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FWIW - I did this in an old T100. Don't know what they are now using for t80, or the 200 series.
I used the new LM4562 for I/V and buffer (4 op amps in all). VERY significant upgrade, and easy & cheap.
History: could not find the BB opa627s which need to be browndog mounted ($18 for the op amp and $3 for the carrier EACH). They are just plane out of stock, so I tried this new National op amp. For about $5 apiece you get a lot of performance. IMO.
Follow Ups:
What power supply voltage are you running these opamps at?
-chas
15 V
In the I/V conversion stage, the stock Cayin CDT-17A uses (4) AD827. For filter/buffer (4)OPA604 for balanced xlr and (2) OPA604 for RCA.I prefer to listen to listen to the RCA outputs, so this is what I have been modding(caps, wires etc).
First I replace (2) OPA604 with (2) OPA627 in buffer stage. The 627 has far more resolution and refinement IMO. But I still was unhappy with the sound.
Few days later, I replaced the AD827 with LM4562 in I/V stage. The LM is MUCH smoother/musical/transparent/refined. I hope that it stays this way because I like what I'm hearing. Gone is that etched high-speed sound of AD. If you are into speed, then the LM is not for you.
(I have (4) LME49710 on the way to me that I will compare to OPA627 and OPA604)
I went back to the AD827 in I/V because the LM4562 is not "fast" enough to my ear in this position.Will try the single chip version in the filter/buffer position and report back on that.
IMHO, the LME49710 is better than the 627 and better than the 845 and better than the 5534. The 627 has some fantastic properties in terms of input current, and it's no slouch in most other areas, but you're paying a lot of money for parameters of little use in audio circuits. I found 845 a bit bright/harsh, and the 5534, though a solid performer for many years, falls short of the modern stuff.
There's usually a few general things you can do to improve things.
Well, here is what I have done. I think every one of them helped the sound get more 'real-er'- Bypass caps (0.1 uF) on the PS electrolytics
- Bypass (since I am cheap) on the output caps for the tube output (pulled out the 2 uF Wima and replaced with Auricap)
- Disabled the headphone section (basically pulled the wiring to/from it)
- 396a instead of 6n3 tubes for the analog out section
- if there was something else, I have forgotten by now....Maybe future stuff - Remove caps and R for the tube input from buffer section (where I put two of the 4562's). Remove the buffer (4562) and low pass filter (5532)??? I.e., go right into the tube input from the I/V chip?? Others, I think, have tried these, but not I.
Have fun!
Jim
just ordered (4) of the for iv stage from digi-key, also bought the last pair of opa627 that percy had left.
hmmm, I wonder if TI is still producing the OPA627? We shall see.
Don't know if you can do a head to head comparison with these two op amps, but if you can, that would be a nice qualitative piece of information.... It is just a pain to do that : )
Jim (trioid)
I just ordered the single version LME49710 to compare to OPA627.
Please, let us know what you hear.
Later,
Jim
I used the same chips on a Mid nineties Sony ES CDP and a Sony DVP-S7000 and got results like yours. The LM4562 is a great sounding Op-amp. Some people have issues with what it's spec sheet says. Personally, I'm enjoying the heck out of the improvrd sound quality.
... but a lot of the paramters for the LM4562 are quite nice. And in the end, there is no comparison between the musical presentation between the OPA2604s and these. IMO.
One very strange thing I noticed (not the first time I have hear this!); it took quite a while (like 50+ hours) before they really settled in.
Someone PLEASE give me an explaination. I work on semiconductors, and I have no clue why the sound quality would change .... and no, I don't think it is me getting used to their sound....
jim (trioid)
Are you saying the 2604 is not musical??
I just recieved the 627 and replaced a pair of 604. So far, the 627 sounds more refined than the 604. And also more ambience/transparency but I see that clinical/clear detail is not its strong point.
This is in the filter/buffer position.
I plan on replacing NE5532 with LM4562 in the IV position.
Also will compare the LME49710 to 627 in the filter/buffer.
No Sir, I am not saying the 2604 is not musical. Subjectivity as much as possible aside, I like the detail and 'bass punch' of the 4562 better than the 2604. {I would hope that we got somewhere with op amps in the past 8+?? years. Me thinks so.}
IMO the whole system you are listening to has to add together to get what you want. The OPA627 is one fine chip (on paper). Musical? I cannot say since I have not had the pleasure of trying one.
GIC - the Ne5532 is also a very fine chip, I think, even though it is cheap. But again, I did not replace it, so I will be watching for your opinion on that. Even though the 5532 is a 'jellybean', it has some impressive characteristics.
Cheers,
Jim
...and they're still good chips.
At somewhere like $8 each they were more well respected.
CAC
good luck.
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