I have found that creating da best universal tube and its golden bias point leads to a need for a universal cure of sorts. I was just trying to keep everyone informed, I can quit anytime.
We want you to show us the varnished PSU box and write the sonic impressions of tube rectification VS SS diode bridge before you fulfill the destiny hourglass and eventually quit your noble mission though.
Salas,
I have my 5U4G wired like this exactly
http://www.vt52.com/info/vt52/schematics/vt52_schema_6b.gif
THe only difference is that I am using my 6.3V secondary to power it. I am taking the suggestion of putting a cl60 thermistor and .15R resistor in series with the filament to reduce it to 5V. Without tube installed, I get 6VAC on across filament pins and 310 across both diode pins and ground. Checked all connections and have good continuity. PLug the 5u4g in and nothing. I am using toroid, so neutral of dual secondaries are tied together to ground with each hot tied to tube diode.
I have my 5U4G wired like this exactly
http://www.vt52.com/info/vt52/schematics/vt52_schema_6b.gif
THe only difference is that I am using my 6.3V secondary to power it. I am taking the suggestion of putting a cl60 thermistor and .15R resistor in series with the filament to reduce it to 5V. Without tube installed, I get 6VAC on across filament pins and 310 across both diode pins and ground. Checked all connections and have good continuity. PLug the 5u4g in and nothing. I am using toroid, so neutral of dual secondaries are tied together to ground with each hot tied to tube diode.
Why you did it like that? Having a center tap in the 6.3V secondary also? Is your 5U4G a used and tested before sample? Me I had wired like that File:VacRect2E.png - Wikipedia, the free encyclopedia
The jury is still out, but i think i like SS rectification better than the tube. It seems that the smoothness, drive , and grunt i gained with this pre, especially with the RCA blackplates, is lost when using the tube rectifier. I have added motorun caps and choke, so i cant say for sure, but i know more later. Going to add the SS and switch, so i can go back and forth. Just wanted to get the tube rectifier up and running. HAven't tried SIlver in oil yet. Will do that after getting psu sorted.
Simple sf4007, although i think i have some fancy stealth diodes around here somewhere. I am going to really clean up the layout(AC hum from rectifier tube), and add SS rectifer and switch before pronouncing judgement. Ill give pics of components and layout, along with opinion for clarity sake.
a very important issue is the amount of capacitance the rectifier tube sees, and the resistance of the transformer plus the feeder resistor or choke to the next section. If wrongly dimensioned (too much) the tube will start to arc or oscillate maybe.
Trick is to get the sweet spot.
The same value goes for the 5R4W and similars.
If i had to define what iam hearing, i would say it a level of sibilance or maybe even decay. Puzzling. Makes methink possible bad layout ans noise, although i dont know how it is getting through regulator. One of myfavorite artist to test amps woth is Allison Krause. She has tone to her voice that is revealing of amps. It shows up in her voice an dalso on drum snares and brushes. Gonna throw in John scofield, Grace Under Pressure and have a listen., then onto Patricia Barber and Night Club.
My handbook sais that the total resistance of transformer windings and first cell must be a minimum of 575 ohms [The datasheet mentions 575 @ 1000 V RMS and 250 @ 750 V - the latter is your target]. With a toroid and 100 ohms you are far from that, I suspect.
View attachment 5R4G.pdf
And 5V AC is the max, can't you dewind (if you understand) a few windings? I have had troubles myself with too high currents/capacitor banks, and in one case one tube arced, in a setting for a 300B amp, while another was OK in the same amp.
If you tap unsymetrical you get bad harmonics too. A resistor bridge between the two legs 1/2 and 7/8 is needed if you don't have a center tap: 2x200 ohm 5 W would be nice, the output from the intersection.
albert
View attachment 5R4G.pdf
And 5V AC is the max, can't you dewind (if you understand) a few windings? I have had troubles myself with too high currents/capacitor banks, and in one case one tube arced, in a setting for a 300B amp, while another was OK in the same amp.
If you tap unsymetrical you get bad harmonics too. A resistor bridge between the two legs 1/2 and 7/8 is needed if you don't have a center tap: 2x200 ohm 5 W would be nice, the output from the intersection.
albert
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Salas,
Are you saying 40uF for first stage. In your. drawing there is 470uF. I can easily combine resistors and make into 160R to 4.7uF(i have1 uF or 2) to choke to 40uF.
Triode Al,
570R wouldgive way too much Vdrop and i would not have enough for regulator. Are you saying standard EI trafos have higher internal resistance and help in ths regard? Also, i do not have CT, although numerous schematics have shown non CT configuration, although it makes senses about signal not being balanced. I had planned to wrap toroid with another winding as suggested by KevinK, i guess i could do two and make sure they are balanced.
Are you saying 40uF for first stage. In your. drawing there is 470uF. I can easily combine resistors and make into 160R to 4.7uF(i have1 uF or 2) to choke to 40uF.
Triode Al,
570R wouldgive way too much Vdrop and i would not have enough for regulator. Are you saying standard EI trafos have higher internal resistance and help in ths regard? Also, i do not have CT, although numerous schematics have shown non CT configuration, although it makes senses about signal not being balanced. I had planned to wrap toroid with another winding as suggested by KevinK, i guess i could do two and make sure they are balanced.
