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Old 21st May 2008, 10:15 PM   #1
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Default Cute little preamp inspired by JBoz/F5

This week I finished a little complementary preamp. Schematics attached.

It started out as a complementary JBoz. After it looked ok on the simulations I removed the cap's and replaced them with resistors. This configuration needs higher voltage rails than the version with capacitors.

I was rather anxious about the DC offset befor the build. After a few minutes warmup the DC offset wandered +-5mV. The DC offset was actually mostly influenced by the volume pot.

After it was up and running I run a test using RMAA 5.5 and a Creative Soundblaster live 24 bit USB. Both output and input volume was set to 75% on the computer. Then the volume pot was used to set correct level for the test. The same procedure was used when testing the JBoz this winter, and these results are used for comparison.

Sound: What can I say? I like it! I took myself in playing louder than usual, and I needed a SPL meter to beware of it.

I have attached schematics, pcb top and bottom, mirrored pcb top and bottom.

Pictures will follow when I locate the camera cable tomorrow.
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File Type: pdf prese2.pdf (71.1 KB, 904 views)
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Old 21st May 2008, 10:20 PM   #2
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The test results 1
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Old 21st May 2008, 10:21 PM   #3
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The test results part #2
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Old 22nd May 2008, 05:32 PM   #4
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Nice work!

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Old 22nd May 2008, 08:29 PM   #5
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Nice work...

Output impedance of your Pre?
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Old 22nd May 2008, 10:23 PM   #6
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The output impedance should be ~2K6 (R14, R21).

The amp got it's new home inside an old Pioneer integrated amp. Removed everything except the input selector and volume pot.

BTW the amp is point to point soldered. Used the PCB layout only as a guide.
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Old 22nd May 2008, 10:24 PM   #7
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Front view, open top.
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Old 28th May 2008, 03:10 PM   #8
Tolu is offline Tolu  Germany
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How about a sound comparison between JBOZ and PreSE?
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Old 28th May 2008, 03:58 PM   #9
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Very original.
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Old 28th May 2008, 04:45 PM   #10
Tolu is offline Tolu  Germany
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But what original?
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