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Old 18th April 2011, 07:16 PM   #1
Helmuth is offline Helmuth  Netherlands
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Default Lageschaar hybrid-connection PSE-KT66

Hi guys,

After starting a kt66 PP-design in 2004 with a early ending, I give it now a good start now with nice C-core OPT.

The amplifier will be a fixed bias PSE KT66 triode without feedback , I have to investigate switch triode to UL-mode. And I will make it switchable to Williamson feedback design what will be the Lageschaar Hybrid-connection.
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Last edited by Helmuth; 18th April 2011 at 07:31 PM.
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Old 18th April 2011, 07:52 PM   #2
Helmuth is offline Helmuth  Netherlands
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I measured today the just received custom made EDIS C-core OPT.

Measured with Hioki 3532-50 LCR bridge. I work at engineering(I do not have a engineer degree) we build switching lamp-drivers so we have nice measurement equipment.(My work Nedap Light Controls)
With 8 Ohm load precise 7,73Ohm. We see Fs at 116kHz. And Z about 3kOhm with 8 ohm load.

Click the image to open in full size.
Click the image to open in full size.

With shorted output.
Click the image to open in full size.Click the image to open in full size.

With open output.Click the image to open in full size.Click the image to open in full size.
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Old 18th April 2011, 08:13 PM   #3
Helmuth is offline Helmuth  Netherlands
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Here a simulation of the loadline at 2k8 thanks to Andrea.

Click the image to open in full size.
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Old 18th April 2011, 10:24 PM   #4
Helmuth is offline Helmuth  Netherlands
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Quote:
Originally Posted by Helmuth View Post
Hi guys,

After starting a kt66 PP-design in 2004 with a early ending, I give it now a good start now with nice C-core OPT.

The amplifier will be a fixed bias PSE KT66 triode without feedback , I have to investigate switch triode to UL-mode. And I will make it switchable to Williamson feedback design what will be the Lageschaar Hybrid-connection.
The copy right for the name and idea of Lageschaar hybrid-connection will be claimed by me Helmuth.Lageschaar date 19-04-2011 and is not free to copy without my permission by others for commercial use.
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Old 19th April 2011, 05:56 PM   #5
Helmuth is offline Helmuth  Netherlands
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Measurements of the OPT connected to a variac and load to see the transformation proportion.

Transformer 1

8 ohm output
Uin=62,33V 50Hz
Uout=2,836V
n1=62,33/2,836=21,97X

4 ohm output
Uin=65,01V
Uin=2,007V
n2=32,4X


Transformer 2

8 ohm output
Uin=62,28V 50Hz
Uout=2,83V
n1=62,28/2,83=22,01X

4 ohm output
Uin=65,03V
Uin=2,006V
n2=32,4X

Load tube is n1^2X8Ohm or n2^2X4 Ohm

22^2X8=3872 to 22^2X6,5=3146
32,4^2X4=4199 to 32,4^2X2,8=2939

I ordered 2800Ohm load so the 8 oHm tab isn't placed right for optimal load.
The 4 Ohm load is near the load line I did aks for.
It depends on what philosophy EDIS uses as minimum load for the OPT to calculate the Ra-load.


Here the result of Trafo1 with the LCR meter with 7,73 Ohm load

Frequency Z(ohm) Ls(H) Q() Rs(ohm)
1001,00 3147,00 0,02 0,04 3144,60

Trafo 2

Frequency Z(ohm) Ls(H) Q() Rs(ohm)
1001,00 3137,40 0,02 0,03 3135,90
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Last edited by Helmuth; 19th April 2011 at 06:05 PM.
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Old 19th April 2011, 07:24 PM   #6
Helmuth is offline Helmuth  Netherlands
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The Tube.
Click the image to open in full size.
Click the image to open in full size.
The review:
1
Everything you read in the review of the Sovtek 6L6WXT+ holds true for this tube. A larger than average curved glass envelope and metal base ring make this a different package than the familiar 6L6. Biasing and current draw are not issues, just the same as any 6L6GC. The sound of the Sovtek KT66 is great and usable for any application. If your amp has “bear trap” tube retainers they will have to go because of the size of the tube's base but also the bear trap clamp will ground the metal base to the chassis and cause a malfunction.

2
Guitar-cable-amplifier. If this describes the rig you use, then this is one of two modern tubes you should consider. This is not a repackaged 5881. Extremely low noise and a lack of microphonics combine with excellent ratings for detail and harmonic content to provide a tube of exceptional quality. These tubes can be used in any application. Plenty of power and great tone. We have tested these tubes with plate voltages ranging from 425 to 500 volts without problem. Biasing can be set from conservative to hot; again, no real problem and great tone will be delivered from most settings.

3
(nelson audio)
This is my first experience with a KT-66 based amplifier. The KT-66, at least in this amp, doesn't sound like a lower powered version of the KT-88, which, to my ears, is one of the most balanced tubes, frequency wise, that I have heard. The KT-66 is basically a guitar amp tube, very similar to the 6L6. Frank said not to think of the tube as a small KT-88, but more like a high powered 300B or 2A3. This makes perfect sense to me, as those tubes aren't known for bass slam or control, but rather for tonal beauty especially in the midrange.

Triode Charateristic.
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File Type: jpg Schermafbeelding 2011-04-19 om 21.11.08.jpg (117.9 KB, 833 views)
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Last edited by Helmuth; 19th April 2011 at 07:28 PM.
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Old 19th April 2011, 07:34 PM   #7
Helmuth is offline Helmuth  Netherlands
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The site of the OTP builder.
Leszek Ogonowski transformatory sieciowe g?o?nikowe single ended SE push-pull PP audio d?awiki wzmacniacze lampowe akcesoria
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Old 20th April 2011, 10:17 AM   #8
DQ828 is offline DQ828  Australia
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I'll follow with interest, not that I understand any of it
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Old 20th April 2011, 04:58 PM   #9
Helmuth is offline Helmuth  Netherlands
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Quote:
Originally Posted by DQ828 View Post
I'll follow with interest, not that I understand any of it
Hi David,

Let me explain.

The output-transformer OPT of the tubamp transforms the resistance of the loudspeaker to the anode of the tube.

In the triode characteristic we can draw a load line. In the middle of the load line you see the bias point/current class A.
Click the image to open in full size.
Is calculated on max voltage divided by load resistance gives max current draw the line. I came out on 2800ohm as a good load to get enough power out of the tube.

Here a nice article.
What is the best load line for a tube

It is all done to use all the power that the tube can give considering acceptable distortion level.

Regards Helmuth
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Last edited by Helmuth; 20th April 2011 at 05:01 PM.
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Old 21st April 2011, 08:41 AM   #10
DQ828 is offline DQ828  Australia
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Quote:
Originally Posted by Helmuth View Post
Hi David,

Let me explain.

The output-transformer OPT of the tubamp transforms the resistance of the loudspeaker to the anode of the tube.

In the triode characteristic we can draw a load line. In the middle of the load line you see the bias point/current class A.
Click the image to open in full size.
Is calculated on max voltage divided by load resistance gives max current draw the line. I came out on 2800ohm as a good load to get enough power out of the tube.

Here a nice article.
What is the best load line for a tube

It is all done to use all the power that the tube can give considering acceptable distortion level.

Regards Helmuth
I'm a slow learner, but wont stop trying
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