try RS1=100R RS2=100R. the desired(exact) reaction level should be set by measurement
Just for curiosity:
I thought the Crescendo Millenium used conventional relays. Is this wrong?
This device has a Vdss = 150V. I'd probably look for something which has Vdss = 50V or 60V, and will happily accept lower Id too (this one can happily pump 80A) while keeping this one's low Rdson.
I was thinking of any of these:
- https://www.mouser.co.uk/datasheet/2/427/sqja42ep-1550625.pdf Vds = 40V, Rdson in single-digit mOhm, 90 cents
- https://www.mouser.co.uk/datasheet/2/408/TK100E06N1_datasheet_en_20140630-1139856.pdf Vds = 60V, TO220 packaging, Rdson 2 mOhm, $1.90 or so
- https://www.mouser.co.uk/datasheet/2/308/FDP070AN06A0-1305836.pdf Vds = 60V, TO220 package, Rdson 6 mOhm, $1.54
I have one doubt about these fellows. Will they work well when passing just a few microAmps or milliAmps of current? And will their leakage current be adequately low for signal switching when they are in the off state?
60A at a push - you don't want to push a TO220 to over 20W dissipation. 40A would be a much more sensible limit for that device in a practical thermal design.
People often think the current rating of a MOSFET is a current rating, when its usually a way to express the absolute maximum dissipation limit assuming perfect heatsink. Using the on-resistance and sensible power dissipation factor will get you a workable continuous current figure. 15W on a TO220 at 0.0083 ohms suggests 42A as a sensible rating if prepared to use a sizable heatsink. For use without heatsink a reasonable limit might be 8A (0.5W dissipation limit).
Thanks. But I'm not really worrying about too high currents here. My question is about switching line level signals feeding 10KOhm type loads, so I'll get milliAmp level currents typically, or sub-milliAmp. My worry is at the other extreme -- do these MOSFETs switch super small current flows correctly? Will the Rdson apply when such low currents are flowing, or do they apply only when, say, 1A or more is flowing?
Just to be sure:
Vds,max must be high enough for the full rail-to-rail voltage, right?
Ah now I understand your concerns
For line levels, I used to be very happy with these:
International Rectifier - PVA1354 | 100V 1 Form A Photo Voltaic Relay in a mod. 8-pin DIP Package
Seems that you might even still get some from "good" resellers
Edit: and leave the MOSFETS away, of course
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The low RDSon MOSFETs for example, used in the RTR SSR DC protect GB that you are getting, works perfectly well for line level signals as seen in the measured FFT data here:
Ready-to-Run (RTR) SSR DC Speaker Protection and Delay GB
Thanks a lot! This is really nice. The PVA1354 seems to have become obsolete, but a very similar device is now active: PVA13N: https://www.infineon.com/dgdl/pva13n.pdf?fileId=5546d462533600a401535683928a291e selling for UKP 5.60 or so on Mouser: PVA1354NPBF Infineon / IR | Mouser United KingdomAh now I understand your concerns
For line levels, I used to be very happy with these:
International Rectifier - PVA1354 | 100V 1 Form A Photo Voltaic Relay in a mod. 8-pin DIP Package
Seems that you might even still get some from "good" resellers
Edit: and leave the MOSFETS away, of course
This is really nice. Rdson is 5 Ohm, not in the milliOhm range, but for signal switching, this is what we would call really low impedance, right? And it reduces the 3-device SSR of the relay switching board into a single 4-pin device. Really neat.
Ya, you're right.
But the IC @fvzeppelin has referred to is neater for signal switching, isn't it? Reduces parts count and board space by 3x or so without increasing parts costs.
On a separate note, I want to learn to measure triple-zero distortion levels the way you guys do, specifically you've done in this thread many times. I have the Focusrite Scarlett 2i2 and ARTA for measurement, I just don't seem to get this low a THD level even in loopback mode with my Focusrite. I know this is OT, but... I need to figure this out.
Tcpip,
The tricks and tips for measuring are all in this thread. If you have a Focusrite, you should be able to do it. Trick is to use the balanced input on the Focusrite and use ASIO driver.
Howto - Distortion Measurements with REW
Regarding using low RDSon MOSFETs for switching, anyway you implement it - layout is critical and also use of optoisolators to drive it. I am working on a small very compact 2-ch SSR DC protect version for head phone amps that might be perfect for analog line-level switching.
Ultimately, a test will be necessary to confirm if it can provide a transparent "like a wire" performance exhibited by the discrete low RDSon SSR MOSFET and opto-isolator based circuits.
The tricks and tips for measuring are all in this thread. If you have a Focusrite, you should be able to do it. Trick is to use the balanced input on the Focusrite and use ASIO driver.
Howto - Distortion Measurements with REW
Regarding using low RDSon MOSFETs for switching, anyway you implement it - layout is critical and also use of optoisolators to drive it. I am working on a small very compact 2-ch SSR DC protect version for head phone amps that might be perfect for analog line-level switching.
Ultimately, a test will be necessary to confirm if it can provide a transparent "like a wire" performance exhibited by the discrete low RDSon SSR MOSFET and opto-isolator based circuits.
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