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PostPosted: 08 Sep 2016, 14:17 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi Everyone, I use these ICs all the time but never really knew how well they performed. Just on a lark I ran one of my SS phono preamps (elsewhere on the site) in MM with a reverse RIAA source on my scope to see where the upper end of the response was. It was flat out to 500K and actually up by 2 db at 1meg. I can only Bode plot that far. Nice clean waveforms as well. this actually can be a problem as it will only find noise up there. I may have to include small ferrite beads or chokes on the inputs and outputs to tame it. BTW the S/N from 10HZ to 30K was -104 dbv with a gain of roughly 38 db. Input shorted and 1 meg on the output side.

Good listening
Bruce

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PostPosted: 09 Sep 2016, 06:55 
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Joined: 18 Aug 2015, 07:38
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Thanks for sharing Bruce. Once again you are showing with technical info what my ears are hearing with your OPA 2134 phono preamp. Clean, dynamic, full soundstage with excellent bass.


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PostPosted: 09 Sep 2016, 08:47 
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gofar99 wrote:
Hi Everyone, I use these ICs all the time but never really knew how well they performed. Just on a lark I ran one of my SS phono preamps (elsewhere on the site) in MM with a reverse RIAA source on my scope to see where the upper end of the response was. It was flat out to 500K and actually up by 2 db at 1meg. I can only Bode plot that far. Nice clean waveforms as well. this actually can be a problem as it will only find noise up there. I may have to include small ferrite beads or chokes on the inputs and outputs to tame it. BTW the S/N from 10HZ to 30K was -104 dbv with a gain of roughly 38 db. Input shorted and 1 meg on the output side.

Good listening
Bruce

Mate, all my phono preamp stages have ferrite beads on the input wires. It is so easy and cheap to do. Thanks for the info. I recently got back the first of your OPAMP phono pres which I called "Mimic". "The Heran" was the first I built - MM\MC - 100\50ohm loading and two selectable inputs. This spent a couple of years in WA - USA. The guy using it sold his second system and I swapped him The Heran for a DC blocker. Good to have it back and it is in pristine condition. I modded it to near a Mimic SE status with better caps.

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
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PostPosted: 09 Sep 2016, 09:37 
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mwhouston wrote:
Mate, all my phono preamp stages have ferrite beads on the input wires...


Sir,
does the wire pass thru the bead just once or is it looped thru the bead?

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PostPosted: 09 Sep 2016, 14:43 
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Hi, I loop mine.

Good listening
Bruce

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PostPosted: 09 Sep 2016, 18:19 
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vixr wrote:
mwhouston wrote:
Mate, all my phono preamp stages have ferrite beads on the input wires...


Sir,
does the wire pass thru the bead just once or is it looped thru the bead?


I use very fine silver plated wire-wrap wire for hookup in a lot of my builds. The wire is fine enough to pass through twice. So it goes through, loops around and through again.

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
Website: retro-thermionic


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PostPosted: 29 Sep 2016, 00:32 
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Joined: 28 Nov 2014, 15:21
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Location: Queensland, Australia.
G'day all, interesting stuff. As a Ham Radio operator I know the value of ferrites in RF suppression applications etc. As for the OPA2134, yes from my own work I've been impressed by what a well designed and 'tough' dual op amp it is, and it sounds great too. Regards, Felix (vk4fuq).


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PostPosted: 04 Oct 2016, 11:56 
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Joined: 18 Aug 2015, 07:38
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Anyone have a preamp, line stage, schematic they have tried with the OPA2134? I have seen Rod Elliott's designs using 5532's.


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PostPosted: 04 Oct 2016, 12:51 
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Joined: 07 Dec 2015, 14:21
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I have been a big fan of them. Jfet input yeah baby!


I swear by them for my guitar fuzz pedals.


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PostPosted: 04 Oct 2016, 17:05 
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Hi, I thought I posted one, but can't seem to find it. The IC makes one a simple design. Select the gain you want, select the input impedance and get clean power. You can modify the attached schematic in any number of ways. A write up on the phono section is under the IC projects part of the site. It explains why I used the unusual power supply. Ignore the red circle on the schematic ...I was hunting for some noise at one time and it looked like it might be the cause. The preamp is capable of a S/N in the -100 dbv range so any noise IMO is not good.

Good listening
Bruce
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