It needs to be air gapped core to prevent saturation from DC. So cannot use standard ferrite round donut. But rectangular toroidal air gapped core made with stacked steel plates can work.
@marconi118
Ciao e grazie! Thank you for the suggestion, I will try to ask them.
I will ask Toroidy as well.
Ciao e grazie! Thank you for the suggestion, I will try to ask them.
I will ask Toroidy as well.
@xrk971 I’ve used toroidal transformers for tube SE amps and they work fine.
I’ve seen toroidy has (low current) chokes in their portfolio. I remember they said their material reacts like a “diffused airgap”.
https://sklep.toroidy.pl/en_US/c/Toroidal-DC-Chokes/145
I’ve seen toroidy has (low current) chokes in their portfolio. I remember they said their material reacts like a “diffused airgap”.
https://sklep.toroidy.pl/en_US/c/Toroidal-DC-Chokes/145
I asked to both of them a couple of prices:
a cheap version with 80 mH and an Rdc < 0.5 Ohm, and the other with the lowest possible Rdc.
a cheap version with 80 mH and an Rdc < 0.5 Ohm, and the other with the lowest possible Rdc.
my plan is to use the 100mH as drain load and the rest as source load to have a bit of gain. coupling of both coils on the same core should be linearize a bit
has been done on SLAPS search here on diyaudio
has been done on SLAPS search here on diyaudio
Cool. What kind of current were you flowing through them? We are talking about 2-4 amps in this case. Normal ferrite core toroidals are notorious for not handling Dc well which is why we have DC blockers for AC mains. OTOH, I have seen Susan Parker use a standard toroidal trafo on the output of her Zeus amp as a test.
http://www.susan-parker.co.uk/zeus-toroid-amp-1.htm
The original application was a two stage vacuum tube amplifier with each pentode stage turned into pseudo triodes via the cathode drive / plate to grid feedback method. See attached curves traced by hand from a pentode tube in this configuration. The uneven spacing is due to the resolution of the power supply's meters.
The concept was applied to a pure semiconductor design in this thread. My involvement starts on post #597 and continues sporadically. The first working FETSET amp appears in post #872
I built a similar amp with high voltage mosfets and an output transformer and it does give a realistic SET sound. I wouldn't use it to replace my 3 WPC 2A3 tube amp, but it makes 20 WPC and a real tube 20 WPC (true) SET would be large and expensive. I have built a few. There are differeces in sound between a 30 watt SET using 845 transmitting tubes on 1100 volts, an UNSET using TV sweep tubes on 650 volts, and a mosfet based "FETSET" using IXTH6N100DZ mosfets on 250 volts into a 600 ohm Toroidy OPT. These differences are minor, mostly involving dynamics, with the FETSET being the most dynamic on drum transients probably due to its high peak current capability.
https://www.diyaudio.com/community/threads/schade-common-gate-scg-preamp.380487/
Attachments
H
HAYK
Why use Rush cascode also for the input stage? Is it better than a simple triode?
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In that case idle current is 100 mA, so peak is 200 mA.
Here idle current is 2.3-2.5 A, absolutely another league.
I've found this document by Toroidy about the Air Gap Toroidal Core Technology: https://sklep.toroidy.pl/public/assets//Toroidy4Audio-presentationEN.pdf
And this study by TDK: https://www.tdk-electronics.tdk.com...be8ac35d54a/ferrites-air-gaps-standard-pb.pdf
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Inexpensive pentodes can be used to get perfect triode curves with an input capacitance of less than 10 pF, no Miller effect, and the capability to swing down to less than 50V. Different anode-to-g1 feedback ratios give different gains and harmonics to that stage, so you can adapt it for different applications.
In my case I did it to see how well it would work and how it sounds. The UNSET board was kind of an experiment and never meant to be a Tubelab product. It's only real issue is not quite enough gain to clip a 20+ watt SE amp from some sources, like an iPhone.......yes people want to drive their high end tube amps with a phone.
I spun off a second board which is only the UNSET output stage. They work better than a typical triode in the power output department. I have seen over 500 watts flow from 4 tubes in push pull.
A recent discussion on big power tube amps has started. I put my breadboard back together and saw 180 watts come from a single pair of tubes into a 3300 ohm load on 650 volts. Previous testing saw a bit over 250 watts from one pair on 2500 ohms. My first step towards the 1 KW (500WPC) amp will be a 100 WPC amp with one pair of 26HU5's on 550 volts or so using the 3300 ohm Edcors. It will be a full on rack mounted amp eventually, but for now it will be used to test and debug a control and monitoring system for the big one.
See post #18 here:
https://www.diyaudio.com/community/threads/musings-on-the-design-of-the-big-one-s.404659/
I spun off a second board which is only the UNSET output stage. They work better than a typical triode in the power output department. I have seen over 500 watts flow from 4 tubes in push pull.
A recent discussion on big power tube amps has started. I put my breadboard back together and saw 180 watts come from a single pair of tubes into a 3300 ohm load on 650 volts. Previous testing saw a bit over 250 watts from one pair on 2500 ohms. My first step towards the 1 KW (500WPC) amp will be a 100 WPC amp with one pair of 26HU5's on 550 volts or so using the 3300 ohm Edcors. It will be a full on rack mounted amp eventually, but for now it will be used to test and debug a control and monitoring system for the big one.
See post #18 here:
https://www.diyaudio.com/community/threads/musings-on-the-design-of-the-big-one-s.404659/