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Old 27th September 2009, 05:08 PM   #5021
ichiban is offline ichiban  United States
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Originally Posted by AndrewT View Post
do they all have multi-paralleled output stages?
I know the Krells have.
The F5 is a single pair.

I've found documents from my 1986 purchase from Audio Concepts in Wisconsin. I was mistaken, that a single Strat could be driven directly.
They recommend a series resistor of 1.5 ohms with a single Strat.
Guess I'll be using the transformers.

PS sorry for the off topic

Last edited by ichiban; 27th September 2009 at 05:10 PM. Reason: ps
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Old 27th September 2009, 10:12 PM   #5022
smyslow is offline smyslow  Europe
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Originally Posted by tinitus View Post
And I was thinking about 15V trafos, with raised bias

Wasnt there something with input driver stage being at the limit with the original supply

Hi tinitus,

my balanced F5 (EUVL's version, see http://www.diyaudio.com/forums/showp...postcount=1216) runs with 15VAC and 1.6A bias current. But I used 2SK1530/2SJ201 instead of the original IRF types. It sounds great!

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Old 27th September 2009, 10:30 PM   #5023
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thanh1973, If you push the rails up to 35v what jfers are you going to use the 2sj74
is a 25v part !
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Old 27th September 2009, 10:57 PM   #5024
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I routinely push these parts to as high as 40V in my own
stuff. They seem to have been spec'd at lower voltage for
Gate current. If you can put up with higher Gate current,
then you'll find them actually breaking down around 42-43 V.

Not that I recommend that you build an amp on this

And has no one mentioned cascoding these?

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Old 27th September 2009, 11:26 PM   #5025
Zen Mod is online now Zen Mod  Serbia
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Originally Posted by Nelson Pass View Post

And has no one mentioned cascoding these?

even my tongue is starting to bump , repeating that

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Old 27th September 2009, 11:43 PM   #5026
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Originally Posted by thanh1973 View Post
So someone got this working with lateral mosfets.
How does it sound?
I got it to work (this was perhaps a year ago) but the pair of F5's -- 2 sets of 2-- use Fairchild devices.
Why, silly hare, are you fleeing from the fierce jaws of the lion now grown tame?
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Old 27th September 2009, 11:46 PM   #5027
tinitus is offline tinitus  Europe
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Smyslow, thanks for schematic
Its saved, and even if not building it, there may be one or two tricks I can learn from

btw, Amplimo 300VA comes in small voltage steps, 12-15-#17#-18-20-22-25-28-30-33-35
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Old 28th September 2009, 12:59 AM   #5028
Blues is offline Blues  United States
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Originally Posted by Nelson Pass View Post

And has no one mentioned cascoding these?

Done that...
Life simplified! Leap into the Warpspeed wormhole... http://www.6moons.com/audioreviews/warpspeed/1.html
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Old 28th September 2009, 02:50 AM   #5029
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Originally Posted by Zen Mod View Post
even my tongue is starting to bump , repeating that

schematic or it didn't happen
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Old 30th September 2009, 03:37 AM   #5030
fritz39 is offline fritz39  United States
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Default System needs a few more dB gain to drive F5

I've got a channel of the F5 up and running and I noticed my input to the
amplifier isn't sufficient to get to full output power. Unfortunately, my
speakers only have about 82 dB efficiency so I know I won't get to ear bleeding
levels, but I would at least like to maximize the output. Given the output of my
cd player, I need about 2-3 dB more gain. Any suggestion on how to achieve
this without destroying the quality of the F5? Thanks.
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