Hello PS forum!
I have build a Tubelab TSE but am getting about 375V on the plates of my 45's. TOO much B+!
The TSE is PCB-based and the last cap in the PS on the B+ rail is a 150uF electrolytic. I am using a Nichicon GJ. The current config is a CLC with a 33uF Jensen, 6H/150 ohm choke then the 150uF. I was thinking of adding a 47uF Obbligato PSU Film in parallel to the 150uF, but what if I use it as follows to allow an additional RC stage to get my B+ down to 275V where I need it?
It looks like R1 will dissipate ~7W, so a 10W will work.
Am I shooting myself in the foot by putting the film in the middle of the supply and not the last cap in the chain? Worst case I could replace both C2 and C3 with 100uF Obbligato films wired off-board?
Thoughts, comments, suggestions?
I have build a Tubelab TSE but am getting about 375V on the plates of my 45's. TOO much B+!
The TSE is PCB-based and the last cap in the PS on the B+ rail is a 150uF electrolytic. I am using a Nichicon GJ. The current config is a CLC with a 33uF Jensen, 6H/150 ohm choke then the 150uF. I was thinking of adding a 47uF Obbligato PSU Film in parallel to the 150uF, but what if I use it as follows to allow an additional RC stage to get my B+ down to 275V where I need it?
It looks like R1 will dissipate ~7W, so a 10W will work.
Am I shooting myself in the foot by putting the film in the middle of the supply and not the last cap in the chain? Worst case I could replace both C2 and C3 with 100uF Obbligato films wired off-board?
Thoughts, comments, suggestions?
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Someone else mentioned just running an LC supply but is that enough filtering for a SET DHT amp?
You'll still have two stages, yes that can work.
Decide on the ripple you will tolerate (say you'd accept 90dB down from max level on the primary of the OPT, less the PSRR of the stage). The first stage supply ripple should be the gain of the output stage more quiet except that the PSRR is much greater due to the CCS, so maybe it needn't be lower.
Rather than removing the first cap, make it just small enough that the supply acts like a choke input one.
Decide on the ripple you will tolerate (say you'd accept 90dB down from max level on the primary of the OPT, less the PSRR of the stage). The first stage supply ripple should be the gain of the output stage more quiet except that the PSRR is much greater due to the CCS, so maybe it needn't be lower.
Rather than removing the first cap, make it just small enough that the supply acts like a choke input one.
I did this today and had 350V on the plate of the 45. I swapped in a 5U4G in place of the GZ34 and got it down to 320V. Biased it to 25mA, plugged it in and MAJOR HUM!!!
No, it hums regardless of which rectifier tube is in.
I had it working hum free before with the CLC as designed. But I had to add a 1K resistor in series with the choke to drop the voltage down to a reasonable plate voltage for the 45's (275V vs. 375V).
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Huh? This is for a Tubelab TSE, not a preamp!
The choke is a Triad C-14X.
Each power tube is 25mA, so 50mA plus about 25mA on the drivers for 75mA total.
With 309V on the primary and 350V out you don't seem to have a choke input filter.
If you use a resistor to drop the voltage as originally intended you just need to make sure the last capacitor will swing the needed current in the amp.
Oups, no preamp, so all the filtering is in the power devision.Then I supose C-L-C and extra R-C to lower the voltage and to get rid of the hum is a good solution.
Your figures are somewhat confusing.From 375V down to 275V with 1k and 75mA ? A current of 75mA drops only 75V on 1k, 375-75=300 not 275 ?
And C-L-C gives 375V but L-C still 320V ? Can only be if the current is very low, not at 75mA.
Mona
Your figures are somewhat confusing.From 375V down to 275V with 1k and 75mA ? A current of 75mA drops only 75V on 1k, 375-75=300 not 275 ?
And C-L-C gives 375V but L-C still 320V ? Can only be if the current is very low, not at 75mA.
Mona
Hmmm ... now you got me curious ... I am running 25mA per 45 output tube and was assuming ~25mA for the pair of 5842 drivers (CCS is set for 12mA). Maybe I need to put my DMM across the HV CT and see what I am actually drawing!
Yup. I tried 1uF and it was still 340V on the plate and it hummed bad that way also. I just switched it back to the 33uF with the 1K series resistor and all is fine. I'll monkey with PSUD later once I get an accurate current reading.
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