Hey Erik,
I think there are a number of drop-in replacements (although they may not be the same package type) for the OPA627/637.
The AD825 is supposed to be quite good and many people seem to prefer it, although there would need to be an adapter to the DIP package in my case.
Otherwise, how about the OPA134 or OPA132? There are a bunch of LM op-amps as well, but I have no experience with them..too bad the other op-amps I have on hand are all duals (I have several 2134 from a CMOY I built!)
There is a fairly long thread about op-amps here, although they are discussing dual opamps
http://www.diyaudio.com/forums/chip-amps/82610-best-sounding-dual-opamps.html
I think there are a number of drop-in replacements (although they may not be the same package type) for the OPA627/637.
The AD825 is supposed to be quite good and many people seem to prefer it, although there would need to be an adapter to the DIP package in my case.
Otherwise, how about the OPA134 or OPA132? There are a bunch of LM op-amps as well, but I have no experience with them..too bad the other op-amps I have on hand are all duals (I have several 2134 from a CMOY I built!)
There is a fairly long thread about op-amps here, although they are discussing dual opamps
http://www.diyaudio.com/forums/chip-amps/82610-best-sounding-dual-opamps.html
LME49713 - this is current feedback opamp. Not for this application. See datasheet.
It's very good in passive riaa as an output stage.
Here - LME49710, very good LME49990 specially as a 1st stage (very low noise).
Or AD8065 but requires max 2x12V supply - 2nd stage. Faster with greater output current.
I think it's much better than OPA627/637 which are overrated. ;-)
It's very good in passive riaa as an output stage.
Here - LME49710, very good LME49990 specially as a 1st stage (very low noise).
Or AD8065 but requires max 2x12V supply - 2nd stage. Faster with greater output current.
I think it's much better than OPA627/637 which are overrated. ;-)
OPA627/637 are like Black Gate N type, not too many people understand how to use them properly 
OTOH, why not try OPA27: http://www.diyaudio.com/forums/analogue-source/133191-phonoclone-3-a-36.html#post2948701
OTOH, why not try OPA27: http://www.diyaudio.com/forums/analogue-source/133191-phonoclone-3-a-36.html#post2948701
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Yes. ;-)
For example LME49990 has 5 times less noise than OPA627/637.
That's why it should be used as a 1st stage in this application with low source impedance - or another bipolar opamp.
For the same reason fet opamp (627/637/132/134/8065 etc.) should be used in a 2nd stage. Here impedance seen on the inputs is much higher.
All about it is written in great book about phono preamps - Amazon.com: The Sound of Silence: Lowest-Noise RIAA Phono-Amps: Designer's Guide (9783642197734): Burkhard Vogel: Books
BG N & 627/637 are not only recipe for very good sound.
;-)
For example LME49990 has 5 times less noise than OPA627/637.
That's why it should be used as a 1st stage in this application with low source impedance - or another bipolar opamp.
For the same reason fet opamp (627/637/132/134/8065 etc.) should be used in a 2nd stage. Here impedance seen on the inputs is much higher.
All about it is written in great book about phono preamps - Amazon.com: The Sound of Silence: Lowest-Noise RIAA Phono-Amps: Designer's Guide (9783642197734): Burkhard Vogel: Books
BG N & 627/637 are not only recipe for very good sound.
;-)
More gain.....
If there is more gain needed (+ 15dB), for instance when a Denon DL-103 is used, it is possible to change the second stage as follows.
R2 = R3 = 1k8
R4 = R6 = 1M
R5 = 100k
C2 = 3.3nF
C3 maybe the same (10uF) but may be changed to a 4.7uF
The gain of the first stage is R1 / cart. imp. x loss factor (due to the parallel RIAA cap)
For a DL-103 this will be 1620 / 40 x 0.9 = 36.45 x
The gain of the second stage is R5 / R3
For the original this will be 33k / 3.3k = 10 x
For the modified 15dB + version this will be 100k / 1.8k = 55.55 x
Output of a DL-103 with the original components = 0.3mV x 36.45 x 10 = 109 mV
Output of a DL-103 with changed components = 0.3mV x 36.45 x 55.55 = 607 mV
Difference in output is 14.9 dB
If you want less gain change R2 and R3 to a higher value, for instance 2.2k instead of 1.8k gives -1.74dB (0.818x) less gain.
RIAA filtering will not change while the values of caps and resistors are switched.
My 2 cents,
Ronald.
If there is more gain needed (+ 15dB), for instance when a Denon DL-103 is used, it is possible to change the second stage as follows.
R2 = R3 = 1k8
R4 = R6 = 1M
R5 = 100k
C2 = 3.3nF
C3 maybe the same (10uF) but may be changed to a 4.7uF
The gain of the first stage is R1 / cart. imp. x loss factor (due to the parallel RIAA cap)
For a DL-103 this will be 1620 / 40 x 0.9 = 36.45 x
The gain of the second stage is R5 / R3
For the original this will be 33k / 3.3k = 10 x
For the modified 15dB + version this will be 100k / 1.8k = 55.55 x
Output of a DL-103 with the original components = 0.3mV x 36.45 x 10 = 109 mV
Output of a DL-103 with changed components = 0.3mV x 36.45 x 55.55 = 607 mV
Difference in output is 14.9 dB
If you want less gain change R2 and R3 to a higher value, for instance 2.2k instead of 1.8k gives -1.74dB (0.818x) less gain.
RIAA filtering will not change while the values of caps and resistors are switched.
My 2 cents,
Ronald.
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Do not underestimate the effect of *good* RCA jacks. I just swapped the low end Cardas (Gold over brass) with Furutech FP903(G) (Gold over copper). There is no comparison, the Furutech is *so* much better.
With the Cardas, vocals could be shouty, with certain wiring configurations. The Furutech is a much better sounding connector. IMO, it is worth the money.
With the Cardas, vocals could be shouty, with certain wiring configurations. The Furutech is a much better sounding connector. IMO, it is worth the money.
Transverse wave function on build and collapse has to go through a situation where it is polluted in rise and fall of signal dynamics (or delta) via the mechanism of lattice polarization differential, at the atomic scale. This simple micro noise of flutter is noticeable due to the fact that the ear does not separate things according to engineering terms and numerical weighting, it simply hears the sum total..and any micro noise or modulation is heard as being on the top of the signal's levels, as an overarching modifier.
Our ears are designed to miss the gross modulation of the hearing mechanism by large subsonic flutter, as in motion, pressure changes and blood flow in veins..but it is designed to be and is....absolutely HYPER sensitive to the slightest micro vibration and any differentials. Thus it hears and interprets even the smallest micro differentials, and associated harmonics.
There is more brain power dedicated to the hearing mechanism than any other function.
Since we are not all the same intelligence and not all the same level of wiring design and not the same level of capacity to learn, then it is no small wonder that some cannot be convinced of these basic facts.
Connected to that, is the understanding that the brain is plastic, hearing is not static, and it is a ear-brain combination that is subject to continual learning and neural connectivity and growth as we age/grow...of course..for the more adventurous and level minded individuals.
Lorentz lost the battle in 1927, thankfully, and science, via engineering emphasis, has tried desperately to undo his loss and revert science back to some form of predicted stagnation of dogmatic numerical proofs providing all facets of reality and potential futures.
Thankfully, some of us fight back against this obvious insanity. The core reason he lost that debate and fundamental aspect of scientific exploration, is that Einstein logically insisted that observation was king, and that reality could never follow theory to perfection (with theory and numbers leading all exploration and reality) and no such thing should ever be proposed. yet we still see some try to impose such thinking. Their motivations are to be deeply in question.
Regardless to all that, I'm interested in this phono stage. I've looked long and hard for some simple phono device/circuit that was premium on all levels. This appears to be it.
I tired the LME49990 as a drop in replacement tonight, socketted on an adapter board. It did not work right, and was the victim of some hum. The sockets I have on the board are supposed to accept machine pins, and the adapter was of that kind. Some grounding issues were evident.
Replaced the OPA627 and all was well.
On a side note.... the red plastic inserts that help to hold the rca pin on the furtech 903 fell out tonight. I could only find one, but it still seem to work well.
Finally, if you do build this, it is *critical* that you get a solid connection from the phono ground lug to power supply common.
My original version used solid core Legenburg UPOCC copper, just because I had a bit left over.... bad idea. Since my build used the rectangular tubes, taking the boards in and out results in solid core wire failing.
Finally, all pissed off, I replaced with normal stranded hookup wire. The improvement in sonics was obvious. Now thinking about replacing the legenburg signal wire with something a bit better....
Replaced the OPA627 and all was well.
On a side note.... the red plastic inserts that help to hold the rca pin on the furtech 903 fell out tonight. I could only find one, but it still seem to work well.
Finally, if you do build this, it is *critical* that you get a solid connection from the phono ground lug to power supply common.
My original version used solid core Legenburg UPOCC copper, just because I had a bit left over.... bad idea. Since my build used the rectangular tubes, taking the boards in and out results in solid core wire failing.
Finally, all pissed off, I replaced with normal stranded hookup wire. The improvement in sonics was obvious. Now thinking about replacing the legenburg signal wire with something a bit better....
For the ground, just cheap 20 gauge stranded hookup wire. Nothing special at all.
There may be modifications coming to my unit. I used Nichicon caps in the power supply section, but I am considering replacing with something else.
Again, since I used the rectangular aluminum tubes, space is at a premium, and I *must* use something of the same size or smaller. In a bigger box, you could substitute larger capacitors.
There may be modifications coming to my unit. I used Nichicon caps in the power supply section, but I am considering replacing with something else.
Again, since I used the rectangular aluminum tubes, space is at a premium, and I *must* use something of the same size or smaller. In a bigger box, you could substitute larger capacitors.