[aych]

Hey! I had 2 questions; seeing if anyone have suggestions around here.
1. Can someone recommend a 'audiophile' quality op amp? I am trying to replace the amp in my C&C XO amp, I heard it was replaceable with a DIP socket.
2. Has anyone replaced it before? any pointers? suggestions?

 

[balou]

there are quite a few threads on this subject. it probably has a dual opamp in it - a few suggestions would be lm4562, opa2107, ad8066, ad8620. there's a statement on the manufacturer site that they use a JFET opamp - maybe a little hint that you should not use bipolar opamps in this design. all the opamps I mentioned above are jfet ones. two popular bipolar ones are the lm6172 and the ad8397. stay away from the former to avoid potential problems and don't ever think of using the latter

Well, I don't think there's much more to say. They promote the ability to change opamps, so it should be quite easy.

 

[aych]

Im sorry, what do you mean by former and latter? Also I heard the burr brown makes good op amps?
Also, does a dual op amp mean a dual channel, or two of them?

 

[Pars]

I'll answer for him. By former, he means the LM6172... by latter the AD8397. Of the opamps he mentioned the OPA is a Burr Brown... the AD opamps are Analog Devices. I wouldn't get too attached to Burr Brown is best or AD is best, depends on the opamp and the circuit.

A dual opamp is 2 channels (or stereo). A single is 1 channel, so normally you need two of them...

 

[NelsonVandal]

LM4562 is bipolar and sounds bipolar but could be used as a drop in replacement for a JFET input opamp. Very low DC-offset. AD8397 isn't as troublesome as people say, when used at low voltage (<= 9V). It can even be used inside a feedback loop.

 

[aych]

I heard the opa627 or the ad843 were good amps. but i only find that they come in singles. anyway i can find a dual channel? or the opa2227 i heard was a good cheaper alternative.
can i put a fet amp in this one since it has a jfet?

 

[Pars]

The OPA2107, although not expressly stated, is a close dual to the OPA627/637, from what I've heard. Not sure about the AD843...

You can get browndog adapters, one or more which adapt two single opamps to a dual

http://cimarrontechnology.com/

Tangent sells these, and they are available elsewhere. You just need to know what package type your singles are going to be (DIP-8 thru-hole or SOIC-8 surface mount are the most common).

 

[aych]

oh. 1 more thing. i finally got brave enough to open it up. its a ad823 inside!

 

[NelsonVandal]

I personally don't like AD823 (I really think it's crap). Some like it though, but I can't understand why. There are many better opamps like AD8066, LM4562 = LME49720, AD8599 etc that you could just drop in. Some require the obove mentioned BrownDog SOIC to DIP adapter. They're quite cheap, and well worth a try. There are many opamp reviews on head-fi, read them and buy some opamps that you find promising. The opamp is the major part in this kind of amps.

Look at the iBasso D1 thread in the amplifier section. Many have replaced the AD823 and report major improvements.

 

[majkel]

If you go singles, stay away from AD843. I don't understand the appreciation for this chip. It is harsh and sounds simply unpleasant. Another expensive but not inteded for audio is OPA627 which sounds a bit thin and laid back, like a living dead. It's good for analysing music, not listening for pleasure.
I also have to agree NelsonVandal. AD823 is mediocre, noisy, harsh and artificial in sound.
Good dual drop-ins, like partly said before are: AD8066, OPA2604, AD8620, OPA2107. They are FET input so they have negligibly low bias and offset currents which is much more important than the offset voltage itself. More attention must be paid when applying bipolar op-amps but LM4562 or AD8599 should be worth a try. LM6172 is nasty as hell so definitely not recommended for DIY beginners. AD8397 is not that problematic but very power hungry and sounding just in your face and a bit bright. When not well paired with differently sounding components, it's sound might be offensive.
The last word goes for single op-amps: the only types I know worth going into one per pckage are AD744, AD825 and AD845. The first one is snappy, realistic, with very good spatial definition but might be a bit cold and sibilant when the application doesn't compensate this effect. The second one is probably my favourite. It's snappy, thick sounding with lots of positive energy in the sound, rather forward in presentation but a bit hazy. Pairs well with other components providing good depth, however it's limited transparency and straightforward presentation create a very nice, intimate atmosphere. Also it sounds pretty colorful. AD845 is something specific, it resembles the sound from tubes, no aggression but it's not laid back the way as most BB's. It's smooth and colorful at one time, calming but not boring. Quite interesting op-amp.

There are people saying that OPA134 x2 sound better than OPA2134, the same can be with OPA604 against OPA2604. The former I can confirm however it's still the same kind of sound, the latter I haven't verified and know the 604 only.

 

[holland]

You don't need the AD8397 for your C&C XO. Don't even consider it. It's too power hungry and has built in buffers, which you don't need. It sounds like the XO has a discrete output stage of up to 1W/channel (I wonder how it sounds!!). Add that to the AD8397 and you'll have no battery in no time.

I would definitely try the LM6172, if it's only an input stage, but yeah, tricky if you've never even touched a meter.

My current favorites (without built in buffers) are AD8066, AD8599, and LM4562. There's something "harsh" about the AD8620 that I don't quite like.

Do some searching, there's been a number of reviews of different opamps by different people.


The question really is more of

1) What kind of sound do you like?
2) How does the opamp affect the sound in the XO? It probably won't be as apparent as the load (headphones) being driven by the opamp itself.

I would tend to look for a fast chip in that situation, slew and settling times.

What's the gain on the opamp stage in the XO? Some opamps are not unity gain stable, and some require a gain of 5 or more.

 

[aych]

oh boy. Lets see if I can help myself out here.. haha. Let me begin with my setup.
Sony SA3000, monster cable mini to mini 12in. panasonic discman, 1st gen =)

I've never touched a meter... if you mean oscilliscope, but I do have some experience with volt / amp meters.

I am looking for something with a little heavier bass, I find the sa3000's to be a tad lacking. I put in a dual op134? the very basic one, and i can say, it does sound quite a bit muddier, and overall worse.

From my research, my understanding on speed, slew and settling,
I was looking at something with high / fast bandwith, and high speed setting too. something with a fast voltage change, and low ground noise?

Am I on the right track?

Thanks for the help people!

 

[aych]

^^

 

[gritzcolin]

Well I too am wondering if anyone experienced has upgraded the opamp in the XO?

 

[aych]

Yea, I just upgraded it with one from national. its alot cleaner, and I prefer it because I listen to alot of female vocals. Its not too difficult, esp. if its a DIP amp already, if its a SOIC then you'll need a browndog.