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Old 25th February 2011, 08:44 PM   #11
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[QUOTE=kevinkr;2480045]I noticed that the input gain setting configuration is not per the recommended configuration in the TI/BB application notes.

this is out of the spec sheet:

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i just took off the 10 ohm res in series
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Old 25th February 2011, 09:49 PM   #12
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Default is the AD797 a better choice

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Old 25th February 2011, 10:25 PM   #13
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The differential input impedance needs to be 47K to properly load the cartridge, I'd change those 10K input resistors to 24K which would be close enough.

the first ina103 preamp i build had 2 times 23.7 kohm and sounded more harsh compare to 2 times 10 kohm.

i had no input cap either, so im not sure what does what but i can tell you dusty springfield (the look of love) is simply perfect.

right now im recording with an Audio-Technica 440MLa and i get the same top end richness. in the past i use to hate this cartridge for the bright top end on my old phono pre.

Martin
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Old 26th February 2011, 09:39 AM   #14
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The AD797 looks good, but with 8 MHz gain bandwidth product you better put .1 disc caps very close on power supply. You would need two since it is a mono part. It has a static warning, must include fets. LM4562 has 45 mhz gain bandwidth, 20V/us slew rate and is $3 at digitech this week for 2 in a dip package. ST33078 sounds really good, 10 mhz gainbandwidth, 5 v/usec slew rate, 15 ma drive, lot less power supply current than Ad797 and is $.60 for stereo DIP package and has no FET's and took a lot of mistakes without blowing up on my disco mixer. I had hoped your conversion of circuit to application note per Kevin's note would get enough gain. Have you thought of increasing the feedback resistor on your power amp op amp to get more gain there? most pro power amps have an op amp on the input. My Peavey power amp uses NJM4560 op amps, another good part. Also available as RC4560 from TI. Any of these parts watch package code, they come in SOT which is useless for amateurs and SIP which doesn't fit most sockets. My ST120 power amp has way more gain than the Peavey, something about a hfe 150 input transistor to make it compatible with the low gain tube PAS2/3 preamp, hugely popular in 1966 and not like modern equipment at all.
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Last edited by indianajo; 26th February 2011 at 09:52 AM.
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Old 28th February 2011, 09:12 PM   #15
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Default tina-ti version

with the ina103 & opa627

103627E.zip

i'm waiting a test 1Khz reference tone LP to know my precise input voltage

Analogue_Test_LP


SPICE-Based Analog Simulation Program - TINA-TI - TI Tool Folder

i have to learn how to input all those different opamp in to tina-ti

i'm progressing

Martin
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Old 28th February 2011, 09:16 PM   #16
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Quote:
Originally Posted by indianajo View Post
The AD797 has a static warning, must include fets.
dont scare me like that

Martin
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Old 28th December 2012, 12:45 PM   #17
granoj is offline granoj  Finland
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Martin, how is it going with this preamp. I`m in a similar situation and luckily found this thread. So I want to archive my vinyl. I would like to use my soundcard since I have the option to apply real time RIAA with the onboard DSP. Im in process of re-wiring my tonearm to balanced configuration and I would really like to stay that way all the way to my computer. I`m using MM cartridges and what I have read, the problem is loading these high gain mic-preamps...Im relatively new to electronics so be gentle Any ideas?

Jarno
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