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Old 5th March 2011, 11:05 AM   #1
fotios is offline fotios  Greece
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Default Preamplifier from Lineup & Fotios for fun

Lineup and me we have designed a line level preamplifier, just for fun . It is based on our discrete module (upgrade of D. Jensen 918) that is also used in our phono preamplifier. There is a module called "JISBOS" and because we use exclusively BJTs from input to output we gave the name "BISBOS" to our discrete OpA. Benefits of BISBOS: 1) No expensive and hard to find jfets for input stage, just ordinary BC550C-560C 2) No need for excess class A idle current 3) No need for matching input transistors, output DC offset can be precisely adjusted from the trim-pot of LTP. 4) Same performance with JISBOS in unity gain (voltage follower) connection. 5) No need for complex power supply / stabilizer circuit, ordinary LM317-337 can do the work, just fine.
Here the schematic of... BISBOS:
Attached Images
File Type: jpg EAL discrete web.jpg (175.9 KB, 1647 views)
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Old 5th March 2011, 11:16 AM   #2
fotios is offline fotios  Greece
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Default Block diagram of preamplifier

Here is the block diagram indicating the external parts connected around the discrete OpA. Cap C2=22pF is used to compensate the input impedance affected from the 100K log volume potentiometer. Sorry guys, i have in my stock only two such pots and no money to buy a 10K .
Besides, is the schematic of voltage stabilizer unit, which is calibrated in +/-24V instead the +/-22V indicated. You can also see a photo of the trial unit on the workbench:
Attached Images
File Type: jpg Lineup Line Buffer.jpg (96.0 KB, 1523 views)
File Type: jpg Lineup P.S..jpg (116.7 KB, 1415 views)
File Type: jpg new21121014.jpg (389.5 KB, 1403 views)
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Old 5th March 2011, 11:39 AM   #3
fotios is offline fotios  Greece
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Default Performance

Here the most interesting part: The performance of the whole circuit captured from the Virtins MI analyzer. To be sincere, when i saw for first time the results i could not believe in my eyes! For this reason i did again and again (at least 10 times) the FFT analysis to be sure. The result was the same. The numbers are too close to those of the Asus Xonar Essence STX that i use as interface! I haven't did yet an audition test. The numbers indicate an almost transparent circuit, with the volume pot at 100% and an input signal of 1.41Vrms (0dBV). In the first picture is shown the performance in Un-weighted mode, and in the second in A-weighted.
Attached Images
File Type: jpg Lineup V follower Unw web.jpg (661.1 KB, 1272 views)
File Type: jpg Lineup V follower Aweight web.jpg (669.9 KB, 303 views)
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Old 5th March 2011, 12:05 PM   #4
fotios is offline fotios  Greece
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Default Bandwidth

Here is the bandwidth captured from simulator . Unfortunately, sound cards have a max bandwidth of 192Ks/sec : 2 = 96KHz. So, they are unsuitable for bandwidth measurement. In the 1st picture is shown the bandwidth with the vol pot at 100% (no attenuation) and is amazing good, very close to JISBOS (this proves that the bandwidth is an issue of topology and not of the type of semiconductors used). In the second picture is shown the bandwidth with the vol pot at 50% (50% attenuation of input signal) For the suspicious (i am one of them ) in the 3rd picture i attach a capture from my DSO , where the rise time is just 260nsec for a square of 10KHz. A square of 100KHz gives a rise time of 300nsec.
Attached Images
File Type: jpg LINEUP LINE PRE web.jpg (403.9 KB, 235 views)
File Type: jpg Lineup Voltage Follower_FR_HALF_web.jpg (326.5 KB, 129 views)
File Type: jpg new21121013.jpg (339.3 KB, 179 views)
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Old 5th March 2011, 06:08 PM   #5
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Default Output noise & DC offset

I ask your forgiveness for my spelling errors. I am self-taught in English. In high school (1970 - 1976) we were taught French. Now, i have forgot French and i haven't any one to talk English. Big problem.
Here is a DSO capture indicating the output noise. It is so small, that the DSO can't compute in RMS so easy; in AVG mode it shows values between 125μV to 250μV. The output DC offset is a "clear zero".
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File Type: jpg Lineup noise small.jpg (294.6 KB, 177 views)
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Old 5th March 2011, 06:43 PM   #6
fotios is offline fotios  Greece
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Default Remote control

I have ready - 5 months ago - a manually / remotely control unit based on a PIC16F887 micro. I developed the mcu code using the nice programming software Flowcode v4 of Matrix Multimedia. The program is written in such way, so as the PIC16F887 can manage Latching type relays. A complete description of this unit here: http://www.eal.gr/MICROS.htm
Here some pictures of control unit.
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File Type: jpg PRE CONTROL 1 DAY.jpg (211.1 KB, 309 views)
File Type: jpg PRE CONTROL 1 DAYLIGHT14m.jpg (440.8 KB, 307 views)
File Type: jpg PRE CONTROL 1 DAYLIGHT7m.jpg (447.0 KB, 221 views)
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Last edited by fotios; 5th March 2011 at 06:49 PM.
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Old 5th March 2011, 09:01 PM   #7
fotios is offline fotios  Greece
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Default Inverter

We have the idea to include and a balanced output in our preamplifier. To this, i checked the... BISBOS in inverting mode with Av = 1. The results of test are very good.
Here is the schematic and a picture of module on workbench:
Attached Images
File Type: jpg LINEUP INVERTER SCH.jpg (85.7 KB, 262 views)
File Type: jpg lineup inverter pic web.jpg (419.2 KB, 202 views)
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Old 5th March 2011, 09:06 PM   #8
fotios is offline fotios  Greece
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Default Inverter performance

Here are the results of FFT analysis captured from Virtins MI FFT software. In the first picture is the performance in Unweighted mode. In the second is in A-Weighting mode. Again an almost transparent circuit.
Attached Images
File Type: jpg Lineup Inverter Unweight web.jpg (665.3 KB, 156 views)
File Type: jpg Lineup Inverter Aweight web.jpg (664.0 KB, 94 views)
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Last edited by fotios; 5th March 2011 at 09:17 PM.
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Old 5th March 2011, 09:14 PM   #9
fotios is offline fotios  Greece
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Default Inverter Bandwidth

Here is the bandwidth of Inverter captured from... simulator . For verification, i attach a second picture that shows the rise time of a 100KHz square wave, captured from DSO.
Attached Images
File Type: jpg LINEUP INVERTER BANDWIDTH web.jpg (493.3 KB, 78 views)
File Type: jpg lineup inverter 100KHz web.jpg (311.8 KB, 98 views)
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Old 5th March 2011, 09:25 PM   #10
lineup is offline lineup  Sweden
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I can confirm this Discrete OP has very low dist and good data.
As you can see from study most testdata.

I am sure we can use BD139-BD140 for replacement in output.
Will not change performance much.
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Last edited by lineup; 5th March 2011 at 09:42 PM.
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