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HPS 6.1
HPS 6.1
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Old 24th January 2019, 10:25 PM   #1
syn08 is offline syn08  Canada
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Default HPS 6.1

Here's for your free non commercial use the last implementation of my phono preamp: HPS 6.1

What's new:

- A new servo in the head amp, allowing the use of an active load in the low noise stage; as a result, the PSRR is improved by an order of magnitude.
- A new power supply, much simpler, using the latest ultra low noise regulators from TI. TPSA7A4700 (positive) and TPSA7A33 (negative).

You will find attached the schematics and the Gerber files (including this time the much requested solder mask). The board size is 124.5 x 81.3mm so the construction is very compact. Any questions, feel free to ask. For the time being, only a few comments:

- It is dual mono, and requires separate raw power supplies (recommended +20V @250 mA -20V @50mA) for each channel (if you want to keep it dual mono all the way). Double the currents if you are using a single power supply for both channels.
- Supply voltages are +/-18V. This being said, you can replace the LME49610 high voltage buffer (now exctinct) with the lower voltage version LME49600
- For the low noise jfets, you can replace the now extinct BF862's with the still in production at OnSemi 2SK3557 or CPH3910 with a less than 5% penalty in noise. For the 2SK3557 choose the -6 rank (lower Idss).
- I have two more versions, one uses the OnSemi CPH5905 integrated cascode (same noise performance as the 2SK3557) and one using standard LM317/LM337 linear regulators (almost the same noise performance, board is slightly larger). The latter was a proof of concept to showcase the very good PSRR of the input stage, but I would still recommend the current version. I may eventually post these versions as well.

And a strong WARNING. This construction is not for the beginners. It is full SMD and while most of the parts are a convenient 1206 size, some are smaller 0402 and the TI ultra low noise regulators are in DFN package, difficult to solder. Skills in SMD soldering and the use of a hot air soldering tool is mandatory for success.

Finally, I have to add the usual disclaimer: I am not into group buys, selling boards, building BOMs for DigiKey or Mouser, etc... life is too short for such, so essentially you are on your own. Information herein is accurate to the best of my knowledge. This will be posted on my web site, as soon as I'll find time to do it (I am hopelessly in behind updating my web site).

Enjoy!

09/17/2019 Schematics corrected here: HPS 6.1
Attached Images
File Type: jpg HPS61.jpg (544.7 KB, 876 views)
Attached Files
File Type: zip HPS61.zip (629.8 KB, 181 views)
File Type: zip HPS61-4-gerbers.zip (106.9 KB, 70 views)

Last edited by syn08; 17th September 2019 at 06:17 PM. Reason: Updated corrected schematics
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Old 26th January 2019, 07:18 AM   #2
kamis is offline kamis  Serbia
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What about bipolar input version HPS 4.3 ?There are no files for it.
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Old 27th January 2019, 04:30 AM   #3
rsavas is online now rsavas  Canada
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Nice to see you back contributing these gems, DFN you say :-) Cool, I'll take a look into it some more. Thx

Last edited by rsavas; 27th January 2019 at 04:34 AM.
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Old 27th January 2019, 07:07 PM   #4
syn08 is offline syn08  Canada
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For those intimidated by the DFN soldering (yes, it needs tools and some practice, YouTube has several videos to start with) here's the version with regular LM317/LM337 regulators. This version also uses the CPH5905 low noise jfet, cascoded with a bipolar device, in the same SOT-23-5 case. As shown, the preamp is fed from +/-22V power supply voltages and requires high voltage opamps, some of which are extinct (LME49610) and some are difficult to source (OPA2604). The prospective builder could easily modify the LM317/337 to fall back to +/-18V and then the same op amps as above could be used.

Due to the excellent PSRR of the low noise stage, using regular LM317/LM337 has absolutely no impact on the measured noise; the CPH5905 JFET (which, according to the data sheet, is a 2SK3557) is onlittle 5-10% noisier than the now extinct BF862. As such, the BF862 HPS version above has 0.33nV/rtHz @1KHz while the CPH5905 version attached here has 0.38nV/rtHz @ 1KHz, but in turn a slightly lower 1/f noise corner frequency. Please use the low Idss grade of the CPH5905.

For any other side effects of using these inexpensive voltage regulators, I was unable to identify any, YMMV.

Attached are the picture, schematics and Gerbers (including the solder mask and silk screen). The comments and disclaimers in the first post of this topic apply here as well.

Coming up (but don't hold your breath, it is in the final design stage) a HPS version that can be powered from 2 x 9V batteries (taking only some 25 mA from the positive supply and 15 mA from the negative supply). Preliminary results show 0.45nV/rtHz with BF862 and 0.5nV/rtHz with 2SK3557. This version uses an extra high Vp and high Idss JFET, to cascode the 8x paralleled low noise JFETs.
Attached Images
File Type: jpg HPS_61.jpg (526.1 KB, 805 views)
Attached Files
File Type: zip HPS61.zip (568.6 KB, 102 views)
File Type: zip HPS61-2-gerbers.zip (98.9 KB, 47 views)
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Old 16th February 2019, 07:32 PM   #5
stinius is offline stinius
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Hi I hadn't seen this thread until now, very impressive.

I like the way you are doing it with one cascode transistor on each jfet instead of one common cascode transistor for all.
Nice Servo BTW.

-Have you used a smt pick and place machine? Every component is perfectly placed.

-What about the temperature of the input devices, is it a difference when you use them in separate packages or both in the same package as in the CPH5905?

Personaly I'm considering buying a manual smt pick and place machine.

Cheers
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Old 19th February 2019, 08:41 PM   #6
syn08 is offline syn08  Canada
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Quote:
Originally Posted by Reodor Felgen View Post
Hi I hadn't seen this thread until now, very impressive.

I like the way you are doing it with one cascode transistor on each jfet instead of one common cascode transistor for all.
Nice Servo BTW.

-Have you used a smt pick and place machine? Every component is perfectly placed.

-What about the temperature of the input devices, is it a difference when you use them in separate packages or both in the same package as in the CPH5905?

Personaly I'm considering buying a manual smt pick and place machine.

Cheers
100% manual soldering. Hot air for DFN, fine point Weller for the rest. Hot air for rework. Cleaned extra flux in isopropylic alcohol.

No major temperature difference between same chip and separate transistors cascode.

Next version is coming up nicely:

- Can be battery powered (bypass the low noise regulators and no gain switching relays, takes 50mA both channels from 2x9V cells). Shown in photo is the full version with +/-18V regulators and gain switching.
- jfet cascode
- 0.45nV/rtHz
- 30% smaller board size, fits in 100x100mm PCB size, $20 for 10pcs, 2 days turn around, including DHL shipping, got them the same week .
Attached Images
File Type: jpg IMG_2029.jpg (782.0 KB, 690 views)

Last edited by syn08; 19th February 2019 at 08:44 PM.
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Old 19th February 2019, 10:14 PM   #7
Bonsai is offline Bonsai  Europe
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Superb SMD soldering job - I take my hat off to you. I can place and solder down to 0805 and the small 6 pin dual transistor packages, SOT23, SOD363 etc but they don't look your solder jobs.
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Old 19th February 2019, 10:43 PM   #8
syn08 is offline syn08  Canada
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Quote:
Originally Posted by Bonsai View Post
Superb SMD soldering job - I take my hat off to you. I can place and solder down to 0805 and the small 6 pin dual transistor packages, SOT23, SOD363 etc but they don't look your solder jobs.
I can easily solder manually 1206, 0805 and 0603 and under the microscope 0402. 0201 is tricky (meaning essentially a low yield), canít do 1005 manually, by any means.
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Old 19th February 2019, 10:50 PM   #9
rsavas is online now rsavas  Canada
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Cool syn08, nice job,
yeah I try to make as much as possible in 100x100mm for the special pcb deals these days. I just used jlcpcb, the import tools is great at reading in the data, determines the board outline auto, the gerber viewer is a nice extra check to see that they read it in correctly.
I like the 685 cap too :-)
I am using glow core 60/40 lead, no-clean solder, it works great with the default leaded HASL plating, ROHS not, this gov work
I did my DFN by hand but you have to open up the solder mask so that you get a hot tip on the trace so it can wick up to the lead. The first pin is the hardest to do.
Whats with all the 90 degree bends? looks like you run the cheapo orcad auto-router, with no miter function :-)
cheers,

Last edited by rsavas; 19th February 2019 at 10:59 PM.
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Old 20th February 2019, 01:41 AM   #10
syn08 is offline syn08  Canada
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Quote:
Originally Posted by rsavas View Post
I am using glow core 60/40 lead, no-clean solder, it works great with the default leaded HASL plating, ROHS not, this gov work
I did my DFN by hand but you have to open up the solder mask so that you get a hot tip on the trace so it can wick up to the lead. The first pin is the hardest to do.
Whats with all the 90 degree bends? looks like you run the cheapo orcad auto-router, with no miter function :-)
cheers,
I use 63/37, and solder DFN by hot air, don't need anything specific, the chip self aligns on the pads nicely. There are several videos on YouTube showing the howto.

Orcad indeed but no auto-router. Routed 100% by hand, but I simply don't care to miter anything (unless required). I'm confident electrons won't trip, impede or otherwise hamper at the 90 degs corners.
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