opamps

[Ember]

any chance that anyone has like some sort of A/B comparison on the differences that an opamp swap can make in a unit. Personally i'm modding the art mp project series but any model and manufacturer is welcome i was just curious as to the impact that opamps can make.

[mshilarious]

It wouldn't really be a generally applicable comparison, because it depends on the rest of the circuit, and what the opamp is doing in the circuit.

ART uses OPA2134 in the MPA Gold, and that is also a good swap into an MP. But any sound samples you'll hear aren't likely to be a simple opamp swap, because most modders will recap the MP and change the tube as well.

[antichef]

sounds fun - I've got a Tube MP (not project) that I socketed (and replaced a bunch of caps), which currently has OP2134s. I've got a few other models I could try. What sort of sound would you want to hear, and through what sort of mic? (I don't have any Neumanns )

Replacing the capacitors cleaned up the sound a lot, but maybe that would help expose any differences in the opamps.

[sweetbeats]

antichef, when you replaced the caps did you use a specific audio grade cap or general prupose? I have a Tube MP OPL.

[antichef]

Originally Posted by sweetbeats

antichef, when you replaced the caps did you use a specific audio grade cap or general prupose? I have a Tube MP OPL.

I just used what they had at Fry's. I just took the unit apart, and I apologize, but I can't seem to remember much of what I did - I must have been partially following the instructions in the BLA pdf. My unit has two opamps (both socketed now), and they're definitely OPA2134s.

[Somnium7]

Installing sockets like antichef did is a great idea. You could then buy or order samples of several different types of opamps and try them out.
Recapping is also a good point that was brought up. You may just want to try doing this first. For electrolytics I recommend Nichicons - almost any series will be an improvement. Bypass (parallel) those with 0.1uf poly (polypropolene) caps and you will be surprised at the difference.

If you want to get hardcore give the poor damn thing a real power supply with decent noise rejection and again you will be amazed compared to whatever crap regulator they put in it.

See my posts about my Toa Rx-7 where I describe not only some different opamp options and their applications but also the effects of recapping and power supply rebuilding. Even though I am working with a large format console the things I did can be applied to any analog audio gear in some fashion.

[sweetbeats]

Somnium7...I'm "going there" with my Tascam 58 and M-520...probably will with the Tascam M-x (mystery mixer) as well...

I know you have a lot going on right now...what a road. May it be going to better and better places for you.

If you have a chance to chime in on any of the above, I sure would value your input.

[mshilarious]

Originally Posted by sweetbeats

Somnium7...I'm "going there" with my Tascam 58 and M-520...probably will with the Tascam M-x (mystery mixer) as well...

I know you have a lot going on right now...what a road. May it be going to better and better places for you.

If you have a chance to chime in on any of the above, I sure would value your input.

Do those Tascams have SIPs or DIPs? SIPs are pretty hard to find these days . . .

[sweetbeats]

dip...

that's in answer to your question, not a personal attack or anything...hahahaha...ha

How's that for the new guy making an old joke?

[evm1024]

here is one persons impressions of opamp sounds in a headphone amp. I would not take it as fact but it is an effort and does catalog many of the common opamps.

Regards, Ethan

http://www.tangentsoft.net/audio/opamps.html

[mshilarious]

Originally Posted by evm1024

here is one persons impressions of opamp sounds in a headphone amp. I would not take it as fact but it is an effort and does catalog many of the common opamps.

Regards, Ethan

http://www.tangentsoft.net/audio/opamps.html

That comparison is a good example of what I was talking about. Most of those chips weren't designed for that kind of load. Many of that guy's comments are very strange. Why is slew rate critical in a headphone amp, when peak-to-peak voltage is probably 3V max? How does the performance of these opamps at 64 ohms (or less) have any relation to how they perform, as designed, with a 600 ohm load? What predictive value does this comparison have for use of these chips in a line-level circuit?

Not much . . .

I use TLV4112 for a headphone-drive opamp. That can dish out the current!

For a more realistic comparison of opamps:

http://www.sg-acoustics.ch/analogue_...distortion.pdf

[evm1024]

Don't miss the point and do recall the grain of salt....

As for Samuel Groner's new paper - a name we both respect and an exciting resource.

--Ethan

[evm1024]

I got a chance to reall all of Samuel's paper and found it quite interesting.... A number of very highly regarded opamps are listed as having marginal desirability for audio applications. Which goes to show us that sonic desirability is hard to measure.

I am specifically thinking of the LT1358 where it is concluded that "This part might be interesting where good high-frequency distortion must be achieved at low quiescent current; otherwise there seams little to recommend this part."

For me the low quiescent current make this part a very desirable upgrade to TL072. Plus reports by Jim Williams and others inidicate that the LT1358 is very nice sounding upgrade.

As was noted before - other components play a significant if not dominate role in the sound". Don't expect magic with an IC change alone (grossly paraphrased....)

--Ethan

[mshilarious]

Originally Posted by evm1024

I got a chance to reall all of Samuel's paper and found it quite interesting.... A number of very highly regarded opamps are listed as having marginal desirability for audio applications. Which goes to show us that sonic desirability is hard to measure.

I am specifically thinking of the LT1358 where it is concluded that "This part might be interesting where good high-frequency distortion must be achieved at low quiescent current; otherwise there seams little to recommend this part."

For me the low quiescent current make this part a very desirable upgrade to TL072. Plus reports by Jim Williams and others inidicate that the LT1358 is very nice sounding upgrade.

Yeah, oddly enough he seems mainly interested in the super-high end, but then tested a number of low-end chips and panned them. I didn't quite get that.

I'm all about low quiescent current. And low noise. I'd like both, but there are certain laws of physics working against me . . .