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Tube rectifier versus 1200v SIC diodes?

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#145
This is the PSU for the output stage of my 6P45S amp... Caps are cheaper than chokes and I've never seen a choke with as low of a drop as the two 5R in it 🙂

With your parts selection, I'd probably go bridge -> 40uF - 8H -> 12+12+68+68uF...

FYI even though it's got 300+mV of ripple, the amp is silent due to the CMRR of the PP output stage.
 

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#149
andyjevans said:
I've been trying out a SIC diode bridge in my driver stage so far, and now tried it out in the SE 6C4C output stage in place of a 5U4. In listening tests I'm finding it hard to find a preference.
The 5U4 is a fuller sound, more rounded, and smoother. The DIC diodes are "faster" sounding - better timing and more detail. This alone makes me want to prefer them. The sound is lighter but a little less smooth.

At first listen I like the diodes, but I would like the smoothness of the 5U4. If I could get the diodes to sound as smooth as the tube rectifier I think I'd go with them, so I'll see if adding chokes and playing around with the caps helps. PSU is C (12uF DC Link) > L (8H, 210mA, large) > C ( Kemet electrolytic 68uF, 550V) > R 750R > C (12uF DC Link).

Any suggestions? I haven't looked into shunt regs yet.
Click to expand...
I surmise you could work on the cap choice if the only purpose is to add smoothness but keep what you like with the SS rectification
I would first swap or bypass the last e-cap with someting like an Orange drop or a clarity cap ESA or even a MKT.
You can also try a Nichicon lythic HV in spite of the Kemet. Maybe the last R with a MOX or a 10W Mills.
Worth a try. You also can to swap the firs e-cap with a plain mkt or idem bypass with an orange drop. With the mkp, does Epcos is making large mkp...also worth a try. Some oil mkp cap, some paper X2 like the PME271...
 
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#151
The datasheet reference to 100 ohm relates only to capacitor input filter conditions. Sag is also introduced from power transformer effective resistance and load ripple due to the amount of power supply filter capacitance - that would also likely be circa 17V for an ss rectified B+ supply operating over a range of 20mA to 175mA - indicating that all ss rectifiers exhibit noticeable sag based on your call.
 
#152
trobbins said:
The datasheet reference to 100 ohm relates only to capacitor input filter conditions. Sag is also introduced from power transformer effective resistance and load ripple due to the amount of power supply filter capacitance - that would also likely be circa 17V for an ss rectified B+ supply operating over a range of 20mA to 175mA - indicating that all ss rectifiers exhibit noticeable sag based on your call.
Click to expand...
If only it were that simple. Sag will be introduced in an non-regulated HT supply depending on the series resistance and the change in current. The series resistance consists of the transformer secondary dcr plus the rectifier resistance and any series resistor added. Tube rectifier resistance is a lot higher than SS and tubes often require an addition series resistor to limit cathode current. The total series resistance is therefore much higher in a tube rectifier . I agree changing to an SS rectifier will not eliminate sag but it will reduce it considerably.

Cheers

Ian
 
#153
ruffrecords said:
If only it were that simple. Sag will be introduced in an non-regulated HT supply depending on the series resistance and the change in current. The series resistance consists of the transformer secondary dcr plus the rectifier resistance and any series resistor added. Tube rectifier resistance is a lot higher than SS and tubes often require an addition series resistor to limit cathode current. In addition the voltage drop across an SS rectifier is l much lower than a tube so you can use a lower secondary voltage which means less turns on the transformer and hence lower dcr. The total series resistance is therefore much higher in a tube rectifier . I agree changing to an SS rectifier will not eliminate sag but it will reduce it considerably.

Cheers

Ian
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#154
Why are we needing to explain the losses in a power supply wrt current draw after all these years?.
Sag (dynamic). Who designs that way - guitar maybe, and then only if you want it.
-
Anyway, anyone try a CCS fed shunt capacitor as B supply ? 🙂
 
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#155
ISCMMS said:
Why are we needing to explain the losses in a power supply wrt current draw after all these years?.
Click to expand...
Probably because a significant number of members of this board are amateur hobbyists with no formal engineering education. I have no problem impatring my knowledge to them, no matter how well known or trivial it may seem.

Cheers

Ian
 
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#156
Hello,
Is there a consensus about Tube SS rectification and input line IHT tube please ?

My basic understanding as a non tech after reading the thread is whatever the SS diode type, both the B+ and the heater powersupply should benefice of soft start, more a delay for the B+ ...at least better if you have an expensive or non easy to get tube (mine is an E188CC from middle 75 philips Holland).

Is a cap multiplier a soft start enough for the B+ ? Are you aware of a pcb that is doing that well enough for the switch on/off of the heater, please ?
I 'd prefer a single start on button for both but have no trouble to have two separate traffo for the heater and the B+.
Currently lurking to K&K Audio kit as a noob but when you putt all together, delay, soft start, HV reg it beginns to cost for an european based people.
Not an easy question I assume and not off topic I hope as it is a line tube so needs to be quiet B+ (even more as in fact I plan tube I/V dac stage with it).
Started from Loesch soft start circuitry with chocke, I see there is no soft start delay for the IHT heater...while people say it is not fragile...you know you want sleep better at nigtht. What could be a 6.3 v reg with progressive start enough for the heater ?lt3080 ? How you know the B+ will start after jf it has a delay start as well ?

I ask because I also want to avoid a tube rectifier as the op. More because by fear of the hassle more vs SS and also to avoid coloration.
 
#160
ISCMMS said:
Anyway, anyone try a CCS fed shunt capacitor as B supply ? 🙂
Click to expand...
Salas SSHV2.
diyiggy said:
I see there is no soft start delay for the IHT heater...while people say it is not fragile...you know you want sleep better at nigtht. What could be a 6.3 v reg with progressive start enough for the heater ?
Click to expand...
I switched on my tube phono and Tungsram ECC82 flashed at turn on ... it will burn out :-( ...or not...
It was about twenty years ago ... and damned tube flashing every day at turn on .. doesn't want to be ruined. 🙂
 
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