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Op Amp Rolling

GXAlan

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Personally I'm pretty skeptical. In his provided measurements, even the lowly TL074 has noise down at redbook level and distortion well below what most people can hear.

It’s interesting that the TL074 is the other op amp used in the Luxman phono EQ. Night and day difference though.

But even then, I agree with you. For Moving Magnet use (34 dB of gain), the combo of the stock op amps were not too bad. It’s only in Moving Coil mode at 52 dB of gain that it is a real issue. Most DACs don’t need this type of gain. My real world problems were also with a very low output moving coil cartridge as well.

I think this is where a nugget of truth can lead down to a cascade of unnecessary op amp rolling.
 

Vigovsky

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An example of replacing a pair of dual operational amplifiers JFET OPA 1642 (SMD, SOIC)
instead of JFET OPA 2134 (SMD, SOIC) in the output stage of one balanced DAC.
I recently made a replacement. Measurements taken from the XLR output.
The result: the output stage with the 1642 has 1.6 dB better dynamic range and lower IMD distortion.
 

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SIY

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The sound is definitely more meaningful and clear, with bass registers and percussion instruments being particularly well-structured tonally.
That is rather unlikely.
 

antcollinet

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It’s interesting that the TL074 is the other op amp used in the Luxman phono EQ. Night and day difference though.

But even then, I agree with you. For Moving Magnet use (34 dB of gain), the combo of the stock op amps were not too bad. It’s only in Moving Coil mode at 52 dB of gain that it is a real issue. Most DACs don’t need this type of gain. My real world problems were also with a very low output moving coil cartridge as well.

I think this is where a nugget of truth can lead down to a cascade of unnecessary op amp rolling.
I'd accept in high gain phono preamp circuits the noise level of the TL074 may be a bit on the high side - and audible for that.


Any line level stuff though - unlikely to be audible.

Not an excuse to design them in to any new gear though.
 

OldHvyMec

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Well, darn it, got my "free for evaluation" Burson Audio V6 VIVID dual op amps today, and as I feared, they won't work in the original Aiyima A04 or A07 - small surrounding caps are too close for the bigger VIVID amps, even with the lifters. Anyone know if these will fit in the A07 MAX? Looks like there is more cap room around the sockets there, but the case is not very deep. Failing that, are there any of the new crop of amps that has a taller case that can accommodate these?
What about the OpAmp plug extension for a dip 8?

 

SIY

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What about the OpAmp plug extension for a dip 8?

If you roll in a high bandwidth opamp, they can be very useful for inducing oscillation. This can destroy a lot of other circuitry, which allows the roller much opportunity to learn something about the circuits he's now repairing. If everything goes well, it can even cause failure of other parts of the electronics chain, which allows the roller to help the economy by needing to buy new gear, thus promoting the audio industry.
 
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sergeauckland

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An example of replacing a pair of dual operational amplifiers JFET OPA 1642 (SMD, SOIC)
instead of JFET OPA 2134 (SMD, SOIC) in the output stage of one balanced DAC.
I recently made a replacement. Measurements taken from the XLR output.
The result: the output stage with the 1642 has 1.6 dB better dynamic range and lower IMD distortion.
So in other words, not worth the effort.
Or have I missed something?

S.
 

Joe Smith

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What about the OpAmp plug extension for a dip 8?

Ah. Well, that's clearly what he should have sent with these instead of just the regular lifters. They seemed interested in getting a new review of someone using an original A07, and if they have a sample of the amp, they should have realized the V6 amps would not fit. Thanks for the link. Perhaps they will send me some of these, if not, I'll just pass the amps on to someone else.
 

audiopip

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As a general point the op amp supply voltage on most TPA35xx amps is 0v to +12. Many pro audio op amp stages use +-15,18 or even 24 volts (OPA604/2604). Running op amps on what is effectively +/-6v will/may compromise the performance and introduce audible defects. Some are more tolerant than others. Just a thought
 

antcollinet

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As a general point the op amp supply voltage on most TPA35xx amps is 0v to +12. Many pro audio op amp stages use +-15,18 or even 24 volts (OPA604/2604). Running op amps on what is effectively +/-6v will/may compromise the performance and introduce audible defects. Some are more tolerant than others. Just a thought
It won‘t compromise performance at all as long as the output voltage doesn’t need to swing too close to the rails. Clearly amps can be designed successfully with this PSU since there are TPA amps that measure as well or better than most of your “pro audio“ amp stages.
 

audiopip

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I'm sorry I didn't explain very well. Lower supply voltage tends to increase sonic differences IMO. When cost is not so crucial split supplies lessen this effect. And of course higher voltages improve headroom.
Hence opamp rolling in these low cost amps may be more audible. First post on this forum not looking for an argument.
 

Doodski

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I'm sorry I didn't explain very well. Lower supply voltage tends to increase sonic differences IMO. When cost is not so crucial split supplies lessen this effect. And of course higher voltages improve headroom.
Hence opamp rolling in these low cost amps may be more audible. First post on this forum not looking for an argument.
The premise that a circuit designed for lower Vcc +/- rails will sound inferior to a higher voltage rail design is a generalization. :D
 

Doodski

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First post on this forum not looking for an argument.
LoL... My first post regarded a dedicated DIN phono cable that I chopped up and made a RCA cable from and boy O'boy did that attract some attention here at ASR... Hehe... So don't get frustrated if you are questioned on stuff. It's just normal here. Nothing personal.... LoL.
 
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