Opamps and Modding thread.

That is a good point, but I suppose it also depends on how much gain is used on the opamps...like if they are being used in a unity gain config. or something then they are probably more or less fulfilling a bufferring role.

I've only got an Audigy 2 and an Live 5.1 and those are both using surface mount components, so it restrict my opions somewhat...

Still, a discrete Class A/DoZ output stage in place of the opamp would be cool - even though it would probably be noisier and have more distortion lol

 

Measured noise with RMAA is still below -80dB. Acutally the Prelude gave me some noise with an opamp installed. Now I can turn up my amplifier to max without hearing any noise.

 

DoctorO,

Have you run the full sweep of RMAA tests with your modded Prelude? If there is insignificant degradation in its measured performance, then that would certainly be an incentive to try the mods out although refining the opamp choice might remove the primary question I have had about the bGears board. "Through the board" caps make their replacement something that a person could reasonably expect to accomplish without a disaster so that board seems to offer several avenues for improvement.

Installing new opamps on the b-Enspirer would be a challenge, but if a full replacement of the surface mount caps like NapalmV5 did can be pulled off, opamp replacement might possibly be something that I could do. It is unfortunate that the Prelude does not allow for an easy replacement of the Center/Sub opamp as well as the Mains'.

With the Enspirer you aren't risking as much.


michael

 

I leave out the last three tests (too much fluctuations to be comparable). Measurements in crosstalk, dynamic range, and noise level became a few db worse, but nothing to worry about imo.

 

I'd be inclined to avoid a capacitor swap...I doubt it will make much difference if proper components were used in the first place.

 

Caps can make alot of difference depending on which ones you change. The caps used on the Prelude are decent quality but there are much higher quality caps out there with a lower ESR ratings etc that are designed specifically for audio applications. Especially coupling caps. Power filtering caps etc. Changing them can make a very noticeable difference in sound quality. When you consider the low quality caps used on other soundcards they can make a large difference.

 

Hmm, but decoupling should make much difference to the sound at all I would've thought, especially if you're just driving an input on an amp?

Power coupling caps are usually just filterring DC - so as long as it's not wildly out of spec and not doing its jod of removing any ripple, it just has to be 'big enough'

It's like having 40000uF of decoupling on a headphone amp - it won't sound any different to 4000uF because you're not throwing so much current around that the voltage across the cap drops - and also, considerring most caps are such huge tollerances anyway - like -10/+50% is often what most electrolytics are rated at. Again, this is why I don't see how a lower ESR rated cap would have an impact. Low ESR caps are deffinetly worth having if you're building a 100W Class A amp which has 1.5A standing current accross the output, but most of the components on the board will be drawing a single figure number of mA, if that...

Please correct me if I'm wrong...I can see why it would make a difference if it was in the signal path, but you're not going to have a huge electrolytic in the signal path in the first place.

 

Better components are always better. Some have more impact on the sound then others of course. Power caps will help but sometimes they can have little audible difference. Caps in their simplest sense are filters. So if you absolutely NEED to have them in the circuit better quality filters are better then cheap ones. Coupling caps are very important and a very big subject just on it's own..You can usually remove them from a soundcard unless you have a significant DC issue as most amps will have decoupling caps on the inputs. These can also be changed or improved for better sound quality. I am shopping around fr a set of coupling caps for one of my amps.
Capacitors in audio are a very large topic and I read quite a few documents on the subject.
People have varying opinions on couplings..power filtering etc.etc.

 

I've just been doing some reading on the subject myself, it's an interesting topic. As usual, Rod Elliot has come to the rescue

http://sound.westhost.com/articles/capacitors.htm

It's a very interesting read, and unlike a lot of articles on audio, he actually includes measured results.

Of course, if one is building something from scratch, you're going to choose appropriate components rather than ones that are being used out of spec, but as I said before, any self respecting company would never use bits beyond their rated spec in a product meant for consumer use.

For my personal use, I would never consider swapping capacitor, but to each his own I suppose

The articles does a much better job of summing up what I was saying:

 

Well everybody has their opinions on the subject. The trouble is most companies will use a part that just fits within tolerances and usually the cheapest ones.
Audio capacitors are a very big market they can change the sound considerably if used in the right positions. If you think they are not needed for anything, don't use them. Audio is subjective.

 

Yep, I agree with you. As it's such a subjective...subject, there isn't really a right or wrong answer.

I suppose it just depends how far you are willing to go - you can always go one better with components...

If you do find components which make an audible difference though, I'd love to hear which parts you find to be best.

 

ive downloaded rightmark so heres my first audio mark ever.. lol

what in the world does that mean, first time ive seen these kinda benches

good/bad ?

i did the generate wav then analyse wav and thats the results

ive ran the playback test but at the end nothing shows up

can u guys tell me how to properly bench @ rmaa.. thanks.. scuze my noobness

 

^ never mind

this will have to do

 

OscilloMeter

modded MX300


modded claro+


modded prelude


modded xmeridian

 

I'm searching for a new opamp again and I was curious if there is an audible difference between the "b" and "s" grades.
I had a pair of OPA627 "AU" so far and could get a pair of OPA637 "BP" rather easily. The OPA 637 "SM" seems to be rather hard to find and extremely pricy. Is it worth the expense?

 

au (ac) bp (dc) if im not mistaken

bp & sm better grades

au or bp is fine/alright for prelude

am/sm badly needed on xmeridian

 

SM grade opamps are the highest graded available. Specifications are very tight. These would be the grade the Military, Aerospace and medical instruments would use. When very tight tolerance are needed with no place for noise and/or distortions in the signal.
Hope that Helps.

 

I haven't tested out any "SM" version yet. I doubt you would hear any difference between the other two version. You MAY hear a difference between the SM and AU version. Depending on what you have for playback gear _the SM version would be more exacting and have less distortion, not to mention a shield to prevent EMI/RFI..... They are pricey....

 

I saw a price of around 120$ for the couple, could that be correct?
I had the AU so far, at least I can say I found it nicer sounding than the stock opamp.
I'm listening to what the card delivers by a so far good set of headphones (Ultrasone HFI 780, looking for a recable there) and a small headphone amp (Meier Audio Headsix).
The difference between the original LM and the OPA 627 AU was rather dramatic, definitely easy to tell apart. Maybe I'll opt for a pair of 637 "B" first and "see" how they sound.

 

120$ sounds a bit high, they’re on ebay for 85:
http://cgi.ebay.de/Burr-Brown-OPamp...ZWD1VQQ_trksidZp1638.m118.l1247QQcmdZViewItem

I got my AD797s from this seller, he’s reliable but shipping might take a while thanks to customs etc...

I recommend trying no opamp first if you have an external amplifier.