DAK808, I was a little unsure about what you mean with your two known hybrid schemes.
In Eli's post #2 schematic, an ss diode is in series with each valve diode that is commonly used in a full-wave rectifier (full-wave defined by PSUD2 schematic use).
I think your second scheme uses a 'bridge' rectifier, where two of the bridge diodes are valve diodes, and two of the bridge diodes are ss diodes - is that correct?
With respect to rectifier noise, the use of valve diodes removes any opportunity for the ss diodes in those two schemes from exhibiting reverse recovery current conduction - that removes one noise aspect of rectification.
Another aspect of noise is when the current in a conducting diode falls rapidly back to zero - the time when the dI/dt of the power transformer secondary winding and diode abruptly changes from di/dt = a large value, to di/dt = zero is a problem when the transformer secondary winding has leakage inductance, as the abrupt change in current cannot be nicely transferred to other windings (via transformer action), and so there is a bit of a transient jiggle of energy.
A valve diode somewhat softly changes its on-state resistance as current approaches zero during a conduction period. That characteristic softens the dI/dt at turn-off, more so than any ss diode can. This is likely to be a benign issue for most amps, especially if the secondary winding leads to the diodes are carefully managed, and it's not easy for such noise to couple over in to the audio circuitry.
There are even more benign noise issues, such as diode off-state capacitance, but perhaps not normally a concern.
Valve diodes can go gassy over time, and the PIV can fall (diodes arcing - flashing). The ss diodes in series with each valve diode anode is appropriate even for the 'bridge' circuit. If using 1N4007 for that position, then multiple series diodes would be appropriate for any secondary VAC above about 300V in a full-wave scheme - if the valve diode can't withstand PIV then the ss diodes have to be able to do that job completely.
Imho, I can't see any advantage in using anything more 'exotic' than 1N4007 ss diodes when applied to these hybrid schemes - there is no benefit in a high current rating (unless you really are building a monster amp), and there is no benefit from enhanced reverse recovery performance (unless the valve diode has gone gassy). I do use UF4007 for these hybrid applications, but that's because I only have them now in my parts box.
In Eli's post #2 schematic, an ss diode is in series with each valve diode that is commonly used in a full-wave rectifier (full-wave defined by PSUD2 schematic use).
I think your second scheme uses a 'bridge' rectifier, where two of the bridge diodes are valve diodes, and two of the bridge diodes are ss diodes - is that correct?
With respect to rectifier noise, the use of valve diodes removes any opportunity for the ss diodes in those two schemes from exhibiting reverse recovery current conduction - that removes one noise aspect of rectification.
Another aspect of noise is when the current in a conducting diode falls rapidly back to zero - the time when the dI/dt of the power transformer secondary winding and diode abruptly changes from di/dt = a large value, to di/dt = zero is a problem when the transformer secondary winding has leakage inductance, as the abrupt change in current cannot be nicely transferred to other windings (via transformer action), and so there is a bit of a transient jiggle of energy.
A valve diode somewhat softly changes its on-state resistance as current approaches zero during a conduction period. That characteristic softens the dI/dt at turn-off, more so than any ss diode can. This is likely to be a benign issue for most amps, especially if the secondary winding leads to the diodes are carefully managed, and it's not easy for such noise to couple over in to the audio circuitry.
There are even more benign noise issues, such as diode off-state capacitance, but perhaps not normally a concern.
Valve diodes can go gassy over time, and the PIV can fall (diodes arcing - flashing). The ss diodes in series with each valve diode anode is appropriate even for the 'bridge' circuit. If using 1N4007 for that position, then multiple series diodes would be appropriate for any secondary VAC above about 300V in a full-wave scheme - if the valve diode can't withstand PIV then the ss diodes have to be able to do that job completely.
Imho, I can't see any advantage in using anything more 'exotic' than 1N4007 ss diodes when applied to these hybrid schemes - there is no benefit in a high current rating (unless you really are building a monster amp), and there is no benefit from enhanced reverse recovery performance (unless the valve diode has gone gassy). I do use UF4007 for these hybrid applications, but that's because I only have them now in my parts box.
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My PSUD2 simulation shows that the current drawn is already exceeding the .75A per section max. This is the reason i wanted to use a SSR in front of the gz34. The new production gz34 are of the same specs as the originals?
I think your second scheme uses a 'bridge' rectifier, where two of the bridge diodes are valve diodes, and two of the bridge diodes are ss diodes - is that correct? Yes, i believe so.
Hi TR, so, this is probably why my psud simu failed to give the voltages i got in my amp. I did not input the correct rectifier scheme. thanks for the tip. I need to brush up on my rectifier terminology.
I just reran the simul. and now i have 360v with the bridge rectifier using Graetz style. There also no "bad messages" with over current or over voltage. So, I must have done something wrong with my initial field test. I will try again.
thanks again.
Hi TR, so, this is probably why my psud simu failed to give the voltages i got in my amp. I did not input the correct rectifier scheme. thanks for the tip. I need to brush up on my rectifier terminology.
I just reran the simul. and now i have 360v with the bridge rectifier using Graetz style. There also no "bad messages" with over current or over voltage. So, I must have done something wrong with my initial field test. I will try again.
thanks again.
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not seen them before....
but i know someone who goes bananas at the sight of sexy tube rectifiers,
so much so, that he sold the line amp and kept the tube rectifier.....imo sick....
i use this exclusively in amps where tube rectifiers are installed...
transformer utilization is better by about 30% than a full wave center taped psu...
since i make my own traffos, insulation and design are more relaxed....
please have a look at Patrick Turner's web page and maybe you will have
a different perspective....http://www.turneraudio.com.au/powersupplies.htm
It's worth appreciating the hybrid 'bridge' rectifier scheme exists.
I have kept a 'failed' power transformer from the junk pile - it had one of its 600-0-600V secondary windings open, so I changed the full-wave valve rectifier to a hybrid bridge using just the good winding, as well as adding in the 'extra protection' 4007 ss diodes in series with each valve anode. If attempting this, I suggest making sure that all the windings are checked with a high voltage insulation resistance tester to be confident that there is no other likely collateral damage within the windings.
I have kept a 'failed' power transformer from the junk pile - it had one of its 600-0-600V secondary windings open, so I changed the full-wave valve rectifier to a hybrid bridge using just the good winding, as well as adding in the 'extra protection' 4007 ss diodes in series with each valve anode. If attempting this, I suggest making sure that all the windings are checked with a high voltage insulation resistance tester to be confident that there is no other likely collateral damage within the windings.
Well, i settled for the series linked ssr as the bridge rectifier scheme was making the voltage too high. So the amp works fine and I am protecting my tube rectifier from high voltage/high current situations. And best part is the amp sounds really good too. There is a sonic imprint that the SSR has imparted or maybe removed. And that there is a little less of roundness or softness to the edges of the sound but it is not hard or dry or sterile. All in all i am quite pleased. If i had enough 5v heater current i would have preferred to use 2 tube rectifiers in parallel. I have another amp with dual tube rectifiers and i prefer the sound of that amp as more lifelike, but, i can hear in this amp qualities that might be preferrable to the twin rectifier amp. Thanx for the help and support.
Yes, the specs are the same as the originals. In your case you still have too much current requirement but for replacement applications (or appropriate new designs) they are a good choice.
No with respect to heater secondary: the diodes designed to be used as damper, has several KV of isolation between heater and cathode, so you can power it from the grounded heater wiring, as it has been done in millions of TVs over the time.
What i mean is i don't have extra filament current for adding another rectifier. So, in order to add your scheme i would also need to add another filament tx.
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