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Simplistic NJFET RIAA
Simplistic NJFET RIAA
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Old 1st November 2017, 09:12 PM   #16861
Salas is offline Salas  Greece
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Simplistic NJFET RIAA
Quote:
Originally Posted by guglielmope View Post
After some hours I super like the sound of this preamp
How is it going after some days? Still happy?
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Old 2nd November 2017, 04:20 AM   #16862
alexkosha is offline alexkosha  United States
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Simplistic NJFET RIAA
Quote:
Originally Posted by Salas View Post
Nice cheap and handy switching PSU modules for general use those. But very noisy indeed. This multiplier did a great ripple eating job at 70kHz as I see in your scope's picture. The second order type has usefully controlled output impedance in the HF too. It skyrockets in high frequencies for those with just a resistor and a cap.
I specifically choose high noise switch PSU (Lambda Alpha 1kW - http://us.tdk-lambda.com/ftp/Specs/alpha1000.pdf) to see how will behave CM with delivered 300mV ripple. Although input noise is high , I'm not sure if DPS5015 buck controller is guilty for it. For sure, it is not adequate filtration on it and would be nice to add some internal noise suppression. BTW, this buck converter is using 60kHz switching frequency which is correlates to scope image Yellow trace. Really want to test CM on one one of my FSPs, but do not want to use perf-board. Would like to make nice PCB.
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Old 2nd November 2017, 11:21 PM   #16863
lampes is offline lampes  Greece
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Hi there/ hi Nick
I'm trying to figure out some parts for the Phono build and i was wondering what is the minimum Voltage for the raw PSU main capacitor. Is 50V ok or is at the edge?
I m trying to figure out the maximum capacitance for the space i have so what is the max allowed diameter for capacitor in this position??

Thanks in advance
Tom
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Old 3rd November 2017, 12:28 AM   #16864
Salas is offline Salas  Greece
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Simplistic NJFET RIAA
50V reservoir capacitors will be alright if you will also use 33V transformers. There is a 36mm diameter footprint on the Raw PCB'S silkscreen for each reservoir that you can possibly jump over to 38mm before a capacitor's barrel hits to nearby components pads.
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Old 3rd November 2017, 12:45 AM   #16865
lampes is offline lampes  Greece
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do i have to work on a lower final voltage because of that? I see regular transformer voltge is 36AC...
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Old 3rd November 2017, 03:11 AM   #16866
Salas is offline Salas  Greece
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33V AC will make circa 46V DC so its enough for the FSP. Because most reported builds due to bias tolerances tend to use lower than 34V regulated rail, about 12V drop across the reg is also ok to work its CCS well. The 36V transformer spec is to cover low mains official tolerances but many builder's transformers overshoot spec because their mains is most of the time high so people with such Tx usually end up with a resistor instead of the wire link from bridge to reservoir on the raw pcb for extra drop. That resistor also makes a little HF filter with the reservoir as a side benefit though.

In general we prefer no more than 50V raw DC to reach the FSP's onboard regs inputs. Large DCin-DCout drop is good for linearizing the CCS MOSFET regarding its own capacitances but after 12-15V drop its a diminishing return and we inherit a hot CCS sink situation that affects the ambient temperature delta in the box so the drifts go wilder. High raw DC input also puts Q2x to strain.
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Old 9th November 2017, 06:46 PM   #16867
cumbb is offline cumbb
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Salas RIAA, MM
One of the best, no doubt!-:

Here within a case of a Luxman 410. For a friend. Drives a Single Mosfet - and
... than out;-))))

Pickup - Speaker: 3 Transes;-)))

Do use ONE PSU for ALL!
AT 91! A wonderful pickup!

1. picture - one side, one channel.

LG
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Last edited by cumbb; 9th November 2017 at 06:49 PM.
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Old 9th November 2017, 10:27 PM   #16868
Salas is offline Salas  Greece
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Is it the Folded circuit or one of the previous? Having all its stages or just the first two?
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Old 10th November 2017, 02:21 PM   #16869
cumbb is offline cumbb
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The "first" two stages - "the complete-st"-)
(does not need much "sound" for horrible pre- and end-amps and multiway speakers and other stuff)-;

An other than the previous RIAA circuits - minimal different.-)

LG
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Old 19th November 2017, 01:51 AM   #16870
Bix is offline Bix  Australia
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Default Need help

Hi Salas and all. I have a nearly finished kit that stopped in itís tracks a few years ago due to lifeís unexpected nature. I really would love to finish this project and hear it sing. I live in Australia, nsw, Byron Bay. Does anybody live around me or know of somebody close by who could help complete this kit. Kind regards Mike C
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