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Old 5th August 2007, 07:54 AM   #1
arupg is offline arupg  Latvia
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Default Which Opamp Do U suggest ??

In my dac where an opamp is the final amplifier driving the RCA outputs, the Stock opamp was a OP275. Replaced this to OPA2134 and the results were better. Now onto OPA2107 and the results are even better.

Adequate PS bypass is present using 470uF electrolytic with 0.1uF Vishay MKP 1837 for V+ to G and V- to G. Supply is well regulated +/-12V.

Which Opamp do you suggest for:

1. Better soundstaging - wide, deep and with real 3-dimensionality.
2. Even tonality - top to bottom. No peakiness.
3. The opamp is heard using B&W 800D speakers with highend amps and a passive controller. The listening chain is neutral and transparent.

Suggestions will be welcomed. Thanks!
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Old 5th August 2007, 10:09 AM   #2
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Hello arupg,

You can find some solutions to this post :
http://www.diyaudio.com/forums/showt...postid=1264799

Eric
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Old 5th August 2007, 12:47 PM   #3
arupg is offline arupg  Latvia
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Eric: Thanks for pointing me towards your Thread.

Unfortunately, it doesn't give much ideas except for LM4562 being hot on the upper high freq with some circuits.

What I'm looking for is a balanced chip as per my post earlier. I am also not sure whether to stick to BB or AD. Lot of people have had good results with AD while some mention that high prices and their SOIC designs have kept them away.
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Old 10th August 2007, 07:55 AM   #4
lucpes is offline lucpes  Europe
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Very simple, while taking into account the requirements for a dual opamp.

AD8620: lots of detail, needs proper power filtering otherwise you might find it "harsh" or lacking bass. Some might find vocals thin.

OPA2107 or OPA2228: more of the laid-back Burr-Brown sound... similar to OPA627 but with somewhat lesser detail than AD8620. Vocals/midrange seem to be better on BB opamps at least to me.

National's LM4562 or the newcomer LME49720MA seem to be the best from what I've read. Did not try them I have three LME49720MA coming over with great hopes.
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Old 10th August 2007, 05:47 PM   #5
arupg is offline arupg  Latvia
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Lucpes: Thank you for giving a detailed feedback on the opamps.

Just to tell you all, I am finding the OPA2107 great but somewhat slightly 'nasal' on some CDs which are a little processed in recording. It does tend to give the overall feeling of "slight hifi sound" rather than sound totally natural.

I wonder whether any corrections is possible by Biasing the OPA2107 into Class-A as recommended by CarlosFM. He also recommended using ideally approx 7 to 8mA of current for the opamp. Premium resistors like Vishay Bulk-foils or Caddock were advised since mounting these to the output of the opamp would have a direct reflection of the resistor's sonics.
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Old 12th August 2007, 06:32 AM   #6
arupg is offline arupg  Latvia
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I biased the OPA2107 for 7mA of current draw and the entire opamp started to sound authoritative. The entire bass line was in a totally new dimension - deep, taut yet wonderfully rounded and natural. The mids were lush, warm and the nasality gone forever. The treble was great, "if a little attenuated". The treble part was the region that just didnt fit wonderfully with the rest of the spectrum.

The opamp was then biased for 5.5mA (looking at the datasheets of 2107 vs 627) and yes, the 2107 cant handle too much Class-A biasing. The treble area opened up beautifully while all that occurred with the 7mA biasing earlier in the bass and mids remained exactly where they were.

Class-A biasing is beginning to reap the goodies!!

Anyone using OPA2107 has had results with Class-A biasing? Feedback will be most appreciated.
Thanks!

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Old 13th August 2007, 03:56 AM   #7
wleediy is offline wleediy  Singapore
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Default 4580 and OPA1632

I have just bought 3 DVD players, 2 of them for US$ 35 each ( under the brand name of Tinwe and Nakamuchi (with USB to play MP3), I also bought a Pioneer A600 DVD player that has SACD and USB inputs playing MP3, this one cost about US$ 240. So sorry about the MP3 thing, but my purpose is just to see how good it can be pushed to. the MP3 has improved to the point that there is little trace of digital sound, it rolls off at the high as well as lack of dynamic/live, however, the ability to compile and to play back 10 CDs in a continues mode at night is very handy...
Anyway, all of them has 4580 output with single rail ps and 27.000 crystal.
Tinwe sounded the best, near first class CD player sound and much better then the Pioneer and even Toshiba 3560. this is some time the reward of fishing around. The walkman size Nakamuchi has lots of motor and digital noise that I can only reduce a bit by adding all kind of lytics at all points of power supply.
The 4580 op amp sounded so so. Adding a 6k resistor to the ground in the Pioneer improved the sound very significantly. It has 12V b+ single ended PS rail.
I have not changed them yet as they are surface mount. I have only the DIP OPA2132/2134, and THS4032 in MSOP. However, I have OPA2846 in SOIC which I will probably try after I get a smaller soldering iron.
As the Pioneer is using PCM1742KE which has about 2.7 volts DC at the output, I really like to build a single BC550 output stage direct coupled to it with a first order filter -3db at 24Kc/s at the collector resistor to see how the sound is vs the Op amp. I might add an emitter output stage if I need a second order filter. I have previously use a direct 1742 output with very fantastic sound, except the gain is on the low side...
So I will try 2846 and the BC550 output to se if I could live with it.

Best rgds to all
WLee
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Old 13th August 2007, 06:38 AM   #8
arupg is offline arupg  Latvia
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Hi WLee:

Nice informative post. Do let us know who wins between Opamp vs BC550.

Good Luck!

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Arup
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Old 13th August 2007, 07:06 AM   #9
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The Tinwe apparently has a 24 bit 192 Khz DAC.
So what chip is it and is the analog stage using JRC4580 ?
If it's a BB chip the player is a steal at $35/- !
How do they sell it so cheap ? Is this the normal street price for this machine?
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Old 13th August 2007, 09:21 AM   #10
wleediy is offline wleediy  Singapore
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Default Op amps and cheap DVD players

hi there,

As I opened all 3 DVD players almost at the same time, I have so far only done the replacing of the rectifier diodes to FR 4007, and increasing the lytics caps to Sanyo green caps, which I find to have nice sound. So far I have not done much with the Tinwe, and I did not see any seperate Dac chip yet. Will take the board out and flip ot to see what is below. on top there is a 4580 for microphone, and 1 more 4580 for the output stage. Well yes, this Tinwe MP4-6800 has karaoke set up for 2 mikes, and remote volume control... talking about value!
I was busy with the Pioneer in the last 2 days, now with a 6K to the ground at the 4580 output, at last the sound is ok, not very satisfying, but it's ok, and I need to at least close some of the chasis. I just put on the tinwe again, well, it sounds much better then the US$ 250 Pioneer still... yet I have only done the minimal on it - replace the rectifier to Fr types, and adding 3 lytics at the 5V and +/- 12 V PS....
The sond is lively and not fatiguing. With good dynamics and nice, thick and round sound, yet delicate high. This is a unique machine, it even has a small fan built in, which for nw I have disconnected it. The only area that Pioneer is better is in the video quality. I bought it in a mall in Jakarta about 2 weeks ago, it was actually being sold for it's ability to track any difficult DVD... the demo showed it playing DVD that has many holes.
Let me take out the board and see what kind of DAC it has.

best rgds

WLee
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