I am running a P-P El34 Ul-Amp currently. I believe the transformer gives something of 290v AC, so I get with my FWB build with SS-Diodes round about 395V when I use in cap-input a value of 200uF.
It goes down to 360V when I use 30uF as the first cap (followed by a 10H choke, followed by a 200uF polyprop).
I want to do a rectifier-shootout, I prepared many different SS-Bridges with hexfreds, Cree etc...and I want as well a GZ34-option in Hybrid-Setup.
The amp will need all the 250mA the GZ34 can deliver.
My questions:
- i have read in the valve wizard that only one current limiting resistor is needed in such a hybrid setup....but which value ? Normally for 350v/250ma I would choose two (for each anode) 100 Ohm for a gz34, correct ? So with only one resistor..still 100Ohm ? Or less because of the SS ?
- Any other reliefs from using a mixture of ss and tube diodes ? I understand a bit more voltage than a pure tube rectifier setup, correct ? What to expect ? 320V ? Anything else ?
- Would the limits of the gz34 change when a full ss bridge would be in front ? So, it gets already a pre-rectified signal, right ?....
It goes down to 360V when I use 30uF as the first cap (followed by a 10H choke, followed by a 200uF polyprop).
I want to do a rectifier-shootout, I prepared many different SS-Bridges with hexfreds, Cree etc...and I want as well a GZ34-option in Hybrid-Setup.
The amp will need all the 250mA the GZ34 can deliver.
My questions:
- i have read in the valve wizard that only one current limiting resistor is needed in such a hybrid setup....but which value ? Normally for 350v/250ma I would choose two (for each anode) 100 Ohm for a gz34, correct ? So with only one resistor..still 100Ohm ? Or less because of the SS ?
- Any other reliefs from using a mixture of ss and tube diodes ? I understand a bit more voltage than a pure tube rectifier setup, correct ? What to expect ? 320V ? Anything else ?
- Would the limits of the gz34 change when a full ss bridge would be in front ? So, it gets already a pre-rectified signal, right ?....
Yes, the inverse voltage limit. All other limits (current, first cap value etc.) remain unchanged.
Thx. Any hint about the resistor values ? So, if 100 Ohm would be used in a center-tapped scenario before each diode, so two resistors in Ct: Only one resistor in FWB aa well with 100 Ohm ? Or would that resistor be different ?
Well, if I take the Philips datasheet:
https://frank.pocnet.net/sheets/030/g/GZ34.pdf
Even though it is the most comprehensive one, there is nothing written about fwb.
If I take some of my rudamentary understand, wht I can see is:
The size of the current limiting resistor is determinted by the Vtr, which is in a centered-tapped two time the VAC of the transformer, but in a fwb only one times the transformer. Sooooooo, this would lead normally to the result that with a fwb the current-limiting resistor only needs to be half of the value (when looking into the specs of the datasheet)
If I than conclude that the current flows always through the one resistor as suggested here:
The Valve Wizard
sooooo...one half cycle through the one diode, the next cycle through the other diode, but the current goes alawys theough this one resistor:
My conclusion would be: The hybrid-Bridge needs only one resistor and for getting 350v/250ma it needs only to be 50 instead of 100 Ohm. (versus a CT-twoway Rectifier which would need two resistor at 100 Ohm each.)...correct thinking or did I make a mistake ?
As a result, the hybrid-bridge would as well have less voltage drop, I guess as the drop across this resistor is now half...?
https://frank.pocnet.net/sheets/030/g/GZ34.pdf
Even though it is the most comprehensive one, there is nothing written about fwb.
If I take some of my rudamentary understand, wht I can see is:
The size of the current limiting resistor is determinted by the Vtr, which is in a centered-tapped two time the VAC of the transformer, but in a fwb only one times the transformer. Sooooooo, this would lead normally to the result that with a fwb the current-limiting resistor only needs to be half of the value (when looking into the specs of the datasheet)
If I than conclude that the current flows always through the one resistor as suggested here:
The Valve Wizard
sooooo...one half cycle through the one diode, the next cycle through the other diode, but the current goes alawys theough this one resistor:
My conclusion would be: The hybrid-Bridge needs only one resistor and for getting 350v/250ma it needs only to be 50 instead of 100 Ohm. (versus a CT-twoway Rectifier which would need two resistor at 100 Ohm each.)...correct thinking or did I make a mistake ?
As a result, the hybrid-bridge would as well have less voltage drop, I guess as the drop across this resistor is now half...?
Last edited:
The resistor is a current limiter, not a voltage limiter. However, the required value may vary a bit with voltage - I'm not sure. Yes, if you use one resistor shared between the two anodes it can be half the value specified for one anode. Bear in mind that the datasheet gives the total resistance - in many cases much (or all) of the resistance will already be included in the transformer resistance so no extra resistor is needed.Blitz said:
In your arrangement each rectifier anode carries only half the total current, but it does this for all the time instead of half the time. The result should be a bit less voltage drop and a bit cooler rectifier.
Thanks a lot for taking the time and pointing to Rlim needs to be 50Ohm...
...I have checked my tranny (Amplimo):
Primary 230V/10ohm
Sec. 290v/32ohm
Which gives an
Rlim= Rsec + Rpri × (Vsec/Vpri)^2 + any extra resistance
Rlim= 32 + 10 x (290/230)^2 = 48 Ohm
So, adding maybe one 10ohm resistor for safety reasons would be good enough I guess...
...I have checked my tranny (Amplimo):
Primary 230V/10ohm
Sec. 290v/32ohm
Which gives an
Rlim= Rsec + Rpri × (Vsec/Vpri)^2 + any extra resistance
Rlim= 32 + 10 x (290/230)^2 = 48 Ohm
So, adding maybe one 10ohm resistor for safety reasons would be good enough I guess...
Update: Its running and it is marvelous !!! Unbelievable.
It clearly outperforms all other solid-state fwb I tried, be it with hexfreds or Crees...
Much larger alley/depth, dynamic like hell but sweet(not soft at all) in the trebles, bass authority...just everything much more natural. Same magnitude as when you go from a Mundorf supreme to a Duelund CAST, but for much less money...the Gz34 I am using is cheap chinese stuff, I understand that this topic alone can be addictive:
Dubstep Girl's Massive 5AR4/5R4/5U4G Rectifier Review/Comparison! (Rectifer Tube Rolling thread)
Currently the GZ34-Hybrid gives me from my 290VAC winding 365V DC when operating into a 30uF-cap. Not bad as the silicon bridges gave me 388v, so a drop of only 23V.
Next steps:
This was just a check of the idea. I believe at 365V and 250mA At idle I am running the gz34 to hard as this is an class a/b-amp. I guess when listening loud the amp will draw more than 250mA. This will kill the gz34, so I will build a setup with two GZ34, each connected as a single diode, so parallel anodes. I would assume that this will still not require any anode resistor as they are now even more robust to deliver the current....
It clearly outperforms all other solid-state fwb I tried, be it with hexfreds or Crees...
Much larger alley/depth, dynamic like hell but sweet(not soft at all) in the trebles, bass authority...just everything much more natural. Same magnitude as when you go from a Mundorf supreme to a Duelund CAST, but for much less money...the Gz34 I am using is cheap chinese stuff, I understand that this topic alone can be addictive:
Dubstep Girl's Massive 5AR4/5R4/5U4G Rectifier Review/Comparison! (Rectifer Tube Rolling thread)
Currently the GZ34-Hybrid gives me from my 290VAC winding 365V DC when operating into a 30uF-cap. Not bad as the silicon bridges gave me 388v, so a drop of only 23V.
Next steps:
This was just a check of the idea. I believe at 365V and 250mA At idle I am running the gz34 to hard as this is an class a/b-amp. I guess when listening loud the amp will draw more than 250mA. This will kill the gz34, so I will build a setup with two GZ34, each connected as a single diode, so parallel anodes. I would assume that this will still not require any anode resistor as they are now even more robust to deliver the current....
Yes, current will rise a bit with signal - although probably less than you think unless you have your music really loud.
- Status
- Not open for further replies.