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Old 20th August 2019, 01:15 AM   #41
rsavas is offline rsavas  Canada
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Join Date: Aug 2012
Location: Ontario
That is a good history lesson thx
Quote:
And yes, slew rate is critical for a phono preamp. The demands on the feedback loop are enormous.
If you run multiple gain stages then this takes that burden away. This is what Doug Self suggests when using the NE5534 in a MM app.
But I still think the jfet is the best choice for a MM IPS, look at Bob Cordell's vinyl trak design or the LSK489 app note. The LM4562 should be fast enough.
I think the final touches could be a DC servo and get rid of C5, if you are bothered by ecaps in the FB.
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Last edited by rsavas; 20th August 2019 at 01:21 AM.
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Old 20th August 2019, 02:52 AM   #42
stocktrader200 is offline stocktrader200  Canada
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low noise npn transistor for front stage into op amp RIAA at lower gain works great.
the jfets may be more noisy then just the op amp in this config.

Last edited by stocktrader200; 20th August 2019 at 02:55 AM.
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Old 20th August 2019, 02:52 PM   #43
rsavas is offline rsavas  Canada
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Join Date: Aug 2012
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Quote:
Originally Posted by stocktrader200 View Post
low noise npn transistor for front stage into op amp RIAA at lower gain works great.
the jfets may be more noisy then(than) just the op amp in this config.
When you say maybe, that means to me that you are not sure. Read the paper, it explains why the jfets were used and not a bjt. If you look, many better receivers/amps used this same jfet ips configuration. You are free to do as you wish and show us your designs. Maybe you are a fan of Doug Self design's, one of my first phono amps I built, used a NE5533, which is a dual 5534 in a 16-pin dip.

Last edited by rsavas; 20th August 2019 at 02:55 PM.
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Old 21st August 2019, 02:33 PM   #44
keilau is offline keilau  United States
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Join Date: Mar 2013
Location: Windy City, US
Quote:
Originally Posted by rsavas View Post
That is a good history lesson thx

If you run multiple gain stages then this takes that burden away. This is what Doug Self suggests when using the NE5534 in a MM app.
But I still think the jfet is the best choice for a MM IPS, look at Bob Cordell's vinyl trak design or the LSK489 app note. The LM4562 should be fast enough.
I think the final touches could be a DC servo and get rid of C5, if you are bothered by ecaps in the FB.
The old (1984) Kenwood Basic C2 preamplifier uses the JFET + op-amp topology for both MM and MC. It worked quite well with LOMC cartridge (Dynavector) for me too. I first got the C2 thinking of temporary use, but ended up keeping it for many years. At 70dB with 0.25mV input, the noise performance is acceptable.
kenwood_basic_c2_phono_schematic.jpg

I switched to a NAD 1600 later when I want the remote control function. It has a all discrete phono stage MM/MC. But I did not like the sound of the NAD and replaced it with a Harman Kardon AP2500. No remote, but the sound is excellent.

The modern op-amp has made the JFET IPS optional. Take a look at Wyn Palmer's new design with DC servo.

Last edited by keilau; 21st August 2019 at 02:50 PM.
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