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
OPA1641 and they come in 1 2 or 4 channel, pity they only come in surface mount, no 8 pin dip bummer, good for swapping.
Cheers George
Cheers George
😀
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 😛
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 😛
Surface mount is not a problem with the adapter.
In this photo is my assembly with triple stack of
844 and OPA1641..... today I also tested a beautiful Vishay BMF.
Listening is very very good 🙂
In this photo is my assembly with triple stack of
844 and OPA1641..... today I also tested a beautiful Vishay BMF.
Listening is very very good 🙂
maybe the default with soic to dip adapters is sometimes the close decoupling than some opas' need ! Like a dac chip, it can be worst on an adapter than directly sold near the ground plane... as far I know, cause not a technician myself...
I understand from TI's information that opa1642 has a good output draw ve capability. This combine with jfet input stage and low noise and distortion spec make it suitable as a buffer, I guess.
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
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.
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.