similar response from Graham which of course I did not understand (now or then). I guess I will be going back to the NE5532 which I like a lot.
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Post by Deleted on Mar 6, 2011 1:25:23 GMT
Funny you mention oscillation, a while back I received a similar response from Graham which of course I did not understand (now or then). I guess I will be going back to the NE5532 which I like a lot. Miguel That's a copout ! Aren't you even game to at least try something as simple as a 4.7uF 35V tantalum capacitor (small) connected between pins 4 and 8 underneath the PCB. The marked +VE side of the capacitor would go to pin 8. Alex
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Post by PinkFloyd on Apr 8, 2011 21:48:01 GMT
Funny you mention oscillation, a while back I received a similar response from Graham which of course I did not understand (now or then). I guess I will be going back to the NE5532 which I like a lot. Miguel That's a copout ! Aren't you even game to at least try something as simple as a 4.7uF 35V tantalum capacitor (small) connected between pins 4 and 8 underneath the PCB. The marked +VE side of the capacitor would go to pin 8. Alex Graham will do anything he can to avoid "paying" for anything half decent.... he's all about cheap parts / max profit..... he will tell you "everything" negative about a part he doesn't use and will do his best to convince you that NE5532 (and other cheap chips) is the ONLY chip on the planet worthy of the "Graham Slee" seal of approval. Of COURSE he (I / you / anybody) could optimise the LM4562 for use in his glorified CMOY "Solo" amp..... if he WERE to use it it would cost him a LOT more...... that's the ONLY reason he doesn't use it......
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Post by Deleted on May 21, 2011 7:16:57 GMT
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