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Old 21st April 2011, 02:51 PM   #21
Snokker is offline Snokker  Netherlands
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Quote:
Originally Posted by Tea-Bag View Post
Did you use MRothatcher's design?

I think with a circlotron that maybe the R085's could be used?
I started with "the amazing circlotron" and swapped the P240's with the
R100's. That worked fine so I started tweaking, changed the transformers >V and thus the inputfets and feedback.
I only tried the R100's (never ever payed that much for a single semiconductor..) but I'll check out the R085's.
Did you use them in a project?
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Old 21st April 2011, 05:03 PM   #22
Tea-Bag is offline Tea-Bag  United States
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I tried as I might to get the R085's working optimally in the de-lite circuit without great success. The R100 in enhanced mode there works well.
I hope to revisit that with a CCS, and play with the Semisouth's more.
Lately I've been distracted by other projects, and spring in general.
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Old 21st April 2011, 11:00 PM   #23
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Originally Posted by Snokker View Post
and thus the inputfets and feedback.
What did you end up doing with the input to handle the higher V? What value of feedback resistor?

I'm thinking seriously of doing something similar. While scrapping old equipment at work, I aquired (for free!) a pair of really nice heatsinks / enclosures to build a pair of monoblocks. My new Twisted Pear DAC really needs to feed a nice balanced amp. I also already have the SS R100's (thanks Teabag).
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Old 22nd April 2011, 12:55 AM   #24
Snokker is offline Snokker  Netherlands
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Originally Posted by william2001 View Post
What did you end up doing with the input to handle the higher V? What value of feedback resistor?
There's no such thing as too much cooling, especially when you get it for free and you have two pairs of R100's waiting to be used
I would advise to start with the "standard" 24V setup. When you think you get grip on this, start moving the pieces!
For the front end I finally used old (the newer types are N channels!!) 2N5465 (IDSS 8,5mA) as I still have plenty of them; leftovers from Hiraga projects... This keeps the front end simple so no cascading or what so ever.
Rs (or R5 in the circloton schematic) ended up in 33Ohms in my case and, more important R11 (the feedback resistor) in 620 Ohm.

I even pushed the envelope with the PS to 35V, but I did not dare to do a full stability test. These SS's are just too expensive...
Have fun.
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Old 22nd April 2011, 02:21 AM   #25
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There's no such thing as too much cooling
There's not even such a thing as enough cooling.

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Old 22nd April 2011, 03:36 AM   #26
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Old 22nd April 2011, 08:00 AM   #27
qusp is offline qusp  Australia
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very cool
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Old 22nd April 2011, 09:42 AM   #28
Snokker is offline Snokker  Netherlands
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Originally Posted by Tea-Bag View Post
All of them sound can sound 'cleaner' than the IRFP240 counterparts. As I've stated elsewhere, Whisky for MOSFET, Vodka for R100 JFET.
I found that the ration of 3th harmonic to the THD is relative higher in the F2J for example and I expected it to be the combination the R100's with the 9240's in the current source. Not typical for a SE design
(<<THD BTW)
And so I started with a circlotron; just one type of output fet
But maybe i ran into conclusions too quick did others find a better match between the two....
And yes, I like whisky better than vodka
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Old 22nd April 2011, 12:51 PM   #29
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Thanks for the info and advice Snokker.
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Old 22nd April 2011, 01:31 PM   #30
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Quote:
Originally Posted by Snokker View Post
I found that the ration of 3th harmonic to the THD is relative higher in the F2J for example and I expected it to be the combination the R100's with the 9240's in the current source. Not typical for a SE design
(<<THD BTW)
And so I started with a circlotron; just one type of output fet
But maybe i ran into conclusions too quick did others find a better match between the two....
And yes, I like whisky better than vodka
Nelson,
Would you agree with this statement. THe F2J was going to be my first SS build. I was going to build the Mfet version first so that i could i have sense of what the original sounded like before switching out for the SS fets. Forigve me if i am presumptuous fro calling you by your first name.
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