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Simplistic NJFET RIAA
Simplistic NJFET RIAA
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Old 14th April 2020, 02:08 PM   #17731
Salas is offline Salas  Greece
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Simplistic NJFET RIAA
Quote:
Originally Posted by MASantos View Post
I changed my FSP from MM gain to LOMC gain, changed all the necessary parts and installed Q2. Gain is now 63db, dead silent!! Amazing clarity compared to my Rega Aria phono stage.

One thing I noticed when adjusting voltages is that I can't get one of the channels to go higher than 34VDC. RAW PSU has both channels at around 50V.
I have VR2 turned all the way high and the max it goes it 34VDC. Between TP1 and TP2 I dialed 3.5V on both channels and reduced the 2nd channel to 34V to match.

Is it worth to change any resistor or LED to be able to bring the voltage to 36V? Where should I start?


What could I
I don't think you are away from optimal rail now but the answer to give it more adjust range is increase the value of R3x a little. Say by one kilo.
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Old 14th April 2020, 02:58 PM   #17732
MASantos is offline MASantos  Portugal
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Quote:
Originally Posted by Salas View Post
I don't think you are away from optimal rail now but the answer to give it more adjust range is increase the value of R3x a little. Say by one kilo.
I might leave it alone then. I have enough gain and sounds great!

Looking forward to seeing the new design!
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Old 14th April 2020, 03:22 PM   #17733
dwinstonwood is offline dwinstonwood  United States
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Originally Posted by Salas View Post
As far as I know it has been halted until the new configuration I designed (I name it UFSP) will be available on tried and tested PCB.
Hi Salas, I'm researching for a phono pre project to build in the future (I'm in no hurry).

My question is: Will you start a new thread/build guide for the UFSP when it's ready, and do you anticipate a possible group buy kit offer for this project?

Thanks!
David
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Old 14th April 2020, 05:03 PM   #17734
Eslheadphone is offline Eslheadphone  United States
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I am looking forward to the new preamp. I am currently collecting parts based on the old version since there is no major change in typology. The only parts I cannot source are the 2SK369 and 2SK117 FETs.
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Old 14th April 2020, 05:43 PM   #17735
Salas is offline Salas  Greece
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Quote:
Originally Posted by dwinstonwood View Post
Hi Salas, I'm researching for a phono pre project to build in the future (I'm in no hurry).

My question is: Will you start a new thread/build guide for the UFSP when it's ready, and do you anticipate a possible group buy kit offer for this project?

Thanks!
David
I will see how it can be best explained for build when ready. Its an update though, not a core different design. Has alike setup to the previous version. In other words its already conceptually known by the builders in this thread. If a general GB will be long to come maybe we can GB it alone if there will be some requests.
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Old 14th April 2020, 05:47 PM   #17736
Salas is offline Salas  Greece
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Originally Posted by Eslheadphone View Post
I am looking forward to the new preamp. I am currently collecting parts based on the old version since there is no major change in typology. The only parts I cannot source are the 2SK369 and 2SK117 FETs.
Beware of fakes! Ask Tea-Bag for help with the semis. There are some additions & changes in values and form factor for passives though and the whole PSU section is new. Don't collect passives beforehand.
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Old 14th April 2020, 10:02 PM   #17737
Eslheadphone is offline Eslheadphone  United States
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I will buy the transistors from teabag. I bought from him before and have been very pleased.
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Old 15th April 2020, 03:04 PM   #17738
MASantos is offline MASantos  Portugal
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Originally Posted by Salas View Post
Beware of fakes! Ask Tea-Bag for help with the semis. There are some additions & changes in values and form factor for passives though and the whole PSU section is new. Don't collect passives beforehand.
Do you feel the updates to the PSU are worth upgrading for those of us with the current version?
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Old 15th April 2020, 03:15 PM   #17739
dwinstonwood is offline dwinstonwood  United States
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Thanks for the info Salas.
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Old 15th April 2020, 03:23 PM   #17740
Salas is offline Salas  Greece
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Originally Posted by MASantos View Post
Do you feel the updates to the PSU are worth upgrading for those of us with the current version?
Hmm, by having applied and listened to the 1.3 PSU on previous main builds maybe there is bit of difference in more depth of tone that some may welcome and others not, depending on system synergy. Nothing spectacular. Seems like the phono was already well served. The previous has no gain switches to change connections between different parts values and although much more of a pain to reconfigure, it has over and done solder joints. Maybe that inspires extra long term peace of mind.

Overall no, personally I wouldn't change an older good build to revision, but if without any, I would build the newer because handier to exchange cart types. Plus without R3x tunings and no K117s in PSU. I would rather sort out any tonal preferences by tuning the C2Y value with reasonable care.
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