I've been looking at old posts for a simple SET schematic for an EL34 tube and bumped into this one.
Near the output transformer is a diode with the letters SD. Is this a Schottky Diode and if so, what would it's value be?
Near the output transformer is a diode with the letters SD. Is this a Schottky Diode and if so, what would it's value be?
An externally hosted image should be here but it was not working when we last tested it.
Looks like the diode is there in an attempt to provide channel to channel isolation (keepting the right and left channel PS from affecting each other). So, yes, it looks like the intent was to use a schottky diode.
IMO, I would say a schottky is not needed in this application, and would probably not use it. Separate R-C networks to each channel would be better. If you want to keep it, though, I would think you should have a capacitor immediately after the diode.
IMO, I would say a schottky is not needed in this application, and would probably not use it. Separate R-C networks to each channel would be better. If you want to keep it, though, I would think you should have a capacitor immediately after the diode.
SD could mean "silicon diode" just as easily as "Schottky diode". No matter, the idea is misguided. There's no way the diode can provide isolation unless one channel's load current drops to zero, and since that will only happen when the output stage is clipping, I don't see a lot of point in fretting about it. Ditch the diode...
Don't know what this should be, in my opinion it is completely useless. The more, if it should be a schottky diode, which genuinely is a low-voltage device. Also, for isolationg each channel from crosstalk of the other via the psu, it is completely useless. Since the AC produced on the tube's plate appears as a modulation of its quiescent current (no tube conducts true AC!), so you have as the result a varying forward continuous current through the diode, so that the AC signal is completely transferred into tu PSU - as if the diode wasn't there. The only way to avoid crosstalk via the PSU is to use 2 separate supply rails. Also, the nonlinear characteristic of this diode adds additional distortion to the power stage.
Simply forget this diode. Its nonsense.
Uli
Simply forget this diode. Its nonsense.
Uli
SD is not schottky diode
SD is what we call SILICON DIODE as EC8010 say, but not schottky diode, schottky diode cannot withstand plate voltage as high as 380V, 50-75V almost the maximum rating for general purpose type.
but if use Silicon Diode as 1N4007 can withstand up to 1kv /1A, or use fast recovery diode as FR157 for maximum 1kv/1.5A rating.
Using silicon diode for B+ separating power supply can reduce crosstalk between each channel as ULIBUB say.
WE always use two diode in series connection for safety reason.
SD is what we call SILICON DIODE as EC8010 say, but not schottky diode, schottky diode cannot withstand plate voltage as high as 380V, 50-75V almost the maximum rating for general purpose type.
but if use Silicon Diode as 1N4007 can withstand up to 1kv /1A, or use fast recovery diode as FR157 for maximum 1kv/1.5A rating.
Using silicon diode for B+ separating power supply can reduce crosstalk between each channel as ULIBUB say.
WE always use two diode in series connection for safety reason.
Hi jduffy ,
I agree entirely with the zigzagflux’s reply ( see post # 2 )
If you put a capacitor ( say 47 uf x 450 V ) after the diode
( no matter what kind of diode ) , you will certainly get a
better channel separation . Because is obvious , if anyone
sees the schematics , that there is only one HV rail for both
channels . Indeed there is only advantage , to use the diode + capacitor set , and NO chances of any kind of drawback in the
final sound quality , at all .
BUT there is not doubt , that a separated RC network for each
channel , will do the “job” much better .
The way it was drawn on the schematics ( without capacitor ) ,
it is useless , and makes no sense , for sure .
Regards ,
Carlos
I agree entirely with the zigzagflux’s reply ( see post # 2 )
If you put a capacitor ( say 47 uf x 450 V ) after the diode
( no matter what kind of diode ) , you will certainly get a
better channel separation . Because is obvious , if anyone
sees the schematics , that there is only one HV rail for both
channels . Indeed there is only advantage , to use the diode + capacitor set , and NO chances of any kind of drawback in the
final sound quality , at all .
BUT there is not doubt , that a separated RC network for each
channel , will do the “job” much better .
The way it was drawn on the schematics ( without capacitor ) ,
it is useless , and makes no sense , for sure .
Regards ,
Carlos
diode can blocking spike from OPT
Agree with REFFERENCE and ZIGZAGFLUX , need a extra capacitor after diode as filter.
If strong signal or noise from electrical appliances inducing to or input to amplifer i, it will causing serious distortion and clipping waveform from power output stage , this will inducing very high spike voltage on output transformer (EMF inducing at inductor) terminals and superimposed to original B+ power supply,
then the series diode can actually block the spike noise , because the diode is at reverse bias status, very high impedance for spike noise path.
Agree with REFFERENCE and ZIGZAGFLUX , need a extra capacitor after diode as filter.
If strong signal or noise from electrical appliances inducing to or input to amplifer i, it will causing serious distortion and clipping waveform from power output stage , this will inducing very high spike voltage on output transformer (EMF inducing at inductor) terminals and superimposed to original B+ power supply,
then the series diode can actually block the spike noise , because the diode is at reverse bias status, very high impedance for spike noise path.
I think it important to state that inductive kickback from a choke or xfmr will easily exceed the reverse voltage rating of a diode, and quickly destroy it. So I would guess this was not the purpose of the diode.
I fail to see how it was intended to be used as a freewheeling diode, so we eliminate that. Channel separation seems to be the best explanation.
However, I think just about everyone is in agreement that it's better left OUT.
I fail to see how it was intended to be used as a freewheeling diode, so we eliminate that. Channel separation seems to be the best explanation.
However, I think just about everyone is in agreement that it's better left OUT.
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