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Old 9th November 2005, 04:46 PM   #31
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Neat little amp! I seem to have missed it the first time around.

By the way, you don't necessarily need to run everything through the output cap. If you're running two or more way speakers, particularly those which are set up for bi-wiring, you can split the high and low pass sections and drive the high pass section straight off the amp's output provided there's no DC path to ground ahead of the series cap in the high pass section.

I've been experimenting with some similar ultra simple followers and even using the big Black Gate 4,700uF N type cap, it sounds significantly better when driving the high pass section straight off the output.

se
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Old 9th November 2005, 05:03 PM   #32
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Quote:
Originally posted by Mad_K
If you replace the resistor with a active current source you can do this, but not in this circuit. If you set the dc level at 20V it will clip very early on the negative side

Hmmm. Yes, you're right. On to a CS, then...

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Old 9th November 2005, 05:29 PM   #33
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Hello Mad_K,
This is a nice little project which I would like to try. Thanks for posting it. Since I am a noobie..... I have a question about the schematic. There is a V+ symbol in the top right of the schematic close to +40V. What should be connected to this point?
Thanks
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Old 9th November 2005, 05:40 PM   #34
Mad_K is offline Mad_K  Norway
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Quote:
Originally posted by TB
Hello Mad_K,
This is a nice little project which I would like to try. Thanks for posting it. Since I am a noobie..... I have a question about the schematic. There is a V+ symbol in the top right of the schematic close to +40V. What should be connected to this point?
Thanks
+40V or thereabout
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Old 9th November 2005, 06:06 PM   #35
TB is offline TB  United States
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Thanks
Would it be possible to use IRF510 transistor in this amp?
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Old 9th November 2005, 06:38 PM   #36
Mad_K is offline Mad_K  Norway
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Quote:
Originally posted by TB
Thanks
Would it be possible to use IRF510 transistor in this amp?
You have to use the heavier cousins in TO247 packackage. IRFP044, IRFP140/N, IRFP150/N, IRFP240, IRFP250/N are the preferred parts, but almost any mosfet that can take the heat will work.
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Old 9th November 2005, 07:03 PM   #37
TB is offline TB  United States
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if I understand correctly output power of SE MOSFET amp depends on used PSU. In your design 40 Volts gives 7 Watts. I would like to use this amp to work with DIY single-drive voight pipes. Used drivers are 8 Ohms with no X-over. I think, those speakers are rather efficient. I do not listen to music at high levels. Would it be possible to lower the amplifier 's output power to maybe 3 Watts by using lower PSU voltage? The reason I ask this question are two R-core transformers which I bought long time ago. Those are 19 Volts @ 2 ampers units. Output voltage after rectification would be 27 volts at 2 amps. Is it enough for lower poweramp?
Thanks again for your help.
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Old 9th November 2005, 07:28 PM   #38
Mad_K is offline Mad_K  Norway
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It is very easy to scale the amplifier down. My prototype runs on 22,5V and gives about 3W. I'm using a 600VA 2*18V transformer (2*18V@17A). You could get by with a 250VA 2*18V (2*18V@7A). I'm afraid your existing transformer are just not heavy enough.

To make a 3,5W (Let's call it SEWA-3,5) simply use a 24VDC supply and reduce the 10 Ohm power resistor to 6,8 Ohm. Current draw will be approximately 2,15A.
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Old 8th February 2006, 08:50 AM   #39
Mad_K is offline Mad_K  Norway
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Default Update

Since my SEWA design has evolved into another design, I'm renaming this circuit the "OTA - One Transistor Amplifier". Further discussion on this design will take place here: OTA - One Transistor Amplifier

M
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Old 16th February 2006, 06:14 AM   #40
Mad_K is offline Mad_K  Norway
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Default SEWA Rev.1

Quote:
Originally posted by janneman



Hmmm. Yes, you're right. On to a CS, then...

Jan Didden
Here is the revised version of The Seven Watt Amplifier.
I've been listening to this design for about 3 months now, and I can honestly say that it really lets me "Live The Music". This new version features an active CCS, higher input impedance (250K), lower power dissipation (45W per channel) and generally better performance.
Attached Files
File Type: pdf sewar1.sch.pdf (64.2 KB, 2030 views)
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