According to Reference Audio Mods http://www.referenceaudiomods.com/parts.html#BG:
We'll be honest, opamps degrade sound. They are not ideal for audio. We much prefer the sound of discrete parts, however, and unfortunately most digital gear are designed with opamps and the only practical way for increased performance is to replace with better opamps. We feel the 2 very best opamps are the Burr Brown OPA627's and the Analog Devices AD825's both offering rather different flavors. The 627's provide a warmer more laid back presentation with tubelike ambience whilst the 825's offer a faster,cleaner, more dynamic sound. The choice lies in your taste for sound, system needs, and musical preferences.
We'll be honest, opamps degrade sound. They are not ideal for audio. We much prefer the sound of discrete parts, however, and unfortunately most digital gear are designed with opamps and the only practical way for increased performance is to replace with better opamps. We feel the 2 very best opamps are the Burr Brown OPA627's and the Analog Devices AD825's both offering rather different flavors. The 627's provide a warmer more laid back presentation with tubelike ambience whilst the 825's offer a faster,cleaner, more dynamic sound. The choice lies in your taste for sound, system needs, and musical preferences.
OpAmps for bass guitar
Thanks for the reply Peter. I am rebuilding a1974 MusicMan HD-130 bass amp that was given to a friend of mine and I may be going overboard but it was free. I understand from the Harmony Central website that this is a real classic from Leo Fender after he sold his company to CBS, it has a crome plated chassis! It has 1968 vintage LM307's, probably older than you are. It has (4) EL-34's in the output section(130 Watts) and the new OpAmps (three stages- input- tone control-current gain) will be feeding a 12AX7 driver/phase splitter. I just need to know what OpAmp will give me bass that will make my spine shake, or does it matter with the tubes on the output. I know of some great tube amps made for bass guitar(MesaBoogie), so tubes can produce great bass. This amp is unique in that bass amps today have tubes in the preamp and solidstate in the power section. So think back to what OpAmp has better bass slam, OPA-627, AD-843, AD-825, AD8010 or whatever and not taking into account any frequency above 2500hz or so.I would appreciate your opinion. KMcC
Thanks for the reply Peter. I am rebuilding a1974 MusicMan HD-130 bass amp that was given to a friend of mine and I may be going overboard but it was free. I understand from the Harmony Central website that this is a real classic from Leo Fender after he sold his company to CBS, it has a crome plated chassis! It has 1968 vintage LM307's, probably older than you are. It has (4) EL-34's in the output section(130 Watts) and the new OpAmps (three stages- input- tone control-current gain) will be feeding a 12AX7 driver/phase splitter. I just need to know what OpAmp will give me bass that will make my spine shake, or does it matter with the tubes on the output. I know of some great tube amps made for bass guitar(MesaBoogie), so tubes can produce great bass. This amp is unique in that bass amps today have tubes in the preamp and solidstate in the power section. So think back to what OpAmp has better bass slam, OPA-627, AD-843, AD-825, AD8010 or whatever and not taking into account any frequency above 2500hz or so.I would appreciate your opinion. KMcC
I think some of the mentioned opamps are overkill (my normal style 
), especially the OPA627! It's very expensive and is also a precision opamp, but it doesn't hurt to use it. I use it in my DAC with execellent results. I'm impressed with the low offset voltage (<0.1mV!).
My professional advise here is to use a opamps with
slew rate > 5 V/µs
noise < 10 nV/SQR Hz
distortion sufficiently low (noone has high distortion)
I think even a TL071 will do the job fine! Avoid LM324/358/741 etc!!!!!
Check for NE5534/32, OPA2134, OPA134, OPA2604, TL0xx
), especially the OPA627! It's very expensive and is also a precision opamp, but it doesn't hurt to use it. I use it in my DAC with execellent results. I'm impressed with the low offset voltage (<0.1mV!).My professional advise here is to use a opamps with
slew rate > 5 V/µs
noise < 10 nV/SQR Hz
distortion sufficiently low (noone has high distortion)
I think even a TL071 will do the job fine! Avoid LM324/358/741 etc!!!!!
Check for NE5534/32, OPA2134, OPA134, OPA2604, TL0xx
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