QUESTIONS ABOUT INPUT RESINSTANCE
My riaa phono preamplifier with 2sk170 first stage has an input resistor 47K for MM cartridge .
I want to connect a pre-pre MC cartridge via selector (or switch).The output of the pre-pre is through 0.56μF cap and 1M resistor ,as the attached hand drawing (!).
QUESTIONS:
1) If assume that, i am implementing what the drawing shows , what input resistance ( Rx=? ) should i put at riaa preamplifier ?
2)If i leave the resistance 47K at the input (as it is now) of the preamplifier and select between the MC pre-pre out or only the 200pF capacitor with MM in, is correct ?
(sorry for the handdrawing , don't handle a desing program)
Thanks in advance.
My riaa phono preamplifier with 2sk170 first stage has an input resistor 47K for MM cartridge .
I want to connect a pre-pre MC cartridge via selector (or switch).The output of the pre-pre is through 0.56μF cap and 1M resistor ,as the attached hand drawing (!).
QUESTIONS:
1) If assume that, i am implementing what the drawing shows , what input resistance ( Rx=? ) should i put at riaa preamplifier ?
2)If i leave the resistance 47K at the input (as it is now) of the preamplifier and select between the MC pre-pre out or only the 200pF capacitor with MM in, is correct ?
(sorry for the handdrawing , don't handle a desing program)
Thanks in advance.
Attachments
Is that about using the 2xK170 pre pre from the older version's pdf?
Just put 47k for Rx. No other 47k no 200pF capacitor either, the JFET input and the TT cable together will provide enough pF.
If you would have to utilize that diagram, Rx should have been 470k at least. In that case the 0.56uF coupling cap could be as low as 33nF.
Just put 47k for Rx. No other 47k no 200pF capacitor either, the JFET input and the TT cable together will provide enough pF.
If you would have to utilize that diagram, Rx should have been 470k at least. In that case the 0.56uF coupling cap could be as low as 33nF.
Yes from older version .
THANKS A LOT SALAS ,YOU ARE TOP OF THE CHIEFS , OR THE ONLY TOP CHIEF. !
THANKS A LOT SALAS ,YOU ARE TOP OF THE CHIEFS , OR THE ONLY TOP CHIEF. !
Are there any news of the forthcoming version of FSP ?
I know of the inclusion of the new UltraBIB power supply, are there any other upgrades/mods in the making ?
I know of the inclusion of the new UltraBIB power supply, are there any other upgrades/mods in the making ?
No other than it also has configurable sensitivity with switches. Its near ready, the phono section PCB tested, but the specialized UBiB section has been tested on proto board only. Half designed on PCB there are some delays with CRT on finishing the PSU section then integrating the sections. He doesn't have much free time during this period.
May i know if the Simplistic NJFET RIAA pcbs or kits still available?
Its not listed in TeaBag's site.
Thanks.
Its not listed in TeaBag's site.
Thanks.
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. Its not a different design as far as the signal circuit goes, its simply reworked for features and to include own 1.3 class PSU section. That's a specialized UBiB of shorter adjust range. Targeted for setting with better stability around the 35V region useful for the phono.
If he has got any spare previous blue FSP till then I am not sure. But he surely hasn't been listing it for a long enough time now.
If he has got any spare previous blue FSP till then I am not sure. But he surely hasn't been listing it for a long enough time now.
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
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.
I might leave it alone then. I have enough gain and sounds great!
Looking forward to seeing the new design!
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 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.
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.
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.
I will buy the transistors from teabag. I bought from him before and have been very pleased.
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.