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L'Amp: A simple SIT Amp
L'Amp: A simple SIT Amp
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Old 12th October 2017, 02:18 PM   #2861
woody is offline woody
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2" inner coil dia the final coil would have an outer diameter of 7.49"

If you already have an iron core choke I saw an idea that wouldn't be
hard to try. That is put a small aircore inductor in seriese with the iron core
choke. I noticed someone did this in an old single ended OTL where they
used perhaps a 10mh aircore inductor in seriese with a 500 mh iron core
inductor.
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Old 12th October 2017, 05:23 PM   #2862
atmasphere is offline atmasphere  United States
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Quote:
Originally Posted by maxlorenz View Post

Dear Atma, active CCS will certainly improve voltage swing headroom (and power handling of the output) but, will it sound better? I tend to prefer passive CCS, in fact the inventor of the circuit -ECdesigns- made extensive test with different configurations and decided that this one was better soundwise.... but I will try a cascoded CCS sooner or later. In fact my next move will be cascoding the VFET, as I am a very big fan of cacoding the output, as my new signature suggests.
I can easily imagine that resistors might sound better if the CCS is not performing correctly. A two stage CCS can perform extremely well though! I advise using an empirical approach to setting the value of the drain resistor that ties to V-.

I find that the best approach is to set the value such that when the gain stage is overloading, that the clipping is symmetrical. Beyond that you want it to allow the maximum gain, so long as that does not interfere with the clipping character.

BTW, this may eliminate the need for the balancing potentiometer. If not, it is advisable to make that part the lowest value to do the job as it degrades the performance of the circuit.

Have fun!
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Old 12th October 2017, 07:53 PM   #2863
maxlorenz is offline maxlorenz  Chile
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Quote:
Originally Posted by atmasphere View Post
I can easily imagine that resistors might sound better if the CCS is not performing correctly. A two stage CCS can perform extremely well though! I advise using an empirical approach to setting the value of the drain resistor that ties to V-.

I find that the best approach is to set the value such that when the gain stage is overloading, that the clipping is symmetrical. Beyond that you want it to allow the maximum gain, so long as that does not interfere with the clipping character.

BTW, this may eliminate the need for the balancing potentiometer. If not, it is advisable to make that part the lowest value to do the job as it degrades the performance of the circuit.

Have fun!
OK.
Thank you very much.

M.
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Old 14th October 2017, 10:10 AM   #2864
Soundhappy is offline Soundhappy  France
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Originally Posted by surya View Post
Hi Soundhappy,

SE version. Its taken from my previous SET amp project

Surya
Hi Surya
Ok do you try experiment ?
Respect (-)(+)phase dots
Greetings
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Old 15th October 2017, 03:02 AM   #2865
Soundhappy is offline Soundhappy  France
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I ready try auto-bias KD-33 version with 12 ohm resistors in serie
my conclusion with bias circuit is better amp
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Old 15th October 2017, 04:14 AM   #2866
surya is offline surya
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Not yet with SK180.
Sure phase is correct refer to Lundahl datasheet

Bests
S

Quote:
Originally Posted by Soundhappy View Post
Hi Surya
Ok do you try experiment ?
Respect (-)(+)phase dots
Greetings
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Old 16th October 2017, 01:33 AM   #2867
gadut is offline gadut  Indonesia
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Quote:
Originally Posted by Soundhappy View Post
I ready try auto-bias KD-33 version with 12 ohm resistors in serie
my conclusion with bias circuit is better amp
My conclusion is different, self bias is better one. but I use 30Vds(from 25Vac and 1.6R choke) and 4ohm bias resistor with 1.7A flows on it
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Last edited by gadut; 16th October 2017 at 01:37 AM.
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Old 16th October 2017, 04:19 AM   #2868
Soundhappy is offline Soundhappy  France
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@ Gadut
I like it very much your version.
Short point to point wiring close to vfet.
Kindest regards
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Old 19th October 2017, 08:48 PM   #2869
stevec67 is offline stevec67  United Kingdom
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At the risk of sounding rather thick, how does this work? I can see how simple the circuit is but how is the negative half of the wave amplified when there isn't a complementary device?

Also, why does it need such a huge heatsink? I can see the bulbs are about 22r and ~2A current, but they can cope with that in free air, and the heavy duty 1r resistor is going to be 2W or so, and that appears not to need to be on the HS. The FET needs to stay cool of course but I've seen less cooling on medium sized motorbikes.
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Old 19th October 2017, 09:02 PM   #2870
Nelson Pass is offline Nelson Pass  United States
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L'Amp: A simple SIT Amp
It's a single-ended circuit biased at the maximum peak current. The
"complement" to it is a resistor. Not efficient, but works fine.
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