This is my first post here, so please be gentle. I've searched around the forums, and either the posts didn't exist or I am really terrible at coming up with the proper search terms(probably the latter).
First of all, my goal is to design and build a stereo single-ended tube amp from scratch. I'm a software architect and my electronics engineering extends, unused, back about 2 decades ago. The rust extends through the paint and most of the body, and is barely salvageable.
My training 20 years ago barely touched on tubes, mostly transistors. Finally, I'm trying to do my modeling on LTspice. I've seen mixed reactions to this on the forum, so hopefully someone can help me out.
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A couple problems I have to start, and hopefully someone can give me a kickstart.
1) The way that LTspice models transformers. I'm sure anyone knows that it links through the K directive and you must provide inductance for all the coils. I e-mailed Edcor(seems to be the cool guys to use) about their power and output transformer values and they replied that they don't even know - at least they were able to get me the turns ratios for their output transformers. I didn't get that far yet, I was trying to model a power transformer just based on turns ratios. The problem is that LTspice requires inductance to define the coils, so I had to make up some numbers based on unknown characteristics. You can see that in the schematic. I was not able to find some typical values to make this work out like I wanted. I have no idea what typical inductance values a power transformer may have, my training only involved turn ratios.
2) I wanted to use a tube rectifier in my model - specifically the 5AR4. I saw, attached to this forum, the .inc model for this rectifier, but I'm unable to find a schematic symbol that works with it. Has someone made this and I've missed it?
3) This may take a bit of an LTspice expert to look at, not that I am one at all, and it may dive into #1 and my gap of knowledge after 20 years of non-practice. In the schematic, I have L4 pumping out to nets H1 and H2, supposed to heat up the filament. This just isn't working. The plate voltage stays flat. The voltage and current oscillate at 60Hz. The analysis across the lines show ~6Vac and ~200mA, about 1.2W. It just isn't "heating up" in the model. If I provide a direct AC voltage source(inserted into the schematic instead of sourcing off of the transformer), it "heats up" after about 4.5 seconds and works normally after that. I am having a lot of trouble figuring out what the difference is to the software.
Anyway, I'm welcoming all sorts of feedback(solicited and unsolicited). I'm looking at this as a learning adventure and to refresh a passion I've had and long lost.
Thanks to anyone who replies.
First of all, my goal is to design and build a stereo single-ended tube amp from scratch. I'm a software architect and my electronics engineering extends, unused, back about 2 decades ago. The rust extends through the paint and most of the body, and is barely salvageable.
My training 20 years ago barely touched on tubes, mostly transistors. Finally, I'm trying to do my modeling on LTspice. I've seen mixed reactions to this on the forum, so hopefully someone can help me out.
A couple problems I have to start, and hopefully someone can give me a kickstart.
1) The way that LTspice models transformers. I'm sure anyone knows that it links through the K directive and you must provide inductance for all the coils. I e-mailed Edcor(seems to be the cool guys to use) about their power and output transformer values and they replied that they don't even know - at least they were able to get me the turns ratios for their output transformers. I didn't get that far yet, I was trying to model a power transformer just based on turns ratios. The problem is that LTspice requires inductance to define the coils, so I had to make up some numbers based on unknown characteristics. You can see that in the schematic. I was not able to find some typical values to make this work out like I wanted. I have no idea what typical inductance values a power transformer may have, my training only involved turn ratios.
2) I wanted to use a tube rectifier in my model - specifically the 5AR4. I saw, attached to this forum, the .inc model for this rectifier, but I'm unable to find a schematic symbol that works with it. Has someone made this and I've missed it?
3) This may take a bit of an LTspice expert to look at, not that I am one at all, and it may dive into #1 and my gap of knowledge after 20 years of non-practice. In the schematic, I have L4 pumping out to nets H1 and H2, supposed to heat up the filament. This just isn't working. The plate voltage stays flat. The voltage and current oscillate at 60Hz. The analysis across the lines show ~6Vac and ~200mA, about 1.2W. It just isn't "heating up" in the model. If I provide a direct AC voltage source(inserted into the schematic instead of sourcing off of the transformer), it "heats up" after about 4.5 seconds and works normally after that. I am having a lot of trouble figuring out what the difference is to the software.
Anyway, I'm welcoming all sorts of feedback(solicited and unsolicited). I'm looking at this as a learning adventure and to refresh a passion I've had and long lost.
Thanks to anyone who replies.
