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Opamps improve CD Player's Sound

So, if I'm following this accurately (as I'm using this for a crash course) we want :

a fast slewrate - but something that won't oscillate.
Low Noise.
Low Distortion.

What else? Does the + and - Feedback play in for this application as well? I'm assuming for Bandwidth, we're talking audio, so we're not looking at a huge range....

Anything else I'm missing?
 
You're actually looking at a frequency response beyond audio, as the function of the analog reconstruction filter is to reject sampling artifacts above 22.05 kHz. In an oversampled multi-bit DAC, there's considerable energy centered on the oversampling frequency (176.4 kHz for a 4x-oversampled system). If the op amp is too slow to follow this signal at its input, it slew limits, erasing detail and adding harshness to the sound. That's why slew rate matters. It's less of an issue with delta-sigma converters because the voltage step from one sample time to the next is small.
 
Again, you are talking about a signal level at the opamp output that is 1V RMS. Let's assume 1V peak, though. So if you have a slew rate of 7V/uS and assuming a linear response, which it is in that voltage region, it should be able to swing 1V in 1/7 of 1uS, or 0.143uS. This is the equivalent of a frequency of 7MHz. I contend that the LM833 would not slew limit with a frequency of 176.4 KHz or even 352.8 KHz for an 8 X oversampling frequency. Or even higher. It is not required to swing rail to rail in this application, so 7V / uS is more than adequate.
 
Wide bandwidth and good slew rate are desireable not for steady state frequencies as the last to posts have computed, but to minimize misbehavior on transients. Transients contain very high harmonic content. One thought about vacuum tube and digital audio is that the tube does not misbehave, an so sounds less harsh. I won't pretend to know what measurements correlate with misbehavior! I use the subjective word because it is fairly easy to heard when present and a blessed relief when absent. Quite often a lesser bandwidth device will sound better by simply rolling off the high order transients. There is a subculture of Nakamichi owners who dub CDs to cassette so they can listen to the music without digital harsh sound. As Dr. Audio says about any of these suggestions "I will have to listen". Amen.
 
Lady Ayeka said:
sorry, i just use it as a visual aid... there are new members joining all the time, so i figure there is always at least a few people out there who have never seen this magnificent player, and might be curious. i see it as my personal duty as one of the few AK evangelists of this CDP to educate and inform...:music:
Click to expand...

IMHO adding the same oversized image repeatedly does nothing to inform or add value. In fact I feel it becomes a visual distraction and makes the affected thread less readable.
 
It would be great to have some photo illustrations of this upgrade. I have looked up what they are and now what they look like, but step by step photos would just be so cool.
 
I agree with EchoWars - settling time is very important. The sample/hold/integrator in my CDP302 was an LF353 which was just about useless so I replaced it with an OP249 which settled the problem (excuse the pun). Also, the audio signal in the reconstruction filter runs at 2V so the 5532 or LM833 would be no good here as there would be distortion at the higher frequencies because the ratio of slew rate to bandwidth is unfavourable in this application. Again OP249s to the rescue. Measured distortion at full output is 0.003% which is acceptable I feel. For general purpose audio I like the OP275 as the distortion is 0.0006% with very low noise. I use a couple in my NAD2200 and the noise level at the output is unmeasurable - just a slight fuzz on the Tektronix 465B at maximum sensitivity.

Bryan
 
I bought 4 of the excellent Brown Dog DIP - SIP adapter boards and used them to upgrade the opamp in my Yamaha CD-3 player. I listened to it before I did the mod and the midrange was hard sounding and very fatiguing. I could only listen to it for 15 minutes or so. The bass was also wimpy. I put in OPA2228P, and now it sounds very nice, very solid bass and no more midrange nastiness. The adapter boards are made of FR4, .062" thick, with plated through holes and nice silk screening. You can use it for a DIP or SOP-8 part to replace a SIP part in your player. They have nice pins captivated and soldered in the board, that do not get loose when you solder the board in. The board is pretty small, so you shouldn't have a problem installing it in a tight space. They are $3.00 each and there is a minimum purchase of 4, money well spent.
 
OP amps upgrade for Yamaha CDP

I have a Yamaha CDX-750E and heard about a change of OP amps being a good thing to do for improved sound quality - I made sure I knew exactly which OP amps to swap and with what.
Well, I swapped them over (did this last year, and I wrote at the time....) - I'm still digesting the amazing change in the sound quality - first impressions, often the most accurate - much more bass ! something I always thought was lacking in this CDP - and a much more subtle soundstage - most noticable listening on headphones :thmbsp:

I was unable to fit the sockets I bought as the drilling pitch for the rows of holes in the PCB did not allow it (set too wide) -the rigid pins on the DIP8 socket were never going to go in :no:

So I now have 2 x BB OPA2228P instead of 2 x uPC4570C - in my CDX-750E and I love it ! :banana:
 
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sorenj07 said:
CMOY headphone amp that's about the size of an iPod. :thmbsp:
Click to expand...
Yeah... It's great to build until you end up breaking it because you don't know what you're doing, then throw it in a drawer for two years. Not that that's ever happened to me. Ever. :D
 
Just upgraded the opamps in my Luxman DZ-111 with OPA2134's I had lying around. It is noticeably better in sound; rounder bass, more clarity, depth and much smoother. It thought itsounded pretty good before, but now it REALLY sounds good!
 
Mike Stehr said:
I replaced all the slop amps in my old Carver tube CD player with BB (2134?) and AD (275?). They seemed to improve the sound over the JRC op-amps that were in the unit.
(Those AD/BB op-amps are probably getting a little long in the tooth nowdays...)

The Carver died, and the op-amps were used with sockets, so all the devices are in a vintage Onkyo CDP now. They improved the sound I suppose, but jacking up the capacitance is more noticed to me. The CD player has bass......
Click to expand...

OP inspired me to try opamp replacement in a dull & lifeless sounding Onkyo DX-710 cdp. I installed LM833NGs in place of the stock JRC4560DX (4ea) and was rewarded with a significant overall improvement in SQ, especially bass. The price paid, however was an attendant harshness that wears me out after about 20 min. of play. BTW, I got the same results from replacing stock JRC4558Ds with LM833NGs in a Sony CDP-350Z.

Questions:
1. Does "jacking up the capacitance" cause the harshness I described?
2. How does an opamp increase capacitance?
2. Are we talking about the "digititis" I often read about being present in the sound from many cdp's?

Please speak slowly as I'm nowhere near being an electronics man. Just an ex-maintenance electrician that can de-solder/solder PCB components.

I stumbled across the answer to my harshness problem (this Internet thing really is too cool, sometimes) which is adding inductance. 27uH in the cdp/preamp interconnects and 47uH in both legs of the 120vac to the cdp. These modest mod.s cleaned up and smoothed out the sound quite well. The oinker now sounds very, very good. No fatigue, all the newly gained SQ is still there, a real pleasure to listen to. :music:
As a result I've put aside plans to purchase a new, $550 Onkyo DX-7555 cdp.

I know what has happened, but I'd like to understand better the how and why.
 
I suspect the harshness you heard could be the opamp's reaction to the capacitance in the cables you are using to connect the player to your amp. The inductors you installed would provide some isolation from that capacitance, and also attenuate the highs. 1K resistors would be better.
 
Mazeppa said:
Questions:
1. Does "jacking up the capacitance" cause the harshness I described?
2. How does an opamp increase capacitance?
2. Are we talking about the "digititis" I often read about being present in the sound from many cdp's?
Click to expand...

What I meant by jacking up the capacitance is taking most of the original electrolytic capacitors thoughout the circuit, and replacing with capacitors of higher capacitance values.
Same voltage rating or higher.

Changing the rectifier diodes in a CDP with high speed diodes like HEXfreds, will make a noticable improvment.
Maybe not in the way of sound, but more in the way of performance I suppose....

Sometimes swapping one particular Op-amp specced for a certain bandwidth to another one of a different specced bandwidth, can cause the op-amp/amps to oscillate at a high frequency. The high frequency oscillation can cause a harshness in the upper midrange and treble......the oscillation affecting lower orders of harmonics in the audio band.
That's just from what I understand. I'm too certain at all to be honest.
 
dr*audio said:
I suspect the harshness you heard could be the opamp's reaction to the capacitance in the cables you are using to connect the player to your amp. The inductors you installed would provide some isolation from that capacitance, and also attenuate the highs. 1K resistors would be better.
Click to expand...

1K resistors will be tried. So maybe not an actual increase of cdp output capacitance, but a reaction to connected capacitance. Hmm, that sounds plausible.

I installed sockets so opamp "rolling" may produce different reactions to the connected capacitance, eh?

BTW, the interconnect inductors also seemed to "tighten up" the bass, would that be expected? I try not to underestimate the ability of my mind to get my ears to hear things that may not be there, but I want to be. Especially possible when getting down to the finer details of what I'm hearing.

Thanks for getting me started on the opamp thing. Made a real gem out of the Onkyo I posted about. Now I'm eyeing my preamps.....

Another thing I'm trying soon are the DIY pro interconnects constructed out of Canare cables and jacks from the sticky in "Thinking Out Loud". They are supposed to be very low in capacitance. Perhaps another good answer to my problem.

This kind of stuff makes this hobby a lot of fun for me.
 
You can certainly try some of the other opamps mentioned in this thread. As to the inductors and the interconnects and the bass...I dunno about that one. It wouldn't make it worse, I am sure of that. It would roll off the highs, though.
 
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