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Chipomatic balanced input RIAA
Chipomatic balanced input RIAA
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Old 12th January 2019, 09:32 AM   #61
Dimdim is offline Dimdim  Greece
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Chipomatic balanced input RIAA
It took about 2 hours of leisurely work.. but to be fair it was done under a stereoscopic microscope.

You're up!
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Old 12th January 2019, 11:18 AM   #62
Salas is online now Salas  Greece
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Chipomatic balanced input RIAA
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That was quick!
Mr. Chipquik
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Old 18th January 2019, 04:28 PM   #63
vgeorge is offline vgeorge  Greece
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Chipomatic balanced input RIAA
Finally finished soldering. (Of course not as good as dimdim) With the exception of the LT regulators - I promised never do that again! - not too difficult. I used just a magnifying glass and a normal size iron.
It works fine electrically, now to make it a practical preamp to test it.
I used 33R for RG in order to get 45 dB gain. I will use some 12dB transformers I already have, for my cart.
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Old 18th January 2019, 05:53 PM   #64
Salas is online now Salas  Greece
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Chipomatic balanced input RIAA
Can skip doing the local LDO reg circuit altogether and directly feed at the rails connector from say an UltraBiB shunt reg. But in order to honor its name it had to have chips all over it
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Old 19th January 2019, 01:20 AM   #65
Marcopolo is offline Marcopolo  Canada
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I like your creative and intuitive mind in audio design.

If I had a challenge to give you that, you could use the Korg Nutube 6P1 Dual Triode in your circuit.

Someone as intuitive as you without being so good designer
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Old 19th January 2019, 01:55 AM   #66
Salas is online now Salas  Greece
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Chipomatic balanced input RIAA
Has -20dB RIAA equalized auxiliary output also, to can bypass the second op_amp stage with different external line level gain flavors. Be it classic triode or Nutube or JFET or BJT. An easy task because there's 30mV RMS flat signal readily provided to start with.
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Old 19th January 2019, 03:07 AM   #67
EUVL is offline EUVL  Europe
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Hope you wouldn't mind a few remarks.

I built my first phono 10 years ago also on a Gain-Filter-Gain topology, first using AD797 / OPA637, later discrete opamps.
I always have a feeling that it lags headroom, because the filtering at HF comes after the first stage.
No scientific proof, just a feeling, when listening against other topologies.
Pass Discrete Opamp in DIP-8 Package

It is soon to be replaced by Scott's phono which is gain and filtering in one stage.
So the above problem will not exist as long as the JFETs have enough bias.
A simplified universal differential or single ended phono preamp

AD8429 is really a great chip.
We used it for a diff probe with great success.
DIY Balanced / Differential oscilloscope probes?
Glad to see someones trying it out for audio.

We have good experience with Panasonice ECHU PPS film caps.
They have distortions down to -140dB level (measured).
One can argue that COG can do better in measurements.
But in listening we prefer ECHU in the end.
Again no scientific proof, but maybe worth trying.

I personally would not use a DIP switch for sensitive signals.
Especially for DIY, everything at the phono frontend I try to avoid contacts and solder wherever possible.

Cute little PCB. Can be placed very close to the TT.


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Old 19th January 2019, 09:38 AM   #68
Marcopolo is offline Marcopolo  Canada
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I would like to acquire your 2 independent channels in a 70mmx60mm card with all the extras and all the modern comforts.
I do not need 4kTV, sofa, espresso machine and a free trip to Mykonos just your prototype.
If you accept of course
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Old 19th January 2019, 09:57 AM   #69
Salas is online now Salas  Greece
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@Patrick

For the time being, i.e. fun proto between mates, its a mix. C0G 1% in the long time constant (no less than 10% 5mm pitch Wima MKP for C1's value available on Mouser) and MKP//FKP C2 combo of various better % in the short constant. Best to be checked and matched for total value with a good LCR meter. MKP1837 1% is not currently stocked in the majors by the way. Although I got some.

I even have 1% NOS film & foil ERO in a drawer that fits dimensions, but that wouldn't go into a real life BOM for others.
The switch exchanges GND ref not switching the signal directly. Its a must for now regarding BAL/SE tests flexibility though.

I had tested C0G for both the low and high turn points as RIAA caps in the past and they reminded me of Silver Mica. Non aggressive and musical if wee bit veiled vs polystyrene in other words. Given the curve is not doctored to suit them better. For the lows maybe more difficult to distinct.

I had an eye on those ECHU for 100% SMD parts use but their 0.6% tanδ kinda held me back vs MKP//FKP Visahy/Wima through hole in the highs.
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Old 19th January 2019, 10:14 AM   #70
Salas is online now Salas  Greece
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Chipomatic balanced input RIAA
Quote:
Originally Posted by Marcopolo View Post
I would like to acquire your 2 independent channels in a 70mmx60mm card with all the extras and all the modern comforts.
I do not need 4kTV, sofa, espresso machine and a free trip to Mykonos just your prototype.
If you accept of course
Its not a real proven project yet and I only got three board samples. If its successful we will see.
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