its nice to read this, having 22V trafos on order
Yep ,sounds about right .....................
Sometimes you need to get hit in the head...
I was soldering the Balanced F5 board last night when I realized it would be a trivial matter to convert my Cascoded board to a Balanced Cascoded F5.
I'm going to try that tonight. According to NP's hints, cascoding helps, and the balanced idea is interesting.
Assuming the transformation goes well, I'll start a new thread for the Balanced Cascoded F5. I'm upset I didn't make this connection faster.
I was soldering the Balanced F5 board last night when I realized it would be a trivial matter to convert my Cascoded board to a Balanced Cascoded F5.
I'm going to try that tonight. According to NP's hints, cascoding helps, and the balanced idea is interesting.
Assuming the transformation goes well, I'll start a new thread for the Balanced Cascoded F5. I'm upset I didn't make this connection faster.
NYCOne: This snippet makes me suspect that you are reporting your bias as 2x the actual bias, leading to overall confusion in later posts?
Confusion indeed.
What is the quiescent current fed from the +ve supply rail?
What is the quiescent current fed to the -ve supply rail?
What is the quiescent current flowing in the PSU Zero Volts line?
Are there any parts of the circuit, even an individual leg of a single component that passes a quiescent current of 2.1A?
Andrew,
As I mentioned in my other thread. I'm happy be wrong in my calculations. Let's clear it up. In post #100 you can see my output section - two IRFP240s and two IRFP9240s.
The method was based on the voltage across each source resistor. I measured ~ 0.6V. I'd assumed that meant 1.3A though each output pair, but if this is incorrect, it's an error of inexperience not intent.
The heat sink was ~30C over room temp, I thought I was biasing a fair bit of current. If that's the temperature increase with 1.3A total, I need gargantuan heat sinks. I'm using the Conrad MF35-151.5
From Conrad's website:
Model: MF35-151.5
Length (Height): 151.5 mm
Thermal Res: 0.21
Weight kg 2.46
What's the correct way to calculate the current based on the measurements?
As I mentioned in my other thread. I'm happy be wrong in my calculations. Let's clear it up. In post #100 you can see my output section - two IRFP240s and two IRFP9240s.
The method was based on the voltage across each source resistor. I measured ~ 0.6V. I'd assumed that meant 1.3A though each output pair, but if this is incorrect, it's an error of inexperience not intent.
The heat sink was ~30C over room temp, I thought I was biasing a fair bit of current. If that's the temperature increase with 1.3A total, I need gargantuan heat sinks. I'm using the Conrad MF35-151.5
From Conrad's website:
Model: MF35-151.5
Length (Height): 151.5 mm
Thermal Res: 0.21
Weight kg 2.46
What's the correct way to calculate the current based on the measurements?
Best voltage for the base of the cascode transistor
I've been on a hiatus - real life work is busy. I'm getting some time to play again and was wondering the best target voltage for the base of the cascode transistor. Many have been using an equal voltage divider. With 24V rails that's a ~12V base. I would guess the "sweet spot" voltage is well known for these transistors. Put another way, should I shoot for a 12V base, 8V, 6V?
I've been on a hiatus - real life work is busy. I'm getting some time to play again and was wondering the best target voltage for the base of the cascode transistor. Many have been using an equal voltage divider. With 24V rails that's a ~12V base. I would guess the "sweet spot" voltage is well known for these transistors. Put another way, should I shoot for a 12V base, 8V, 6V?
I'm going back to what NP said - there's always a benefit to a cascode. The 24V rail was a demonstration point, I intend to use a few Xformers until I resolve which I like. Since changing resistors is easy, I thought I'd ask what experience folks have had with cascodes. The PCB is done and populated, the only issue is what voltage divider to use. Or as I put in my last post, what is the sweet spot for the JFETs? I'd think someone has done this before.
You may find these links useful
http://www.firstwatt.com/pdf/art_sweet_spot.pdf
http://www.firstwatt.com/pdf/art_zv9.pdf
Maybe it wasn't obvious in my post, I was referring to these articles and Nelson's comments in the forum when I posed the question in this thread. I may have missed the portion of the articles where they show 2SK170BL and 2SJ74BL cascode results, but that's what I was hoping to elicit.
Basically, assuming there's a benefit to cascoding, as we're all pointing to the same articles, what have folks experienced in terms of best base voltage for the front end transistors in the F5?
8V has been put forth by one person, any other experiences?
Basically, assuming there's a benefit to cascoding, as we're all pointing to the same articles, what have folks experienced in terms of best base voltage for the front end transistors in the F5?
8V has been put forth by one person, any other experiences?
I think from Nelson's point of view, the cascode holds 'technical' advantages
lower distortion figures have been mentioned
but in lack of skills, I really dont know much about any of this
but those here who have tried haven't been able to actually hear any difference
well, could be it comes down to careful implementing and adjusting
maybe thats one part we are missing still
and ofcourse there's the possibility to drive the curcuit harder
which is the obvious one
but again, I'm always cautious about what other people claim to hear, or not
like reviews, always taken with a grain of salt, so to speak
I want to hear it myself, before forming any opinion about it
not good to just pass on other peoples opinions, unquestioningly
but honestly
when I build something that seems to work to my satisfaction, I leave it be as is
once it works ok, I do not experiment further
maybe I will miss out on something, I dont know
my personal opinion is that many so called 'improvements' are merely just changes
no worse no better
in many cases just a matter of personal preferences, and as such very individual
could just exclusively relate to a certain setup
and in the end subjective and personal
oh, well, adjustments, yes
that I can do forever, and never ending
simple ones, ofcourse
lower distortion figures have been mentioned
but in lack of skills, I really dont know much about any of this
but those here who have tried haven't been able to actually hear any difference
well, could be it comes down to careful implementing and adjusting
maybe thats one part we are missing still
and ofcourse there's the possibility to drive the curcuit harder
which is the obvious one
but again, I'm always cautious about what other people claim to hear, or not
like reviews, always taken with a grain of salt, so to speak
I want to hear it myself, before forming any opinion about it
not good to just pass on other peoples opinions, unquestioningly
but honestly
when I build something that seems to work to my satisfaction, I leave it be as is
once it works ok, I do not experiment further
maybe I will miss out on something, I dont know
my personal opinion is that many so called 'improvements' are merely just changes
no worse no better
in many cases just a matter of personal preferences, and as such very individual
could just exclusively relate to a certain setup
and in the end subjective and personal
oh, well, adjustments, yes
that I can do forever, and never ending
simple ones, ofcourse
True, 8V has been mentioned a few times.
I bought a 12V 800VA transformer for the Balanced-Cascoded circuit. I hope to have time to try it in 2 weeks. I have a 26V transformer for testing, but its too small for the final version.
Based on NP's advice, I'm pushing toward a Balanced-Cascoded amp with 12V xformer, and a standard Cascoded F5 with 26V xformer.
I was able to finish my OB speakers, so I have a real means of evaluating differences in the amps (finally).
I bought a 12V 800VA transformer for the Balanced-Cascoded circuit. I hope to have time to try it in 2 weeks. I have a 26V transformer for testing, but its too small for the final version.
Based on NP's advice, I'm pushing toward a Balanced-Cascoded amp with 12V xformer, and a standard Cascoded F5 with 26V xformer.
I was able to finish my OB speakers, so I have a real means of evaluating differences in the amps (finally).
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