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Old 15th March 2007, 04:41 AM   #71
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Interesting schematic, Lee. Is the 2SJ a smoother sounding fet than the P3310? I was wondering if it would be of benefit to switch the two; let the 3310 be the current source?

Have you given your idea a listen, or are you going for the pcb first?

Fun stuff to play with, I'm sure.

I'm having a ball with my ZV7-TJBC (jfet; buffered; cascoded). What a fine experience. I've received three pcbs from Express PCB and will construct a final prototype amplifier, soon. At this moment, I'm designing a pcb with ground-plane in a joint effort with Magura; more fun than any human should have... am I a lucky guy, or what?

One last thing; this regards candy stores: Apex Jr. is an excellent place to shop; great products at incredible prices! I just purchased four 200 v/a transformers with steel casings for $15.00 each. They work beautifully in the 20 volt version of my ZV7-TJBC. I also purchased two 1600 v/a transformers for $45.00 each for the larger amplifiers...uhhh, my electric bill went up $30.00 a month...ooops. (If I keep bragging Steve up, I'm going to have to charge an advertising fee...ha )

Keep us posted on your success, Lee. Your enthusiasm is a breath of fresh air.

John
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Old 22nd December 2016, 11:57 PM   #72
OllBoll is offline OllBoll  Sweden
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I have a mission:

I have previously played with a L loaded R100 Zen, but with my current speakers it has too high distortion at 100-200 hz. So now I want to build a more powerful and better performing amp with a similar sound signature. I also want it to be a current source amp with 100 ohm or higher output impedance.

As I also currently have 6x unused R085s here is my idea. The R085s are unmatched so I have setup individual pots for each.

My questions, however, are:
  1. Is there some flaw in the design?
  2. Does the R values look alright? I'm not sure on the 1R source resistors for the R085, should I have lower values or higher or does it look alright? Should I have higher values on the R085 gate stoppers?
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Old 23rd December 2016, 12:28 AM   #73
Zen Mod is online now Zen Mod  Serbia
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why wasting R085 on cascode duty , when you can use regular IRFP there ?
say that you can use pair of IRFP150 , to cover 1A5 x 45V dissipation

you don't need source resistors there at all , current is defined with LU , while those up are just voltage umbrella

wanna trade some of your R085 for some of my LU ?
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Old 23rd December 2016, 01:33 AM   #74
OllBoll is offline OllBoll  Sweden
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Quote:
Originally Posted by Zen Mod View Post
why wasting R085 on cascode duty , when you can use regular IRFP there ?
say that you can use pair of IRFP150 , to cover 1A5 x 45V dissipation

you don't need source resistors there at all , current is defined with LU , while those up are just voltage umbrella

wanna trade some of your R085 for some of my LU ?
Won't they perform better than say IRFP240s? Or is the distortion caused by the upper parts is overshadowed by that of the lower part?

And in that case I guess it would be a better idea to try a R085 in the lower position and se how it compares to to the LU1014D?

Sadly I already have 10x LU1014Ds to play with. If you have a surplus of R100s or R125s lying around though I might take you up on that as I have previously found them less fiddly to sound good but I don't have as many of them.
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Old 23rd December 2016, 02:57 AM   #75
Zen Mod is online now Zen Mod  Serbia
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if biasing of cascodes is done properly , they're pretty much invisible , while doing work intended

LU cascoded , or SS , as active part - you must judge what's better to your pleasuring apparatus

sorry , don't have SS surplus ; several pairs for my own playground , and that would be exactly enough

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Old 23rd December 2016, 02:58 AM   #76
OllBoll is offline OllBoll  Sweden
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Or is it like this?

The think I don't yet understand though is how they play with each other. If we start simple and ignore modulated cascodes, if the top IRFP part now is just an umbrella does that mean that it does not contribute to the output signal and is equivalent to wasting the watts it dissapates.

Or do the two devices now act kind of like a single device, but where only the lower device takes care of the voltage gain and it is buffered from variances in Vds thus performing better? But both contribute to the output signal like if they were a single device so I don't waste say half of my output power.

And lastly, is there a general guideline for about how much % of my voltage I should put over each device?

Thanks again for being so helpful Zen!
Not the first time you help me when I ask dumb questions
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Old 23rd December 2016, 10:28 AM   #77
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cascoded part and cascode - you can look at them as one part , so no wasting of voltage

for proper cascoding (setting) of LU - best literature is Papa's article about Zv9 , but you already know that

regarding cascodes generally ..... Papa's articles page , then http://www.firstwatt.com/pdf/art_cas_amp.pdf

start with that
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