An SS-bridge is a nogo with this transfo.It has a CT and you can't connect the two sec. in parallel.Two semi-diodes is possible but not advisable.You have to adapt the cathode resistor and the serie-one at the zeners since the voltage will be much higher (~500v).A GZ34 is nice but rather expensive.
Mona
Mona
lilstripe,
If you want to go with a Classic Tone lay down style transformer, give a consideration to using their model 40-18048 transformer. This transformer sells for $76.58 on their site. With this transformer, which is a non center taped secondary you would need to go with a bridge rectifier such as 4 ea. UF4007 (ultra fast silicon diodes) in place of the 5U4 rectifier tube. Or you can keep the 5U4 and add two UF4007 diodes to make up a hybrid bridge, your choice. If you need a sketched up schematic on how to do this let us know. I offer this as a way to keep your costs down in doing your project.
Mickeystan
If you want to go with a Classic Tone lay down style transformer, give a consideration to using their model 40-18048 transformer. This transformer sells for $76.58 on their site. With this transformer, which is a non center taped secondary you would need to go with a bridge rectifier such as 4 ea. UF4007 (ultra fast silicon diodes) in place of the 5U4 rectifier tube. Or you can keep the 5U4 and add two UF4007 diodes to make up a hybrid bridge, your choice. If you need a sketched up schematic on how to do this let us know. I offer this as a way to keep your costs down in doing your project.
Mickeystan
Not to get into a religious debate over SS vs Tube Rectification, I think I'll stick with the all tube setup. I've built a ton of SS stuff over the years, this was my venture into the all tube world and a $25 delta isn't a big deal for this project.
So back to my question, would the GZ34 be a better option to keep the B+ up closer to the original design or stick with the 5U4?
So back to my question, would the GZ34 be a better option to keep the B+ up closer to the original design or stick with the 5U4?
lilstripe, I would not go with the GZ34 rectifier tube. I and several of my audio friends have had nothing but reliability and arc over issues with this tube. I would go with the 5U4GB and/or the 5U4GB along with two UF4007 in a hybrid bridge. The latter choice is a must if you want to stay with a tube in the rectification role and want to do it with the lower cost lay down transformer that had no center tap on the secondary HV winding. That my opinion, others may differ about the GZ34 tube.
Mickeystan
Mickeystan
LJT
lilstripe
The purpose of elevating all the heaters at this point is due to the use of a single 6.3v winding feeding all the amplifier stage heaters where there is no ground referenced center tap as a part of the winding. The original implementation only elevated the top 6SN7 of the srpp stage due to its cathode being operated at approx. 1/2 the stage B+ supply as a means of assuring the top half of this 6SN7 was not violating the heater to cathode max. potential specification.
All other heaters to amplifier tubes were ground referenced originally. The new all heater elevated scheme now is dc referencing of all the amplifier heaters to assure the amplifier is nice and quiet from an ac induced hum perspective while still preventing the srpp top tube from being operated outside of heater to cathode dc voltage. Doing the dc elevation this way is also beneficial for the front end of the amplifier as the gain is the greatest at the input stage. In other words, elevating heaters, prevents unwanted heater ac currents from getting summed with the intended audio signal which contributes a unwanted hum.
Hope this makes sense.
Mickeystan
The original designer of this amplifier place the capacitor there as a means of suppressing 60 hz hum from being a part of the elevated heater dc offset voltage.
lilstripe
The purpose of elevating all the heaters at this point is due to the use of a single 6.3v winding feeding all the amplifier stage heaters where there is no ground referenced center tap as a part of the winding. The original implementation only elevated the top 6SN7 of the srpp stage due to its cathode being operated at approx. 1/2 the stage B+ supply as a means of assuring the top half of this 6SN7 was not violating the heater to cathode max. potential specification.
All other heaters to amplifier tubes were ground referenced originally. The new all heater elevated scheme now is dc referencing of all the amplifier heaters to assure the amplifier is nice and quiet from an ac induced hum perspective while still preventing the srpp top tube from being operated outside of heater to cathode dc voltage. Doing the dc elevation this way is also beneficial for the front end of the amplifier as the gain is the greatest at the input stage. In other words, elevating heaters, prevents unwanted heater ac currents from getting summed with the intended audio signal which contributes a unwanted hum.
Hope this makes sense.
Mickeystan
lilstripe, if we get into changing design we could talk about alternatives for a long time and we would end up with something that would no longer even come close to Triode Dick's design. I have built mostly push pull tube amps in my life and only a few SE designs. If I wanted to play with Triode Dick's design in a very non invasive way, I would try replacing the 807 with a 6DQ5 sweep tube as I have built with this tube and find it perform very well in audio applications. I would try both tubes (807 and 6DQ5) just for the fun of playing with it. If you familar with using spice tools, you should load up the design and do some modeling to see what you can learn.
Have fun,
Mickeystan
Have fun,
Mickeystan
Well, start with puting a much smaller C at the elevation devider, not 100µF , 1µF is enough.
And you could try some local feedback, like this.
Mona
Attachments
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.