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BC550 BC560 Very low noise RIAA
BC550 BC560 Very low noise RIAA
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Old 10th January 2019, 12:53 PM   #181
carlmart is offline carlmart  Brazil
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The main problem is finding complementary low noise transistors nowadays.
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Old 10th January 2019, 12:57 PM   #182
schillg11 is offline schillg11  Germany
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BC850 and BC860 are the equivalents
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Old 10th January 2019, 12:59 PM   #183
carlmart is offline carlmart  Brazil
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Maybe THAT's.

THAT Corporation 300-series Low-Noise Matched Transistor Array ICs
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Old 10th January 2019, 03:55 PM   #184
carlmart is offline carlmart  Brazil
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I've looked around to see what is available that might be used for the transistors.

It's interesting that neither the BC560/BC860 or BC550/BC580 are labelled as low noise types.

The types that come as low noise on Mouser have no PNP complementary.

Apparently there's another complementary option to the SLN BCs, which are:

MMBT4124 ON Semiconductor / Fairchild | Mouser

MMBT4126 ON Semiconductor / Fairchild | Mouser

They come in TO92 and SMT versions, so you can choose. Even so, pairing between NPN and PNP versions would probably be quite difficult or not even possible.

But I wonder if a THAT quad, with two NPNs and two PNPs, being low noise, would not work.

340P14-U THAT | Mouser

Last edited by carlmart; 10th January 2019 at 04:06 PM.
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Old 10th January 2019, 04:04 PM   #185
catd is offline catd  Europe
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Hi.
What would be the particular benefit of making a RIAA stage particularly compact or particularly small, as with the addressed SMD components?
Even if you could put the whole (pre-)amp in your pocket, you always need the turntable, and that will make the whole thing cumbersome/stationary again.
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Old 10th January 2019, 04:32 PM   #186
carlmart is offline carlmart  Brazil
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I am not a fan of SMD projects or parts, so I'm probably the wrong person to answer your question.

Benefits:

1) Very small distance between parts. That sometimes is difficult to achieve with through hole parts.

2) Availability. Nowadays it's easier to get SMD parts than through-hole, particularly semiconductors. Sometimes they are even cheaper.

3) Small size. You can put the preamp on the turntable, eliminating interconnect cables between cartridge and preamp. Shielding it would also be easier.

Cons:

1) Anti-DIY. Most SMD parts are extremely difficult to handle.

2) Fragility. SMD parts are more easy to ruin, particularly by heat, when soldering.

3) Loss. You can lose the part quite easily, which is a problem with expensive active devices.

4) Soldering. You need specific tools, not cheap.

5) Thin tracks. SMD parts belong in SMD pcb designs. Tracks are very thin and very damage-prone.

Well, the list may be longer on both for and cons.
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Old 12th January 2019, 10:12 AM   #187
carlmart is offline carlmart  Brazil
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One thing I noticed in these simulations we have been making is that there's no amplification between input and output.

Is that due to the anti-RIAA input filter.

How can we simulate filter and amplification distortion.
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Old 12th January 2019, 11:07 AM   #188
catd is offline catd  Europe
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??? don't know, is this what you want:
see attached pic of frequency response.
red: input signal after reverse RIAA
green: output signal.
amplification at 1kHz = 35db

Distortion:
In LTSpice try to change the signal, which you want to examine
e.g. from: ".four {f} V(o) " (output)
to: ".four {f} V(e)" (amp input = reverse riaa output)
Attached Images
File Type: jpg fr_ampl.jpg (70.0 KB, 259 views)
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Old 14th January 2019, 05:16 PM   #189
carlmart is offline carlmart  Brazil
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What I mean is if you look at the input sinusoidal level and compare to the output sinusoidal level, there was no amplification.
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Old 18th January 2019, 06:32 PM   #190
catd is offline catd  Europe
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Quote:
Originally Posted by catd View Post
With the servo you can omit the resistors PP and PN (= 0 ohms).
In the real amp (pic, post #157) with pots "PP" / "PN" set to the 100 Ohm region I noticed the output transistors getting a bit hot.
With the above mentioned 0 Ohms the simulation shows 130mW dissipation. To high for a TO92-Device without cooling, I think.
I changed the pots to around 5kOhm. The simulation then shows around 75mW dissipation.
In the real amp then is a light warming.
With the pots (PP, PN) it is possible to set the output dc offset to about 1mV or lower.
Less to do for a DC-Servo.
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