Juma discrete buffer
George,
did you try Juma buffer http://www.diyaudio.com/forums/analog-line-level/300007-cfp-unity-gain-buffer.html#post4908701 In place of opa627
other option Is Patrick discrete bf862 buffer http://www.diyaudio.com/forums/pass-labs/140488-b1-turbo-chip.html
George,
did you try Juma buffer http://www.diyaudio.com/forums/analog-line-level/300007-cfp-unity-gain-buffer.html#post4908701 In place of opa627
other option Is Patrick discrete bf862 buffer http://www.diyaudio.com/forums/pass-labs/140488-b1-turbo-chip.html
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No I didn't, but I did have a very good supply just for the buffer, even tried battery with a couple using two with centre tap.
Cheers George
Juma' buffer and discrete buffer
I have the JFET's and plan to try that at some point in the near future. My cousin is mounting the fet's on adapter boards for me. Discrete buffer.... Had a first listen. Had to make a few changes on the PCM1704 buffer to get it to play happy. Impressive based on a few hours listen. The discrete circuit is bipolar input and that meant a change of impedance and gain structure. I should listen to it for at least a week before making any conclusions. It isn't a subtle thing at all so far.
I have the JFET's and plan to try that at some point in the near future. My cousin is mounting the fet's on adapter boards for me. Discrete buffer.... Had a first listen. Had to make a few changes on the PCM1704 buffer to get it to play happy. Impressive based on a few hours listen. The discrete circuit is bipolar input and that meant a change of impedance and gain structure. I should listen to it for at least a week before making any conclusions. It isn't a subtle thing at all so far.
Mr. Torchwood
You have ignited a great curiosity by presenting the OPA1641 as an external buffer instead of OPA627. I immediately seized by Mouser, assembled and tested. You were absolutely right. The mini spider sounds damn good. Very well .... to the point that I prefer it to 627 (always with gain = 2). If we care for the cost .... 1641 wins across the board. Wonderful discovery.
I look forward to your considerations on the evidence that you will do on the discrete buffers
Many Thanks Torchwood
You have ignited a great curiosity by presenting the OPA1641 as an external buffer instead of OPA627. I immediately seized by Mouser, assembled and tested. You were absolutely right. The mini spider sounds damn good. Very well .... to the point that I prefer it to 627 (always with gain = 2). If we care for the cost .... 1641 wins across the board. Wonderful discovery.
I look forward to your considerations on the evidence that you will do on the discrete buffers
Many Thanks Torchwood
OPA1642 is certainly god enough... it exists in soic package (that's ok with a dip 8 adaptator to swap and big enough for easy definitiv soldering)
I believe if it's the topology of the powersuppy of this last stage which explain most of the time the biggest difference ?
They all will give different result in relation to the decouling cap used also...
Is there somewhere a good shematic of supply for these "buffers" (can we even talk about buffer with x2 gain ?) !
Where it could be interressant to use a 1641 is in I/V, no ?.... But as says George, don't want to buy microscope to tweak my DACS either
Some people recommend to put decoupling cap across +/- supply pins. This would allow very small loop if the cap is sticked on top op the opamp. However, i am not sure about the effectiveness of this method.
btw , i have a 1642 on hand as well ! I liked also a lot the old NJM 4080D (yes a headphone opamp as well)... always found it neutral but musical with the good choosed decoupling caps (more real than than opa2604 for instance in a buffer or input stage for a low cost pre -I have it on a NAD amp with just two pots for gain !)... noot too much time to tweak halas...
that's why some serious tweakers have heat-gun for welling and desoldering... I'm not a fellow of this clan
To me that's a good way to end up killing a surface mount opamp.
Solder once and leave it be is the way I look at them.
Cheers George
George
I do not love the rolling of opamp indeed I detest this practice, but to try one you have to adapt
SOIC to DIP
100pcs FR-4 SOP to DIP Converter Adapter SOP8 SOIC8 TSSOP8 to DIP8 Tinned | eBay Try these I have them on order. FR4 cheap and plentiful. I have used these in the past and easy with standard soldering iron due to long pads.
OPA1641 VS OPA627
Your very welcome. A member of my audio club found them and it is our opinion that it is a great substitute to the rather expensive OPA627 (SOIC). Love the option of singles, duals and quads. He is using his in an active high pass crossover to a line array mid tweeter DIY loudspeaker. I hope to hear it this season at the Audio Society of Minnesota. OPA627... I don't remember where I heard it however the 627's are so expensive because it uses an older fabrication technique and I was told there was only one factory still able to produce them. Wish I could remember where I heard that. Anyway I will use the ones I have on hand however have no plans to purchase any additional 627's in the future. 
Mr. Torchwood
You have ignited a great curiosity by presenting the OPA1641 as an external buffer instead of OPA627. I immediately seized by Mouser, assembled and tested. You were absolutely right. The mini spider sounds damn good. Very well .... to the point that I prefer it to 627 (always with gain = 2). If we care for the cost .... 1641 wins across the board. Wonderful discovery.
I look forward to your considerations on the evidence that you will do on the discrete buffers
Many Thanks Torchwood
Your very welcome. A member of my audio club found them and it is our opinion that it is a great substitute to the rather expensive OPA627 (SOIC). Love the option of singles, duals and quads.
He is using his in an active high pass crossover to a line array mid tweeter DIY loudspeaker. I hope to hear it this season at the Audio Society of Minnesota. OPA627... I don't remember where I heard it however the 627's are so expensive because it uses an older fabrication technique and I was told there was only one factory still able to produce them. Wish I could remember where I heard that. Anyway I will use the ones I have on hand however have no plans to purchase any additional 627's in the future.