Did you manage to and did it work alright?
Simplistic NJFET RIAA
- Thread starter Salas
- Start date
Did you manage to and did it work alright?
Thanks for the interest;
I am workin slowly and trying to take some good pictures of a progress timeline.
At this point i managed to get both Phono channels up and the rail @ 35V (they stabilize in a couple of secs since they have huge heatsinks)
My issue at this point:
But TP1-TP2 voltage alias Q3(Base<->colector) stays @ 0.3V and i do not know why (leds are lit with proper luminosity)
I used 2SA970BL's for Q3's and I did not anticipate will have those so my board does not reflect the footprint (maybe i soldered the twisted legs wrong 😀 although i triple checked )
I measured each resistor and Jfet as i soldered it to the pcb so maybe with your help i will troubleshoot the issue.
Thanks again,
C.
Sorted, without even knowing what was the holdup ; will run a quick re-soldering check; now rails @32.8x and stable 3.6 V TP1-2
Hello ; as promised
Ahead of finish but that's my build; Phono + filter + incredibly stupidly oversized power supply 🙂 but it got remote powerup(those little relay switches) so it can be stashed out of reach.
The preamp has no control over the sources in the back(yet) but thats out of this threads scope ; and i have no more energy to finish it these days🙂 weekend maybe.
Ahead of finish but that's my build; Phono + filter + incredibly stupidly oversized power supply 🙂 but it got remote powerup(those little relay switches) so it can be stashed out of reach.
The preamp has no control over the sources in the back(yet) but thats out of this threads scope ; and i have no more energy to finish it these days🙂 weekend maybe.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The build contains an extra pre-amplifier and its corresponding shunts.
I built it as all in one solution to correct my speaker response curve and it can be adjusted for any future setups I might have as easy as taking a measurement; obtain curve and adjust the correcting LC filter.
In short ; the extra part is a -20Db LC filter that corrects my speaker response and a +20Db jfet preamplifier with buffer + DC Shunt.
Si I got what i needed:
-Phono pre (that can go thru the equalizer or not)
-Line in hardcoded(expandable to external passive) equalizer
-Line in jfet buffer much like B1
all with their shunted supply.
Also my power supply powers the m2tech hiface evo converter.
My mistake indeed is getting those wima bulky capacitors ; could've gone much smaller and headache free... but that's the first try ... got 5 more pcb's to try on 🙂 (or rather not)
The sound is as it should be ; i could not describe it ; description is a rather subjective action with very little perception actually involved 🙂 but for me is perfect.
Regarding hot rod i do not know what is that.
Since is aboout sinking ; I polished the heatsinks where they meet with the mosfets; used 0.01mm mica foil and siliconic grease(found it best by far in the heat transfer department compared with arctic cool cpu soultions) so the heat transfer is almost ideal in these conditions, although is not really needed.
I did not see this practice of polishing the contact surface of the mosfets ; not even in builds like AlephJ or F5 Turbo ; where heat transfer is as critical as its dissipation; so contact surface should be almost a mirror(aluminium oxidates in the same microsecond is exposed to atmosphere so no mirror there ; but smooth)
Thanks , and again; Hot ROD? 😀?
Thanks for the description. As much elaborate as it looks.
Hot rod is like in cars i.e. modification for boost. Say you make each R1x in the shunts two thirds or half its now value and the sinks turn to toasters. Then you sit and listen carefully to try find differences that excuse your new contribution to global warming 😀
Hot rod is like in cars i.e. modification for boost. Say you make each R1x in the shunts two thirds or half its now value and the sinks turn to toasters. Then you sit and listen carefully to try find differences that excuse your new contribution to global warming 😀
Oh Thanks for explanation ; good one ... i read in the meantime the Hot-Rod related topics of your and community previous builds🙂
And i walk to the postal office to get a lot of packs so... i try to balance things.
But ... why would i try to hot rod the power supply ? what benefits it has ? This preamp(s) do not draw spikes of current that the shunt must compensate drawing much more power...
Oh is just to warm up the sinks? 😀
p.s.
my design is based on all your work here ; and it is available freely including my engineering tweaks ; sources and everything. But is a tight and more than it shows amount of work , but it has potential and is designed to even include wireless control of all functions via a (soon to be written) app 😀... like a remote control but a bit more ... and if you laugh... don't ... i still have some room for that in the case (for now is on "manual") 😀
These shunts can show less rail modulation THD when the standing current ratio to the used one is even higher but mainly manifests in line preamps and less in the phono. Some hear a better sonic some say meh... hearing small or no change, saying its already good.
how can they hear something like that? they have recording and sound spectrographic sound analyzer built in their brains... i would like to see that 🙂
...Introduction to Spectral Analysis — Sound Analysis Pro
Is just ridiculous 🙂 since the brain has no recording capability ... ant the only way to compare is to compare sensations not sound results. sensations are influenced by the cognitive process ... so is just a joke like comparing wires or stuff like that 🙂 the tester just reward himself with a thought that is better without tangible evidence (i know that since i experience such mirages myself)
but going beyond this; i get that a power reserve can only do good; but how much this draws ; and how much is considered a good reserve , and how to achieve such reserve? Hot roding as suggested? And how much to lower the 15Ohm resitsor ... how to calculate that 😀 ... I must stop ; and hope for an answer to at least 2 questions(preferably tlast two) 😀
Measure how much voltage drop there is across R1x then divide by 15 that's the current running in the CCS says Mr. Ohm. Its about 3X than what a phono channel draws. Its good. Want to try more for checking tricks of your sensations? Then make it something like 10 Ohm or 8.2 Ohm or 7.5 Ohm depending on how much heat from two shunts each your big sinks feel comfortable with.
did it 🙂 managed to apply Ohm's teachings and seems a bit of a overkill since power drawn by the preamps with 1mV input white noise in the phono is the same.... @ 7.5R ; i can use it as a radiator; is not even funny. using the normal 15 R stays @ constant 26.75 C ; it ~doubles by halving the R1x with ... i do not know any hearable difference . Next would be for me to use a white noise sample ; and comparing results obtained @15R and 7.5R using the APX. My guts say nothing much will differ.. (but hey... guts have no sound processing capabilities...)
Trying it just because is possible ...
If any ideas come to mind... share.
did it ; installed a rig in place of R1X that allowed me to switch values without opening the case;
I measured the riaa preamp differences using the testing equipment available ; with absolutely no variations between 15; 10 and 7.5 ohm R1X values, the samples recorded @2.5mV output are absolutely identical in produced results ... compared with a custm made by one of our colleagues sound analyzer capable of compare recorded white noise(aperiodical signal); as far as periodical signal goes as expected on THD THD+N Phase ... everything i knew how to read and interpret... there is no difference.
But in doing so ; i discovered an issue ... I seem to have grounding problems since i hear and read humming relatively loud(~10mV) with no load.
I coupled as suggested the power supply to the main ground ;
Severed the psu's case ground at the preamp's side of the umbilical but i done something different since i had not enough pins in the connector and sent thru the umbilical all the 4(-) negatives on one wire and in pre; tied it from the center of the starred ground to the turntable grounding post and implicitly to the box.
Is my grounding issue due to the fact that all 4(-) are tied together giving a humming 0 reference? Or what can i do to hear dead silence and only the default white noise generated by the first's stage fet?
Please help ; it bugs me greately ; the sound given brings tear to the eyes ... its a shame after so much work to have a weird hum.
Thanks!
I measured the riaa preamp differences using the testing equipment available ; with absolutely no variations between 15; 10 and 7.5 ohm R1X values, the samples recorded @2.5mV output are absolutely identical in produced results ... compared with a custm made by one of our colleagues sound analyzer capable of compare recorded white noise(aperiodical signal); as far as periodical signal goes as expected on THD THD+N Phase ... everything i knew how to read and interpret... there is no difference.
But in doing so ; i discovered an issue ... I seem to have grounding problems since i hear and read humming relatively loud(~10mV) with no load.
I coupled as suggested the power supply to the main ground ;
Severed the psu's case ground at the preamp's side of the umbilical but i done something different since i had not enough pins in the connector and sent thru the umbilical all the 4(-) negatives on one wire and in pre; tied it from the center of the starred ground to the turntable grounding post and implicitly to the box.
Is my grounding issue due to the fact that all 4(-) are tied together giving a humming 0 reference? Or what can i do to hear dead silence and only the default white noise generated by the first's stage fet?
Please help ; it bugs me greately ; the sound given brings tear to the eyes ... its a shame after so much work to have a weird hum.
Thanks!
Yours is a custom config and board combo circuits thing, not the standard phono build. So nobody is familiar. If you can post some audio blocks, psus, and grounds sketched overview maybe the members can help you with better ideas about its grounding.
I've done my best to draw the diagram;
The umbilical has cut the shield connection between Power and Preamp chases.
In the preamp modules; the negative raw supply(gnd) (pin 7 umbilical) powers the board goes to star and from the star center goes to chasis GND bolt.
An externally hosted image should be here but it was not working when we last tested it.
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I will include it; maybe it helps:
My ground currently goes from the *-GND-CASE pad ; and I provided a large bar as well closer to the preamplifier
An externally hosted image should be here but it was not working when we last tested it.
I tried to disconnect the mains grounding altogether (the green cable, IEC connector; center.)
I tried without resistor and anti parallel diodes altogether.
Will try with no 10R as well.
Edit:
No mains ground loop; i get my earth(ground) exclusive from the Salas's FSP supply(first on the right in the block diagram) for all the audio system to avoid loops and since is the most noise sensitive is the first.
Edit2
is the gathering of negatives harmful in any way?
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