LC Audio has now discontinued their AD825 upgrade, stating that the there are better chips on the market now.
http://www.lcaudio.dk/com/ad825.htm
However, they don´t state which chips they have in mind.
Of course, "better" is subjective, depends on usage, design taste etc.
But does anyone have an idea which opamps they might be talking about?
Or experiences with newer opamps in preamp circuits?
I will be using it in a preamp based on a single opamp. Just one single stage after the volume pot to drive the rather lowish (10k) input impedance of my power amp.
(presently using OP37, as I had some lying around... i know they aren't top of the league!)
I will try out the AD825's, but any other recommendations? AD8610?
http://www.lcaudio.dk/com/ad825.htm
However, they don´t state which chips they have in mind.
Of course, "better" is subjective, depends on usage, design taste etc.
But does anyone have an idea which opamps they might be talking about?
Or experiences with newer opamps in preamp circuits?
I will be using it in a preamp based on a single opamp. Just one single stage after the volume pot to drive the rather lowish (10k) input impedance of my power amp.
(presently using OP37, as I had some lying around... i know they aren't top of the league!)
I will try out the AD825's, but any other recommendations? AD8610?
Thanks!
Thanks a lot - will keep you all posted on what I find out.
I had some hassels with the OP37 in the beginning, was in doubt if they could be used at all as they are not unity gain compensated.
The first version definately sounded "funny" somehow - boombox-type bass and white noise in the trebles.
I thought capacitive load might be a problem; decided to bypass resistor in feedback loop with 30pF as recommended several places. Was not a succes, and made the thing produce DC offset (?!? don't really understand why).
So I removed the caps and increased the resistor in series with the output (recommendation from AD) which was a very big improvement. Maybe the load was simply too small?
I haven't got around to intense listening tests yet; but my impression is that the bass still isn't quite right - a little inflated and resonant, but not deep.
I guess I will try increasing the output resistor a little more, and add more decoupling caps (presently only using 100nF's).
Cheers - cdl
Thanks a lot - will keep you all posted on what I find out.
I had some hassels with the OP37 in the beginning, was in doubt if they could be used at all as they are not unity gain compensated.
The first version definately sounded "funny" somehow - boombox-type bass and white noise in the trebles.
I thought capacitive load might be a problem; decided to bypass resistor in feedback loop with 30pF as recommended several places. Was not a succes, and made the thing produce DC offset (?!? don't really understand why).
So I removed the caps and increased the resistor in series with the output (recommendation from AD) which was a very big improvement. Maybe the load was simply too small?
I haven't got around to intense listening tests yet; but my impression is that the bass still isn't quite right - a little inflated and resonant, but not deep.
I guess I will try increasing the output resistor a little more, and add more decoupling caps (presently only using 100nF's).
Cheers - cdl
Attachments
cdl said:Hmmm - and OPA627 even comes in DIP package so I can just plop it in... definately a must-try if I can lay my hands on some!
...oh better check the pin connections first...
Pins are almost exactly the same on the OP27/37 and OPA627. Perfect drop-ins, except for the DC trim you will probably not use.
There is another difference between them: the OPs are all bipolar types, and the OPA627 has a FET input.
The 27/37 types are more sensitive to power supply quality, and will probably respond more dramatically to improvements there.
The 37 should be used on greater than x5 gains, but neither should be used with more than x10 gains.
But the 627/637 types should bring improvements all along, do not hold any doubts about that.
It would be an easy way to upgrade what you have now, with minimum fuss.
Carlos
OPA627's are a good choice. Subjectively, they sound very clean and effortless as long as the outputs aren't overdriven
(i.e. >600ohms) If greater load driving capabilities are needed, you can use the BUF634 in the feedback loop to drive very low loads and retain good distortion characteristics
(i.e. >600ohms) If greater load driving capabilities are needed, you can use the BUF634 in the feedback loop to drive very low loads and retain good distortion characteristics
Thanks for the tips - have used the last couple of days ordering engineering samples
Some of them should be arriving today, so with a bit of luck I will experiment in the weekend!
Does anyone know of any changes to a standard opamp circuit that should be made in order to accomodate the current-feedback types?
B.T.W. those SOIC to DIP adapters are painfully expensive at Farnell - cost as much as the opamp itself!
/cdl
Some of them should be arriving today, so with a bit of luck I will experiment in the weekend!
Does anyone know of any changes to a standard opamp circuit that should be made in order to accomodate the current-feedback types?
B.T.W. those SOIC to DIP adapters are painfully expensive at Farnell - cost as much as the opamp itself!
/cdl
Search word OP37 and I get thisBricolo said:
http://focus.ti.com/general/docs/si...numRecords=25&searchTerm=op37&statusCode=null
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