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OpAmp in preamp
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Old 18th September 2002, 01:02 AM   #1
Kevin McCready is offline Kevin McCready
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Question OpAmp in preamp

Can anyone give me their two cents on what OpAmp has great bass impact, slam, dynamics etc. irregardless how it's upper frequency sounds.It will be going into a tube driver for a tube output section and will be used for bass guitar.
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Old 18th September 2002, 01:10 AM   #2
Peter Daniel is offline Peter Daniel  Canada
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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.
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Old 18th September 2002, 01:44 AM   #3
Kevin McCready is offline Kevin McCready
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Default 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
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Old 18th September 2002, 08:06 AM   #4
peranders is offline peranders  Sweden
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OpAmp in preamp
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
/Per-Anders (my first name) or P-A as my friends call me
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Old 18th September 2002, 08:30 AM   #5
sonnya is offline sonnya  Denmark
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Go for AD8610!! this baby does sound good! But remember! it does not eat more than +/-13V supply voltage!

Add some biascurrent to the output to one of the rails through a current source or just a resistor so you run the output in class A. Makes the sound warmer!

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