To comment on that part, my experience beyond the practical terms for this phono circuit, suggests that degeneration helps with stages gain and thermal stability (gain is moot to tightly control if under loop feedback circuitry) while full matching helps in THD % and its trend uniformity between channels in mirrored and differential circuits as well as in situations where sweet spot cancellation techniques are employed, especially when to avoid various trimmers.
The power supply is completed and I'm part way through stuffing the boards so might be there by the weekend.
Good luck!
Up to 1 Ohm 2W just for smoothing out the charge cycle and reduce its byproducts since your voltage level is good and you don't have to waste much for simply adjusting it.
P.S. I was thinking of maybe adding a small board for the guide's supply at the time of latecomers boards round just for visual synergy but I want to know that enough members have firstly followed and if happy with it and its grounding scheme works in many systems alike. Because the PSU part is contentious I am not sure if to bother though. Your builds will indicate.
Hi Salas im also struggling to reach 7,75v on a quartet,
i have about 150leds and only a a few are as high as 1,91v (adds up to 7,64V)
im using a 9v battery and about 1,4Kohm
ill do a test with a string of 4, and test the total, what size of resistor / what current should i test with?
Per
Having same Vftotal quartets and triplets is priority to absolute value because it keeps the cascode voltage bias the same between channels. Don't worry much for guide's refVftot when in the close neighborhood if you can't reach it or just mix a green LED but its not the best thing to do aesthetically.
Test for 4-5mA current. Itest=(Vtest-Vftot)/R
Use 15V-20V. You can also use the K117 Q7 prepared for the board in IDSS mode instead of a resistor to feed them current. That will be even closer to the specific in circuit conditions. If without lab PSU stack 2x 9V batteries up.
Attachments
Thanks Salas. Does that mean a total Vf of quartet of leds of 7.6V is acceptable as long as both sides are matched?. I can only get max of 1.9V Vf of the red led and the green ones measures way too high ( starting from 2.85V upwards).
Quan
Quan
green @ 2.85Vf must be quite unusual.
Mine measure similar to red, but on average slightly higher than red.
I did have some very low voltage red (1.55Vf to 1.6Vf), but unfortunately have used them all up.
Mine measure similar to red, but on average slightly higher than red.
I did have some very low voltage red (1.55Vf to 1.6Vf), but unfortunately have used them all up.
Yes you can use 7.6V matched between channels. Its we got VR2X & VR1 to still bias right in all somewhat different cases.
Super Vfw green leds these must be.... anyway, with the low current we are using here, IMO best option would be orange/yellow leds.
I have used 7,5 volts with good results.
